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Journal Cover Ecological Applications
  [SJR: 2.781]   [H-I: 167]   [165 followers]  Follow
   Full-text available via subscription Subscription journal
   ISSN (Print) 1051-0761 - ISSN (Online) 1939-5582
   Published by John Wiley and Sons Homepage  [1597 journals]
  • Mapping floral resources for honey bees in New Zealand at the catchment
    • Authors: A.-G. E Ausseil; J. R. Dymond, L. Newstrom
      Abstract: Honey bees require nectar and pollen from flowers: nectar for energy and pollen for growth. The demand for nectar and pollen varies during the year, with more pollen needed in spring for colony population growth, and more nectar needed in summer to sustain the maximum colony size and collect surplus nectar stores for winter. Sufficient bee forage is therefore necessary to ensure a healthy bee colony. Land-use changes can reduce the availability of floral resources suitable for bees, thereby increasing the susceptibility of bees to other stressors such as disease and pesticides. In contrast, land-based management decisions to protect or plant bee forage can enhance pollen and nectar supply to bees while meeting other goals such as riparian planting for water-quality improvement. Commercial demand for honey can also put pressure on floral resources through over-crowding of hives. To help understand and manage floral resources for bees, we developed a spatial model for mapping monthly nectar and pollen production from maps of land cover. Based on monthly estimated production data we mapped potential monthly supply of nectar and pollen to a given apiary location in the landscape. This is done by summing the total production within the foraging range of the apiary while subtracting the estimated nectar converted to energy for collection. Ratios of estimated supply over theoretical hive demand may then be used to infer a potential landscape carrying capacity to sustain hives. This model framework is quantitative and spatial, utilising estimated flight energy costs for nectar foraging. It can contribute to management decisions such as where apiaries could be placed in the landscape depending on floral resources and where nectar limited areas may be located. It can contribute to planning areas for bee protection or planting such as in riparian vegetation. This would aid managed bee health, wild pollinator protection and honey production. We demonstrate the methods in a case study in New Zealand where there is a growing demand for mānuka (Leptospermum scoparium) honey production.This article is protected by copyright. All rights reserved.
      PubDate: 2018-03-12T09:05:58.572378-05:
      DOI: 10.1002/eap.1717
  • Impacts of biomass production at civil airports on grassland bird
           conservation and aviation strike risk
    • Authors: Tara J. Conkling; Jerrold L. Belant, Travis L. DeVault, James A. Martin
      Abstract: Growing concerns about climate change, foreign oil dependency, and environmental quality have fostered interest in perennial native grasses (e.g. switchgrass [Panicum virgatum]) for bioenergy production while also maintaining biodiversity and ecosystem function. However, biomass cultivation in marginal landscapes such as airport grasslands may have detrimental effects on aviation safety as well as conservation efforts for grassland birds. In 2011–2013 we investigated effects of vegetation composition and harvest frequency on seasonal species richness and habitat use of grassland birds and modeled relative abundance, aviation risk, and conservation value of birds associated with biomass crops. Avian relative abundance was greater in switchgrass monoculture plots during the winter months, whereas Native Warm-Season Grass (NWSG) mixed species plantings were favored by species during the breeding season. Conversely, treatment differences in aviation risk and conservation value were not biologically significant. Only 2.6% of observations included avian species of high hazard to aircraft, providing support for semi-natural grasslands as a feasible landcover option at civil airports. Additionally, varied harvest frequencies across a mosaic of switchgrass monocultures and NWSG plots allows for biomass production with multiple vegetation structure options for grassland birds to increase seasonal avian biodiversity and habitat use.This article is protected by copyright. All rights reserved.
      PubDate: 2018-03-08T02:05:53.331852-05:
      DOI: 10.1002/eap.1716
  • Applying a dryland degradation framework for rangelands: the case of
    • Authors: C. Jamsranjav; R. S. Reid, M. E. Fernández-Giménez, A. Tsevlee, B. Yadamsuren, M. Heiner
      Abstract: Livestock-caused rangeland degradation remains a major policy concern globally and the subject of widespread scientific study. This concern persists in part because it is difficult to isolate the effects of livestock from climate and other factors that influence ecosystem conditions. Further, degradation studies seldom use multiple plant and soil indicators linked to a clear definition of and ecologically grounded framework for degradation assessment that distinguishes different levels of degradation. Here, we integrate two globally applicable rangeland degradation frameworks and apply them to a broad-scale empirical data set for the country of Mongolia. We compare our assessment results with two other recent national rangeland degradation assessments in Mongolia to gauge consistency of findings across assessments and evaluate the utility of our framework. We measured livestock-use impacts across Mongolia's major ecological zones: mountain and forest steppe, eastern steppe, steppe, and desert steppe. At 143 sites in 36 counties, we measured livestock-use and degradation indicators at increasing distances from livestock corrals in winter-grazed pastures. At each site, we measured multiple indicators linked to our degradation framework, including plant cover, standing biomass, palatability, species richness, forage quality, vegetation gaps, and soil surface characteristics. Livestock use had no effect on soils, plant species richness, or standing crop biomass in any ecological zone, but subtly affected plant cover and palatable plant abundance. Livestock effects were strongest in the steppe zone, moderate in the desert steppe, and limited in the mountain/forest and eastern steppes. Our results aligned closely with those of two other recent country-wide assessments, suggesting that our framework may have widespread application. All three assessments found that very severe and irreversible degradation is rare in Mongolia (1–18% of land area), with most rangelands slightly (33–53%) or moderately (25–40%) degraded. We conclude that very severe livestock-induced rangeland degradation is overstated in Mongolia. However, targeted rangeland restoration coupled with monitoring, adaptive management and stronger rangeland governance are needed to prevent further degradation where heavy grazing could cause irreversible change. Given the broad applicability of our degradation framework for Mongolia, we suggest it be tested for application in other temperate grasslands throughout Central Asia and North America.
      PubDate: 2018-03-06T09:40:43.242817-05:
      DOI: 10.1002/eap.1684
  • Satellite sensor requirements for monitoring essential biodiversity
           variables of coastal ecosystems
    • Authors: Frank E. Muller-Karger; Erin Hestir, Christiana Ade, Kevin Turpie, Dar A. Roberts, David Siegel, Robert J. Miller, David Humm, Noam Izenberg, Mary Keller, Frank Morgan, Robert Frouin, Arnold G. Dekker, Royal Gardner, James Goodman, Blake Schaeffer, Bryan A. Franz, Nima Pahlevan, Antonio G. Mannino, Javier A. Concha, Steven G. Ackleson, Kyle C. Cavanaugh, Anastasia Romanou, Maria Tzortziou, Emmanuel S. Boss, Ryan Pavlick, Anthony Freeman, Cecile S. Rousseaux, John Dunne, Matthew C. Long, Eduardo Klein, Galen A. McKinley, Joachim Goes, Ricardo Letelier, Maria Kavanaugh, Mitchell Roffer, Astrid Bracher, Kevin R. Arrigo, Heidi Dierssen, Xiaodong Zhang, Frank W. Davis, Ben Best, Robert Guralnick, John Moisan, Heidi M. Sosik, Raphael Kudela, Colleen B. Mouw, Andrew H. Barnard, Sherry Palacios, Collin Roesler, Evangelia G. Drakou, Ward Appeltans, Walter Jetz
      Abstract: The biodiversity and high productivity of coastal terrestrial and aquatic habitats are the foundation for important benefits to human societies around the world. These globally distributed habitats need frequent and broad systematic assessments, but field surveys only cover a small fraction of these areas. Satellite-based sensors can repeatedly record the visible and near-infrared reflectance spectra that contain the absorption, scattering, and fluorescence signatures of functional phytoplankton groups, colored dissolved matter, and particulate matter near the surface ocean, and of biologically structured habitats (floating and emergent vegetation, benthic habitats like coral, seagrass, and algae). These measures can be incorporated into Essential Biodiversity Variables (EBVs), including the distribution, abundance, and traits of groups of species populations, and used to evaluate habitat fragmentation. However, current and planned satellites are not designed to observe the EBVs that change rapidly with extreme tides, salinity, temperatures, storms, pollution, or physical habitat destruction over scales relevant to human activity. Making these observations requires a new generation of satellite sensors able to sample with these combined characteristics: (1) spatial resolution on the order of 30 to 100-m pixels or smaller; (2) spectral resolution on the order of 5 nm in the visible and 10 nm in the short-wave infrared spectrum (or at least two or more bands at 1,030, 1,240, 1,630, 2,125, and/or 2,260 nm) for atmospheric correction and aquatic and vegetation assessments; (3) radiometric quality with signal to noise ratios (SNR) above 800 (relative to signal levels typical of the open ocean), 14-bit digitization, absolute radiometric calibration
      PubDate: 2018-03-06T09:27:15.9921-05:00
      DOI: 10.1002/eap.1682
  • Current and historical land use influence soil-based ecosystem services in
           an urban landscape
    • Authors: Carly Ziter; Monica G. Turner
      Abstract: Urban landscapes are increasingly recognized as providing important ecosystem services (ES) to their occupants. Yet, urban ES assessments often ignore the complex spatial heterogeneity and land-use history of cities. Soil-based services may be particularly susceptible to land-use legacy effects. We studied indicators of three soil-based ES, carbon storage, water quality regulation, and runoff regulation, in a historically agricultural urban landscape and asked (1) How do ES indicators vary with contemporary land cover and time since development' (2) Do ES indicators vary primarily among land-cover classes, within land-cover classes, or within sites' (3) What is the relative contribution of urban land-cover classes to potential citywide ES provision' We measured biophysical indicators (soil carbon [C], available phosphorus [P], and saturated hydraulic conductivity [Ks]) in 100 sites across five land-cover classes, spanning an ~125-year gradient of time since development within each land-cover class. Potential for ES provision was substantial in urban green spaces, including developed land. Runoff regulation services (high Ks) were highest in forests; water quality regulation (low P) was highest in open spaces and grasslands; and open spaces and developed land (e.g., residential yards) had the highest C storage. In developed land covers, both C and P increased with time since development, indicating effects of historical land-use on contemporary ES and trade-offs between two important ES. Among-site differences accounted for a high proportion of variance in soil properties in forests, grasslands, and open space, while residential areas had high within-site variability, underscoring the leverage city residents have to improve urban ES provision. Developed land covers contributed most ES supply at the citywide scale, even after accounting for potential impacts of impervious surfaces. Considering the full mosaic of urban green space and its history is needed to estimate the kinds and magnitude of ES provided in cities, and to augment regional ES assessments that often ignore or underestimate urban ES supply.
      PubDate: 2018-03-06T09:26:58.842189-05:
      DOI: 10.1002/eap.1689
  • Supplementing non-target taxa: bird feeding alters the local distribution
           of mammals
    • Authors: J. Hunter Reed; David N. Bonter
      Abstract: Although the effects of bird feeding on avian species have been extensively examined, few studies evaluate the indirect effects of bird feeding on non-target taxa. Bird seed could provide direct nourishment to several mammalian species (e.g., Lagomorpha, Rodentia, and Cetartiodactyla), potentially altering their distribution and behavior with possible unintended consequences for some avian populations, particularly those not directly benefiting from the resource. To examine how bird feeders may influence the presence and behavior of mammals, we used camera traps to quantify differences in the distribution and richness of mammal species frequenting sites with bird feeders and control sites (lacking feeders) in Ithaca, New York, USA. We recorded 15,684 images capturing 12 mammal species with gray squirrel (Sciurus carolinensis) and raccoon (Procyon lotor) detected significantly more often at feeder sites than at control sites. Detections of white-tailed deer (Odocoileus virginianus) marginally increased near feeders whereas detections of several carnivorous species were unrelated to the presence of bird feeders. We recorded larger gray squirrel and raccoon group sizes and greater mammal richness at feeder sites than at nearby control sites. We detected squirrels and raccoons less when snow covered the ground than on snow-free days. Ambient temperature was not a strong predictor of mammal detections. Camera trapping revealed strong, species-specific patterns in the timing of daily visitation to areas with feeders. Because many mammals depredate bird nests, the local increases in mammal richness and activity near bird feeders may create an ecological trap for avian species nesting in close proximity to supplemental feeding stations.
      PubDate: 2018-03-06T09:26:26.537171-05:
      DOI: 10.1002/eap.1683
  • Stormwater wetlands can function as ecological traps for urban frogs
    • Authors: Michael Sievers; Kirsten M. Parris, Stephen E. Swearer, Robin Hale
      Abstract: Around cities, natural wetlands are rapidly being destroyed and replaced with wetlands constructed to treat stormwater. Although the intended purpose of these wetlands is to manage urban stormwater, they are inhabited by wildlife that might be exposed to contaminants. These effects will be exacerbated if animals are unable to differentiate between stormwater treatment wetlands of varying quality and some function as ‘ecological traps’ (i.e. habitats that animals prefer despite fitness being lower than in other habitats). To examine if urban stormwater wetlands can be ecological traps for frogs, we tested if survival, metamorphosis-related measures and predator avoidance behaviours of frogs differed within mesocosms that simulated stormwater wetlands with different contaminant levels, and paired this with a natural oviposition experiment to assess breeding-site preferences. We provide the first empirical evidence that these wetlands can function as ecological traps for frogs. Tadpoles had lower survival and were less responsive to predator olfactory cues when raised in more polluted stormwater wetlands, but also reached metamorphosis earlier and at a larger size. A greater size at metamorphosis was likely a result of increased per capita food availability due to higher mortality combined with eutrophication, although other compensatory effects such as selective-mortality removing smaller individuals from low-quality mesocosms may also explain these results. Breeding adults laid comparable numbers of eggs across wetlands with high and low contaminant levels, indicating no avoidance of the former. Since stormwater treatment wetlands are often the only available aquatic habitat in urban landscapes we need to better understand how they perform as habitats to guide management decisions that mitigate their potential ecological costs. This may include improving wetland quality so that fitness is no longer compromised, preventing colonisation by animals, altering the cues animals use when selecting habitats, pretreating contaminated water prior to release, providing off-line wetlands nearby or simply not constructing stormwater treatment wetlands in sensitive areas. Our study confirms the potential for urban stormwater treatment wetlands to function as ecological traps and highlights the need for greater awareness of their prevalence and impact at landscape scales.This article is protected by copyright. All rights reserved.
      PubDate: 2018-03-01T13:55:26.556075-05:
      DOI: 10.1002/eap.1714
  • Complementary crops and landscape features sustain wild bee communities
    • Authors: Kyle T. Martins; Cécile H. Albert, Martin J. Lechowicz, Andrew Gonzalez
      Abstract: Wild bees, which are important for commercial pollination, depend on floral and nesting resources both at farms and in the surrounding landscape. Mass-flowering crops are only in bloom for a few weeks and unable to support bee populations that persist throughout the year. Farm fields and orchards that flower in succession potentially can extend the availability of floral resources for pollinators. However, it is unclear whether the same bee species or genera will forage from one crop to the next, which bees specialize on particular crops, and to what degree inter-crop visitation patterns will be mediated by landscape context. We therefore studied local- and landscape-level drivers of bee diversity and species turnover in apple orchards, blueberry fields and raspberry fields that bloom sequentially in southern Quebec, Canada. Despite the presence of high bee species turnover, orchards and small fruit fields complemented each other phenologically by supporting two bee genera essential to their pollination: mining bees (Andrena spp.) and bumble bees (Bombus spp.). A number of bee species specialized on apple, blueberry or raspberry blossoms, suggesting that all three crops could be used to promote regional bee diversity. Bee diversity (rarefied richness, wild bee abundance) was highest across crops in landscapes containing hedgerows, meadows and suburban areas that provide ancillary nesting and floral resources throughout the spring and summer. Promoting phenological complementarity in floral resources at the farmstead and landscape scales is essential to sustaining diverse wild bee populations.This article is protected by copyright. All rights reserved.
      PubDate: 2018-03-01T13:55:23.446781-05:
      DOI: 10.1002/eap.1713
  • Using ideal distributions of the time since habitat was disturbed to build
           metrics for evaluating landscape condition
    • Authors: Ayesha I. T. Tulloch; Jane McDonald, Peter Cosier, Carla Sbrocchi, John Stein, David Lindenmayer, Hugh P. Possingham
      Abstract: Developing a standardized approach to measuring the state of biodiversity in landscapes undergoing disturbance is crucial for evaluating and comparing change across different systems, assessing ecosystem vulnerability and the impacts of destructive activities, and helping direct species recovery actions. Existing ecosystem metrics of condition fail to acknowledge that a particular community could be in multiple states, and the distribution of states could worsen or improve when impacted by a disturbance process, depending on how far the current landscape distribution of states diverges from pre-anthropogenic impact baseline conditions. We propose a way of rapidly assessing regional-scale condition in ecosystems where the distribution of age classes representing increasing time since last disturbance is suspected to have diverged from an ideal benchmark reference distribution. We develop two metrics that (1) compare the observed mean time since last disturbance with an expected mean and (2) quantify the summed shortfall of vegetation age-class frequencies relative to a reference age-class distribution of time since last disturbance. We demonstrate the condition metrics using two case studies: (1) fire in threatened southwestern Australian proteaceaous mallee-heath and (2) impacts of disturbance (fire and logging) in the critically endangered southeastern Australian mountain ash Eucalyptus regnans forest on the yellow-bellied glider Petaurus australis. We explore the effects of uncertainty in benchmark time since last disturbance, and evaluate metric sensitivity using simulated age-class distributions representing alternative ecosystems. By accounting for and penalizing too-frequent and too-rare disturbances, the summed shortfall metric is more sensitive to change than mean time since last disturbance. We find that mountain ash forest is in much poorer condition (summed shortfall 38.5 out of 100 for a 120-yr benchmark disturbance interval) than indicated merely by loss of extent (84% of vegetation remaining). Proteaceaous mallee-heath is in worse condition than indicated by loss of extent for an upper benchmark interval of 80 yr, but condition almost doubles for the minimum tolerable time since last disturbance interval of 20 yr. To fully describe ecosystem degradation, we recommend that our summed shortfall metric, focused on habitat quality and informed by biologically meaningful baselines, be added to existing condition measures focused on vegetation extent. This will improve evaluation of change in ecosystem states and enhance management of ecosystems in poor condition.
      PubDate: 2018-02-28T15:25:31.699207-05:
      DOI: 10.1002/eap.1676
  • Biological control effects of non-reproductive host mortality caused by
           insect parasitoids
    • Authors: Joe M. Kaser; Anne L. Nielsen, Paul K. Abram
      Abstract: As the rate of spread of invasive species increases, consumer-resource communities are often populated by a combination of exotic and native species at all trophic levels. In parasitoid-host communities, these novel associations may lead to disconnects between parasitoid preference and performance, and parasitoid oviposition may result in death of the parasitoid offspring, death of the host, or death of both. Despite their relevance for biological control risk and efficacy assessments, the direct and indirect population-level consequences of parasitoids attacking and killing their hosts without successfully reproducing (non-reproductive mortality) are poorly understood. Non-reproductive mortality induced by egg parasitoids (parasitoid-induced host egg abortion) may be particularly important for understanding the population dynamics of the invasive agricultural pest Halyomorpha halys (Hemiptera: Pentatomidae) and endemic stink bugs in North America, which are attacked by a suite of both native and introduced egg parasitoids. It is unclear, however, how various factors controlling parasitoid foraging and developmental success manifest at the population level. We constructed two related versions of a two host-one parasitoid model to evaluate the population-level consequences of non-reproductive host mortality. Egg abortion can result in strong negative or positive enemy-mediated indirect effects, taking the form of apparent competition (-/-), apparent parasitism (-/+), apparent amensalism (-/0), or apparent commensalism (0/+). For parasitoids limited in their reproductive output by the number of eggs they can produce, higher non-reproductive host mortality can reduce the strength of the positive indirect effect in cases of apparent parasitism, and it can reduce the negative indirect effect on the more suitable host in cases of apparent competition. For time-limited parasitoids, unsuitable hosts with high levels of non-reproductive parasitoid-induced mortality can be strongly suppressed in the presence of a suitable host, while the suitable host is only negligibly impacted (i.e. apparent amensalism). We evaluate these model-derived hypotheses within the context of H. halys and its native and non-native parasitoids in North America, and discuss their application to risk assessment in biological control programs.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-27T07:21:01.839406-05:
      DOI: 10.1002/eap.1712
  • Controls on denitrification potential in nitrate-rich waterways and
           riparian zones of an irrigated agricultural setting
    • Authors: Alex J. Webster; Peter M. Groffman, Mary L. Cadenasso
      Abstract: Denitrification, the microbial conversion of NO3- to N gases, is an important process contributing to whether lotic and riparian ecosystems act as sinks for excess NO3- from agricultural activities. Though agricultural waterways and riparian zones have been a focus of denitrification research for decades, almost none of this research has occurred in the irrigated agricultural settings of arid and semi-arid climates. In this study, we conducted a broad survey of denitrification potential in riparian soils and channel sediment from 79 waterway reaches in the irrigated agricultural landscape of California's Central Valley. With this approach, we sought to capture the wide range of variation that arose from diverse waterway management and fluctuating flow conditions, and use this variation to identify promising management interventions. We explored associations of denitrification potentials with surface water NO3--N, organic matter, flow conditions, vegetation cover, near-channel riparian bank slope, and channel geomorphic features using generalized linear mixed models. We found strong associations of sediment denitrification potentials with reach flow conditions, which we hypothesize was the result of variation in microbial communities’ tolerance to dry-wet cycles. Denitrification potentials in riparian soils, in contrast, did not appear affected by flow conditions, but instead were associated with organic matter, vegetation cover, and bank slope in the riparian zone. These results suggest a strong need for further work on how denitrification responds to varying flow conditions and dry-wet cycles in non-perennial lotic ecosystems. Our findings also demonstrate that denitrifier communities respond to key features of waterway management, which can therefore be leveraged to control denitrification through a variety of management actions.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-21T09:25:22.291301-05:
      DOI: 10.1002/eap.1709
  • Forest structure provides the income for reproductive success in a
           southern population of Canada lynx
    • Authors: Megan K. Kosterman; John R. Squires, Joseph D. Holbrook, Daniel H. Pletscher, Mark Hebblewhite
      Abstract: Understanding intrinsic and extrinsic drivers of reproductive success is central to advancing animal ecology and characterizing critical habitat. Unfortunately, much of the work examining drivers of reproductive success is biased toward particular groups of organisms (e.g., colonial birds, large herbivores, capital breeders). Long-lived mammalian carnivores that are of conservation concern, solitary, and territorial present an excellent situation to examine intrinsic and extrinsic drivers of reproductive success, yet they have received little attention. Here, we used a Canada lynx (Lynx canadensis) dataset, from the southern periphery of their range, to determine if reproductive success in a solitary carnivore was consistent with capital or income breeding. We radio-marked and monitored 36 female Canada lynx for 98 lynx years. We evaluated how maternal characteristics and indices of food supply (via forest structure) in core areas influenced variation in body condition and reproductive success. We characterized body condition as mass/length and reproductive success as whether a female produced a litter of kittens for a given breeding season. Consistent with life-history theory, we documented a positive effect of maternal age on body condition and reproductive success. In contrast to predictions of capital breeding, we observed no effect of pre-pregnancy body condition on reproductive success in Canada lynx. However, we demonstrated statistical effects of forest structure on reproductive success in Canada lynx, consistent with predictions of income breeding. The forest characteristics that defined high success included (1) abundant and connected mature forest and (2) intermediate amounts of small-diameter regenerating forest. These attributes are consistent with providing abundant, temporally stable, and accessible prey resources (i.e., snowshoe hares; Lepus americanus) for lynx and reinforce the bottom-up mechanisms influencing Canada lynx populations. Collectively, our results suggest that lynx on the southern range periphery exhibit an income breeding strategy and that forest structure supplies the income important for successful reproduction. More broadly, our insights advance the understanding of carnivore ecology and serve as an important example on integrating long-term field studies with ecological theory to advance landscape management.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-19T02:25:31.421765-05:
      DOI: 10.1002/eap.1707
  • Correcting for missing and irregular data in home-range estimation
    • Authors: C. H. Fleming; D. Sheldon, W. F. Fagan, P. Leimgruber, T. Mueller, D. Nandintsetseg, M. J. Noonan, K. A. Olson, E. Setyawan, A. Sianipar, J. M. Calabrese
      Abstract: Home-range estimation is an important application of animal tracking data that is frequently complicated by autocorrelation, sampling irregularity, and small effective sample sizes. We introduce a novel, optimal weighting method that accounts for temporal sampling bias in autocorrelated tracking data. This method corrects for irregular and missing data, such that oversampled times are downweighted and undersampled times are upweighted to minimize error in the home-range estimate. We also introduce computationally efficient algorithms that make this method feasible with large datasets. Generally speaking, there are three situations where weight optimization improves the accuracy of home-range estimates: with marine data, where the sampling schedule is highly irregular, with duty cycled data, where the sampling schedule changes during the observation period, and when a small number of homerange crossings are observed, making the beginning and end times more independent and informative than the intermediate times. Using both simulated data and empirical examples including reef manta ray, Mongolian gazelle, and African buffalo, optimal weighting is shown to reduce the error and increase the spatial resolution of home-range estimates. With a conveniently packaged and computationally efficient software implementation, this method broadens the array of datasets with which accurate space-use assessments can be made.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-16T01:45:26.357711-05:
      DOI: 10.1002/eap.1704
  • Conservation value of low-productive forests measured as the amount and
           diversity of dead wood and saproxylic beetles
    • Authors: Aino Hämäläinen; Joachim Strengbom, Thomas Ranius
      Abstract: In many managed landscapes, low-productive land comprises most of the remaining relatively untouched areas, and is often over-represented within protected areas. The relationship between the productivity and conservational value of a site is poorly known; however, it has been hypothesized that biodiversity increases with productivity due to higher resource abundance or heterogeneity, and that the species communities of low-productive land are a nested sub-set of communities from more productive land. We tested these hypotheses for dead wood-dependent beetles by comparing their species richness and composition, as well as the amount and diversity of dead wood, between low-productive (potential forest growth < 1 m3 ha−1 year−1) and productive Scots pine-dominated stands in Sweden. We included four stand types: stands situated on (i) thin soils and (ii) mires (both low-productive), (iii) managed stands, and (iv) unmanaged stands set aside for conservation purposes (both productive). Beetle species richness and number of red-listed species were highest in the productive set-asides. Species richness was positively correlated with the volume and diversity of dead wood, but volume appeared to be a better predictor than diversity for the higher species richness in set-asides. Beetle species composition was similar among stand types, and the assemblages in low-productive stands were largely subsets of those in productive set-asides. However, 11% of all species and 40% of red-listed species only occurred in productive stands, while no species were unique to low-productive stands. We conclude that low-productive forests are less valuable for conservation than productive forest land. Given the generally similar species composition among stand types, a comparable conservational effect could be obtained by setting aside a larger area of low-productive forest in comparison to the productive. In terms of dead wood volumes, 1.8–3.6 ha of low-productive forest has the same value as 1 ha of unmanaged productive forest. This figure can be used to estimate the conservation value of low productive forests; however, as productive forests harbored some unique species, they are not completely exchangeable.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-15T09:06:08.217427-05:
      DOI: 10.1002/eap.1705
  • A conservation planning tool for greater sage-grouse using indices of
           species distribution, resilience, and resistance
    • Authors: Mark A. Ricca; Peter S. Coates, K. Benjamin Gustafson, Brianne E. Brussee, Jeanne C. Chambers, Shawn P. Espinosa, Scott C. Gardner, Sherri Lisius, Pilar Ziegler, David. J. Delehanty, Michael L. Casazza
      Abstract: Managers require quantitative yet tractable tools that can identify areas for restoration yielding effective benefits for targeted wildlife species and the ecosystems they inhabit. As a contemporary example of high national significance for conservation, the persistence of greater sage-grouse (Centrocercus urophasianus, hereafter ‘sage-grouse’) in the Great Basin ecoregion is compromised, in part, by strongly interacting stressors of conifer encroachment, annual grass invasion, and larger and more frequent wildfires occurring in sagebrush ecosystems. Associated restoration treatments to a sagebrush-dominated state are often costly and risk yielding relatively little ecological benefit to sage-grouse if implemented without first estimating how sage-grouse may respond to treatments, or considering underlying processes influencing sagebrush ecosystem resilience to disturbance and resistance to invasive species. We describe example applications of a spatially-explicit conservation planning tool (CPT) to inform initial prioritization of treatments focused on: 1) removal of conifers (i.e., pinyon-juniper); and 2) post-wildfire restoration aimed at improving habitat conditions for the Bi-State Distinct Population Segment of sage-grouse (an allopatric sub-population at the southwestern edge of the species’ range along the California-Nevada state line). The CPT is designed to measure ecological benefits to sage-grouse for a given management action by employing a composite index comprised of resource selection functions and estimates of abundance and space use. For pinyon-juniper removal, we simulated changes in land cover composition following the removal of sparsely distributed trees with low canopy cover and intact understories, and ranked treatments on the basis of spatially-explicit changes in ecological benefits per dollar-unit of cost. For wildfire restoration, we formulated a spatially-explicit conditional model to simulate scenarios for land cover changes (e.g., sagebrush to annual grass) given estimated fire-severity and underlying ecosystem processes influencing resilience to disturbance and resistance to invasion by annual grasses. For both applications, we compared CPT output rankings to land cover changes along with sagebrush resistance and resilience metrics. Model results demonstrated how the CPT can be an important step in identifying management projects that yield the highest quantifiable benefit to sage-grouse while avoiding potentially costly misallocation of resources, and highlighted the importance of considering both changes in sage-grouse ecological response and factors influencing sagebrush ecosystem resilience to disturbance and resistance to invasion. This framework can be adapted to help inform other management questions aimed at improving habitat for species of conservation concern across sagebrush and other ecosystems.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-14T00:06:55.784583-05:
      DOI: 10.1002/eap.1690
  • Restoration of Eastern oyster populations with positive density dependence
    • Authors: Jacob L Moore; Brandon Puckett, Sebastian J Schreiber
      Abstract: Positive density dependence (i.e. Allee effects) can create a threshold of population states below which extinction of the population occurs. The existence of this threshold, which can often be a complex, multi-dimensional surface, rather than a single point, is of particular importance in degraded populations for which there is a desire for successful restoration. Here, we incorporated positive density dependence into a closed, size- and age-structured integral projection model parameterized with empirical data from an Eastern oyster, Crassostrea virginica, population in Pamlico Sound, North Carolina. To understand the properties of the threshold surface, and implications for restoration, we introduced a general method based on a linearization of the threshold surface at its unique, unstable equilibrium. We estimated the number of oysters of a particular age (i.e. stock enhancement), or the surface area of dead shell substrate required (i.e. habitat enhancement), to move a population from an extinction trajectory to a persistence trajectory. The location of the threshold surface was strongly affected by changes in the amount of local larval retention. Traditional stock enhancement with oysters less than a year old (i.e. spat) required three times as many oysters relative to stock enhancement with oysters between ages three and seven, while the success of habitat enhancement depended upon the initial size distribution of the population. The methodology described here demonstrates the importance of considering positive density dependence in oyster populations, and also provides insights into effective management and restoration strategies when dealing with a high dimensional threshold separating extinction and persistence.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-13T14:30:42.332702-05:
      DOI: 10.1002/eap.1694
  • Depressional Wetlands Affect Watershed Hydrological, Biogeochemical, and
           Ecological Functions
    • Authors: Grey R. Evenson; Heather E. Golden, Charles R. Lane, Daniel L. McLaughlin, Ellen D'Amico
      Abstract: Depressional wetlands of the extensive U.S. and Canadian Prairie Pothole Region afford numerous ecosystem processes that maintain healthy watershed functioning. However, these wetlands have been lost at a prodigious rate over past decades due to drainage for development, climate effects, and other causes. Options for management entities to protect the existing wetlands – and their functions – may focus on conserving wetlands based on spatial location vis-à-vis a floodplain or on size limitations (e.g., permitting smaller wetlands to be destroyed but not larger wetlands). Yet the effects of such management practices and the concomitant loss of depressional wetlands on watershed-scale hydrological, biogeochemical, and ecological functions are largely unknown. Using a hydrological model, we analyzed how different loss scenarios by wetland size and proximal location to the stream network affected watershed storage (i.e., inundation patterns and residence times), connectivity (i.e., streamflow contributing areas), and export (i.e., streamflow) in a large watershed in the Prairie Pothole Region of North Dakota, USA. Depressional wetlands store consequential amounts of precipitation and snowmelt. The loss of smaller depressional wetlands (< 3.0 ha) substantially decreased landscape-scale inundation heterogeneity, total inundated area, and hydrological residence times. Larger wetlands act as hydrologic “gatekeepers,” preventing surface runoff from reaching the stream network, and their modeled loss had a greater effect on streamflow due to changes in watershed connectivity and storage characteristics of larger wetlands. The wetland management scenario based on stream proximity (i.e., protecting wetlands 30-m and ~450-m from the stream) alone resulted in considerable landscape heterogeneity loss and decreased inundated area and residence times. With more snowmelt and precipitation available for runoff with wetland losses, contributing area increased across all loss scenarios. We additionally found that depressional wetlands attenuated peak flows; the probability of increased downstream flooding from wetland loss was also consistent across all loss scenarios. It is evident from this study that optimizing wetland management for one end-goal (e.g., protection of large depressional wetlands for flood attenuation) over another (e.g., protecting of small depressional wetlands for biodiversity) may come at a cost for overall watershed hydrological, biogeochemical, and ecological resilience, functioning, and integrity.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-13T11:25:23.230031-05:
      DOI: 10.1002/eap.1701
  • Management of a stage-structured insect pest: an application of
           approximate optimization
    • Authors: Sean C. Hackett; Michael B. Bonsall
      Abstract: Ecological decision problems frequently require the optimization of a sequence of actions over time where actions may have both immediate and downstream effects. Dynamic programming can solve such problems only if the problem dimensionality is sufficiently low. Approximate dynamic programming (ADP) provides a suite of methods applicable to problems of arbitrary complexity at the expense of guaranteed optimality. The most easily generalised method is the lookahead policy: a brute-force algorithm which identifies reasonable actions by constructing and solving a series of temporally truncated approximations of the full problem over a defined planning horizon. We develop and apply this approach to a pest management problem inspired by the Mediterranean fruit fly, Ceratitis capitata. The model aims to minimise the cumulative costs of management actions and medfly-induced losses over a single 16-week season. The medfly population is stage-structured and grows continuously while management decisions are made at discrete, weekly intervals. For each week, the model chooses between inaction, insecticide application or one of six sterile insect release ratios. Lookahead policy performance is evaluated over a range of planning horizons, two levels of crop susceptibility to medfly and three levels of pesticide persistence. In all cases, the actions proposed by the lookahead policy are contrasted to those of a myopic policy which minimises costs over only the current week. We find that lookahead policies always out-performed a myopic policy and decision quality is sensitive to the temporal distribution of costs relative to the planning horizon: it is beneficial to extend the planning horizon when it excludes pertinent costs. However, longer planning horizons may reduce decision quality when major costs are resolved imminently. ADP methods such as the lookahead policy based approach developed here render questions intractable to dynamic programming amenable to inference but should be applied carefully as their flexibility comes at the expense of guaranteed optimality. However, given the complexity of many ecological management problems, the capacity to propose a strategy that is “good enough” using a more representative problem formulation may be preferable to an optimal strategy derived from a simplified model.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-12T08:30:22.909639-05:
      DOI: 10.1002/eap.1700
  • Host-pathogen metapopulation dynamics suggest high elevation refugia for
           boreal toads
    • Authors: Brittany A. Mosher; Larissa L. Bailey, Erin Muths, Kathryn P. Huyvaert
      Abstract: Emerging infectious diseases are an increasingly common threat to wildlife. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is an emerging infectious disease that has been linked to amphibian declines around the world. Few studies exist that explore amphibian-Bd dynamics at the landscape scale, limiting our ability to identify which factors are associated with variation in population susceptibility and to develop effective in situ disease management. Declines of boreal toads (Anaxyrus boreas boreas) in the Southern Rocky Mountains are largely attributed to chytridiomycosis but variation exists in local extinction of boreal toads across this metapopulation. Using a large-scale historic dataset, we explored several potential factors influencing disease dynamics in the boreal toad-Bd system: geographic isolation of populations, amphibian community richness, elevational differences, and habitat permanence. We found evidence that boreal toad extinction risk was lowest at high elevations where temperatures may be sub-optimal for Bd growth and where small boreal toad populations may be below the threshold needed for efficient pathogen transmission. In addition, boreal toads were more likely to recolonize high elevation sites after local extinction, again suggesting that high elevations may provide refuge from disease for boreal toads. We illustrate a modeling framework that will be useful to natural resource managers striving to make decisions in amphibian-Bd systems. Our data suggest that in the southern Rocky Mountains high elevation sites should be prioritized for conservation initiatives like reintroductions.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-12T02:50:43.123162-05:
      DOI: 10.1002/eap.1699
  • Seascape Models Reveal Places to Focus Coastal Fisheries Management
    • Authors: Kostantinos A Stamoulis; Jade MS Delevaux, Ivor D Williams, Matthew Poti, Joey Lecky, Bryan Costa, Matthew S Kendall, Simon J Pittman, Mary K Donovan, Lisa M Wedding, Alan M Friedlander
      Abstract: To design effective marine reserves and support fisheries, more information on fishing patterns and impacts for targeted species is needed, as well as better understanding of their key habitats. However, fishing impacts vary geographically and are difficult to disentangle from other factors that influence targeted fish distributions. We developed a set of fishing effort and habitat layers at high resolution and employed machine learning techniques to create regional-scale seascape models and predictive maps of biomass and body length of targeted reef fishes for the main Hawaiian Islands. Spatial patterns of fishing effort were shown to be highly variable and seascape models indicated a low threshold beyond which targeted fish assemblages were severely impacted. Topographic complexity, exposure, depth, and wave power were identified as key habitat variables which influenced targeted fish distributions and defined productive habitats for reef fisheries. High targeted reef fish biomass and body length were found in areas not easily accessed by humans, while model predictions when fishing effort was set to zero showed these high values to be more widely dispersed among suitable habitats. By comparing current targeted fish distributions with those predicted when fishing effort was removed, areas with high recovery potential on each island were revealed, with average biomass recovery of 517% and mean body length increases of 59% on Oahu, the most heavily fished island. Spatial protection of these areas would aid recovery of nearshore coral reef fisheries.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-08T17:40:31.17972-05:0
      DOI: 10.1002/eap.1696
  • Applying network theory to animal movements to identify properties of
           landscape space use
    • Authors: Guillaume Bastille-Rousseau; Iain Douglas-Hamilton, Stephen Blake, Joseph M. Northrup, George Wittemyer
      Abstract: Network (graph) theory is a popular analytical framework to characterize the structure and dynamics among discrete objects, particularly effective at identifying critical hubs and patterns of connectivity. The identification of such attributes is a fundamental objective of animal movement research, yet network theory has rarely been applied directly to animal relocation data. We develop an approach that allows the analysis of movement data using network theory by defining occupied pixels as nodes and connection among these pixels as edges. We first quantify node-level (local) metrics and graph-level (system) metrics on simulated movement trajectories to assess the ability of these metrics to pull out known properties in movement paths. We then apply our framework to empirical data from African elephants (Loxodonta africana), giant Galapagos tortoises (Chelonoidis sp.), and mule deer (Odocoileous hemionus). Our results indicate that certain node-level metrics, namely degree, weight, and betweenness, perform well in capturing local patterns of space use, such as the definition of core areas and paths used for inter-patch movement. These metrics were generally applicable across data sets, indicating their robustness to assumptions structuring analysis or strategies of movement. Other metrics capture local patterns effectively, but were sensitive to specified graph properties, indicating case specific applications. Our analysis indicates that graph-level metrics are unlikely to outperform other approaches for the categorization of general movement strategies (central place foraging, migration, nomadism). By identifying critical nodes, our approach provides a robust quantitative framework to identify local properties of space use which can be used to evaluate the effect of the loss of specific nodes on range wide connectivity. Our network approach is intuitive, and can be implemented across imperfectly sampled or large-scale datasets efficiently, providing a framework for conservationists to analyze movement data. Functions created for the analyses are available within the R package moveNT.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-08T15:00:21.835986-05:
      DOI: 10.1002/eap.1697
  • A semiarid fruit agroecosystem as a conservation-friendly option for small
           mammals in an anthropized landscape in Mexico
    • Authors: Mónica E. Riojas-López; Eric Mellink, Jaime Luévano
      Abstract: Many studies have addressed the potential of low-input agroecosystems for biological conservation. However, most have been carried out on annual agroecosystems in temperate, developed countries. As agricultural surface will increase and natural protected areas alone will not warrant the conservation of biodiversity, it is crucial to include different types of agroecosystems in research and conservation efforts. In Mexico, perennial, low-input, fruit-oriented nopal orchards (Opuntia spp.), one of the few crops suitable for semiarid areas, are the 10th out of 61 most important fruit crops grown in the country. We assessed their value for conservation in an anthropized landscape by comparing their rodent assemblages with those in adjacent habitats and determined the influence of the latter on the rodent communities inside them. We live-trapped rodents in 12 orchards and adjacent natural xeric shrubland, grassland, and cropland. We captured 19 different species, of which 17 used the orchards. Four are Mexican endemics. Orchards have higher α diversity, species richness, and abundance than cropland and grassland and are not different from shrubland. The dominant rodent species are the same in orchards and shrubland, and where these two meet they integrate into one habitat. Within-habitat quality is a critical driver of the composition and diversity of rodent communities in the orchards studied, and the neighboring habitats do not modify them substantially. Increasing within-patch heterogeneity beyond a certain level is at the expense of habitat integrity and produces small-scale fragmentation reducing habitat quality. At a landscape scale, orchards contribute importantly to regional rodent diversity compared with other land use types, and appear to increase habitat connectivity between patches of shrubland. Orchards’ higher α diversity would give them higher ecological resilience and make them better suited than grassland and cropland to contribute to the conservation of local biota. Nopal orchards should be considered conservation allies and incorporated in regional conservation plans. Regrettably, their future is unwarranted as producers face low revenues and lack of governmental support. Our confirmation that orchards have an important, positive impact on biodiversity can be used as a strong argument to lobby for incentives to safeguard this environmental friendly, low-input agroecosystem.
      PubDate: 2018-02-07T09:01:29.221743-05:
      DOI: 10.1002/eap.1663
  • Logging and fire regimes alter plant communities
    • Authors: Elle J. Bowd; David B. Lindenmayer, Sam C. Banks, David P. Blair
      Abstract: Disturbances are key drivers of plant community composition, structure and function. Plant functional traits, including life forms and reproductive strategies are critical to the resilience and resistance of plant communities in the event of disturbance. Climate change and increasing anthropogenic disturbance are altering natural disturbance regimes, globally. When these regimes shift beyond the adaptive resilience of plant functional traits, local populations and ecosystem functions can become compromised. We tested the influence of multiple disturbances, of varying intensity and frequency, on the composition and abundance of vascular plant communities and their respective functional traits (life forms and reproductive strategies) in the wet sclerophyll, Mountain Ash Eucalyptus regnans forests of south-eastern Australia. Specifically, we quantified the effect of the type and number of disturbances (including fires, clearcut logging and salvage logging) on plant community composition. We found that clearcut and salvage logging and the number of fires significantly influenced plant community composition and functional traits. Specifically, multiple fires resulted in lower populations of species that depend on on-site seeding for persistence. This includes the common tree species, Eucalyptus regnans, Pomaderris aspera and Acacia dealbata. In contrast, clearcut and salvage logged sites supported abundant on-site seeder species. However, species that depend on resprouting by surviving individuals, such as common and keystone ‘tree ferns’ Dicksonia antarctica and Cyathea australis declined significantly. Our data have important implications for understanding the relationship between altered disturbance regimes and plant communities and the respective effects on ecosystem function. In a period of rapid global environmental change, with disturbances predicted to increase and intensify, it is critical to address the impact of altered disturbance regimes on biodiversity.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-07T06:00:20.009138-05:
      DOI: 10.1002/eap.1693
  • Pre-outbreak forest conditions mediate the effects of spruce beetle
           outbreaks on fuels in subalpine forests of Colorado
    • Authors: Nathan Mietkiewicz; Dominik Kulakowski, Thomas T. Veblen
      Abstract: Over the past 30 years, forest disturbances have increased in size, intensity, and frequency globally, and are predicted to continue increasing due to climate change, potentially relaxing the constraints of vegetation properties on disturbance regimes. However, the consequences of the potentially declining importance of vegetation in determining future disturbance regimes are not well understood. Historically, bark beetles preferentially attack older trees and stands in later stages of development. However, as climate warming intensifies outbreaks by promoting growth of beetle populations and compromising tree defenses, smaller diameter trees and stands in early stages of development now are being affected by outbreaks. To date, no study has considered how stand age and other pre-outbreak forest conditions mediate the effects of outbreaks on surface and aerial fuel arrangements. We collected fuels data across a chronosequence of post-outbreak sites affected by spruce beetle (SB) between the 1940s and the 2010s, stratified by young (130 yr) post-fire stands. Canopy and surface fuel loads were calculated for each tree and stand, and available crown fuel load, crown bulk density, and canopy bulk densities were estimated. Canopy bulk density and density of live canopy individuals were reduced in all stands affected by SB, though foliage loss was proportionally greater in old stands as compared to young stands. Fine surface fuel loads in young stands were three times greater shortly (
      PubDate: 2018-02-05T15:15:37.888829-05:
      DOI: 10.1002/eap.1661
  • Estimating abundance of an open population with an N-mixture model using
           auxiliary data on animal movements
    • Authors: Alison C. Ketz; Therese L. Johnson, Ryan J. Monello, John A. Mack, Janet L. George, Benjamin R. Kraft, Margaret A. Wild, Mevin B. Hooten, N.Thompson Hobbs
      Abstract: Accurate assessment of abundance forms a central challenge in population ecology and wildlife manage Many statistical techniques have been developed to estimate population sizes because populations change over time and space, and to correct for the bias resulting from animals that are present in a study area but not observed. The mobility of individuals makes it difficult to design sampling procedures that account for movement into and out of areas with fixed jurisdictional boundaries. Aerial surveys are the gold standard used to obtain data of large mobile species in geographic regions with harsh terrain, but these surveys can be prohibitively expensive and dangerous. Estimating abundance with ground based census methods have practical advantages, but it can be difficult to simultaneously account for temporary emigration and observer error to avoid biased results. Contemporary research in population ecology increasingly relies on telemetry observations of the states and locations of individuals to gain insight on vital rates, animal movements, and population abundance. Analytical models that use observations of movements to improve estimates of abundance have not been developed. Here we build upon existing multi-state mark recapture methods using a hierarchical N-mixture model with multiple sources of data, including telemetry data on locations of individuals, to improve estimates of population sizes. We used a state-space approach to model animal movements to approximate the number of marked animals present within the study area at any observation period, thereby accounting for a frequently changing number of marked individuals. We illustrate the approach using data on a population of elk (Cervus elaphus nelsoni) in Northern Colorado, USA. We demonstrate substantial improvement compared to existing abundance estimation methods and corroborate our results from the ground based surveys with estimates from aerial surveys during the same seasons. We develop a hierarchical Bayesian N-mixture model using multiple sources of data on abundance, movement and survival to estimate the population size of a mobile species that uses remote conservation areas. The model improves accuracy of inference relative to previous methods for estimating abundance of open populations.This article is protected by copyright. All rights reserved.
      PubDate: 2018-02-05T10:18:56.666899-05:
      DOI: 10.1002/eap.1692
  • Intermediate-severity wind disturbance in mature temperate forests: Legacy
           structure, carbon storage, and stand dynamics
    • Authors: Garrett W. Meigs; William S. Keeton
      Abstract: Wind is one of the most important natural disturbances influencing forest structure, ecosystem function, and successional processes worldwide. This study quantifies the stand-scale effects of intermediate-severity windstorms (i.e., “blowdowns”) on (1) live and dead legacy structure, (2) aboveground carbon storage, and (3) tree regeneration and associated stand dynamics at four mature, mixed hardwood-conifer forest sites in the northeastern United States. We compare wind-affected forests to adjacent reference conditions (i.e., undisturbed portions of the same stands) 0-8 years post-blowdown using parametric (ANOVA) and nonparametric (NMS ordination) analyses. We supplement inventory plots and downed coarse woody detritus (DCWD) transects with hemispherical photography to capture spatial variation in the light environment. Although recent blowdowns transferred a substantial proportion of live overstory trees to DCWD, residual live tree basal area was high (19-59% of reference areas). On average, the initial post-blowdown ratio of DCWD carbon to standing live tree carbon was 2.72 in blowdown stands and 0.18 in reference stands, indicating a large carbon transfer from live to dead pools. Despite these dramatic changes, structural complexity remained high in blowdown areas, as indicated by the size and species distributions of overstory trees, abundance of sound and rotten downed wood, spatial patterns of light availability, and variability of understory vegetation. Furthermore, tree species composition was similar between blowdown and reference areas at each site, with generally shade-tolerant species dominating across multiple canopy strata. Community response to intermediate-severity blowdown at these sites suggests a dynamic in which disturbance maintains late-successional species composition rather than providing a regeneration opportunity for shade-intolerant, pioneer species. Our findings suggest that intermediate-severity wind disturbances can contribute to stand-scale structural complexity as well as development towards late-successional species composition, at least when shade-tolerant regeneration is present pre-blowdown. Advance regeneration thus enhances structural and compositional resilience to this type of disturbance. This study provides a baseline for multi-cohort silvicultural systems designed to restore heterogeneity associated with natural disturbance dynamics.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-24T10:45:29.117005-05:
      DOI: 10.1002/eap.1691
  • Dispersal and population state of an endangered island lizard following a
           conservation translocation
    • Authors: Nicole F. Angeli; Ian F. Lundgren, Clayton G. Pollock, Zandy M. Hillis-Starr, Lee A. Fitzgerald
      Abstract: Population size is widely used as a unit of ecological analysis, yet to estimate population size requires accounting for observed and latent heterogeneity influencing dispersion of individuals across landscapes. In newly established populations, such as when animals are translocated for conservation, dispersal and availability of resources influence patterns of abundance. We developed a process to estimate population size using N-mixture models and spatial models for newly established and dispersing populations. We used our approach to estimate the population size of critically endangered St. Croix ground lizards (Ameiva polops) five years after translocation of 57 individuals to Buck Island, an offshore island of St. Croix, United States Virgin Islands. Estimates of population size incorporated abiotic variables, dispersal limits, and operative environmental temperature available to the lizards to account for low species detection. Operative environmental temperature and distance from the translocation site were always important in fitting the N-mixture model indicating effects of dispersal and species biology on estimates of population size. We found that the population is increasing its range across the island by 5–10% every six months. We spatially interpolated site-specific abundance from the N-mixture model to the entire island, and we estimated 1,473 (95% CI, 940–1,802) St. Croix ground lizards on Buck Island in 2013 corresponding to survey results. This represents a 26-fold increase since the translocation. We predicted the future dispersal of the lizards to all habitats on Buck Island, with the potential for the population to increase by another five times in the future. Incorporating biologically relevant covariates as explicit parameters in population models can improve predictions of population size and the future spread of species introduced to new localities.
      PubDate: 2018-01-19T09:45:34.707392-05:
      DOI: 10.1002/eap.1650
  • Landscape simplification reduces classical biological control and crop
    • Authors: Heather Grab; Bryan Danforth, Katja Poveda, Greg Loeb
      Abstract: Agricultural intensification resulting in the simplification of agricultural landscapes is known to negatively impact the delivery of key ecosystem services such as the biological control of crop pests. Both conservation and classical biological control may be influenced by the landscape context in which they are deployed; yet studies examining the role of landscape structure in the establishment and success of introduced natural enemies and their interactions with native communities are lacking. In this study, we investigated the relationship between landscape simplification, classical and conservation biological control services and importantly, the outcome of these interactions for crop yield. We showed that agricultural simplification at the landscape scale is associated with an overall reduction in parasitism rates of crop pests. Additionally, only introduced parasitoids were identified, and no native parasitoids were found in crop habitat, irrespective of agricultural landscape simplification. Pest densities in the crop were lower in landscapes with greater proportions of semi-natural habitats. Furthermore, farms with less semi-natural cover in the landscape and consequently, higher pest numbers, had lower yields than farms in less agriculturally dominated landscapes. Our study demonstrates the importance of landscape scale agricultural simplification in mediating the success of biological control programs and highlights the potential risks to native natural enemies in classical biological control programs against native insects. Our results represent an important contribution to an understanding of the landscape-mediated impacts on crop yield that will be essential to implementing effective policies that simultaneously conserve biodiversity and ecosystem services.
      PubDate: 2018-01-18T10:05:23.050853-05:
      DOI: 10.1002/eap.1651
  • Land-surveys show regional variability of historical fire regimes and
           structure of dry forests of the western USA
    • Authors: William L. Baker; Mark A. Williams
      Abstract: An understanding of how historical fire and structure in dry forests (ponderosa pine, dry mixed conifer) varied across the western USA remains incomplete. Yet, fire strongly affects ecosystem services, and forest restoration programs are underway. We used General Land Office survey reconstructions from the late-1800s across 11 landscapes covering ∼1.9 million ha in four states to analyze spatial variation in fire regimes and forest structure. We first synthesized the state of validation of our methods using 20 modern validations, 53 historical cross-validations, and corroborating evidence. These show our method creates accurate reconstructions with low errors. One independent modern test reported high error, but did not replicate our method and made many calculation errors. Using reconstructed parameters of historical fire regimes and forest structure from our validated methods, forests were found to be non-uniform across the 11 landscapes, but grouped together in three geographical areas. Each had a mixture of fire severities, but dominated by low-severity fire and low median tree density in Arizona, mixed-severity fire and intermediate to high median tree density in Oregon-California, and high-severity fire and intermediate median tree density in Colorado. Programs to restore fire and forest structure could benefit from regional frameworks, rather than one-size-fits-all.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-18T09:10:28.845857-05:
      DOI: 10.1002/eap.1688
  • Refining mortality estimates in shark demographic analyses: A Bayesian
           inverse matrix approach
    • Authors: Jonathan J Smart; André E Punt, William T White, Colin A Simpfendorfer
      Abstract: Leslie matrix models are an important analysis tool in conservation biology that are applied to a diversity of taxa. The standard approach estimates the finite rate of population growth (λ) from a set of vital rates. In some instances, an estimate of λ is available, but the vital rates are poorly understood and can be solved for using an inverse matrix approach. However, these approaches are rarely attempted due to pre-requisites of information on the structure of age or stage-classes. This study addressed this issue by using a combination of Monte Carlo simulations and the sample-importance-resampling (SIR) algorithm to solve the inverse matrix problem without data on population structure. This approach was applied to the grey reef shark (Carcharhinus amblyrhynchos) from the Great Barrier Reef (GBR) in Australia to determine the demography of this population. Additionally, these outputs were applied to another heavily fished population from Papua New Guinea (PNG) that requires estimates of λ for fisheries management. The SIR analysis determined that natural mortality (M) and total mortality (Z) based on indirect methods have previously been overestimated for C. amblyrhynchos, leading to an underestimated λ. The updated Z distributions determined using SIR provided λ estimates that matched an empirical λ for the GBR population and corrected obvious error in the demographic parameters for the PNG population. This approach provides opportunity for the inverse matrix approach to be applied more broadly to situations where information on population structure is lacking.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-18T09:10:24.996579-05:
      DOI: 10.1002/eap.1687
  • Using field data to quantify chemical impacts on wildlife population
    • Authors: Jelle P. Hilbers; Renske P.J. Hoondert, Aafke M. Schipper, Mark A.J. Huijbregts
      Abstract: Environmental pollution is an important driver of biodiversity loss. Yet, to date, the effects of chemical exposure on wildlife populations have been quantified for only a few species, mainly due to a lack of appropriate laboratory data to quantify chemical impacts on vital rates. In this study we developed a method to quantify the effects of toxicant exposure on wildlife population persistence based on field monitoring data. We established field-based vital rate-response functions for toxicants, using quantile regression to correct for the influences of confounding factors on the vital rates observed, and combined the response curves with population viability modelling. We then applied the method to quantify the impact of DDE on three bird species: the white-tailed eagle, bald eagle and osprey. Population viability was expressed via five population extinction vulnerability metrics: population growth rate (r1), critical patch size (CPS), minimum viable population size (MVP), probability of population extirpation (PE) and median time to population extirpation (MTE). We found that past DDE exposure concentrations increased population extirpation vulnerabilities of all three bird species. For example, at DDE concentrations of 25 mg/kg ww egg (the maximum historic exposure concentration reported in literature for the osprey), r1 became small (white-tailed eagle and osprey) or close to zero (bald eagle), the CPS increased up to almost the size of Connecticut (white-tailed eagle and osprey) or West Virginia (bald eagle), the MVP increased up to approximately 90 (white-tailed eagle and osprey) or 180 breeding pairs (bald eagle), the PE increased up to almost certain extirpation (bald eagle) or only slightly elevated levels (white-tailed eagle and osprey) and the MTE became within decades (bald eagle) or remained longer than a millennium (white-tailed eagle and osprey). Our study provides a method to derive species-specific field-based response curves of toxicant exposure, which can be used to assess population extinction vulnerabilities and obtain critical levels of toxicant exposure based on maximum permissible effect levels. This may help conservation managers to better design appropriate habitat restoration and population recovery measures, such as reducing toxicant levels, increasing the area of suitable habitat or reintroducing individuals.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-16T06:40:22.960857-05:
      DOI: 10.1002/eap.1685
  • Disturbance reduces the differentiation of mycorrhizal fungal communities
           in grasslands along a precipitation gradient
    • Authors: Geoffrey L. House; James D. Bever
      Abstract: Given that mycorrhizal fungi play key roles in shaping plant communities, greater attention should be focused on factors that determine the composition of mycorrhizal fungal communities and their sensitivity to anthropogenic disturbance. We investigate changes in arbuscular mycorrhizal (AM) fungal community composition across a precipitation gradient in North American grasslands as well as changes occurring with varying degrees of site disturbance that have resulted in invasive plant establishment. We find strong differentiation of AM fungal communities in undisturbed remnant grasslands across the precipitation gradient, whereas communities in disturbed grasslands were more homogeneous. These changes in community differentiation with disturbance are consistent with more stringent environmental filtering of AM fungal communities in undisturbed sites that may also be promoted by more rigid functional constraints imposed on AM fungi by the native plant communities in these areas. The AM fungal communities in eastern grasslands were particularly sensitive to anthropogenic disturbance, with disturbed sites having low numbers of AM fungal operational taxonomic units (OTUs) commonly found in undisturbed sites, and also the proliferation of AM fungal OTUs in disturbed sites. This proliferation of AM fungi in eastern disturbed sites coincided with increased phosphorus availability and is consistent with evidence suggesting the fungi represented by these OTUs would provide reduced benefits to native plants. The differentiation of AM fungal communities along the precipitation gradient in undisturbed grasslands but not in disturbed sites is consistent with AM fungi aiding plant adaptation to climate, and suggests they may be especially important targets for conservation and restoration in order to help maintain or re-establish diverse grassland plant communities.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-04T08:56:06.749733-05:
      DOI: 10.1002/eap.1681
  • Elevated CO2 induces substantial and persistent declines in forage quality
           irrespective of warming in mixedgrass prairie
    • Authors: David J. Augustine; Dana M. Blumenthal, Tim L. Springer, Daniel R. LeCain, Stacey A. Gunter, Justin D. Derner
      Abstract: Increasing atmospheric [CO2] and temperature are expected to affect the productivity, species composition, biogeochemistry, and therefore the quantity and quality of forage available to herbivores in rangeland ecosystems. Both elevated CO2 (eCO2) and warming affect plant tissue chemistry through multiple direct and indirect pathways, such that the cumulative outcomes of these effects are difficult to predict. Here, we report on a 7-year study examining effects of CO2 enrichment (to 600 ppm) and infrared warming (+1.5°C day/3°C night) under realistic field conditions on forage quality and quantity in a semiarid, mixedgrass prairie. For the 3 dominant forage grasses, warming effects on in vitro dry matter digestibility (IVDMD) and tissue [N] were detected only in certain years, varied from negative to positive, and were relatively minor. In contrast, eCO2 substantially reduced IVDMD (2 most abundant grasses) and [N] (all 3 dominant grass species) in most years, except the two wettest years. Furthermore, eCO2 reduced IVDMD and [N] independent of warming effects. Reduced IVDMD with eCO2 was related both to reduced [N] and increased acid detergent fiber (ADF) content of grass tissues. For the 6 most abundant forage species (representing 96% of total forage production), combined warming+eCO2 increased forage production by 38% and reduced forage [N] by 13% relative to ambient climate. Although the absolute magnitude of the decline in IVDMD and [N] due to combined warming+eCO2 may seem small (e.g. from 63.3 to 61.1% IVDMD and 1.25 to 1.04% [N] for Pascopyrum smithii), such shifts could have substantial consequences for the rate at which ruminants gain weight during the primary growing season in the largest remaining rangeland ecosystem in North America. With forage production increases, declining forage quality could potentially be mitigated by adaptively increasing stocking rates, and through management such as prescribed burning, fertilization at low rates, and legume interseeding to enhance forage quality.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-03T06:35:48.249182-05:
      DOI: 10.1002/eap.1680
  • Complex demographic heterogeneity from anthropogenic impacts in a coastal
           marine predator
    • Authors: D Oro; D Álvarez, A Velando
      Abstract: Environmental drivers, including anthropogenic impacts, affect vital rates of organisms. Nevertheless, the influence of these drivers may depend on the physical features of the habitat and how they affect life history strategies depending on individual covariates such as age and sex. Here, the long-term monitoring (1994-2014) of marked European shags in eight colonies in two regions with different ecological features, such as foraging habitat, allowed us to test several biological hypotheses about how survival changes by age and sex in each region by means of multi-event capture-recapture modelling. Impacts included fishing practices and bycatch, invasive introduced carnivores and the severe Prestige oil spill. Adult survival was constant but, unexpectedly, it was different between sexes. This difference was opposite in each region. The impact of the oil spill on survival was important only for adults (especially for females) in one region and lasted a single year. Juvenile survival was time-dependent but this variability was not synchronized between regions, suggesting a strong signal of regional environmental variability. Mortality due to bycatch was also different between sex, age and region. Interestingly the results showed that the size of the fishing fleet is not necessarily a good proxy for assessing the impact of bycatch mortality, which may be more dependent on the fishing grounds and the fishing gears employed in each season of the year. Anthropogenic impacts affected survival differently by age and sex, which was expected for a long-lived organism with sexual size dimorphism. Strikingly, these differences varied depending on the region, indicating that habitat heterogeneity is demographically important to how environmental variability (including anthropogenic impacts) and resilience influence population dynamics.This article is protected by copyright. All rights reserved.
      PubDate: 2018-01-03T06:35:34.287844-05:
      DOI: 10.1002/eap.1679
  • Issue Information
    • Pages: 263 - 265
      PubDate: 2018-03-01T15:00:02.536189-05:
      DOI: 10.1002/eap.1711
  • Comparing fishers’ and scientific estimates of size-at-maturity and
           maximum body size as indicators for overfishing
    • Authors: Elizabeth L. Mclean; Graham E. Forrester
      Abstract: We tested whether fishers’ local ecological knowledge (LEK) of two fish life-history parameters, size-at-maturity (SAM) at maximum body size (MS), was comparable to scientific estimates (SEK) of the same parameters, and whether LEK influenced fishers’ perceptions of sustainability. Local ecological knowledge was documented for 82 fishers from a small-scale fishery in Samaná Bay, Dominican Republic, whereas SEK was compiled from the scientific literature. Size-at-maturity estimates derived from LEK and SEK overlapped for most of the 15 commonly harvested species (10 of 15). In contrast, fishers’ maximum size estimates were usually lower than (8 species), or overlapped with (5 species) scientific estimates. Fishers’ size-based estimates of catch composition indicate greater potential for overfishing than estimates based on SEK. Fishers’ estimates of size-at-capture relative to size-at-maturity suggest routine inclusion of juveniles in the catch (9 of 15 species), and fishers’ estimates suggest that harvested fish are substantially smaller than maximum body size for most species (11 of 15 species). Scientific estimates also suggest that harvested fish are generally smaller than maximum body size (13 of 15), but suggest that the catch is dominated by adults for most species (9 of 15 species), and that juveniles are present in the catch for fewer species (6 of 15). Most Samaná fishers characterized the current state of their fishery as poor (73%) and as having changed for the worse over the past 20 years (60%). Fishers stated that concern about overfishing, catching small fish, and catching immature fish contributed to these perceptions, indicating a possible influence of catch size-composition on their perceptions. Future work should test this link more explicitly because we found no evidence that the minority of fishers with more positive perceptions of their fishery reported systematically different estimates of catch-size composition than those with the more negative majority view. Although fishers’ and scientific estimates of size-at-maturity and maximum size parameters sometimes differed, the fact that fishers make routine quantitative assessments of maturity and body size suggests potential for future collaborative monitoring efforts to generate estimates usable by scientists and meaningful to fishers.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-29T00:10:32.542134-05:
      DOI: 10.1002/eap.1675
  • Underestimation of N2O emissions in a comparison of the DayCent, DNDC, and
           EPIC models
    • Authors: Richard K. Gaillard; Curtis D. Jones, Pete Ingraham, Sarah Collier, Roberto Cesar Izaurralde, William Jokela, William Osterholz, William Salas, Peter Vadas, Matthew Ruark
      Abstract: Process-based models are increasingly used to study agroecosystem interactions and N2O emissions from agricultural fields. The widespread use of these models to conduct research and inform policy benefits from periodic model comparisons that assess the state of agroecosystem modeling and indicate areas for model improvement. This work provides an evaluation of simulated N2O flux from three process-based models: DayCent, DNDC, and EPIC. The models were calibrated and validated using data collected from two research sites over five years that represent cropping systems and nitrogen fertilizer management strategies common to dairy cropping systems. We also evaluated the use of a multi-model ensemble strategy, which inconsistently outperformed individual model estimations. Regression analysis indicated a cross-model bias to underestimate high magnitude daily and cumulative N2O flux. Model estimations of observed soil temperature and water content did not sufficiently explain model underestimations, and we found significant variation in model estimates of heterotrophic respiration, denitrification, soil NH4+, and soil NO3-, which may indicate that additional types of observed data are required to evaluate model performance and possible biases. Our results suggest a bias in the model estimation of N2O flux from agroecosystems that limits the extension of models beyond calibration and as instruments of policy development. This highlights a growing need for the modeling and measurement communities to collaborate in the collection and analysis of the data necessary to improve models and coordinate future development.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-28T18:06:01.146812-05:
      DOI: 10.1002/eap.1674
  • Vegetation cover in relation to socioeconomic factors in a tropical city
           assessed from sub-meter resolution imagery
    • Authors: Sebastián Martinuzzi; Olga M. Ramos-González, Tischa A. Muñoz-Erickson, Dexter H. Locke, Ariel E. Lugo, Volker C. Radeloff
      Abstract: Fine-scale information about urban vegetation and social-ecological relationships is crucial to inform both urban planning and ecological research, and high spatial resolution imagery is a valuable tool for assessing urban areas. However, urban ecology and remote sensing have largely focused on cities in temperate zones. Our goal was to characterize urban vegetation cover with sub-meter resolution aerial imagery, and identify social-ecological relationships of urban vegetation patterns in a tropical city, the San Juan Metropolitan Area, Puerto Rico. Our specific objectives were to: i) map vegetation cover using sub-meter spatial resolution (0.3 m) imagery; ii) quantify the amount of residential and non-residential vegetation; and iii) investigate the relationship between patterns of urban vegetation versus socioeconomic and environmental factors. We found that 61% of the San Juan Metropolitan Area was green, and that our combination of high spatial resolution imagery and object-based classification was highly successful for extracting vegetation cover in a moist tropical city (97% accuracy). In addition, simple spatial pattern analysis allowed us to separate residential from non-residential vegetation with 76% accuracy, and patterns of residential and non-residential vegetation varied greatly across the city. Both socioeconomic (e.g., population density, building age, detached homes) and environmental variables (e.g., topography) were important in explaining variations in vegetation cover in our spatial regression models. However, important socioeconomic drivers found in cities in temperate zones, such as income and home value, were not important in San Juan. Climatic and cultural differences between tropical and temperate cities may result in different social-ecological relationships. Our study provides novel information for local land use planners, highlights the value of high spatial resolution remote sensing data to advance ecological research and urban planning in tropical cities, and emphasizes the need for more studies in tropical cities.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-28T18:05:48.381091-05:
      DOI: 10.1002/eap.1673
  • First signs of macroinvertebrate recovery following enhanced restoration
           of boreal streams used for timber floating
    • Authors: Francesca Pilotto; Christer Nilsson, Lina E. Polvi, Brendan G. McKie
      Abstract: Although ecological restoration generally succeeds in increasing physical heterogeneity, many projects fail to enhance biota. Researchers have suggested several possible explanations, including insufficient restoration intensity, or time-lags in ecological responses that prevent detection of significant changes in short-term monitoring programs. This study aims to evaluate whether benthic macroinvertebrate communities responded to an expanded set of stream restoration measures within a study period of one to five years after completion of the restoration project. We studied ten forest streams in northern Sweden that were channelized in the past for timber floating. Managers subjected six of these streams to habitat restoration, on each of these we selected two reaches, located in close proximity but differing in restoration intensity. In “basic” restored reaches, the restoration managers broke up the channelized banks and returned cobbles and small boulders to the main channel. In “enhanced” restoration reaches, they added additional large wood and boulders to reaches previously subjected to basic restoration, and rehabilitated gravel beds. The remaining four streams were not restored, and thus represent the baseline impacted (channelized) condition. We surveyed stream benthic assemblages before the enhanced restoration (year 2010) and three times afterwards between 2011 and 2015. Five years after restoration, macroinvertebrate assemblages at the enhanced restored reaches were more differentiated from channelized conditions than those at basic-restored reaches. This reflected increased relative abundances of the insect orders Ephemeroptera and Trichoptera and the bivalve molluscs Sphaeriidae, and decreased relative abundances of Chironomidae (Diptera). Analysis of functional traits provided further insights on the mechanistic explanations driving the recovery, e.g., indicating that the augmented channel retention capacity at enhanced restored reaches favored taxa adapted to slow flow conditions and more effectively retained passive aquatic dispersers. The increased restoration intensity in enhanced restored reaches has resulted in shifts in the composition of benthic macroinvertebrate assemblages, including increases in more sensitive taxa. These shifts became fully apparent five years after the enhanced restoration. Our results emphasize the value of longer-term monitoring to assess ecological responses following restoration, and of undertaking additional restoration as a valuable management option for previously restored sites that failed to achieve biotic recovery.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-26T23:50:24.767214-05:
      DOI: 10.1002/eap.1672
  • Fine-scale spatial climate variation and drought mediate the likelihood of
    • Authors: Sean A. Parks; Marc-André Parisien, Carol Miller, Lisa M. Holsinger, L. Scott Baggett
      Abstract: In many forested ecosystems, it is increasingly recognized that the probability of burning is substantially reduced within the footprint of previously burned areas. This self-limiting effect of wildland fire is considered a fundamental emergent property of ecosystems and is partly responsible for structuring landscape heterogeneity (i.e. mosaics of different age classes), thereby reducing the likelihood of uncharacteristically large fires in regions with active fire regimes. However, the strength and longevity of this self-limiting phenomenon is not well understood in most fire-prone ecosystems. In this study, we quantify the self-limiting effect in terms of its strength and longevity for five fire-prone study areas of western North America and investigate how each measure varies along a spatial climatic gradient and according to temporal (i.e. annual) climatic variation. Results indicate that the longevity (i.e. number of years) of the self-limiting effect ranges between 15 years in the warm and dry study area in the southwestern US to 33 years in the cold, northern study areas in located in northwestern Montana and the boreal forest of Canada. We also found that spatial climatic variation has a strong influence on wildland fire's self-limiting capacity. Specifically, the self-limiting effect within each study area was stronger and lasted longer in areas with low mean moisture deficit (i.e. wetter and cooler settings) compared to areas with high mean moisture deficit (warmer and drier settings). Lastly, our findings show that annual climatic variation influences wildland fire's self-limiting effect: drought conditions weakened the strength and longevity of the self-limiting effect in all study areas, albeit at varying magnitudes. Overall, our study provides support for the idea that wildland fire contributes to spatial heterogeneity in fuel ages that subsequently mediate future fire sizes and effects. However, our findings show that the strength and longevity of the self-limiting effect varies considerably according to spatial and temporal climatic variation, providing land and fire managers relevant information for effective planning and management of fire and highlighting that fire itself is an important factor contributing to fire-free intervalsThis article is protected by copyright. All rights reserved.
      PubDate: 2017-12-26T23:45:39.048134-05:
      DOI: 10.1002/eap.1671
  • Grazing alters net ecosystem C fluxes and the global warming potential of
           a subtropical pasture
    • Authors: Nuria Gomez-Casanovas; Nicholas J DeLucia, Carl J Bernacchi, Elizabeth H Boughton, Jed P Sparks, Samuel D Chamberlain, Evan H DeLucia
      Abstract: The impact of grazing on C fluxes from pastures in subtropical and tropical regions, and on the environment is uncertain, although these systems account for a substantial portion of global C storage. We investigated how cattle grazing influences net ecosystem CO2 and CH4 exchange in subtropical pastures using the eddy covariance technique. Measurements were made over several wet-dry seasonal cycles in a grazed pasture, and in an adjacent pasture during the first three years of grazer exclusion. Grazing increased soil wetness but did not affect soil temperature. By removing aboveground biomass, grazing decreased ecosystem respiration (Reco) and Gross Primary Productivity (GPP). As the decrease in Reco was larger than the reduction in GPP, grazing consistently increased the net CO2 sink strength of subtropical pastures (55, 219 and 187 more C m−2 in 2013, 2014 and 2015). Enteric ruminant fermentation and increased soil wetness due to grazers, increased total net ecosystem CH4 emissions in grazed relative to ungrazed pasture (27% - 80%). Unlike temperate, arid, and semi-arid pastures, where differences in CH4 emissions between grazed and ungrazed pastures are mainly driven by enteric ruminant fermentation, our results showed that the effect of grazing on soil CH4 emissions can be greater than CH4 produced by cattle. Thus, our results suggest that the interactions between grazers and soil hydrology affecting soil CH4 emissions play an important role in determining the environmental impacts of this management practice in a subtropical pasture. Although grazing increased total net ecosystem CH4 emissions and removed aboveground biomass, it increased the net storage of C and decreased the global warming potential associated with C fluxes of pasture by increasing its net CO2 sink strength.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-26T23:45:36.175599-05:
      DOI: 10.1002/eap.1670
  • Seed dispersal as an ecosystem service: Frugivore loss leads to decline of
           a socially valued plant, Capsicum frutescens
    • Authors: Monika H. Egerer; Evan C. Fricke, Haldre S. Rogers
      Abstract: Species interactions, both mutualistic and antagonistic, are widely recognized as providing important ecosystem services. Fruit-eating animals influence plant recruitment by increasing germination during gut passage and moving seeds away from conspecifics. However, relative to studies focused on the importance of frugivores for plant population maintenance, few studies target frugivores as ecosystem service providers, and frugivores are underappreciated as ecosystem service providers relative to other mutualists such as pollinators. Here we use an accidental experiment to elucidate the role of seed dispersal by frugivores for maintaining a culturally and economically important plant, the donne’ sali chili (Capsicum frutescens) in the Mariana Islands. One of the islands (Guam) has lost nearly all of its native forest birds due to an invasive snake (Boiga irregularis), whereas nearby islands have relatively intact bird populations. We hypothesized that frugivore loss would influence chili recruitment and abundance, which could have economic and cultural impacts. By using video cameras, we confirmed that birds were the primary seed dispersers. We used captive bird feeding trials to obtain gut-passed seeds to use in a seedling emergence experiment. The experiment showed that gut-passed seeds emerged sooner and at a higher proportion than seeds from whole fruits. Consistent with our findings that birds benefit chilies, we observed lower chili abundance on Guam than on islands with birds. In a survey questionnaire of island residents, the majority of residents reported an association between the wild chili and local cultural values and traditions. In addition, we identified a thriving market for chili products, suggesting benefits of wild chilies to people in the Marianas both as consumers and producers. Our study therefore documents seed dispersal as both a cultural and a supporting ecosystem service. We provide a comprehensive case study on how seed-dispersed plants decline in the absence of their disperser, and how to apply mixed-methods in ecosystem service assessments. Furthermore, we suggest that scientists and resource managers may utilize fruit-frugivore mutualisms concerning socially valuable plants to gather support for frugivore and forest conservation efforts.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-22T01:38:01.872502-05:
      DOI: 10.1002/eap.1667
  • How to kill a tree – Empirical mortality models for eighteen species and
           their performance in a dynamic forest model
    • Authors: Lisa Hülsmann; Harald Bugmann, Maxime Cailleret, Peter Brang
      Abstract: Dynamic Vegetation Models (DVMs) are designed to be suitable for simulating forest succession and species range dynamics under current and future conditions based on mathematical representations of the three key processes regeneration, growth and mortality. However, mortality formulations in DVMs are typically coarse and often lack an empirical basis, which increases the uncertainty of projections of future forest dynamics and hinders their use for developing adaptation strategies to climate change. Thus, sound tree mortality models are highly needed. We developed parsimonious, species-specific mortality models for 18 European tree species using> 90 000 records from inventories in Swiss and German strict forest reserves along a considerable environmental gradient. We comprehensively evaluated model performance and incorporated the new mortality functions in the dynamic forest model ForClim. Tree mortality was successfully predicted by tree size and growth. Only a few species required additional covariates in their final model to consider aspects of stand structure or climate. The relationships between mortality and its predictors reflect the indirect influences of resource availability and tree vitality, which are further shaped by species-specific attributes such as maximum longevity and shade tolerance. Considering that the behavior of the models was biologically meaningful, and that their performance was reasonably high and not impacted by changes in the sampling design, we suggest that the mortality algorithms developed here are suitable for implementation and evaluation in DVMs. In the DVM ForClim, the new mortality functions resulted in simulations of stand basal area and species composition that were generally close to historical observations. However, ForClim performance was poorer than when using the original, coarse mortality formulation. The difficulties of simulating stand structure and species composition, which were most evident for Fagus sylvatica L. and in long-term simulations, resulted from feedbacks between simulated growth and mortality as well as from extrapolation to very small and very large trees. Growth and mortality processes and their species-specific differences should thus be revisited jointly, with a particular focus on small and very large trees in relation to their shade tolerance.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-21T09:55:36.618719-05:
      DOI: 10.1002/eap.1668
  • The spatial sensitivity of the spectral diversity-biodiversity
           relationship: an experimental test in a prairie grassland
    • Authors: Ran Wang; John A. Gamon, Jeannine Cavender-Bares, Philip A. Townsend, Arthur I. Zygielbaum
      Abstract: Remote sensing has been used to detect plant biodiversity in a range of ecosystems based on the varying spectral properties of different species or functional groups. However, the most appropriate spatial resolution necessary to detect diversity remains unclear. At coarse resolution, differences among spectral patterns may be too weak to detect. In contrast, at fine resolution, redundant information may be introduced. To explore the effect of spatial resolution, we studied the scale-dependence of spectral diversity in a prairie ecosystem experiment at Cedar Creek Ecosystem Science Reserve, Minnesota, USA. Our study involved a scaling exercise comparing synthetic pixels resampled from high-resolution images within manipulated diversity treatments. Hyperspectral data were collected using several instruments on both ground and airborne platforms. We used the coefficient of variation (CV) of spectral reflectance in space as the indicator of spectral diversity and then compared CV at different scales ranging from 1mm2 to 1m2 to conventional biodiversity metrics, including species richness, Shannon's Index, Simpson's Index, phylogenetic species variation, and phylogenetic species evenness. In this study, higher species richness plots generally had higher CV. CV showed higher correlations with Shannon's index and Simpson's index than species richness alone, indicating evenness contributed to the spectral diversity. Correlations with species richness and Simpson's index were generally higher than with phylogenetic species variation and evenness measured at comparable spatial scales, indicating weaker relationships between spectral diversity and phylogenetic diversity metrics than with species diversity metrics. High resolution imaging spectrometer data (1mm2 pixels) showed the highest sensitivity to diversity level. With decreasing spatial resolution, the difference in CV between diversity levels decreased and greatly reduced the optical detectability of biodiversity. The optimal pixel size for distinguishing α diversity in these prairie plots appeared to be around 1mm to 10cm, a spatial scale similar to the size of an individual herbaceous plant. These results indicate a strong scale-dependence of the spectral diversity-biodiversity relationships, with spectral diversity best able to detect a combination of species richness and evenness, and more weakly detecting phylogenetic diversity. These findings can be used to guide airborne studies of biodiversity and develop more effective large-scale biodiversity sampling methods.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-21T09:55:22.950193-05:
      DOI: 10.1002/eap.1669
  • Optimal timing of biodiversity offsetting for metapopulations
    • Authors: Darren M. Southwell; Geoffrey W. Heard, Michael A. McCarthy
      Abstract: Biodiversity offsetting schemes permit habitat destruction provided that losses are compensated by gains elsewhere. While hundreds of offsetting schemes are used around the globe, the optimal timing of habitat creation in such projects is poorly understood. Here, we developed a spatially explicit metapopulation model for a single-species subject to a habitat compensation scheme. Managers could compensate for destruction of a patch by creating a new patch either before, at the time of, or after patch loss. Delaying patch creation is intuitively detrimental to species persistence, but allowed managers to invest financial compensation, accrue interest, and create a larger patch at a later date. Using stochastic dynamic programming, we found the optimal timing of patch creation that maximizes the number of patches occupied at the end of a 50 year habitat compensation scheme when a patch is destroyed after 10 years. Two case studies were developed for Australian species subject to habitat loss but with very different traits: the endangered growling grass frog (Litoria raniformis) and the critically endangered Mount Lofty Ranges southern emu-wren (Spititurus malachurus intermedius). Our results show that adding a patch either before, or well-after habitat destruction can be optimal, depending on the occupancy state of the metapopulation, the interest rate, the area of the destroyed patch and metapopulation parameters of the focal species. Generally, it was better to delay patch creation when the interest rate was high, when the species had a relatively high colonization rate, when the patch nearest the new patch was occupied, and when the destroyed patch was small. Our framework can be applied to single-species metapopulations subject to habitat loss, and demonstrates that considering the timing of habitat compensation could improve the effectiveness of offsetting schemes.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-20T00:20:32.93186-05:0
      DOI: 10.1002/eap.1666
  • Finding Politically Feasible Conservation Policies: The Case of Wildlife
    • Authors: Timothy C. Haas; Sam M. Ferreira
      Abstract: Conservation management is of increasing importance in ecology as most ecosystems nowadays are essentially managed ones. Conservation managers work within a political-ecological system when they develop and attempt to implement a conservation plan that is designed to meet particular conservation goals. In this article, we develop a decision support tool that can identify a conservation policy for a managed wildlife population that is both sustainable and politically feasible. Part of our tool consists of a simulation model composed of interacting influence diagrams. We build, fit, and use our tool on the case of rhino horn trafficking between South Africa and Asia. Using these diagrams, we show how a rhino poacher's belief system can be modified by such a policy and locate it in a perceived risks-benefits space before and after policy implementation. We statistically fit our model to observations on group actions and rhino abundance. We then use this fitted model to compute a politically feasible conservation policy.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-16T01:29:48.621016-05:
      DOI: 10.1002/eap.1662
  • Demographic drivers of a refugee species: large-scale experiments guide
           strategies for reintroductions of hirola
    • Authors: Abdullahi H. Ali; Matthew J. Kauffman, Rajan Amin, Amos Kibara, Juliet King, David Mallon, Charles Musyoki, Jacob R. Goheen
      Abstract: Effective reintroduction strategies require accurate estimates of vital rates and the factors that influence them. The hirola (Beatragus hunteri) is the rarest antelope on Earth, with a global population size of
      PubDate: 2017-12-09T14:35:36.979166-05:
      DOI: 10.1002/eap.1664
  • Exacerbated grassland degradation and desertification in Central Asia
           during 2000-2014
    • Authors: Geli Zhang; Chandrashekhar M. Biradar, Xiangming Xiao, Jinwei Dong, Yuting Zhou, Yuanwei Qin, Yao Zhang, Fang Liu, Mingjun Ding, Richard J. Thomas
      Abstract: Grassland degradation and desertification is a complex process, including both state conversion (e.g., grasslands to deserts) and gradual within-state change (e.g., greenness dynamics). Existing studies hardly separated the two components and analyzed it as a whole based on time series vegetation index data, which however cannot provide a clear and comprehensive picture for grassland degradation and desertification. Here we proposed an integrated assessment strategy, by considering both state conversion and within-state change of grasslands, to investigate grassland degradation and desertification process in Central Asia. First, annual maps of grasslands and sparsely vegetated land were generated to track the state conversions between them. The results showed increasing grasslands were converted to sparsely vegetated lands from 2000 to 2014, with desertification region concentrating in the latitude range of 43-48°N. A frequency analysis of grassland versus sparsely vegetated land classification in last 15 years allowed a recognition of persistent desert zone (PDZ), persistent grassland zone (PGZ), and transitional zone (TZ). The TZ was identified in southern Kazakhstan as one hotspot which was vulnerable and unstable for desertification. Furthermore, the trend analysis of Enhanced Vegetation Index during thermal growing season (EVITGS) was investigated in individual zones using Linear Regression and Mann-Kendall approaches. An overall degradation across the area was found; moreover, the second desertification hotspot was identified in the northern Kazakhstan with significant decreasing in EVITGS, which was located in PGZ. Finally, attribution analyses of grassland degradation and desertification were conducted by considering precipitation, temperature, and three different drought indices. We found persistent droughts were the main factor for grassland degradation and desertification in Central Asia. Considering both state conversion and gradual within-state change processes, this study provided reference information for identification of desertification hotspots to support further grassland degradation and desertification treatment, and the method could be useful to be extended to other regions.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-02T10:48:02.20339-05:0
      DOI: 10.1002/eap.1660
  • Making do with less: must sparse data preclude informed harvest strategies
           for European waterbirds'
    • Authors: Fred A. Johnson; Mikko Alhainen, Anthony D. Fox, Jesper Madsen, Matthieu Guillemain
      Abstract: The demography of many European waterbirds is not well understood because most countries have conducted little monitoring and assessment, and coordination among countries on waterbird management has little precedent. Yet intergovernmental treaties now mandate the use of sustainable, adaptive harvest strategies, whose development is challenged by a paucity of demographic information. In this study, we explore how a combination of allometric relationships, fragmentary monitoring and research information, and expert judgment can be used to estimate the parameters of a theta-logistic population model, which in turn can be used in a Markov decision process to derive optimal harvesting strategies. We show how to account for considerable parametric uncertainty, as well as for different management objectives. We illustrate our methodology with a poorly understood population of taiga bean geese (Anser fabalis fabalis), which is a popular game bird in Fennoscandia. Our results for taiga bean geese suggest that they may have demographic rates similar to other, well-studied species of geese, and our model-based predictions of population size are consistent with the limited monitoring information available. Importantly, we found that by using a Markov decision process, a simple scalar population model may be sufficient to guide harvest management of this species, even if its demography is age-structured. Finally, we demonstrated how two different management objectives can lead to very different optimal harvesting strategies, and how conflicting objectives may be traded off with each other. This approach will have broad application for European waterbirds by providing preliminary estimates of key demographic parameters, by providing insights into the monitoring and research activities needed to corroborate those estimates, and by producing harvest management strategies that are optimal with respect to the managers’ objectives, options, and available demographic information.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-02T10:42:57.996306-05:
      DOI: 10.1002/eap.1659
  • Using ricelands to provide temporary shorebird habitat during migration
    • Authors: Gregory H. Golet; Candace Low, Simon Avery, Katie Andrews, Christopher J. McColl, Rheyna Laney, Mark D. Reynolds
      Abstract: To help mitigate large wetland losses in California, The Nature Conservancy launched a dynamic conservation incentive program to create temporary wetland habitats in harvested and fallow rice fields for shorebirds migrating along the Pacific Flyway. Farmers were invited to participate in a reverse auction bidding process and winning bids were selected based on their cost and potential to provide high quality shorebird habitat. This was done in 2014 and 2015, for separate enrollment periods that overlapped with spring and fall migration, both before and after the traditional post-harvest flooding period. To assess the success of the program we monitored shorebird use of fields that were enrolled (treatments), and others that were subject to typical rice farm management (controls). To put these observations in context, we used satellites to simultaneously monitor the extent of shallow-water habitat across the ~215,000 hectares of ricelands in the area. Results showed that providing habitat during migration, when it is typically unavailable in rice fields, yielded the largest average shorebird densities ever reported for agriculture in the region. Treatment fields had significantly greater shorebird density, richness and diversity than control fields in both spring and fall (especially September – early October, and late March – early April), but in fall the difference was greater. Shorebird responses to habitat provisioning, and regional habitat conditions, were variable from year to year, and highly dynamic within a given season. Overall, shorebirds densities were found to be negatively related to the total amount of flooded habitat in the rice landscape. Factors that affected habitat availability included allocation schedules of water deliveries from reservoirs, and rainfall patterns, both of which were influenced by drought. Collectively, these results suggest that appropriately managed agricultural lands have great potential to provide high value habitat for shorebirds during times of habitat deficit, including migration, and that fall may be a particularly impactful time to create additional habitat. Migratory species face great challenges due to the climate change, conversion of historical stopover sites, and other factors, but dynamic conservation programs offer promise that, at least in certain instances, their needs can still be met.This article is protected by copyright. All rights reserved.
      PubDate: 2017-12-02T10:37:55.424945-05:
      DOI: 10.1002/eap.1658
  • Taking Error Into Account When Fitting Models Using Approximate Bayesian
    • Authors: Elske van der Vaart; Dennis Prangle, Richard M. Sibly
      Abstract: Stochastic computer simulations are often the only practical way of answering questions relating to ecological management. However, due to their complexity, such models are difficult to calibrate and evaluate. Approximate Bayesian Computation (ABC) offers an increasingly popular approach to this problem, widely applied across a variety of fields. However, ensuring the accuracy of ABC's estimates has been difficult. Here, we obtain more accurate estimates by incorporating estimation of error into the ABC protocol. We show how this can be done where the data consist of repeated measures of the same quantity and errors may be assumed to be normally distributed and independent. We then derive the correct acceptance probabilities for a probabilistic ABC algorithm, and update the ‘coverage test’ with which accuracy is assessed. We apply this method – which we call ‘error-calibrated ABC’ – to a toy example and a realistic 14-parameter simulation model of earthworms that is used in environmental risk assessment. A comparison with exact methods and the diagnostic ‘coverage test’ show that our approach improves estimation of parameter values and their credible intervals for both models.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-25T18:35:23.841338-05:
      DOI: 10.1002/eap.1656
  • Megafaunal effects on vegetation structure throughout a densely wooded
           African landscape
    • Authors: Andrew B. Davies; Angela Gaylard, Gregory P. Asner
      Abstract: Megafauna strongly affect vegetation structure and composition, often leading to management concern. However, the extent of their influence across large scales and varying ecosystems remains largely unknown. Using high resolution airborne Light Detection and Ranging (LiDAR), we investigated landscape-scale changes in vegetation height and three-dimensional (3D) structure across landscapes of varying elephant densities and presence over time, and in response to surface water distribution and terrain variability in the heavily-managed thicket biome of the Addo Elephant National Park, South Africa. Elephants caused up to a 4-fold reduction in vegetation height and altered the vertical profile, but increased vegetation height variability. Vegetation height also increased with elevation and distance from water, particularly in areas that elephants had long occupied at high densities. Slope had opposing effects on vegetation height, with height increasing with slope in areas long exposed to elephants, but decreasing where elephants had only recently been granted access. Our results suggest that elephants are the primary agents of vegetation change in this ecosystem, but the strength of their effects varies across the landscape, enabling management to use water and terrain as mitigation tools. We further highlight the necessity of landscape-level experimental studies on megafaunal effects to untangle mechanisms and establish causality.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-25T18:30:29.371749-05:
      DOI: 10.1002/eap.1655
  • Hierarchical multi-taxa models inform riparian vs. hydrologic restoration
           of urban streams in a permeable landscape
    • Authors: Daniel C. Gwinn; Jennifer Middleton, Leah Beesley, Paul Close, Belinda Quinton, Tim Storer, Peter M. Davies
      Abstract: The degradation of streams caused by urbanization tends to follow predictable patterns; however, there is a growing appreciation for heterogeneity in stream response to urbanization due to the local geoclimatic context. Furthermore, there is building evidence that streams in mildly sloped, permeable landscapes respond uncharacteristically to urban stress calling for a more nuanced approach to restoration. We evaluated the relative influence of local-scale riparian characteristics and catchment-scale imperviousness on the macroinvertebrate assemblages of streams in the flat, permeable urban landscape of Perth, Western Australia. Using a hierarchical multi-taxa model, we predicted the outcomes of stylized stream restoration strategies to increase the riparian integrity at the local scale or decrease the influences of imperviousness at the catchment scale. In the urban streams of Perth, we show that local-scale riparian restoration can influence the structure of macroinvertebrate assemblages to a greater degree than managing the influences of catchment-scale imperviousness. We also observed an interaction between the effect of riparian integrity and imperviousness such that the effect of increased riparian integrity was enhanced at lower levels of catchment imperviousness. This study represents one of few conducted in flat, permeable landscapes and the first aimed at informing urban stream restoration in Perth, adding to the growing appreciation for heterogeneity of the Urban Stream Syndrome and its importance for urban stream restoration.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-25T18:30:23.694933-05:
      DOI: 10.1002/eap.1654
  • Early ecological outcomes of natural regeneration and tree plantations for
           restoring agricultural landscapes
    • Authors: Ricardo G. César; Vanessa S. Moreno, Gabriel D. Coletta, Robin L. Chazdon, Silvio F.B. Ferraz, Danilo. R. A. de Almeida, Pedro H. S. Brancalion
      Abstract: Mixed tree plantings and natural regeneration are the main restoration approaches for recovering tropical forests worldwide. Despite substantial differences in implementation costs between these methods, little is known regarding how they differ in terms of ecological outcomes, which is key information for guiding decision-making and cost-effective restoration planning. Here, we compared the early ecological outcomes of natural regeneration and tree plantations for restoring the Brazilian Atlantic Forest in agricultural landscapes. We assessed and compared vegetation structure and composition in young (7-20 years old) mixed tree plantings (PL), second-growth tropical forests established on former pastures (SGp), on former Eucalyptus spp. plantations (SGe), and in old-growth reference forests (Ref). We sampled trees DBH 1-5 cm (saplings) and trees DBH>5 cm (trees) in a total of 32 20 x 45 m plots established in these landscapes. Overall, the ecological outcomes of natural regeneration and restoration plantations were markedly different. SGe forests showed higher abundance of large (DBH>20 cm) non-native species – of which 98% were re-sprouting Eucalyptus trees – than SGp and PL, and higher total aboveground biomass; however, aboveground biomass of native species was higher in PL than in SGe. PL forests had lower abundance of native saplings and lianas than both naturally established second-growth forests, and lower proportion of animal dispersed saplings than SGe, probably due to higher isolation from native forest remnants. Rarefied species richness of trees was lower in SGp, intermediate in SGe and Ref and higher in PL, whereas rarefied species richness of saplings was higher in SG than in Ref. Species composition differed considerably among regeneration types. Although these forests are inevitably bound to specific landscape contexts and may present varying outcomes as they develop through longer time frames, the ecological particularities of forests established through different restoration approaches indicate that naturally established forests may not show similar outcomes to mixed tree plantings. The results of this study underscore the importance that restoration decisions need to be based on more robust expectations of outcomes that allow for a better analysis of the cost-effectiveness of different restoration approaches before scaling-up forest restoration in the tropics.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-24T11:00:40.698865-05:
      DOI: 10.1002/eap.1653
  • Mechanism matters: the cause of fluctuations in boom-bust populations
           governs optimal habitat restoration strategy
    • Authors: Gina K. Himes Boor; Cheryl B. Schultz, Elizabeth E. Crone, William F. Morris
      Abstract: Many populations exhibit boom-bust dynamics in which abundance fluctuates dramatically over time. Past research has focused on identifying whether the cause of fluctuations is primarily exogenous, e.g., environmental stochasticity coupled with weak density dependence, or endogenous, e.g., over-compensatory density dependence. Far fewer studies have addressed whether the mechanism responsible for boom-bust dynamics matters with respect to at-risk species management. Here, we ask whether the best strategy for restoring habitat across a landscape differs under exogenously versus endogenously driven boom-bust dynamics. We used spatially explicit individual-based models to assess how butterfly populations governed by the two mechanisms would respond to habitat restoration strategies that varied in the level of resource patchiness – from a single large patch to multiple patches spaced at different distances. Our models showed that the restoration strategy that minimized extinction risk and boom-bust dynamics would be markedly different depending on the governing mechanism. Exogenously governed populations fared best in a single large habitat patch, whereas for endogenously driven populations, boom-bust dynamics were dampened and extinction risk declined when the total restored area was split into multiple patches with low to moderate inter-patch spacing. Adding environmental stochasticity to the endogenous model did not alter this result. Habitat fragmentation lowered extinction risk in the endogenously driven populations by reducing their growth rate, precluding both “boom” phases and, more importantly, “bust” phases. Our findings suggest that: 1) successful restoration will depend on understanding the causes of fluctuations in at-risk populations; 2) the level and pattern of spatiotemporal environmental heterogeneity will also affect the ideal management approach; and 3) counter-intuitively, for at-risk species with endogenously governed boom-bust dynamics, lowering the intrinsic population growth rate may decrease extinction risk.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-21T21:10:55.689549-05:
      DOI: 10.1002/eap.1652
  • Herbivory and drought generate short-term stochasticity and long-term
           stability in a savanna understory community
    • Authors: Corinna Riginos; Lauren M. Porensky, Kari E. Veblen, Truman P. Young
      Abstract: Rainfall and herbivory are fundamental drivers of grassland plant dynamics, yet few studies have examined long-term interactions between these factors in an experimental setting. Understanding such interactions is important, as rainfall is becoming increasingly erratic and native wild herbivores are being replaced by livestock. Livestock grazing and episodic low rainfall are thought to interact, leading to greater community change than either factor alone. We examined patterns of change and stability in herbaceous community composition through four dry periods, or droughts, over 15 years of the Kenya Long-term Exclosure Experiment (KLEE), which consists of six different combinations of cattle, native wild herbivores (e.g., zebras, gazelles), and mega-herbivores (giraffes, elephants). We used principal response curves to analyze the trajectory of change in each herbivore treatment relative to a common initial community and asked how droughts contributed to community change in these treatments. We examined three measures of stability (resistance, variability, and turnover) that correspond to different temporal scales and found that each had a different response to grazing. Treatments that included both cattle and wild herbivores had higher resistance (less net change over 15 years) but were more variable on shorter time scales; in contrast, the more lightly-grazed treatments (no herbivores or wild herbivores only) showed lower resistance due to the accumulation of consistent, linear, short-term change. Community change was greatest during and immediately after droughts in all herbivore treatments. But, while droughts contributed to directional change in the less grazed treatments, it contributed to both higher variability and resistance in the more heavily grazed treatments. Much of the community change in lightly grazed treatments (especially after droughts) was due to substantial increases in cover of the palatable grass Brachiaria lachnantha. These results illustrate how herbivory and drought can act together to cause change in grassland communities at the moderate to low end of a grazing intensity continuum. Livestock grazing at a moderate intensity in a system with a long evolutionary history of grazing contributed to long-term stability. This runs counter to often-held assumptions that livestock grazing leads to directional, destabilizing shifts in grassland systems.This article is protected by copyright. All rights reserved.
      PubDate: 2017-11-15T10:48:28.267256-05:
      DOI: 10.1002/eap.1649
  • Uncovering state-dependent relationships in shallow lakes using Bayesian
           latent variable regression
    • Authors: Kelsey Vitense; Mark A. Hanson, Brian R. Herwig, Kyle D. Zimmer, John Fieberg
      Abstract: Ecosystems sometimes undergo dramatic shifts between contrasting regimes. Shallow lakes, for instance, can transition between two alternative stable states: a clear state dominated by submerged aquatic vegetation and a turbid state dominated by phytoplankton. Theoretical models suggest that critical nutrient thresholds differentiate three lake types: highly resilient clear lakes, lakes that may switch between clear and turbid states following perturbations, and highly resilient turbid lakes. For effective and efficient management of shallow lakes and other systems, managers need tools to identify critical thresholds and state-dependent relationships between driving variables and key system features. Using shallow lakes as a model system for which alternative stable states have been demonstrated, we developed an integrated framework using Bayesian latent variable regression (BLR) to classify lake states, identify critical total phosphorus (TP) thresholds, and estimate steady state relationships between TP and chlorophyll a (Chla) using cross-sectional data. We evaluated the method using data simulated from a stochastic differential equation model and compared its performance to k-means clustering with regression (KMR). We also applied the framework to data comprising 130 shallow lakes. For simulated datasets, BLR had high state classification rates (median/mean accuracy>97%) and accurately estimated TP thresholds and state-dependent TP/Chla relationships. Classification and estimation improved with increasing sample size and decreasing noise levels. Compared to KMR, BLR had higher classification rates and better approximated the TP/Chla steady state relationships and TP thresholds. We fit the BLR model to three different years of empirical shallow lake data, and managers can use the estimated bifurcation diagrams to prioritize lakes for management according to their proximity to thresholds and chance of successful rehabilitation. Our model improves upon previous methods for shallow lakes because it allows classification and regression to occur simultaneously and inform one another, directly estimates TP thresholds and the uncertainty associated with thresholds and state classifications, and enables meaningful constraints to be built into models. The BLR framework is broadly applicable to other ecosystems known to exhibit alternative stable states in which regression can be used to establish relationships between driving variables and state variables.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-30T09:40:25.672659-05:
      DOI: 10.1002/eap.1645
  • Cumulative effects of wildfires on forest dynamics in the eastern Cascade
           Mountains, USA
    • Authors: Matthew J. Reilly; Mario Elia, Thomas A. Spies, Matthew J. Gregory, Giovanni Sanesi, Raffaele Lafortezza
      Abstract: Wildfires pose a unique challenge to conservation in fire-prone regions, yet few studies quantify the cumulative effects of wildfires on forest dynamics (i.e. changes in structural conditions) across landscape and regional scales. We assessed the contribution of wildfire to forest dynamics in the eastern Cascade Mountains, USA from 1985 to 2010 using imputed maps of forest structure (i.e. tree size and canopy cover) and remotely-sensed burn severity maps. We addressed three questions: (1) How do dynamics differ between the region as a whole and the unburned portion of the region', (2) How do dynamics vary among vegetation zones differing in biophysical setting and historical fire frequency', (3) How have forest structural conditions changed in a network of late successional reserves (LSRs)' Wildfires affected 10% of forests in the region, but the cumulative effects at this scale were primarily slight losses of closed-canopy conditions and slight gains in open-canopy conditions. In the unburned portion of the region (the remaining 90%), closed-canopy conditions primarily increased despite other concurrent disturbances (e.g. harvest, insects). Although the effects of fire were largely dampened at the regional scale, landscape scale dynamics were far more variable. The warm ponderosa pine and cool mixed conifer zones experienced less fire than the region as a whole despite experiencing the most frequent fire historically. Open-canopy conditions increased slightly in the mixed conifer zone, but declined across the ponderosa pine zone even with wildfires. Wildfires burned 30% of the cold subalpine zone, which experienced the greatest increase in open-canopy conditions and losses of closed-canopy conditions. LSRs were more prone to wildfire than the region as a whole, and experienced slight declines in late seral conditions. Despite losses of late seral conditions, wildfires contributed to some conservation objectives by creating open habitats (e.g. sparse early seral and woodland conditions) that otherwise generally decreased in unburned landscapes despite management efforts to increase landscape diversity. This study demonstrates the potential for wildfires to contribute to regional scale conservation objectives, but implications for management and biodiversity at landscape scales vary geographically among biophysical settings, and are contingent upon historical dynamics and individual species habitat preferences.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-23T10:45:33.183586-05:
      DOI: 10.1002/eap.1644
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