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Journal Cover Ecological Applications
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   Full-text available via subscription Subscription journal
   ISSN (Print) 1051-0761 - ISSN (Online) 1939-5582
   Published by John Wiley and Sons Homepage  [1579 journals]
  • Ecosystem Regime Shifts Disrupt Trophic Structure
    • Authors: Tessa N. Hempson; Nicholas A.J. Graham, M. Aaron MacNeil, Andrew S. Hoey, Shaun K. Wilson
      Abstract: Regime shifts between alternative stable ecosystem states are becoming commonplace due to the combined effects of local stressors and global climate change. Alternative states are characterised as substantially different in form and function to pre-disturbance states, disrupting the delivery of ecosystem services and functions. On coral reefs, regime shifts are typically characterised by a change in the benthic composition from coral- to macroalgal-dominance. Such fundamental shifts in the benthos are anticipated to impact associated fish communities that are reliant on the reef for food and shelter, yet there is limited understanding of how regime shifts propagate through the fish community over time, relative to initial or recovery conditions. This study addresses this knowledge gap using long-term data of coral reef regime shifts and recovery on Seychelles reefs following the 1998 mass bleaching event. It shows how trophic structure of the reef fish community becomes increasingly dissimilar between alternative reef ecosystem states (regime-shifted vs recovering) with time since disturbance. Regime-shifted reefs developed a concave trophic structure, with increased biomass in base trophic levels as herbivorous species benefitted from increased algal resources. Mid trophic level species, including specialists such as corallivores, declined with loss of coral habitat, while biomass was retained in upper trophic levels by large-bodied, generalist invertivores. Recovering reefs also experienced an initial decline in mid trophic level biomass, but moved towards a bottom-heavy pyramid shape, with a wide range of feeding groups (e.g. planktivores, corallivores, omnivores) represented at mid trophic levels. Given the importance of coral reef fishes in maintaining the ecological function of coral reef ecosystems and their associated fisheries, understanding the effects of regime shifts on these communities is essential to inform decisions that enhance ecological resilience and economic sustainability.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-16T04:01:23.316218-05:
      DOI: 10.1002/eap.1639
       
  • Feces nitrogen release induced by different large herbivores in a dry
           grassland
    • Authors: Jingzhi Wang; Deli Wang, Chunqiang Li, Timothy R. Seastedt, Cunzhu Liang, Ling Wang, Wei Sun, Maowei Liang, Yu Li
      Abstract: Large herbivores have pronounced effects on nutrient cycling in grasslands. These organisms are known to alter the quality and quantity of plant production as well as the amounts and quality of plant litter and animal wastes. The generalization that the relative quality of detritus inputs is enhanced by herbivores is well known, but how this process is affected by diet selection processing and feces production of different large herbivores remains largely unstudied. Here, we measured how these differences for cattle and sheep on a dry grassland might influence nitrogen (N) mineralization from feces. We found that cattle of larger body size tended to select low quality grass Stipa grandis as the major food source. In contrast, the subdominant grass Leymus chinensis with relatively high N content was a majority in the diet of smaller sheep, when palatable forbs were insufficient in the field. This diverse diet quality resulted in a C/N ratio of cattle feces that was higher than that of sheep feces. Relatively higher labile C availability in the cattle feces, namely relatively higher cellulose/hemicellulose contents, promoted microbial growth and in turn accelerated cattle feces decomposition. A surprise finding was that the feces from cattle mineralized about twice as much N as feces from sheep, despite the latter having slightly higher N content. From a grassland productivity perspective, increasing the proportion of large body-sized species in grazing herbivore assemblages perhaps is beneficial to forage productivity and nutrient recycling by the rapid degradation of feces.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-16T03:55:24.630213-05:
      DOI: 10.1002/eap.1640
       
  • Modeling plant composition as community-continua in a forest landscape
           with LiDAR and hyperspectral remote sensing
    • Authors: C. R Hakkenberg; R. K Peet, D. L Urban, C Song
      Abstract: In light of the need to operationalize the mapping of forest composition at landscape scales, this study uses multi-scale nested vegetation sampling in conjunction with LiDAR-hyperspectral remotely-sensed data from the G-LiHT airborne sensor to map vascular plant compositional turnover in a compositionally- and structurally-complex North Carolina Piedmont forest. Reflecting a shift in emphasis from remotely sensing individual crowns to detecting aggregate optical-structural properties of forest stands, predictive maps reflect the composition of entire vascular plant communities - inclusive of those species smaller than the resolution of the remotely-sensed imagery, intertwined with proximate taxa, or otherwise obscured from optical sensors by dense upper canopies. Stand-scale vascular plant composition is modeled as community-continua: where discrete community-unit classes at different compositional resolutions provide interpretable context for continuous gradient maps that depict n-dimensional compositional complexity as a single, consistent RGB color combination. In total, derived remotely-sensed predictors explain 71%, 54%, and 48% of the variation in the first three components of vascular plant composition, respectively. Among all remotely-sensed environmental gradients, topography derived from LiDAR ground returns, forest structure estimated from LiDAR all returns, and morphological-biochemical traits determined from hyperspectral imagery each significantly correspond to the three primary axes of floristic composition in the study site. Results confirm the complementarity of LiDAR and hyperspectral sensors for modeling the environmental gradients constraining landscape turnover in vascular plant composition and hold promise for predictive mapping applications spanning local land management to global ecosystem modeling.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-10T08:51:14.68451-05:0
      DOI: 10.1002/eap.1638
       
  • Chlorpyrifos interacts with other agricultural stressors to alter stream
           communities in laboratory microcosms
    • Authors: Ana M. Chará-Serna; John S. Richardson
      Abstract: Chlorpyrifos is one of the most widely used agricultural insecticides in the world, but to date there is limited empirical information about its potential to interact with other common agricultural stressors. We conducted a 15-day, community-level microcosm experiment evaluating individual and combined effects of chlorpyrifos, nutrient enrichment, and sedimentation on stream invertebrate communities (abundance, biomass, richness, size structure, composition) and ecosystem processes (primary productivity and leaf decomposition). We found that sedimentation was the most detrimental stressor, with significant negative impacts on most invertebrate community and ecosystem function variables. Even though chlorpyrifos did not cause significant invertebrate mortality in the microcosms, it still altered ecosystem function by lowering leaf decomposition rates, probably through sublethal inhibition of invertebrate shredders. Furthermore, we observed a significant reversal interaction between chlorpyrifos and sediment for small-sized invertebrates collected in gravel (abundance in sediment x insecticide microcosms was 2.4 times lower than predicted by additivity), as well as an antagonistic interaction with nutrients on invertebrate richness in the same microhabitat (richness in nutrient x insecticide microcosms was 1.6 times higher than predicted by additivity). Our results suggest that chlorpyrifos has the potential to alter freshwater ecosystem function and interact non-additively with other common agricultural stressors. These findings are in keeping with a growing body of research highlighting that multiple stressor interactions and ecosystem processes should be considered when evaluating the impacts of organic toxicants on freshwater ecosystems.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-10T08:50:23.284327-05:
      DOI: 10.1002/eap.1637
       
  • Fuel-reduction management alters plant composition, carbon and nitrogen
           pools, and soil thaw in Alaskan boreal forest
    • Authors: April M. Melvin; Gerardo Celis, Jill F. Johnstone, A. David McGuire, Helene Genet, Edward A. G. Schuur, T. Scott Rupp, Michelle C. Mack
      Abstract: Increasing wildfire activity in Alaska's boreal forests has led to greater fuel-reduction management. Management has been implemented to reduce wildfire spread, but the ecological impacts of these practices are poorly known. We quantified the effects of hand-thinning and shearblading on above- and belowground stand characteristics, plant species composition, carbon (C) and nitrogen (N) pools, and soil thaw across 19 black spruce (Picea mariana) dominated sites in interior Alaska treated 2-12 years prior to sampling. The density of deciduous tree seedlings was significantly higher in shearbladed areas compared to unmanaged forest (6.4 vs. 0.1 stems m−2), and unmanaged stands exhibited the highest mean density of conifer seedlings and layers (1.4 stems m−2). Understory plant community composition was most similar between unmanaged and thinned stands. Shearblading resulted in a near complete loss of aboveground tree biomass C pools while thinning approximately halved the C pool size (1.2 kg C m−2 compared to 3.1 kg C m−2 in unmanaged forest). Significantly smaller soil organic layer (SOL) C and N pools were observed in shearbladed stands (3.2 kg C m−2 and 116.8 g N m−2) relative to thinned (6.0 kg C m−2 and 192.2 g N m−2) and unmanaged (5.9 kg C m−2 and 178.7 g N m−2) stands. No difference in C and N pool sizes in the uppermost 10 cm of mineral soil was observed among stand types. Total C stocks for measured pools was 2.6 kg C m−2 smaller in thinned stands and 5.8 kg C m−2 smaller in shearbladed stands when compared to unmanaged forest. Soil thaw depth averaged 13 cm deeper in thinned areas and 46 cm deeper in shearbladed areas relative to adjacent unmanaged stands, although variability was high across sites. Deeper soil thaw was linked to shallower SOL depth for unmanaged stands and both management types, however for any given SOL depth, thaw tended to be deeper in shearbladed areas compared to unmanaged forest. These findings indicate that fuel-reduction management alters plant community composition, C and N pools, and soil thaw depth, with consequences for ecosystem structure and function beyond those intended for fire management.This article is protected by copyright. All rights reserved.
      PubDate: 2017-10-07T10:35:39.955678-05:
      DOI: 10.1002/eap.1636
       
  • Invertebrate community response to coarse woody debris removal for
           bioenergy production from intensively managed forests
    • Authors: Steven M. Grodsky; Christopher E. Moorman, Sarah R. Fritts, Joshua W. Campbell, Clyde E. Sorenson, Matthew A. Bertone, Steven B. Castleberry, T. Bently Wigley
      Abstract: Increased market viability of harvest residues as forest bioenergy feedstock may escalate removal of coarse woody debris in managed forests. Meanwhile, many forest invertebrates use coarse woody debris for cover, food, and reproduction. Few studies have explicitly addressed effects of operational-scale woody biomass harvesting on invertebrates following clearcutting. Therefore, we measured invertebrate community response to large-scale harvest residue removal and micro-site manipulations of harvest residue availability in recently clearcut, intensively managed loblolly pine (Pinus taeda) forests in North Carolina (NC; n = 4) and Georgia (GA; n = 4), USA. We captured 39,794 surface-active invertebrates representing 171 taxonomic groups using pitfall traps situated among micro-site locations (i.e., purposefully retained piles of hardwood stems and piles of conifer stems and areas without coarse woody debris in NC; windrows and no windrows in GA). Micro-site locations were located within six, large-scale treatments (7.16 – 14.3 ha) in clearcuts. Large-scale treatments represented intensive harvest residue removal, 15% and 30% harvest residue retention, and no harvest residue removal. In NC, ground beetles (Coleoptera: Carabidae) and crickets (Orthoptera: Gryllidae) were three times more abundant in treatments with no harvest residue removal than those with the most intensive harvest residue removal and were reduced in treatments that retained 15% or 30% of harvest residues, although not significantly. Invertebrate taxa richness was greater at micro-site locations with retained hardwood and pine (Pinus spp.) harvest residues than those with minimal amounts of coarse woody debris. In both states, relative abundances of several invertebrate taxa, including cave crickets (Orthoptera: Rhaphidophoridae), fungus gnats (Diptera: Mycetophilidae and Sciaridae), millipedes (Diplopoda), and wood roaches (Blattodea: Ectobiidae), were greater at micro-site locations with retained harvest residues than those with minimal coarse woody debris. Intensified woody biomass harvesting without retention of>15% of harvest residue volume may reduce invertebrate taxa richness and abundances of some key invertebrate taxa in regenerating stands. Further, harvest residue management during and after woody biomass harvesting may be an important consideration for maintaining invertebrate diversity and conserving invertebrates that are influential in the maintenance of ecosystem function and integrity in young forests.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-26T01:35:20.305342-05:
      DOI: 10.1002/eap.1634
       
  • Using species traits to predict detectability of animals on aerial surveys
    • Authors: S. Schlossberg; M. J. Chase, C. R. Griffin
      Abstract: In animal surveys, detectability can vary widely across species. We hypothesized that detectability of animals should be a function of species traits such as mass, color, and mean herd size. We also hypothesized that models of detectability based on species traits can be used to predict detectability for new species not in the original dataset, leading to substantial benefits for ecology and conservation. We tested these hypotheses with double-observer aerial surveys of 10 mammal species in northern Botswana. We combined all 10 species and modeled their detectability with species traits (mass, mean herd size, color) as predictors while controlling for observer effects, vegetation, and herd size. We found support for effects of mass and an interaction between herd size and mean herd size on detectability. This model accurately predicted the ratio of herds detected by two observers vs. one observer for 8 of 10 species. To test whether a model based on species traits could be applied to a new species, we serially deleted each species from the dataset, fit a trait-based model to the remaining nine species, and used this model to predict detectability for the deleted species. The model was able to reproduce the species-trait model for seven species and accurately predicted the ratio of detections by one or two observers for a different set of seven species; the model was successful by both measures for five species. To our knowledge, this represents the first time that a mechanistic model for detectability of animals has been used to predict detectability for new species. Prediction failed for species with extreme values of traits, suggesting that predicting detectability is not possible near or beyond the boundaries of one's dataset. The approach taken in this paper can potentially be used with a variety of taxa and may provide new opportunities to apply detectability corrections where they have not been possible before.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-25T03:28:03.163501-05:
      DOI: 10.1002/eap.1632
       
  • Scenarios reveal pathways to sustain future ecosystem services in an
           agricultural landscape
    • Authors: Jiangxiao Qiu; Stephen R. Carpenter, Eric G. Booth, Melissa Motew, Samuel C. Zipper, Christopher J. Kucharik, Xi Chen, Steven P. Loheide, Jenny Seifert, Monica G. Turner
      Abstract: Sustaining food production, water quality, soil retention, flood and climate regulation in agricultural landscapes is a pressing global challenge given accelerating environmental changes. Scenarios are stories about plausible futures, and scenarios can be integrated with biophysical simulation models to explore quantitatively how the future might unfold. However, few studies have incorporated a wide range of drivers (e.g., climate, land-use, management, population, human diet) in spatially explicit, process-based models to investigate spatial-temporal dynamics and relationships of a portfolio of ecosystem services. Here, we simulated nine ecosystem services (three provisioning and six regulating services) at 220-m×220-m from 2010 to 2070 under four contrasting scenarios in the 1345-km2 Yahara Watershed (Wisconsin, USA) using Agro-IBIS, a dynamic model of terrestrial ecosystem processes, biogeochemistry, water and energy balance. We asked: (1) How does ecosystem service supply vary among alternative future scenarios' (2) Where on the landscape is the provision of ecosystem services most susceptible to future social-ecological changes' (3) Among alternative future scenarios, are relationships (i.e., tradeoffs, synergies) among food production, water and biogeochemical services consistent over time' Our results showed that food production varied substantially with future land-use choices and management, and its tradeoffs with water quality and soil retention persisted under most scenarios. However, pathways to mitigate or even reverse such tradeoffs through technological advances and sustainable agricultural practices were apparent. Consistent relationships among regulating services were identified across scenarios (e.g., tradeoffs of freshwater supply vs. flood and climate regulation, and synergies among water quality, soil retention and climate regulation), suggesting opportunities and challenges to sustaining these services. In particular, proactive land-use changes and management may buffer water quality against undesirable future climate changes, but changing climate may overwhelm management efforts to sustain freshwater supply and flood regulation. Spatially, changes in ecosystem services were heterogeneous across the landscape, underscoring the power of local actions and fine-scale management. Our research highlights the value of embracing spatial and temporal perspectives in managing ecosystem services and their complex interactions, and provides a system-level understanding for achieving sustainability of the food-water-climate nexus in agricultural landscapes.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-25T03:27:38.086912-05:
      DOI: 10.1002/eap.1633
       
  • Last-century forest productivity in a managed dry-edge Scots pine
           population: the two sides of climate warming
    • Authors: Laura Marqués; Jaime Madrigal-González, Miguel A. Zavala, J. Julio Camarero, Florian Hartig
      Abstract: Climate change in the Mediterranean, associated with warmer temperatures and more frequent droughts, is expected to impact forest productivity and the functioning of forests ecosystems as carbon reservoirs in the region. Climate warming can positively affect forest growth by extending the growing season, whereas increasing summer drought generally reduces forest productivity and may cause growth decline, trigger dieback, hamper regeneration and increase mortality. Forest management could potentially counteract such negative effects by reducing stand density and thereby competition for water. The effectiveness of such interventions, however, has so far mostly been evaluated for short time periods at the tree and stand levels, which limits our confidence regarding the efficacy of thinning interventions over longer time scales under the complex interplay between climate, stand structure and forest management. In this study, we use a century-long historical dataset to assess the effects of climate and management on forest productivity and regeneration. We consider rear-edge Scots pine (Pinus sylvestris) populations covering continental and Mediterranean conditions along an altitudinal gradient in Central Spain. We use linear mixed-effects models to disentangle the effects of altitude, climate, and stand volume on forest growth and ingrowth (recruitment and young trees'growth). We find that warming tends to benefit these tree populations - warmer winter temperature has a significant positive effect on both forest growth and ingrowth - and the effect is more pronounced at low elevations. However, drought conditions severely reduce growth and ingrowth, in particular when competition (stand volume) is high. We conclude that summer droughts are the main threat to Scots pine populations in the region, and that a reduction of stand volume can partially mitigate the negative impacts of more arid conditions. Mitigation and adaptation measures could therefore manage stand structure to adopt for the anticipated impacts of climate change in Mediterranean forest ecosystems.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-25T03:21:07.525968-05:
      DOI: 10.1002/eap.1631
       
  • Cultivar mixtures: A meta-analysis of the effect of intraspecific
           diversity on crop yield
    • Authors: Emily R. Reiss; Laurie E. Drinkwater
      Abstract: Extensive research has shown that greater plant community diversity leads to higher levels of productivity and other ecosystem services, and such increased diversity has been suggested as a way to improve yield and agricultural sustainability. Increasing intraspecific diversity with cultivar mixtures is one way to increase diversity in agricultural systems. We examined the relationship between intraspecific diversity and yield in cultivar mixtures using a meta-analysis of 91 studies and>3600 observations. Additionally, we investigated how environmental and management factors might influence this relationship, and if the yield stability of cultivar mixtures differed from that of monocultures. We found that the yield increased by 2.2% overall in cultivar mixtures relative to their monoculture components. Mixtures with more cultivars and those with more functional trait diversity showed higher relative yields. Under biotic stressors, such as disease pressure, and abiotic stressors, such as low levels of soil organic matter and nutrient availability, this diversity effect was stronger, resulting in higher relative yields. Finally, cultivar mixtures generally showed higher yield stability compared to monocultures, especially in response to annual weather variability at a site over time. This practice of mixing cultivars can be integrated into intensified cropping systems where species monocultures dominate, as well as in smallholder cropping systems where low-cost improvements are in demand. Overall, these results suggest that cultivar mixtures are a viable strategy to increase diversity in agroecosystems, promoting increased yield and yield stability, with minimal environmental impact.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-22T08:30:39.039994-05:
      DOI: 10.1002/eap.1629
       
  • Template for using biological trait groupings when exploring large-scale
           variation in seafloor multifunctionality
    • Authors: Anna Villnäs; Judi Hewitt, Martin Snickars, Mats Westerbom, Alf Norkko
      Abstract: Understanding large-scale spatial variation in ecosystem properties and associated functionality is key for successful conservation of ecosystems. This study provides a template for how to estimate differences in ecosystem functionality over large spatial scales by using groupings of biological traits. We focus on trait groupings that describe three important benthic ecosystem properties, namely bioturbation, community stability and juvenile dispersal. Recognizing that groups of traits interact and are constrained within an organism, we statistically define important functional trait subgroups that describe each ecosystem property. The sub-groups are scored according to their weighted ecological impact to gain an overall estimation of the cumulative expression of each ecosystem property at individual sites. Furthermore, by assigning each property a value relative to its observed maximum, and by summing up the individual property values, we offer an estimate of benthic ecosystem multifunctionality. Based on a spatially extensive benthic data set, we were able to identify coastal areas with high and low potential for the considered benthic ecosystem properties and the measure of ecosystem multifunctionality. Importantly, we show that a large part of the spatial variation in functional trait sub-groups and in benthic ecosystem multifunctionality was explained by environmental change. Our results indicate that through this simplification it is possible to estimate the functionality of the seafloor. Such information is vital in marine spatial planning efforts striving to balance the utilization with the preservation of natural resources.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-22T08:30:34.192724-05:
      DOI: 10.1002/eap.1630
       
  • Purpose, Processes, Partnerships, and Products: 4Ps to advance
           Participatory Socio-Environmental Modeling
    • Authors: Steven Gray; Alexey Voinov, Michael Paolisso, Rebecca Jordan, Todd BenDor, Pierre Bommel, Pierre Glynn, Beatrice Hedelin, Klaus Hubacek, Josh Introne, Nagesh Kolagani, Bethany Laursen, Christina Prell, Laura Schmitt-Olabisi, Alison Singer, Eleanor Sterling, Moira Zellner
      Abstract: Including stakeholders in environmental model building and analysis is an increasingly popular approach to understanding ecological change. This is because stakeholders often hold valuable knowledge about socio-environmental dynamics and collaborative forms of modeling produce important boundary objects used to collectively reason about environmental problems. Although the number of participatory modeling (PM) case studies and the number of researchers adopting these approaches has grown in recent years, the lack of standardized reporting and limited reproducibility have prevented PM's establishment and advancement as a cohesive field of study. We suggest a four-dimensional framework (4P) that includes reporting on dimensions of: (1) the Purpose for selecting a PM approach (the why); (2) the Process by which the public was involved in model building or evaluation (the how); (3) the Partnerships formed (the who); and (4) the Products that resulted from these efforts (the what). We highlight four case studies that use common PM software-based approaches (fuzzy cognitive mapping, agent-based modeling, system dynamics, and participatory geospatial modeling) to understand human-environment interactions and the consequences of ecological changes, including bushmeat hunting in Tanzania and Cameroon, agricultural production and deforestation in Zambia, and groundwater management in India. We demonstrate how standardizing communication about PM case studies can lead to innovation and new insights about model-based reasoning in support of ecological policy development. We suggest that our 4P framework and reporting approach provides a way for new hypotheses to be identified and tested in the growing field of PM.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-18T11:05:20.454154-05:
      DOI: 10.1002/eap.1627
       
  • Climatic and anthropogenic drivers of northern Amazon fires during the
           2015/2016 El Niño event
    • Authors: Marisa G. Fonseca; Liana O. Anderson, Egidio Arai, Yosio E. Shimabukuro, Haron A. M. Xaud, Maristela R. Xaud, Nima Madani, Fabien H. Wagner, Luiz E. O. C. Aragão
      Abstract: The strong El Niño Southern Oscillation (ENSO) event that occurred in 2015/2016 caused extreme drought in the northern Brazilian Amazon, especially in the state of Roraima, increasing fire occurrence. Here we map the extent of precipitation and fire anomalies and quantify the effects of climatic and anthropogenic drivers on fire occurrence during the 2015/2016 dry season (from December 2015 to March 2016) in the state of Roraima. To achieve these objectives we first estimated the spatial pattern of precipitation anomalies, based on long-term data from the TRMM (Tropical Rainfall Measuring Mission), and the fire anomaly, based on MODIS (Moderate Resolution Imaging Spectroradiometer) active fire detections during the referred period. Then, we integrated climatic and anthropogenic drivers in a Maximum Entropy (MaxEnt) model to quantify fire probability, assessing (i) the model accuracy during the 2015/2016 and the 2016/2017 dry seasons; (ii) the relative importance of each predictor variable on the model predictive performance; and (iii) the response curves, showing how each environmental variable affects the fire probability. Approximately 59% (132,900 km2) of the study area was exposed to precipitation anomalies ≤ -1 standard deviation (SD) in January and ~48% (~106,800 km2) in March. About 38% (86,200 km2) of the study area experienced fire anomalies ≥ 1 SD in at least one month between December 2015 and March 2016. The distance to roads and the direct ENSO effect on fire occurrence were the two most influential variables on model predictive performance. Despite the improvement of governmental actions of fire prevention and firefighting in Roraima since the last intense ENSO event (1997/1998), we show that fire still gets out of control in the state during extreme drought events. Our results indicate that if no prevention actions are undertaken, future road-network expansion and a climate-induced increase in water stress will amplify fire occurrence in the northern Amazon, even in its humid dense forests. As an additional outcome of our analysis, we conclude that the model and the data we used may help to guide on-the-ground fire-prevention actions and firefighting planning and therefore minimize fire-related ecosystems degradation, economic losses and carbon emissions in Roraima.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-18T09:45:29.744833-05:
      DOI: 10.1002/eap.1628
       
  • Assessing fire impacts on the carbon stability of fire-tolerant forests
    • Authors: Lauren T. Bennett; Matthew J. Bruce, Josephine Machunter, Michele Kohout, Saravanan Jangammanaidu Krishnaraj, Cristina Aponte
      Abstract: The carbon stability of fire-tolerant forests is often assumed but less frequently assessed, limiting potential to anticipate threats to forest carbon posed by predicted increases in forest fire activity. Assessing the carbon stability of fire-tolerant forests requires multi-indicator approaches that recognise the myriad of ways that fires influence the carbon balance including combustion, deposition of pyrogenic material, and tree death, post-fire decomposition, recruitment, and growth. Five years after a large-scale wildfire in south-eastern Australia, we assessed the impacts of low- and high-severity wildfire, with and without prescribed fire (≤ 10 years before), on carbon stocks in multiple pools, and on carbon stability indicators (carbon stock percentages in live trees and in small trees, and carbon stocks in char and fuels) in fire-tolerant eucalypt forests. Relative to unburnt forest, high-severity wildfire decreased short-term (five-year) carbon stability by significantly decreasing live tree carbon stocks and percentage stocks in live standing trees (reflecting elevated tree mortality), by increasing the percentage of live tree carbon in small trees (those vulnerable to the next fire), and by potentially increasing the probability of another fire through increased elevated fine fuel loads. In contrast, low-severity wildfire enhanced carbon stability by having negligible effects on above-ground stocks and indicators, and by significantly increasing carbon stocks in char and, in particular, soils, indicating pyrogenic carbon accumulation. Overall, recent preceding prescribed fire did not markedly influence wildfire effects on short-term carbon stability at stand scales. Despite wide confidence intervals around mean stock differences – indicating uncertainty about the magnitude of fire effects in these natural forests – our assessment highlights the need for active management of carbon assets in fire-tolerant eucalypt forests under contemporary fire regimes. Decreased live tree carbon and increased reliance on younger cohorts for carbon recovery after high-severity wildfire, could increase vulnerabilities to imminent fires, leading to decisions about interventions to maintain the productivity of some stands. Our multi-indicator assessment also highlights the importance of considering all carbon pools, particularly pyrogenic reservoirs like soils, when evaluating the potential for prescribed fire regimes to mitigate the carbon costs of wildfires in fire-prone landscapes.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-16T15:26:54.613065-05:
      DOI: 10.1002/eap.1626
       
  • Long-term agricultural management does not alter the evolution of a
           soybean-rhizobium mutualism
    • Authors: Jennifer E. Schmidt; Dylan J. Weese, Jennifer A. Lau
      Abstract: Leguminous crops, like soybeans, often rely on biologically fixed nitrogen via their symbiosis with rhizobia rather than synthetic nitrogen inputs. However, agricultural management practices may influence the effectiveness of biological nitrogen fixation. While the ecological effects of agricultural management on rhizobia have received some attention, the evolutionary effects have been neglected in comparison. Resource mutualism theory predicts that evolutionary effects are likely, however. Both fertilization and tillage are predicted to cause the evolution of rhizobia that provide fewer growth benefits to plant hosts and fix less nitrogen. This study capitalized on an LTER (Long Term Ecological Research) experiment that manipulated agricultural management practices in a corn-soybean-wheat row crop system for 24 years to investigate whether four different management practices (conventional, no-till, low chemical input, and certified organic) cause rhizobia populations to evolve to become more or less cooperative. We found little evidence that 24 years of varying management practices affect the net growth benefits rhizobia provide to soybeans, although soybean plants inoculated with soils collected from conventional treatments tended to have lower biological nitrogen fixation rates than plants inoculated with soils from the no-till, low input, and organic management treatments. These findings suggest that rhizobia will continue to provide adequate growth benefits to leguminous crops in the future, even in intensively managed systems.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-16T15:26:52.238942-05:
      DOI: 10.1002/eap.1625
       
  • Survey design for precise fire management conservation targets
    • Authors: Holly Sitters; Julian Di Stefano, Timothy Wills, Matthew Swan, Alan York
      Abstract: Common goals of ecological fire management are to sustain biodiversity and minimize extinction risk. A novel approach to achieving these goals determines the relative proportions of vegetation growth stages (equivalent to successional stages, which are categorical representations of time since fire) that maximize a biodiversity index. The method combines data describing species abundances in each growth stage with numerical optimization to define an optimal growth-stage structure which provides a conservation-based operational target for managers. However, conservation targets derived from growth-stage optimization are likely to depend critically on choices regarding input data. There is growing interest in use of growth-stage optimization as a basis for fire management, thus understanding of how input data influence the outputs is crucial. Simulated datasets provide a flexible platform for systematically varying aspects of survey design and species inclusions. We used artificial data with known properties, and a case-study dataset from southeastern Australia, to examine the influence of (i) survey design (total number of sites, and their distribution among growth stages) and (ii) species inclusions (total number of species and their level of specialization) on the precision of conservation targets. Based on our findings, we recommend that survey designs for precise estimates would ideally involve at least 80 sites, and include at least 80 species. Greater numbers of sites and species will yield increasingly reliable results, but fewer might be sufficient in some circumstances. An even distribution of sites among growth stages was less important than the total number of sites, and omission of species is unlikely to have a major influence on results as long as several species specialize on each growth stage. We highlight the importance of examining the responses of individual species to growth stage before feeding survey data into the growth-stage optimization black box, and advocate use of a resampling procedure to determine the precision of results. Collectively, our findings form a reproducible guide to designing ecological surveys that yield precise conservation targets through growth-stage optimization, and ultimately help sustain biodiversity in fire-prone systems.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-12T20:05:46.269902-05:
      DOI: 10.1002/eap.1624
       
  • Long-term trends in trait structure of riverine communities facing
           predation risk increase and trophic resource decline
    • Authors: Adrien Latli; Jean-Pierre Descy, Cédric P Mondy, Mathieu Floury, Laurent Viroux, William Otjacques, Jonathan Marescaux, Eric Depiereux, Michael Ovidio, Philippe Usseglio-Polatera, Patrick Kestemont
      Abstract: Many large European rivers have undergone multiple pressures which have strongly impaired ecosystem functioning at different spatial and temporal scales. Global warming and other environmental changes have favoured the success of invasive species, deeply modifying the structure of aquatic communities in large rivers. Some exogenous species could alter trophic interactions within assemblages by increasing the predation risk for potential prey species (top-down effect) and limiting the dynamics of others via resource availability limitation (bottom-up effect). Furthermore, large transboundary rivers are complex aquatic ecosystems which have often been poorly investigated so that data for assessing long-term ecological trends are missing. In this study, we propose an original approach for investigating long-term combined effects of global warming, trophic resource decrease, predation risk and water quality variations on the trait-based structure of macroinvertebrate and fish assemblages over 26 years (1985-2011) and 427-km stretch of the river Meuse (France and Belgium). The study of temporal variations in biological, physiological and ecological traits of macroinvertebrate and fish allowed identifying community trends and distinguishing impacts of environmental perturbations from those induced by biological alterations. We provide evidence, for this large European river, of an increase in water temperature (close to 1°C) and a decrease in phytoplankton biomass (- 85%), as well as independent effects of these changes on both invertebrate and fish communities. The reduction of trophic resources in the water column by invasive molluscs has dramatically affected the density of omnivorous fish in favour of invertebrate-feeders, while scrapers became the major feeding guild among invertebrates. Macroinvertebrate and fish communities have shifted from large-sized organisms with low fecundity to prolific, small-sized organisms, with early maturity, as a response to increased predation pressure.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-05T10:45:51.32343-05:0
      DOI: 10.1002/eap.1621
       
  • Impacts of different land management histories on forest change
    • Authors: Brandon M. Collins; Danny L. Fry, Jamie M. Lydersen, Richard Everett, Scott L. Stephens
      Abstract: Many western North American forest types have experienced considerable changes in ecosystem structure, composition, and function as a result of both fire exclusion and timber harvesting. These two influences co-occurred over a large portion of dry forests making it difficult to know the strength of either one on its own or the potential for an interaction between the two. In this study we used contemporary re-measurements of a systematic historical forest inventory to investigate forest change in the Sierra Nevada. The historical data opportunistically spanned a significant land management agency boundary, which protected part of the inventory area from timber harvesting. This allowed for a robust comparison of forest change between logged and unlogged areas. In addition, we assessed the effects of recent management activities aimed at forest restoration relative to the same areas historically, and to other areas without recent management. Based on analyses of 22,007 trees (historical: 9573; contemporary: 12,434) live basal area and tree density significantly increased from 1911 to present in both logged and unlogged areas. Both shrub cover and the proportion of live basal area occupied by pine species declined from 1911 to present in both areas, but statistical significance was inconsistent. The most notable difference between logged and unlogged areas was in the density of large trees, which declined significantly in logged areas, but was unchanged in unlogged areas. Recent management activities had a varied impact on the forest structure and composition variables analyzed. In general, areas with no recent management activities experienced the greatest change from 1911 to present. If approximating historical forest conditions is a land management goal the documented changes in forest structure and composition from 1911 to present indicate that active restoration, including fire use and mechanical thinning, is needed in many areas.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-05T10:45:36.505617-05:
      DOI: 10.1002/eap.1622
       
  • Urbanization reduces and homogenizes trait diversity in stream
           macroinvertebrate communities
    • Authors: Thomas R. Barnum; Donald E. Weller, Meghan Williams
      Abstract: More than half the world's population lives in urban areas, so quantifying the effects of urbanization on ecological communities is important for understanding whether anthropogenic stressors homogenize communities across environmental and climatic gradients. We examined the relationship of impervious surface coverage (a marker of urbanization) and the structure of stream macroinvertebrate communities across the state of Maryland and within each of Maryland's three ecoregions: Coastal Plain, Piedmont, and Appalachian, which differ in stream geomorphology and community composition. We considered three levels of trait organization: individual traits, unique combinations of traits, and community metrics (functional richness, functional evenness, and functional divergence) and three levels of impervious surface coverage (low (10%). The prevalence of an individual trait modality differed very little between low impervious surface and high impervious surface sites. The arrangement of trait combinations in community trait space for each ecoregion differed when impervious surface coverage was low, but the arrangement became more similar among ecoregions as impervious surface coverage increased. Furthermore, trait combinations that occurred only at low or medium impervious surface coverage were clustered in a subset of the community trait space, indicating impervious surface affected the presence of only a subset of trait combinations. Functional richness declined with increasing impervious surface, providing evidence for environmental filtering. Community metrics that include abundance were also sensitive to increasing impervious surface coverage–functional divergence decreased while functional evenness increased. These changes demonstrate that increasing impervious surface coverage homogenizes the trait diversity of macroinvertebrate communities in streams, despite differences in initial community composition and stream geomorphology among ecoregions. Community metrics were also more sensitive to changes in the abundance rather than the gain or loss of trait combinations, showing the potential for trait-based approaches to serve as early warning indicators of environmental stress for monitoring and biological assessment programs.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-05T02:05:45.420872-05:
      DOI: 10.1002/eap.1619
       
  • Rangifer management controls a climate-sensitive tundra state transition
    • Authors: Kari Anne Bråthen; Virve Tuulia Ravolainen, Audun Stien, Torkild Tveraa, Rolf A. Ims
      Abstract: Rangifer (caribou/reindeer) management has been suggested to mitigate the temperature-driven transition of arctic tundra into a shrubland state, yet how is uncertain. Here we study this much focused ecosystem state transition in riparian areas, where palatable willows (Salix) are dominant tall shrubs and highly responsive to climate change. For the state transition to take place, small life stages must become tall and abundant. Therefore we predicted that the performance of small life stages (potential recruits) of the tall shrubs were instrumental to the focal transition, where Rangifer managed at high population density would keep the small-stage shrubs in a “browse trap” independent of summer temperature. We used a large-scale quasi-experimental study design that included real management units that spanned a wide range of Rangifer population densities and summer temperatures in order to assess the relative importance of these two driving variables. Ground-surveys provided data on density and height of the small shrub life stages, while the distributional limit (shrubline) of established shrublands (the tall shrub life stage) was derived from aerial photographs. Where Rangifer densities were above a threshold of approximately 5 animals km−2 we found, in accordance with the expectation of a “browse trap”, that the small life stages of shrubs in grasslands were at low height and low abundance. At Rangifer densities below this threshold the small life stages of shrubs were taller and more abundant indicating Rangifer were no longer in control of the grassland state. For the established shrubland state, we found that the shrubline was at a 100 m lower elevation in the management units where Rangifer have been browsing in summer as opposed to the migratory ranges with no browsing in summer. In both seasonal ranges the shrubline increased 100 m per 1°C increment in temperature. Our study supports the proposal that Rangifer management within a sustainable range of animal densities can mitigate the much-focused transition from grassland to shrubland in a warming arctic.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-04T19:01:45.826503-05:
      DOI: 10.1002/eap.1618
       
  • Predictive Mapping of the Biotic Condition of Conterminous-USA Rivers and
           Streams
    • Authors: Ryan A. Hill; Eric W. Fox, Scott G. Leibowitz, Anthony R. Olsen, Darren J. Thornbrugh, Marc H. Weber
      Abstract: Understanding and mapping the spatial variation in stream biological condition could provide an important tool for conservation, assessment, and restoration of stream ecosystems. The USEPA's 2008-2009 National Rivers and Streams Assessment (NRSA) summarizes the percent of stream lengths within the conterminous US that are in good, fair, or poor biological condition based on a multimetric index of benthic invertebrate assemblages. However, condition is usually summarized at regional or national scales, and these assessments do not provide substantial insight into the spatial distribution of conditions at unsampled locations. We used random forests to model and predict the probable condition of several million kilometers of streams across the conterminous US based on nearby and upstream landscape features, including human-related alterations to watersheds. To do so, we linked NRSA sample sites to the USEPA's StreamCat Dataset; a database of several hundred landscape metrics for all 1:100,000-scale streams and their associated watersheds within the conterminous US. The StreamCat data provided geospatial indicators of nearby and upstream land use, land cover, climate, and other landscape features for modeling. Nationally, the model correctly predicted the biological condition class of 75% of NRSA sites. Although model evaluations suggested good discrimination among condition classes, we present maps as predicted probabilities of good condition, given upstream and nearby landscape settings. Inversely, the maps can be interpreted as the probability of a stream being in poor condition, given human-related watershed alterations. These predictions are available for download from the USEPA's StreamCat website (https://w w w .epa. gov/national-aquatic-resource-surveys/streamcat). Finally, we illustrate how these predictions could be used to prioritize streams for conservation or restoration.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-04T19:01:37.964027-05:
      DOI: 10.1002/eap.1617
       
  • What mediates tree mortality during drought in the southern Sierra
           Nevada'
    • Authors: Tarin Paz-Kagan; Philip G. Brodrick, Nicholas R. Vaughn, Adrian J. Das, Nathan L. Stephenson, Koren R. Nydick, Gregory P. Asner
      Abstract: Severe drought has the potential to cause selective mortality within a forest, thereby inducing shifts in forest species composition. The southern Sierra Nevada foothills and mountains of California have experienced extensive forest dieback due to drought stress and insect outbreak. We used high-fidelity imaging spectroscopy (HiFIS) and light detection and ranging (LiDAR) from the Carnegie Airborne Observatory (CAO) to estimate the effect of forest dieback on species composition in response to drought stress in Sequoia National Park. Our aims were: (1) to quantify site-specific conditions that mediate tree mortality along an elevation gradient in the southern Sierra Nevada Mountains; (2) to assess where mortality events have a greater probability of occurring; and (3) to estimate which tree species have a greater likelihood of mortality along the elevation gradient. A series of statistical models were generated to classify species composition and identify tree mortality, and the influences of different environmental factors were spatially quantified and analyzed to assess where mortality events have a greater likelihood of occurring. A higher probability of mortality was observed in the lower portion of the elevation gradient, on southwest and west-facing slopes, in areas with shallow soils, on shallower slopes, and at greater distances from water. All of these factors are related to site water balance throughout the landscape. Our results also suggest that mortality is species-specific along the elevation gradient, mainly affecting Pinus ponderosa and Pinus lambertiana at lower elevations. Selective mortality within the forest may drive long-term shifts in community composition along the elevation gradient.This article is protected by copyright. All rights reserved.
      PubDate: 2017-09-04T19:01:24.864093-05:
      DOI: 10.1002/eap.1620
       
  • Effects of a large wildfire on vegetation structure in a variable fire
           mosaic
    • Authors: C.N Foster; P.S Barton, N.M Robinson, C.I MacGregor, D.B Lindenmayer
      Abstract: Management guidelines for many fire-prone ecosystems highlight the importance of maintaining a variable mosaic of fire histories for biodiversity conservation. Managers are encouraged to aim for fire mosaics that are temporally and spatially dynamic, include all successional states of vegetation, and also include variation in the underlying “invisible mosaic” of past fire frequencies, severities and fire return intervals. However, establishing and maintaining variable mosaics in contemporary landscapes is subject to many challenges, one of which is deciding how the fire mosaic should be managed following the occurrence of large, unplanned wildfires. A key consideration for this decision is the extent to which the effects of previous fire history on vegetation and habitats persist after major wildfires, but this topic has rarely been investigated empirically.In this study we tested to what extent a large wildfire interacted with previous fire history to affect the structure of forest, woodland and heath vegetation in Booderee National Park in south-eastern Australia. In 2003, a summer wildfire burnt 49.5% of the park, increasing the extent of recently burnt vegetation (< 10 years post-fire) to more than 72% of the park area. We tracked the recovery of vegetation structure for nine years following the wildfire and found that the strength and persistence of fire effects differed substantially between vegetation types. Vegetation structure was modified by wildfire in forest, woodland and heath vegetation, but among-site variability in vegetation structure was reduced only by severe fire in woodland vegetation. There also were persistent legacy effects of the previous fire regime on some attributes of vegetation structure including forest ground and understorey cover, and woodland midstorey and overstorey cover. For example, woodland midstorey cover was greater on sites with higher fire frequency, irrespective of the severity of the 2003 wildfire. Our results show that even after a large, severe wildfire, underlying fire histories can contribute substantially to variation in vegetation structure. This highlights the importance of ensuring that efforts to reinstate variation in vegetation fire age after large wildfires do not inadvertently reduce variation in vegetation structure generated by the underlying invisible mosaic.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-29T08:10:20.907315-05:
      DOI: 10.1002/eap.1614
       
  • Modelling the effects of spatial heterogeneity and temporal variation in
           extinction probability on mosquito populations
    • Authors: Yehonatn Alcalay; Ido Tsurim, Ofer Ovadia
      Abstract: Spatial synchrony plays an important role in dictating the dynamics of spatial and stage-structured populations. Here we argue that, unlike Moran effect where spatial synchrony is driven by exogenous factors, spatial correlation in intrinsic/local scale processes, can affect the level of spatial synchrony among distinct sub-populations, and therefore the persistence of the entire population. To explore this mechanism, we modelled the consequences of spatial heterogeneity in aquatic habitat quality, and that of temporal variation in local extinction probability, on the persistence of stage-structured mosquito populations. As a model system, we used two widely distributed mosquito species, Aedes albopictus and Culex pipiens, both key vectors of a range of infectious diseases. Spatial heterogeneity in aquatic habitat quality led to increased population persistence, and this pattern was more pronounced at intermediate dispersal rates, and in the long-dispersing species (C. pipiens). The highest regional persistence was obtained at high dispersal rates. This is probably because dispersal, in our model, did not carry any additional costs. Population persistence of both species was negatively correlated with increased temporal variation in local extinction probability. These differences were stronger in the short-dispersing species (A. albopictus), especially at intermediate dispersal rates. The dispersal of A. albopictus adults in each time step was limited to the nearest habitat patches, weakening the positive effect of spatial heterogeneity in aquatic habitat quality on population persistence. In contrary, C. pipiens adults could disperse into more remote sub-populations, resulting in much higher recolonization rates. Hence, the negative effect of temporal variation in local extinction probability on patch occupancy disappeared at intermediate dispersal rates. We suggest that effectively controlling these two mosquito species requires making few spatially synchronized control efforts (i.e., generating high temporal variation in local extinction probability), rather than many asynchronized local control efforts. Finally, our model can be easily fitted to other organisms characterized by complex life cycles, and it can be also used to examine alternative scenarios, including the effect of spatial configuration of local habitat patches and dispersal kernel shape on population persistence.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-29T03:00:39.255013-05:
      DOI: 10.1002/eap.1612
       
  • Strong indirect herbicide effects on mycorrhizal associations through
           plant community shifts and secondary invasions
    • Authors: Y Lekberg; Viktoria Wagner, Alexii Rummel, Morgan McLeod, Philip W. Ramsey
      Abstract: Million of acres of US wildlands are sprayed with herbicides to control invasive species, but relatively little is known about non-target effects of herbicide use. We combined greenhouse, field and laboratory experiments involving the invasive forb spotted knapweed (Centaurea stoebe) and native bunchgrasses to assess direct and indirect effects of the forb-specific herbicide picloram on arbuscular mycorrhizal fungi (AMF), which are beneficial soil fungi that colonize most plants.Picloram had no effect on bunchgrass viability and their associated AMF in the greenhouse, but killed spotted knapweed and reduced AM colonization of a subsequent host grown. Results were similar in the field where AMF abundance in bunchgrass-dominated plots was unaffected by herbicides one year after spraying based on 16:1ω5 phospholipid fatty acid (PLFA) and neutral lipid fatty acid (NLFA) concentrations. In spotted knapweed-dominated plots, however, picloram application shifted dominance from spotted knapweed, a good AMF host, to bulbous bluegrass (Poa bulbosa), a poor AMF host. This coincided with a 63% reduction in soil 16:1ω5 NLFA concentrations but no reduction of 16:1ω5 PLFA. Because 16:1ω5 NLFA quantifies AMF storage lipids and 16:1ω5 PLFA occurs in AMF membrane lipids, we speculate that the herbicide-mediated reduction in host quality reduced fungal carbon storage, but not necessarily fungal abundance after one year in the field. Overall, in greenhouse and field experiments, AMF were only affected when picloram altered host quantity and quality. This apparent lack of direct effect was supported by our in-vitro trial where picloram applied to AMF mycelia did not reduce fungal biomass and viability.We show that the herbicide picloram can have profound, indirect effects on AMF within a year. Depending on herbicide-mediated shifts in host quality, rapid interventions may be necessary post herbicide applications to prevent loss of AMF abundance. Future research should assess consequences of these potential shifts for the restoration of native plants that differ in mycorrhizal dependency.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-29T03:00:28.923055-05:
      DOI: 10.1002/eap.1613
       
  • Fit to predict' Ecoinformatics for predicting the catchability of a
           pelagic fish in near real-time
    • Authors: Kylie L. Scales; Elliott L. Hazen, Sara M. Maxwell, Heidi Dewar, Suzanne Kohin, Michael G. Jacox, Christopher A. Edwards, Dana K. Briscoe, Larry B. Crowder, Rebecca L. Lewison, Steven J. Bograd
      Abstract: The ocean is a dynamic environment inhabited by a diverse array of highly migratory species, many of which are under direct exploitation in targeted fisheries. The timescales of variability in the marine realm coupled with the extreme mobility of ocean-wandering species such as tuna and billfish complicates fisheries management. Developing ecoinformatics solutions that allow for near real-time prediction of the distributions of highly mobile marine species is an important step towards the maturation of dynamic ocean management and ecological forecasting.Using 25 years (1990-2014) of NOAA fisheries’ observer data from the California drift gillnet fishery, we model relative probability of occurrence (presence-absence) and catchability (total catch) of broadbill swordfish Xiphias gladius in the California Current System (CCS). Using freely-available environmental datasets and open source software, we explore the physical drivers of regional swordfish distribution. Comparing models built upon remotely-sensed datasets with those built upon a data-assimilative configuration of the Regional Ocean Modelling System (ROMS), we explore trade-offs in model construction and address how physical data can affect predictive performance and operational capacity.Swordfish catchability was found to be highest in deeper waters (>1500m) with surface temperatures in the 14-20°C range, isothermal layer depth (ILD) of 20-40m, positive sea surface height anomalies and during the new moon (
      PubDate: 2017-08-21T09:21:03.981438-05:
      DOI: 10.1002/eap.1610
       
  • Mammal diversity and metacommunity dynamics in urban green spaces:
           implications for urban wildlife conservation
    • Authors: Travis Gallo; Mason Fidino, Elizabeth W. Lehrer, Seth B. Magle
      Abstract: As urban growth expands and natural environments fragment, it is essential to understand the ecological roles fulfilled by urban green spaces. To evaluate how urban green spaces function as wildlife habitat, we estimated mammal diversity and metacommunity dynamics in city parks, cemeteries, golf courses, and natural areas throughout the greater Chicago, IL, USA region. We found similar α-diversity (with the exception of city parks), but remarkably dissimilar communities in different urban green spaces. Additionally, the type of urban green space greatly influenced species colonization and persistence rates. For example, coyotes (Canis latrans) had the highest, but white-tailed deer (Odocoileus virginianus) the lowest, probability of persistence in golf courses compared to other green space types. Further, most species had a difficult time colonizing city parks even when sites were seemingly available. Our results indicate that urban green spaces contribute different, but collectively important, habitats for maintaining and conserving biodiversity in cities.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-21T09:20:21.852745-05:
      DOI: 10.1002/eap.1611
       
  • Subcatchment deltas and upland features influence multiscale aquatic
           ecosystem recovery in damaged landscapes
    • Authors: Brian W. Kielstra; Shelley E. Arnott, John M. Gunn
      Abstract: Assessing biological recovery in damaged aquatic environments requires the consideration of multiple spatial and temporal scales. Past research has focused on assessing lake recovery from atmospheric or catchment disturbance at regional or catchment levels. Studies have also rarely considered the influences of adjacent terrestrial characteristics on within-lake habitats, such as subcatchment delta confluences. We used Hyalella azteca, a ubiquitous freshwater amphipod, as a sensitive indicator to assess the importance of local subcatchment scale factors in the context of multiscale lake recovery within the metal mining region of Sudbury, Canada following a period of major reductions in atmospheric pollution. At the regional scale, data from repeated surveys of 40 lakes showed higher probabilities of H. azteca occurrence with higher lake water conductivity, alkalinity, and pH and lower metal concentrations. The importance of metals decreased through time and the importance of higher conductivity, alkalinity, and pH increased. At the subcatchment scale, a subset of six lakes sampled across a colonization gradient revealed higher H. azteca abundances at subcatchment delta sites than non-delta sites in early colonization stages, and that abundance at delta sites was correlated with both within-lake habitat and terrestrial subcatchment characteristics. For example, wetland cover reduced the strength of positive associations between H. azteca abundance and macrophyte density. A single lake from this subset also revealed higher abundances at delta sites associated with higher concentrations of terrestrial organic matter and larger subcatchments. Our results demonstrate that factors affecting recovery can change with the scale of study, and that managing terrestrial-aquatic linkages is important for facilitating recovery processes within damaged lake ecosystems.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-07T07:15:20.831655-05:
      DOI: 10.1002/eap.1609
       
  • State-dependent behavior alters endocrine-energy relationship:
           implications for conservation and management
    • Authors: Brett R. Jesmer; Jacob R. Goheen, Kevin L. Monteith, Matthew J. Kauffman
      Abstract: Glucocorticoids (GC) and triiodothyronine (T3) are two endocrine markers commonly used to quantify resource limitation, yet the relationships between these markers and the energetic state of animals has been studied primarily in small-bodied species in captivity. Free-ranging animals, however, adjust energy intake in accordance with their energy reserves, a behavior known as state-dependent foraging. Further, links between life-history strategies and metabolic allometries cause energy intake and energy reserves to be more strongly coupled in small animals relative to large animals. Because GC and T3 may reflect energy intake or energy reserves, state-dependent foraging and body size may cause endocrine-energy relationships to vary among taxa and environments. To extend the utility of endocrine markers to large-bodied, free-ranging animals, we evaluated how state-dependent foraging, energy reserves, and energy intake influenced fecal GC and fecal T3 concentrations in free-ranging moose (Alces alces). Compared with individuals possessing abundant energy reserves, individuals with few energy reserves had higher energy intake and high fecal T3 concentrations, thereby supporting state-dependent foraging. Although fecal GC did not vary strongly with energy reserves, individuals with higher fecal GC tended to have fewer energy reserves and substantially greater energy intake than those with low fecal GC. Consequently, individuals with greater energy intake had both high fecal T3 and high fecal GC concentrations, a pattern inconsistent with previous documentation from captive animal studies. We posit that a positive relationship between GC and T3 may be expected in animals exhibiting state-dependent foraging if GC is associated with increased foraging and energy intake. Thus, we recommend that additional investigations of GC- and T3-energy relationships be conducted in free-ranging animals across a diversity of body size and life-history strategies before these endocrine markers are applied broadly to wildlife conservation and management.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-04T11:05:33.061321-05:
      DOI: 10.1002/eap.1608
       
  • A pesticide paradox: Fungicides indirectly increase fungal infections
    • Authors: Jason R. Rohr; Jenise Brown, William A. Battaglin, Taegan A. McMahon, Rick A. Relyea
      Abstract: There are many examples where the use of chemicals have had profound unintended consequences, such as fertilizers reducing crop yields (paradox of enrichment) and insecticides increasing insect pests (by reducing natural biocontrol). Recently, the application of agrochemicals, such as agricultural disinfectants and fungicides, has been explored as an approach to curb the pathogenic fungus, Batrachochytrium dendrobatidis (Bd), which is associated with worldwide amphibian declines. However, the long-term, net effects of early-life exposure to these chemicals on amphibian disease risk have not been thoroughly investigated. Using a combination of laboratory experiments and analysis of data from the literature, we explored the effects of fungicide exposure on Bd infections in two frog species. Extremely low concentrations of the fungicides azoxystrobin, chlorothalonil, and mancozeb were directly toxic to Bd in culture. However, estimated environmental concentrations of the fungicides did not reduce Bd on Cuban tree frog (Osteopilus septentrionalis) tadpoles exposed simultaneously to any of these fungicides and Bd, and fungicide exposure actually increased Bd-induced mortality. Additionally, exposure to any of these fungicides as tadpoles resulted in higher Bd abundance and greater Bd-induced mortality when challenged with Bd post-metamorphosis, an average of 71 days after their last fungicide exposure. Analysis of data from the literature revealed that previous exposure to the fungicide itraconazole, which is commonly used to clear Bd infections, made the critically endangered booroolong frog (Litoria booroolongensis) more susceptible to Bd. Finally, a field survey revealed that Bd prevalence was positively associated with concentrations of fungicides in ponds. Although fungicides show promise for controlling Bd, these results suggest that, if fungicides do not completely eliminate Bd or if Bd re-colonizes, exposure to fungicides has the potential to do more harm than good. To ensure that fungicide applications have the intended consequence of curbing amphibian declines, researchers must identify which fungicides do not compromise the pathogen resistance mechanisms of amphibians.This article is protected by copyright. All rights reserved.
      PubDate: 2017-08-01T09:45:50.000304-05:
      DOI: 10.1002/eap.1607
       
  • Modelling plant interspecific interactions from experiments of perennial
           crop mixtures to predict optimal combinations
    • Authors: Virginia Halty; Matías Valdés, Mauricio Tejera, Valentín Picasso, Hugo Fort
      Abstract: The contribution of plant species richness to productivity and ecosystem functioning is a long standing issue in Ecology, with relevant implications for both conservation and agriculture. Both experiments and quantitative modelling are fundamental to the design of sustainable agroecosystems and the optimization of crop production.We modelled communities of perennial crop mixtures by using a generalized Lotka-Volterra model, i.e. a model such that the interspecific interactions are more general than purely competitive. We estimated model parameters -carrying capacities and interaction coefficientsfrom, respectively, the observed biomass of monocultures and bicultures measured in a large diversity experiment of seven perennial forage species in Iowa, United States.The sign and absolute value of the interaction coefficients showed that the biological interactions between species pairs included amensalism, competition, and parasitism (asymmetric positive-negative interaction), with various degrees of intensity.We tested the model fit by simulating the combinations of more than two species and comparing them with the polycultures experimental data. Overall, theoretical predictions are in good agreement with the experiments.Using this model, we also simulated species combinations that were not sown. From all possible mixtures (sown and not sown) we identified which are the most productive species combinations.Our results demonstrate that a combination of experiments and modelling can contribute to the design of sustainable agricultural systems in general and to the optimization of crop production in particular.This article is protected by copyright. All rights reserved.
      PubDate: 2017-07-28T01:15:50.30046-05:0
      DOI: 10.1002/eap.1605
       
  • Predicting life history parameters for all fishes worldwide
    • Authors: James T. Thorson; Stephan B. Munch, Jason M. Cope, Jin Gao
      Abstract: Scientists and resource managers need to know life history parameters (e.g., average mortality rate, individual growth rate, maximum length or mass, and timing of maturity) to understand and respond to risks to natural populations and ecosystems. For over one-hundred years, scientists have identified “life history invariants” (LHI) representing pairs of parameters whose ratio is theorized to be constant across species. LHI then promise to allow prediction of many parameters from field-measurements of a few important traits. Using LHI in this way, however, neglects any residual patterns in parameters when making predictions. We therefore apply a multivariate model for eight variables (seven parameters and temperature) in all 32,000 marine fishes, and include taxonomic structure for residuals (with levels for class, order, family, genus, and species). We illustrate that this approach predicts variables probabilistically for taxa with many or few data. We then use this model to resolve three questions regarding life-history parameters in fishes. Specifically we show that: (1) on average there is a 1.24% decrease in the Brody growth coefficient for every 1% increase in maximum size; (2) the ratio of natural mortality rate and growth coefficient is not a LHI but instead varies systematically based on the timing of maturation, where movement along this life-history axis is predictably correlated with species taxonomy; and (3) three variables must be known per species to precisely predict remaining life-history variables. We distribute our predictive model as an R package to allow future life-history predictions for fishes to be conditioned on taxonomy and life-history data for fishes worldwide. This package also contains predictions (and predictive intervals) for mortality, maturity, size, and growth parameters for all described fishes.This article is protected by copyright. All rights reserved.
      PubDate: 2017-07-26T17:25:56.581437-05:
      DOI: 10.1002/eap.1606
       
  • Reproductive plasticity and landscape heterogeneity benefit a
           ground-nesting bird in a fire-prone ecosystem
    • Authors: J. Matthew Carroll; Torre J. Hovick, Craig A. Davis, R. Dwayne Elmore, Samuel D. Fuhlendorf
      Abstract: Disturbance is critical for the conservation of rangeland ecosystems worldwide and many of these systems are fire dependent. Although it is well established that restoring fire as an ecological process can lead to increased biodiversity in grasslands and shrublands, the underlying mechanisms driving community patterns are poorly understood for fauna in fire-prone landscapes. Much of this uncertainty stems from the paucity of studies that examine the effects of fire at scales relevant to organism life histories. We assessed the response of a non-migratory ground-dwelling bird to disturbance (i.e., prescribed fire) and environmental stochasticity over the course of a 4 year period, which spanned years of historic drought and record rainfall. Specifically, we investigated the nesting ecology of northern bobwhite (Colinus virginianus; hereafter bobwhite) to illuminate possible avenues by which individuals respond to dynamic landscape patterns during a critical reproductive stage (i.e., nesting) in a mixed-grass shrubland in western Oklahoma, USA. We found that bobwhites exhibited extreme plasticity in nest substrate use among time since fire categories (TSF) and subsequently maintained high nest survival (e.g., 57 – 70%). Bobwhites were opportunistic in nest substrate use among TSF categories (i.e., 72% of nest sites in shrubs in 0-12 months post fire compared to 71% in herbaceous vegetation in>36 months post fire), yet nesting decisions were first filtered by similar structural components (i.e., vertical and horizontal cover) within the vicinity of nest sites regardless of TSF category. Despite being a non-migratory and comparatively less mobile ground-nesting bird species, bobwhites adjusted to dynamic vegetation mosaics on a fire-prone landscape under stochastic climatic conditions which culminated in stable and high nest survival. Broadly, our findings provide a unique depiction of organism response strategies to fire at scales relevant to a critical life-stage, a topic that has been previously understudied and poorly understood. We also demonstrate how doing so can better inform conservation practices aimed at restoring fire regimes on grassland and shrubland landscapes.This article is protected by copyright. All rights reserved.
      PubDate: 2017-07-24T02:30:19.802093-05:
      DOI: 10.1002/eap.1604
       
  • Drivers of woody canopy water content responses to drought in a
           Mediterranean-type ecosystem
    • Authors: Tarin Paz-Kagan; Gregory P. Asner
      Abstract: Severe droughts increase physiological stress in woody plant species, which can lead to mortality, fundamentally altering the composition, structure, and biogeography of forests in many regions. Little is known, however, about the factors determining the physiological response of woody plants to drought at landscape scales. Our objective was to understand woody plant species responses to ongoing changes in climate, using remotely sensed canopy water content (CWC) as an indicator of plant physiological and phenological status. We used fused imaging spectroscopy and light detection and ranging (LiDAR) from the Carnegie Airborne Observatory (CAO) to quantify the factors affecting species compositional changes in CWC in a diverse Mediterranean-type ecosystem (Jasper Ridge Biological Preserve, CA) between 2013 and 2015. Mapped CWC was spatially variable in both of the observation years, and proved to be most closely tied to species composition and distribution across the landscape. The secondary predictors of CWC were elevation and soil substrate. In contrast, we found that CWC change was much more related to environmental factors than to the species composition. We suggest that the effect of environment on CWC change is mediated through species resistance and resilience to drought. Monitoring CWC change with imaging spectroscopy is a powerful approach to identifying species-level responses to climatic events and long-term change, which may provide support for policy decisions and conservation at large spatial scales.This article is protected by copyright. All rights reserved.
      PubDate: 2017-07-20T07:35:39.119396-05:
      DOI: 10.1002/eap.1603
       
  • Metacommunity Theory Meets Restoration: Isolation May Mediate How
           Ecological Communities Respond to Stream Restoration
    • Authors: Christopher M. Swan; Bryan L. Brown
      Abstract: An often-cited benefit of river restoration is an increase in biodiversity or shift in composition to more desirable taxa. Yet, hard manipulations of habitat structure often fail to elicit a significant response in terms of biodiversity patterns. In contrast to conventional wisdom, the dispersal of organisms may have as large an influence on biodiversity patterns as environmental conditions. This influence of dispersal may be particularly influential in river networks which are linear branching, or dendritic, and thus constrain most dispersal to the river corridor. As such, some locations in river networks, such as isolated headwaters, are expected to respond less to environmental factors and less by dispersal than more well-connected downstream reaches. We applied this metacommunity framework to study how restoration drives biodiversity patterns in river networks. By comparing assemblage structure in headwater versus more well-connected mainstem sites, we learned that headwater restoration efforts supported higher biodiversity, exhibited more stable ecological communities compared with adjacent, un-restored reaches. Such differences were not evident in mainstem reaches. Consistent with theory and mounting empirical evidence, we attribute this finding to a relatively higher influence of dispersal-driven factors on assemblage structure in more well-connected, higher order reaches. An implication of this work is that, if biodiversity is to be a goal of restoration activity, such local manipulations of habitat should elicit a more profound response in small, isolated streams than in larger downstream reaches. These results offer another significant finding supporting the notion that restoration activity cannot proceed in isolation of larger scale, catchment level degradation.This article is protected by copyright. All rights reserved.
      PubDate: 2017-07-17T22:25:32.212547-05:
      DOI: 10.1002/eap.1602
       
  • Detrital shadows: estuarine food web connectivity depends on fluvial
           influence and consumer feeding mode
    • Authors: Emily Howe; Charles A. Simenstad, Andrea Ogston
      Abstract: We measured the influence of landscape setting on estuarine food web connectivity in five macrotidal Pacific Northwest estuaries across a gradient of freshwater influence. We used stable isotopes (δ13C, δ15N, δ34S) in combination with a Bayesian mixing model to trace primary producer contributions to suspension- and deposit-feeding bivalve consumers (Mytilus trossulus and Macoma nasuta) transplanted into three estuarine vegetation zones: emergent marsh, mudflat, Japanese eelgrass (Zostera japonica), and native eelgrass (Zostera marina). Fluvial discharge and consumer feeding mode strongly influenced the strength and spatial scale of observed food web linkages, while season played a secondary role. Mussels displayed strong cross-ecosystem connectivity in all estuaries, with decreasing marine influence in the more fluvial estuaries. Mussel diets indicated homogenization of detrital sources within the water column of each estuary. In contrast, the diets of benthic deposit-feeding clams indicated stronger compartmentalization in food web connectivity, especially in the largest river delta where clam diets were trophically disconnected from marsh sources of detritus. This suggests detritus deposition is patchy across space, and less homogenous than the suspended detritus pool. In addition to fluvial setting, other estuary-specific environmental drivers, such as marsh area or particle transport speed, influenced the degree of food web linkages across space and time, often accounting for unexpected patterns in food web connectivity. Transformations of the estuarine landscape that alter river hydrology or availability of detritus sources can thus potentially disrupt natural food web connectivity at the landscape scale, especially for sedentary organisms which cannot track their food sources through space.This article is protected by copyright. All rights reserved.
      PubDate: 2017-07-17T22:22:50.261942-05:
      DOI: 10.1002/eap.1600
       
  • Patterns of mortality in a montane mixed-conifer forest in San Diego
           County, California
    • Authors: Mary Pyott Freeman; Douglas A. Stow, Li An
      Abstract: We examine spatial patterns of conifer tree mortality and their changes over time for the montane mixed-conifer forests of San Diego County. These forest areas have recently experienced extensive tree mortality due to multiple factors. A spatial contextual image processing approach was utilized with high spatial resolution digital airborne imagery to map dead trees for the years 1997, 2000, 2002, and 2005 for three study areas: Palomar, Volcan, and Laguna mountains. Plot-based fieldwork was conducted to further assess mortality patterns. Mean mortality remained static from 1997 to 2002 (4, 2.2, and 4.2 trees ha−1 for Palomar, Volcan, and Laguna) and then increased by 2005 to 10.3, 9.7 and 5.2 trees ha−1, respectively. The increase in mortality between 2002 and 2005 represents the temporal pattern of a discrete disturbance event, attributable to the 2002-2003 drought. Dead trees are significantly clustered for all dates, based on spatial cluster analysis, indicating that they form distinct groups, as opposed to spatially random single dead trees. Other tests indicate no directional shift or spread of mortality over time, but rather an increase in density. While general temporal and spatial mortality processes are uniform across all study areas, the plot-based species and quantity distribution of mortality, and diameter distributions of dead versus living trees, vary by study area. The results of this study improve our understanding of stand- to landscape-level forest structure and dynamics, particularly by examining them from the multiple perspectives of field and remotely sensed data.This article is protected by copyright. All rights reserved.
      PubDate: 2017-07-17T22:22:47.770381-05:
      DOI: 10.1002/eap.1601
       
  • Watershed Versus Within-Lake Drivers of Nitrogen: Phosphorus Dynamics in
           Shallow Lakes
    • Authors: Luke J. Ginger; Kyle D. Zimmer, Brian R. Herwig, Mark A. Hanson, William O. Hobbs, Gaston E. Small, James B. Cotner
      Abstract: Research on lake eutrophication often identifies variables affecting amounts of phosphorus (P) and nitrogen (N) in lakes, but understanding factors influencing N:P ratios is important given its influence on species composition and toxin production by cyanobacteria. We sampled 80 shallow lakes in Minnesota (USA) for three years to assess effects of watershed size, proportion of watershed as both row crop and natural area, fish biomass, and lake alternative state (turbid versus clear) on total N: total P (TN:TP), ammonium, total dissolved phosphorus (TDP), and seston stoichiometry. We also examined N:P stoichiometry in 20 additional lakes that shifted states during the study. Lastly, we assessed importance of denitrification by measuring denitrification rates in sediment cores from a subset of 34 lakes, and by measuring seston δ15N in four additional experimental lakes before and after they were experimentally manipulated from turbid to clear states. Results showed alternative state had the largest influence on overall N:P stoichiometry in these systems, as it had the strongest relationship with TN:TP, seston C:N:P, ammonium, and TDP. Turbid lakes had higher N at given levels of P than clear lakes, with TN and ammonium two-fold and 1.4-fold higher in turbid lakes, respectively. In lakes that shifted states, TN was three-fold higher in turbid lakes, while TP was only two-fold higher, supporting the notion N is more responsive to state shifts than is P. Seston δ15N increased after lakes shifted to clear states, suggesting higher denitrification rates may be important for reducing N levels in clear states, and potential denitrification rates in sediment cores were among the highest recorded in the literature. Overall, our results indicate lake state was a primary driver of N:P dynamics in shallow lakes, and lakes in clear states had much lower N at a given level of P relative to turbid lakes, likely due to higher denitrification rates. Shallow lakes are often managed for the clear-water state due to increased value as wildlife habitat. However, our results indicate lake state also influences N biogeochemistry, such that managing shallow lakes for the clear-water state may also mitigate excess N levels at a landscape scale.This article is protected by copyright. All rights reserved.
      PubDate: 2017-07-10T11:10:27.04232-05:0
      DOI: 10.1002/eap.1599
       
  • Natural succession on abandoned cropland effectively decreases the soil
           erodibility and improves the fungal diversity
    • Authors: Chao Zhang; Guobin Liu, Zilin Song, Dong Qu, Linchuan Fang, Lei Deng
      Abstract: Changes in plants and soils during natural succession have been evaluated, but little is known about the effects of succession on the activities of soil microbes and their interactions with soil erodibility. We conducted a field study on the Chinese Loess Plateau, typical of this semiarid area, to determine the effect of secondary succession on the stability of soil structure against erosion and on the composition of soil fungal communities. Characteristics of plant, soil, and fungal communities were assessed across a 30-year chronosequence of grassland developed from abandoned cropland. The diversity and composition of the fungal communities were determined using high-throughput sequencing of the internal transcribed spacer. Six grasslands were selected to represent different successional age-classes: 0 (cropland), 5, 10, 15, 20, and 30 y. Short-term decreases (initial 5 y) in the amounts of soil organic carbon, total nitrogen, available phosphorus, and fungal biomass and in fungal diversity had returned to original levels (i.e. cropland) within 15 y and were much higher after continued succession. Abandoning cropland for succession caused the soil erodibility (K) decrease and the aboveground coverage, soil nutrient levels, content of larger (> 5 mm) water-stable aggregate, mean aggregate weight diameter, and diversity of the fungal communities improvement including arbuscular mycorrhizas, ectomycorrhizas (EMF), and saprotrophs. The fungal communities were dominated by Ascomycota, Zygomycota, Basidiomycota, and Glomeromycota during the succession. The successional patterns of the plant and fungal communities were similar, although distinct fungal communities were not observed in the two initial stages, suggesting that fungal succession may develop more slowly than plant succession. Plant-roots biomass, EMF, and soil organic-carbon content accounted for most of the variation of soil erodibility (28.6, 19.5, and 11.8%, respectively), indicating their importance in shaping soil structure to prevent erosion. Our results demonstrated that abandoning cropland for natural succession could decrease soil erodibility and increase fungal diversity. EMF plays an important role in soil stability against erosion in the Loess Plateau. Abandoning cropland for natural succession should be recommended for alleviating soil erosion and improving the degraded soils in this area.This article is protected by copyright. All rights reserved.
      PubDate: 2017-07-06T05:35:57.534346-05:
      DOI: 10.1002/eap.1598
       
  • Predicting the abundance of forest types across the eastern U.S. through
           inverse modelling of tree demography
    • Authors: Mark C. Vanderwel; Danaë M.A. Rozendaal, Margaret E.K. Evans
      Abstract: Global environmental change is expected to induce widespread changes in the geographic distribution and biomass of forest communities. Impacts have been projected from both empirical (statistical) and mechanistic (physiology-based) modelling approaches, but there remains an important gap in accurately predicting abundance across species’ ranges from spatial variation in individual-level demographic processes. We address this issue by using a cohort-based forest dynamics model (CAIN) to predict spatial variation in the abundance of six plant functional types (PFTs) across the eastern U.S. The model simulates tree-level growth, mortality, and recruitment, which we parameterized from data on both individual-level demographic rates and population-level abundance using Bayesian inverse modelling. Across a set of 1° grid cells, we calibrated local growth, mortality, and recruitment rates for each PFT to obtain a close match between predicted age-specific PFT basal area in forest stands and that observed in 46 603 Forest Inventory and Analysis plots. The resulting models produced a strong fit to PFT basal area across the region (R2= 0.66-0.87), captured successional changes in PFT composition with stand age, and predicted the overall stem diameter distribution well. The mortality rates needed to accurately predict basal area were consistently higher than observed mortality, possibly because sampling effects led to biased individual-level mortality estimates across spatially heterogeneous plots. Growth and recruitment rates did not show consistent directional changes from observed values. Relative basal area was most strongly influenced by recruitment processes, but the effects of growth and mortality tended to increase as stands matured. Our study illustrates how both top-down (population-level) and bottom-up (individual-level) data can be combined to predict variation in abundance from size, environmental, and competitive effects on tree demography. Evidence for how demographic processes influence variation in abundance, as provided by our model, can help in understanding how these forests may respond to future environmental change.This article is protected by copyright. All rights reserved.
      PubDate: 2017-07-04T03:31:37.847708-05:
      DOI: 10.1002/eap.1596
       
  • Impact of disease on the survival of three commercially fished species
    • Authors: John M. Hoenig; Maya L. Groner, Matthew W. Smith, Wolfgang K. Vogelbein, David M. Taylor, Donald F. Landers, John Swenarton, David T. Gauthier, Philip Sadler, Mark Matsche, Ashley Haines, Hamish J. Small, Roger Pradel, Remi Choquet, Jeffrey D. Shields
      Abstract: Recent increases in emergent infectious diseases have raised concerns about the sustainability of some marine species. The complexity and expense of studying diseases in marine systems often dictate that conservation and management decisions are made without quantitative data on population-level impacts of disease. Mark-recapture is a powerful, underutilized, tool for calculating impacts of disease on population size and structure, even in the absence of etiological information.We applied logistic regression models to mark-recapture data to obtain estimates of disease-associated mortality rates in three commercially-important marine species: snow crab (Chionoecetes opilio) in Newfoundland, Canada, that experience sporadic epizootics of bitter crab disease; striped bass (Morone saxatilis) in the Chesapeake Bay, USA, that experience chronic dermal and visceral mycobacteriosis; and American lobster (Homarus americanus) in the Southern New England stock, that experience chronic epizootic shell disease. All three diseases decreased survival of diseased hosts. Survival of diseased adult male crabs was 1% (0.003 – 0.022, 95% CI) that of uninfected crabs indicating nearly complete mortality of infected crabs in this life stage. Survival of moderately and severely diseased striped bass (which comprised 15% and 11% of the population, respectively) was 84% (70 – 100%, 95% CI), and 54% (42- 68%, 95% CI) and that of healthy striped bass. The disease-adjusted yearly natural mortality rate for striped bass was 0.29, nearly double the previously accepted value, which did not include disease. Survival of moderately and severely diseased lobsters was 30% (15 – 60%, 95% CI) that of healthy lobsters and survival of mildly diseased lobsters was 45% (27 – 75%, 95% CI) that of healthy lobsters. High disease mortality in ovigerous females may explain the poor recruitment and rapid declines observed in this population. Stock assessments should account for disease-related mortality when resource management options are evaluated.This article is protected by copyright. All rights reserved.
      PubDate: 2017-07-04T03:25:18.872753-05:
      DOI: 10.1002/eap.1595
       
  • Understanding the demographic drivers of realized population growth rates
    • Authors: David N. Koons; Todd W. Arnold, Michael Schaub
      Abstract: Identifying the demographic parameters (e.g., reproduction, survival, dispersal) that most influence population dynamics can increase conservation effectiveness and enhance ecological understanding. Life table response experiments (LTRE) aim to decompose the effects of change in parameters on past demographic outcomes (e.g., population growth rates). But the vast majority of LTREs and other retrospective population analyses have focused on decomposing asymptotic population growth rates, which do not account for the dynamic interplay between population structure and vital rates that shape realized population growth rates (λt = Nt+1/Nt) in time-varying environments. We provide an empirical means to overcome these shortcomings by merging recently developed “transient life-table response experiments” with integrated population models (IPMs). IPMs allow for the estimation of latent population structure and other demographic parameters that are required for transient LTRE analysis, and Bayesian versions additionally allow for complete error propagation from the estimation of demographic parameters to derivations of realized population growth rates and perturbation analyses of growth rates. By integrating available monitoring data for lesser scaup over 60 years, and conducting transient LTREs on IPM estimates, we found that the contribution of juvenile female survival to long-term variation in realized population growth rates was 1.6 and 3.7 times larger than that of adult female survival and fecundity, respectively. But a persistent long-term decline in fecundity explained 92% of the decline in abundance between 1983 and 2006. In contrast, an improvement in adult female survival drove the modest recovery in lesser scaup abundance since 2006, indicating that the most important demographic drivers of lesser scaup population dynamics are temporally dynamic. In addition to resolving uncertainty about lesser scaup population dynamics, the merger of IPMs with transient LTREs will strengthen our understanding of demography for many species as we aim to conserve biodiversity during an era of non-stationary global change.This article is protected by copyright. All rights reserved.
      PubDate: 2017-07-04T02:35:22.702229-05:
      DOI: 10.1002/eap.1594
       
  • Modeling the impacts of two age–related portfolio effects on recruitment
           variability with and without a marine reserve
    • Authors: Carey R. McGilliard; André E. Punt, Ray Hilborn, Tim Essington
      Abstract: Many rockfish species are long-lived and thought to be susceptible to being overfished. Hypotheses about the importance of older female rockfish to population persistence have led to arguments that marine reserves are needed to ensure the sustainability of rockfish populations. However, the implications of these hypotheses for rockfish population dynamics are still unclear. We modeled two mechanisms by which reducing the proportion of older fish in a population has been hypothesized to influence sustainability, and explored whether these mechanisms influenced mean population dynamics and recruitment variability. We explored whether populations with these mechanisms could be managed more sustainably with a marine reserve in addition to a constant fishing mortality rate (F) than with a constant F alone. Both hypotheses can be seen as portfolio effects whereby risk of recruitment failure is spread over a “portfolio” of maternal ages. First, we modeled a spawning window effect whereby mothers of different ages spawned in different times or locations (windows) with local environmental conditions. Second, we modeled an offspring size effect whereby older mothers produced larger offspring than younger mothers, where length of a starvation period over which offspring could survive increased with maternal age. Recruitment variability resulting from both models was 55-65% lower than for models without maternal age-related portfolio effects in the absence of fishing and increased with increases in Fs for both models. An offspring size effect caused lower output reproductive rates such that the specified reproductive rate input as a model parameter was no longer the realized rate measured as the reproductive rate observed in model results; this quirk is not addressed in previous analyses of offspring size effects. We conducted a standardization such that offspring size effect and control models had the same observed reproductive rates.A comparison of long-term catch, the probability of falling below a biomass threshold, and recruitment variability over a range of exploitation rates for models with an age–related portfolio effect showed no benefit of a marine reserve implemented in addition to a constant F (as compared to a constant F alone) for populations with sedentary adults and sedentary or mobile larvae.This article is protected by copyright. All rights reserved.
      PubDate: 2017-07-01T07:33:39.373523-05:
      DOI: 10.1002/eap.1593
       
  • Defaunation and habitat disturbance interact synergistically to alter
           seedling recruitment
    • Authors: Alys Granados; Jedediah F. Brodie, Henry Bernard, Michael J. O'Brien
      Abstract: Vertebrate granivores destroy plant seeds, but whether animal-induced seed mortality alters plant recruitment varies with habitat context, seed traits, and among granivore species. An incomplete understanding of seed predation makes it difficult to predict how widespread extirpations of vertebrate granivores in tropical forests might affect tree communities, especially in the face of habitat disturbance. Many tropical forests are simultaneously affected by animal loss as well as habitat disturbance, but the consequences of each for forest regeneration are often studied separately or additively, and usually on a single plant demographic stage. The combined impacts of these threats could affect plant recruitment in ways that are not apparent when studied in isolation. We used wire cages to exclude large (elephants), medium, (sambar deer, bearded pigs, muntjac deer) and small (porcupines, chevrotains) ground-dwelling mammalian granivores and herbivores in logged and unlogged forests in Malaysian Borneo. We assessed the interaction between habitat disturbance (selective logging) and experimental defaunation on seed survival, germination, and seedling establishment in five dominant dipterocarp tree species spanning a 21-fold gradient in seed size. Granivore-induced seed mortality was consistently higher in logged forest. Germination of unpredated seeds was reduced in logged forest and in the absence of small to large-bodied mammals. Experimental defaunation increased germination and reduced seed removal but had little effect on seed survival. Seedling recruitment however, was more likely where logging and animal loss occurred together. The interacting effects of logging and hunting could therefore, actually increased seedling establishment, suggesting that the loss of mammals in disturbed forest could have important consequences for forest regeneration and composition.This article is protected by copyright. All rights reserved.
      PubDate: 2017-06-29T02:50:20.204806-05:
      DOI: 10.1002/eap.1592
       
  • Breeding density, fine-scale tracking and large-scale modeling reveal the
           regional distribution of four seabird species
    • Authors: Ewan D. Wakefield; Ellie Owen, Julia Baer, Matthew J. Carroll, Francis Daunt, Stephen G. Dodd, Jonathan A. Green, Tim Guilford, Roddy A. Mavor, Peter I. Miller, Mark A. Newell, Stephen F. Newton, Gail S. Robertson, Akiko Shoji, Louise M. Soanes, Stephen C. Votier, Sarah Wanless, Mark Bolton
      Abstract: Population-level estimates of species’ distributions can reveal fundamental ecological processes and facilitate conservation. However, these may be difficult to obtain for mobile species, especially colonial central-place foragers (CCPFs; e.g. bats, corvids, social insects), because it is often impractical to determine the provenance of individuals observed beyond breeding sites. Moreover, some CCPFs, especially in the marine realm (e.g. pinnipeds, turtles and seabirds) are difficult to observe because they range 10s to 10,000s km from their colonies. It is hypothesized that the distribution of CCPFs depends largely on habitat availability and intraspecific competition. Modeling these effects may therefore allow distributions to be estimated from samples of individual spatial usage. Such data can be obtained for an increasing number of species using tracking technology. However, techniques for estimating population-level distributions using the telemetry data are poorly developed. This is of concern because many marine CCPFs, such as seabirds, are threatened by anthropogenic activities. Here, we aim to estimate the distribution at sea of four seabird species, foraging from approximately 5500 breeding sites in Britain and Ireland. To do so, we GPS-tracked a sample of 230 European shags Phalacrocorax aristotelis, 464 black-legged kittiwakes Rissa tridactyla, 178 common murres Uria aalge and 281 razorbills Alca torda from 13, 20, 12 and 14 colonies respectively. Using Poisson point process habitat use models, we show that distribution at sea is dependent on: (i) density-dependent competition among sympatric conspecifics (all species) and parapatric conspecifics (kittiwakes and murres); (ii) habitat accessibility and coastal geometry, such that birds travel further from colonies with limited access to the sea; and (iii) regional habitat availability. Using these models, we predict space use by birds from unobserved colonies and thereby map the distribution at sea of each species at both the colony and regional level. Space use by all four species’ British breeding populations is concentrated in the coastal waters of Scotland, highlighting the need for robust conservation measures in this area. The techniques we present are applicable to any CCPF.This article is protected by copyright. All rights reserved.
      PubDate: 2017-06-27T01:07:38.270043-05:
      DOI: 10.1002/eap.1591
       
  • Experimental warming alters migratory caribou forage quality
    • Authors: Tara J. Zamin; Steeve D. Côté, Jean-Pierre Tremblay, Paul Grogan
      Abstract: Global declines in caribou and reindeer (Rangifer) populations have drawn attention to the myriad of stressors that these arctic and boreal forest herbivores currently face. Arctic warming has resulted in increased tundra shrub growth and therefore Rangifer forage quantity. However, its effects on forage quality have not yet been addressed although they may be critical to Rangifer body condition and fecundity. We investigated the impact of summer warming on the quality of forage available to the Bathurst caribou herd using experimental greenhouses (n=5) located in mesic birch hummock tundra in the central Canadian Low Arctic. Leaf forage quality and digestibility characteristics associated with nutrients (nitrogen and phosphorus), phenolics, and fiber were measured on the deciduous shrub Betula glandulosa (an important Rangifer diet component) at six time points through the growing season, and on five other very common vascular plant and lichen species in late-summer.Experimental warming reduced B. glandulosa leaf nitrogen concentrations by ~10% in both late June and mid-July, but not afterwards. It also reduced late summer forage quality of the graminoid Eriophorum vaginatum by increasing phenolic concentrations. Warming had mixed effects on forage quality of the lichen Cetraria cucullata in that it increased concentrations of nutrients and tended to decrease fiber contents, but it also increased phenolics. Altogether, these warming-induced changes in forage quality over the growing season, and response differences among species, highlight the importance of Rangifer adaptability in diet selection. Furthermore, the early season reduction in B. glandulosa nitrogen content is a particular concern given the importance of this time for calf growth. Overall, our demonstration of the potential for significant warming impacts on forage quality at critical times for these animals underscores the importance of effective Rangifer range conservation to ensure sufficient appropriate habitat to support adaptability in forage selection in a rapidly changing environment.This article is protected by copyright. All rights reserved.
      PubDate: 2017-06-27T01:02:37.605291-05:
      DOI: 10.1002/eap.1590
       
  • Prediction in ecology: a first-principles framework
    • Authors: Michael C. Dietze
      Abstract: Quantitative predictions are ubiquitous in ecology, yet there is limited discussion on the nature of prediction in this field. Herein I derive a general quantitative framework for analyzing and partitioning the sources of uncertainty that control predictability. The implications of this framework are assessed conceptually and linked to classic questions in ecology, such as the relative importance of endogenous (density dependent) versus exogenous factors, stability versus drift, and the spatial scaling of processes. The framework is used to make a number of novel predictions and reframe approaches to experimental design, model selection, and hypothesis testing. Next, the quantitative application of the framework to partitioning uncertainties is illustrated using a short-term forecast of net ecosystem exchange. Finally, I advocate for a new comparative approach to studying predictability across different ecological systems and processes and lay out a number of hypotheses about what limits predictability and how these limits should scale in space and time.This article is protected by copyright. All rights reserved.
      PubDate: 2017-06-24T09:18:10.896582-05:
      DOI: 10.1002/eap.1589
       
  • Pairing field methods to improve inference in wildlife surveys while
           accommodating detection covariance
    • Authors: John Clare; Shawn T. McKinney, John E. DePue, Cynthia S. Loftin
      Abstract: It is common to use multiple field sampling methods when implementing wildlife surveys to compare method efficacy or cost-efficiency, integrate distinct pieces of information provided by separate methods, or evaluate method-specific biases and misclassification error. Existing models that combine information from multiple field methods or sampling devices permit rigorous comparison of method-specific detection parameters, enable estimation of additional parameters such as false-positive detection probability, and improve occurrence or abundance estimates, but with the assumption that the separate sampling methods produce detections independently of one another. This assumption is tenuous if methods are paired or deployed in close proximity simultaneously, a common practice that reduces the additional effort required to implement multiple methods and reduces the risk that differences between method-specific detection parameters are confounded by other environmental factors. We develop occupancy and spatial capture-recapture models that permit covariance between the detections produced by different methods, use simulation to compare estimator performance of the new models to models assuming independence, and provide an empirical application based upon American marten (Martes americana) surveys using paired remote cameras, hair-catches, and snow tracking. Simulation results indicate existing models that assume that methods independently detect organisms produce biased parameter estimates and substantially understate estimate uncertainty when this assumption is violated, while our reformulated models are robust to either methodological independence or covariance. Empirical results suggested that remote-cameras and snow-tracking had comparable probability of detecting present martens, but that snow-tracking also produced false-positive marten detections that could potentially substantially bias distribution estimates if not corrected for. Remote cameras detected marten individuals more readily than passive hair-catches. Inability to photographically distinguish individual sex did not appear to induce negative bias in camera density estimates; instead, hair-catches appeared to produce detection competition between individuals that may have been a source of negative bias. Our model reformulations broaden the range of circumstances in which analyses incorporating multiple sources of information can be robustly used, and our empirical results demonstrate that using multiple field-methods can enhance inferences regarding ecological parameters of interest and improve understanding of how reliably survey methods sample these parameters.This article is protected by copyright. All rights reserved.
      PubDate: 2017-06-23T09:56:50.174427-05:
      DOI: 10.1002/eap.1587
       
  • Evidence of fuels management and fire weather influencing fire severity in
           an extreme fire event
    • Authors: Jamie M. Lydersen; Brandon M. Collins, Matthew L. Brooks, John R. Matchett, Kristen L. Shive, Nicholas A. Povak, Van R. Kane, Douglas F. Smith
      Abstract: Following changes in vegetation structure and pattern, along with a changing climate, large wildfire incidence has increased in forests throughout the western U.S. Given this increase there is great interest in whether fuels treatments and previous wildfire can alter fire severity patterns in large wildfires. We assessed the relative influence of previous fuels treatments (including wildfire), fire weather, vegetation and water balance on fire severity in the Rim Fire of 2013. We did this at three different spatial scales to investigate whether the influences on fire severity changed across scales. Both fuels treatments and previous low to moderate severity wildfire reduced the prevalence of high severity fire. In general, areas without recent fuels treatments and areas that previously burned at high severity tended to have a greater proportion of high severity fire in the Rim Fire. Areas treated with prescribed fire, especially when combined with thinning, had the lowest proportions of high severity. Proportion of the landscape burned at high severity was most strongly influenced by fire weather and proportional area previously treated for fuels or burned by low to moderate severity wildfire. The proportion treated needed to effectively reduce the amount of high fire severity fire varied by spatial scale of analysis, with smaller spatial scales requiring a greater proportion treated to see an effect on fire severity. When moderate and high severity fire encountered a previously treated area, fire severity was significantly reduced in the treated area relative to the adjacent untreated area. Our results show that fuels treatments and low to moderate severity wildfire can reduce fire severity in a subsequent wildfire, even when burning under fire growth conditions. These results serve as further evidence that both fuels treatments and lower severity wildfire can increase forest resilience.This article is protected by copyright. All rights reserved.
      PubDate: 2017-06-23T09:45:19.19783-05:0
      DOI: 10.1002/eap.1586
       
  • Long-term belowground effects of grassland management: the key role of
           liming
    • Authors: Jemma Heyburn; Paul McKenzie, Michael J. Crawley, Dario A. Fornara
      Abstract: The functioning of human-managed grassland ecosystems strongly depends on how common management practices will affect grassland ‘belowground compartment’ including soil biogeochemistry and plant roots. Key questions remain about how animal grazing, liming (e.g. the addition of CaCO3 to soils), and nutrient fertilization might affect, in the long-term, soil nutrient cycling and multiple root traits. Here we focus on a mesotrophic grassland located in Berkshire, UK, where contrasting levels of rabbit grazing, liming and different inorganic fertilizers have been applied since 1991. We ask how (1) soil nitrogen (N) availability and cycling, (2) total root mass, (3) root mass decomposition, and (4) arbuscular mycorrhizal fungal (AMF) root colonisation might respond to 22 years of very different management. We found that liming strongly affected total root mass, root decomposition, root AMF colonisation as well as soil N availability and cycling and that these effects were mainly driven by liming-induced increases in soil pH. Increases in soil pH were associated with significant (1) decreases in root mass, (2) increases in root mass decomposability and in the mineralization of N in decomposing root detritus, and (3) increases in AMF infection. Soil pH was also significantly related to greater N availability (i.e. soil NO3 levels) and to lower δ15N natural abundance, which suggests more efficient N uptake by plants in limed soils as we found in our study. The application of multiple nutrients (NPKMg) also reduced total root mass, while N-only fertilization was associated with greater AMF infection. Surprisingly the long-term impact of grazing was generally weak and not significant on most plant and soil parameters. Despite soil pH affecting most belowground variables, changes in soil pH were not associated with any change in soil C and N stocks. Because liming can improve nutrient cycling (and benefits soil pH and grass yields) without negatively affecting soil C sequestration, we suggest that regular liming applications may provide management solutions for increasing the long-term sustainability of permanent grassland.This article is protected by copyright. All rights reserved.
      PubDate: 2017-06-21T05:10:33.162975-05:
      DOI: 10.1002/eap.1585
       
  • Issue Information
    • Pages: 1981 - 1983
      PubDate: 2017-10-02T09:20:00.059273-05:
      DOI: 10.1002/eap.1635
       
 
 
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