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Abstract: Abstract Evidence points out that increasing plant productivity associated with greater erect shrub abundance alters soil organic carbon (SOC) stocks in the Arctic. However, the underlying plant economic traits remain poorly examined, which limits our understanding of plant–environment interactions driving tundra carbon cycling. We explored how erect shrub abundance leads to SOC variation in a High Arctic tundra (Bylot Island, Nunavut, Canada), where the only erect shrub, Salix richardsonii, has settled along currently active and abandoned channel zones of alluvial fans. The effects of vegetation and local environmental changes on SOC were evaluated through a paired sampling of soil materials and plant aboveground functional traits associated with plant carbon supply and nutrient demand processes. The occurrence of S. richardsonii, characterized by a tenfold increase in aboveground biomass, induced a 28% increase in SOC compared to adjacent plots dominated by prostrate shrubs and graminoids. Yet, this vegetation effect was solely observed along active channels, where higher SOC was associated with greater leaf and stem biomass. A path analysis showed that shrub leaf area index and total leaf nutrient content best represented plant carbon supply and nutrient demand dynamics, respectively, and jointly regulated SOC variation. This study underscores that vegetation structural changes associated with increasing erect shrub abundance in the Arctic can promote soil organic carbon storage, but that this pattern may be mediated by strong plant–environment interactions. Accounting for changes in functional traits driving plant carbon supply and nitrogen demand proves important for a better mechanistic understanding of how shrubification impacts tundra carbon cycling. PubDate: 2023-03-17
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Abstract: Abstract Drought timing determines the degree to which dry events impact ecosystems, with the ability of key processes to withstand change differing between drought periods. Findings indicate that drought timing effects vary across ecosystems, with few studies focusing on alpine grasslands. We conducted a mesocosm experiment using small grassland monoliths collected in September from the high Alps and left to overwinter at 0 °C until the experiment began in lowland Italy under late-winter outdoor conditions. Together with watered controls, we imposed three different drought treatments (zero precipitation): (1) one-month early-drought immediately after simulated snowmelt; (2) one-month mid-drought a month after melt-out; and (3) continuous two-month drought across the entire experimental period. Ecosystem responses were assessed by measuring CO2 fluxes, while vegetation responses were investigated by measuring aboveground net primary production (ANPP) of graminoids and forbs and post-harvest resprouting after one-month rehydration. We found that ecosystem respiration and gross ecosystem production (GEP) during the day were more negatively affected by mid-season drought compared to drought starting early in the season. By the end of treatments, GEP reduction under mid-season drought was similar to that of a continuous two-month drought. ANPP reduction was similar in early- and mid-drought treatments, showing a greater decrease under an enforced two-month period without precipitation. Plant resprouting, however, was only reduced in full- and mid-season drought pots, with forbs more negatively affected than graminoids. Seasonal soil moisture variation can account for these patterns: remaining winter moisture allowed almost full canopy development during the first month of the season, despite precipitation being withheld, while soil moisture depletion in the second month, resulting from higher temperatures and greater biomass, caused a collapse of gas exchange and diminished plant resprouting. Our data illustrates the importance of the timing of zero-precipitation periods for both plant and ecosystem responses in alpine grasslands. PubDate: 2023-03-14
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Abstract: Abstract Anticipating consequences of disturbance interactions on ecosystem structure and function is a critical management priority as disturbance activity increases with warming climate. Across the Northern Hemisphere, extensive tree mortality from recent bark beetle outbreaks raises concerns about potential fire behavior and post-fire forest function. Silvicultural treatments (that is, partial or complete cutting of forest stands) may reduce outbreak severity and subsequent fuel loads, but longevity of pre-outbreak treatment effects on outbreak severity and post-outbreak fuel profiles remains underexplored. Further, treatments may present tradeoffs for other management objectives focused on ecosystem services (for example, carbon storage). We measured structure in old-growth subalpine forests following a recent (early 2000s) severe mountain pine beetle (MPB; Dendroctonus ponderosae) outbreak to examine effects of historical (1940s) cutting intensity on gray stage (~10 years after peak of outbreak) post-outbreak (1) fuel profiles and (2) aboveground biomass carbon. Compared to control (uncut) stands, historically cut stands subjected to the same MPB outbreak had approximately half the post-outbreak surface fuel loads, about 2–3x greater live canopy fuel loads, and greater within-stand spatial heterogeneity of dead canopy cover and available canopy fuel load. Post-outbreak total aboveground biomass carbon was similar across all stands, though historically cut stands had about 2x greater carbon in live biomass compared to uncut stands. These findings suggest tradeoffs with altered post-outbreak potential fire behavior and carbon storage in cut stands. Additional implications of historical silvicultural treatments for wildlife habitat, firefighting operations, and long-term carbon trajectories highlight temporal legacies of management on directing forest response to interacting disturbances. PubDate: 2023-03-13
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Abstract: Abstract Land-use changes affect terrestrial ecosystem carbon (C), nitrogen (N), and phosphorus (P) dynamics directly by altering above- and belowground litter inputs and decomposition, although the determining factors and their linkage to soil C, N, and P pools remain limited. Here, we investigated litter, soil, and microbial attributes during leaf and fine-root decomposition linked with soil C, N, and P pools under subtropical land-use change (that is, cropland, shrubland, and woodland). We found that leaf litter decomposed faster in shrubland than in woodland and cropland, while the fine root of cropland decomposed more than those of shrubland and woodland. Leaf and fine-root decomposition was not correlated, whereas leaf and fine-root litter quality was positively correlated. Leaf litter decomposition was considerably dependent on litter quality and soil moisture, whereas fine-root decomposition was predominantly predicted by bacterial biomass. Litter C quality in afforested lands (woodland and shrubland) substantially stimulated soil organic C accumulation primarily by the input of new fine-root-derived soil organic C. Soil total N accumulation in woodland was tightly associated with litter quality of fine root and microbial attributes, but soil total P formation in shrubland was strongly correlated with leaf litter quality and microbial attributes. These findings indicated that the variations in decomposition of leaf and fine root were mediated by different combinations of litter, soil, and microbial traits, which caused the difference in the soil C, N, and P accumulation following land-use change. Overall, our results revealed contrasting dynamics of above- and belowground litter decomposition, uncovered diverse influences on soil C, N, and P pools, and provided novel insights into accurately predicting soil C, N, and P dynamics after afforestation. PubDate: 2023-03-07
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Abstract: Abstract Seagrass beds in Florida Bay are home to many ecologically and economically important species. Anthropogenic press perturbation via alterations in hydrology and pulse perturbations such as drought can lead to hypersalinity, hypoxia, and sulfide toxicity, ultimately causing seagrass die-offs. Florida Bay has undergone two large-scale seagrass die-offs, the first in the late 1980s and early 1990s and the second in 2015. Post-die-off events, samples were collected for stable isotope analysis. Using historical (1998–1999) and contemporary (2018) stable isotope data, we examine how food webs in Florida Bay have changed in response to seagrass die-off over time by measuring contributions of basal sources to energy usage and using trophic niche analysis to compare niche size and overlap. We examined three consumer species sampled in both time periods (Orthopristis chrysoptera, Lagodon rhomboides, and Eucinostomus gula) in our study. Seagrass production comprised the majority of source usage in both datasets. However, contemporary consumers had a mean increase of 18% seagrass usage and a mean decrease in epiphyte usage of 7%. The shift in trophic niche from epiphyte usage (green pathway) toward seagrass usage (brown pathway) may indicate that food web browning is occurring in Florida Bay. PubDate: 2023-02-24
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Abstract: Abstract Many vegetated coastal ecosystems are formed through ecosystem engineering by clonal vegetation. Recent work highlights that the spatial shoot organization of the vegetation determines local sediment accretion and subsequently emerging landscape morphology. While this key engineering trait has been found to differ between species and prevailing environmental conditions, it remains unknown how the interplay of both factors drive shoot organization and therefore landscape morphology. Here, we compared the spatial shoot organization of young, clonally expanding plants of the two dominant European dune grass species: sand couch (Elytrigia juncea) and marram grass (Ammophila arenaria) across a range of coastal dune environments (from Denmark to France). Our results reveal that, on average, sand couch deployed a more dispersed shoot organization than marram grass, which has a patchy (Lévy-like) organization. Whereas sand couch exhibited the same expansion strategy independent of environmental conditions, marram grass demonstrated a large intraspecific variation which correlated to soil organic matter, temperature and grain size. Shoot patterns ranged from a clumped organization correlating to relatively high soil organic matter contents, temperature and small grain sizes, to a patchy configuration with intermediate conditions, and a dispersed organization with low soil organic matter, temperature and large grain size. We conclude that marram grass is flexible in adjusting its engineering capacity in response to environmental conditions, while sand couch instead follows a fixed expansion strategy, illustrating that shoot organization results from the interaction of both species-specific and environmental-specific trait expression. PubDate: 2023-02-21
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Abstract: Abstract Asymbiotic N2 fixation (ANF) is a major nitrogen (N) input pathway to terrestrial ecosystems. However, there is considerable uncertainty about how lithology affects ANF. Here, we measured ANF rates in soil, litter, and moss in forests underlain by limestone (limestone forest), dolomite (dolomite forest), and clasolite (clasolite forest), respectively, in southwest China. Effects of lithology on soil ANF rate varied seasonally. The rate was highest in the dolomite forest during the wet season, but was highest in the limestone forest during the dry season. The overall soil ANF rate was significantly higher in the limestone forest than in the clasolite forest. Litter ANF rate was significantly higher in the limestone forest and dolomite forest than in the clasolite forest regardless of season. There was no significant difference in moss ANF rate among the three types of forests in both seasons. The annual N2 fixation rate was highest in the limestone forest (1.72 ± 0.27 kg N ha−1 y−1) but lowest in the clasolite forest (0.70 ± 0.08 kg N ha−1 y−1). In the wet season, the variation of ANF rates was best explained by soil nitrate and available iron for soil, and by litter N and calcium content for litter. In the dry season, the variation of ANF rates was best explained by soil water content, ammonia and total phosphorus for soil, and by litter water content and calcium content for litter. No strong explanatory variables were identified for ANF in moss during the wet or dry season. Our findings suggest that lithology significantly affected ANF in soil and litter, but not in moss, and hence should be considered in Earth system models to facilitate better prediction of N inputs via biological N2 fixation under global change. PubDate: 2023-02-08
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Abstract: Abstract Anthropic activities have modelled and simplified southern European forest landscapes for centuries. Over recent decades, new drivers related to human-mediated global change have induced the redistribution of tree species and an increase in more complex forests. However, the current large-scale patterns and drivers of these changes are yet to be fully described for the Mediterranean Basin. In this frame, this work identifies and examines changes in dominance and composition from pure to mixed forests across bioclimatic gradients and forest types in Iberian forests over recent decades based on data from the Spanish National Forest Inventory from 1960 to 2020. Then, considering different environmental, anthropic, and disturbance variables we also identify some of the most important drivers associated with the shifts observed from 1986 to 2020. Our results confirm an ongoing increase in mixed forests involving the replacement of conifers by broadleaved species. These shifts are greater in the Atlantic biogeoregion and in pure broadleaved deciduous forests. Climate warming-associated disturbances such as drought severity together with land use legacies and forest types showed the strongest relationships with the observed changes in the studied forests. Our results support the premise put forward by palaeoecologists which states that the increase in tree mixtures is a natural process reversing the historical human-induced simplification of Iberian forests. The increasing importance of mixed forest in southern Europe makes decisive the revision of forest classifications as well as forest management and conservation plans in order to include these increasingly abundant novel stands in forest policies. PubDate: 2023-02-07
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Abstract: Abstract Trends for increased vegetation greenness based on satellite-derived data have been repeatedly published for the temperate grassland biome (including forest steppes) of eastern Inner Asia since 1982. Although this greening trend has been attenuated or partially reversed by drought in the early twenty-first century, linear increases in the Normalized Difference Vegetation Index (NDVI) or other parameters of vegetation greenness are nevertheless evident when the period since 1982 is regarded. However, the question arises whether these trends are part of a long-term trend driven by climate change, as simultaneously forests in the region show widespread drought-induced growth reductions and mortality outbreaks. Therefore, we hypothesized that the post-1982 greening trend was neither part of a long-term trend nor unprecedented. To test this hypothesis, we analyzed monthly maximum NDVI data from AVHRR time series and correlated these data with standardized tree-ring data of Larix sibirica from two regions of western Mongolia. We used linear regression to model the NDVI from tree-ring anomalies and to reconstruct the NDVI since 1940. These reconstructions show that the availability of satellite-based NDVI data coincidentally began during a dry period of low vegetation greenness in the early 1980s and was followed by a wet phase in the 1990s, producing the linear greening trend. No positive long-term trend in the reconstructed NDVI was observed from 1940 to 2010. This result rules out a recent climate change-driven greening trend for the grasslands and forest steppes of western Mongolia and calls into question its existence for all of eastern Inner Asia. PubDate: 2023-02-02
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Abstract: Abstract Silicon is an essential or beneficial element in many organisms. Silicon uptake by vegetation strongly influences terrestrial silicon dynamics; however, little is known about the changes in plant silicon cycling during secondary succession. We hypothesized that the community-weighted mean (CWM) leaf silicon concentration changes along a secondary successional gradient because of turnover of species that differ in silicon uptake. We also hypothesized that the concentration of water-soluble soil silicon should increase with silicon input to the upper soil layer by increasing leaf litterfall. This study tested these predictions using chronosequence plots with stand ages of 16–100 years of secondary succession in a cool-temperate forest in Hokkaido, Japan. We measured the levels of leaf silicon in 36 woody species, leaf litter silicon, and water-extractable soil silicon and examined their correlations with stand age. The leaf silicon concentration varied by 17-fold from 0.6 to 10.3 mg Si g−1, with strong phylogenetic signals among woody species. Reflecting the turnover of species and change in their abundance, the CWM leaf and leaf litter silicon concentrations increased with stand age. In contrast, water-extractable soil silicon concentration decreased despite an increase in leaf-litter silicon flux. The water-extractable soil silicon concentration was strongly and positively correlated with the soil carbon concentration, which decreased with stand age. Our results suggest that during secondary succession, forest silicon dynamics are largely associated with changes in the abundance of silicon-accumulating woody plants and soil carbon dynamics, which potentially influences other silicon-dependent organisms in the ecosystem. PubDate: 2023-01-30
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Abstract: Abstract Inter-annual climatically driven growth variability of above-ground biomass compartments (for example, tree stems and foliage) controls the intensity of carbon sequestration into forest ecosystems. However, understanding the differences between the climatic response of stem and foliage at the landscape level is limited. In this study, we examined the climate-growth response of stem and leaf biomass and their relationship for Pinus sylvestris (PISY) and Picea abies (PCAB) in topographically complex landscapes. We used tree-ring width chronologies and time series of the normalized difference vegetation index (NDVI) derived from high-resolution Landsat scenes as proxies for stem and leaf biomass, respectively. We then compared growth variability and climate-growth relationships of both biomass proxies between topographical categories. Our results show that the responses of tree rings to climate differ significantly from those found in NDVI, with the stronger climatic signal observed in tree rings. Topography had distinct but species-specific effects: At moisture-limited PISY stands, stem biomass (tree rings) was strongly topographically driven, and leaf biomass (NDVI) was relatively insensitive to topographic variability. In landscapes close to the climatic optimum of PCAB, the relationship between stem and leaf biomass was weak, and their correlations with climate were often inverse, with no significant effects of topography. Different climatic signals from NDVI and tree rings suggest that the response of canopy and stem growth to climate change might be decoupled. Furthermore, our results hint toward different prioritizations of biomass allocation in trees under stressful conditions which might change allometric relationships between individual tree compartments in the long term. PubDate: 2023-01-26
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Abstract: Abstract Shifts in plant functional groups associated with climate change have the potential to influence peatland carbon storage by altering the amount and composition of organic matter available to aquatic microbial biofilms. The goal of this study was to evaluate the potential for plant subsidies to regulate ecosystem carbon flux (CO2) by governing the relative proportion of primary producers (microalgae) and heterotrophic decomposers (heterotrophic bacteria) during aquatic biofilm development in an Alaskan fen. We evaluated biofilm composition and CO2 flux inside mesocosms with and without nutrients (both nitrogen and phosphorus), organic carbon (glucose), and leachates from common peatland plants (moss, sedge, shrub, horsetail). Experimental mesocosms were exposed to either natural sunlight or placed under a dark canopy to evaluate the response of decomposers to nutrients and carbon subsidies with and without algae, respectively. Algae were limited by inorganic nutrients and heterotrophic bacteria were limited by organic carbon. The quality of organic matter varied widely among plants and leachate nutrient content, more so than carbon quality, influenced biofilm composition. By alleviating nutrient limitation of algae, plant leachates shifted the biofilm community toward autotrophy in the light-transparent treatments, resulting in a significant reduction in CO2 emissions compared to the control. Without the counterbalance from algal photosynthesis, a heterotrophic biofilm significantly enhanced CO2 emissions in the presence of plant leachates in the dark. These results show that plants not only promote carbon uptake directly through photosynthesis, but also indirectly through a surrogate, the phototrophic microbes. PubDate: 2023-01-26
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Abstract: Abstract Frugivory and seed dispersal by fish is an important mutualistic interaction in complex and species-rich tropical rivers. The local ecological knowledge (LEK) held by fishers can provide new information on relationships between fishes and plants in less studied rivers. This study aims to investigate the feeding interactions between frugivorous fish and plants through interaction networks based on the fishers' LEK in three rivers in the Brazilian Amazon (Negro, Tapajós and Tocantins). A total of 418 fishers were interviewed in 24 communities (eight in each river). The studied fishes were tambaqui (Colossoma macropomum), matrinxã (Brycon spp.), pacu (Myloplus spp.), pacu manteiga (Mylossoma duriventre), pirapitinga (Piaractus brachypomus), and jaraqui (Semaprochilodus spp.). The interviewed fishers cited a total of 92 plants consumed by the six frugivorous fishes in the three rivers. The interaction networks showed a higher nestedness in the Tocantins, greater connectance and modularity in the Tapajós and more specialization in the Negro, where the protected areas may have contributed to a more complex and specialized interaction network. The more nested network in the Tocantins River indicated the loss of specialized interactions in disturbed communities. The Tapajós River network showed the highest number of interactions between fish and plants, but this river has been threatened by environmental changes. Fishers' LEK associated to network analyses can advance our understanding on ecological interactions. This approach can be also useful to evaluate and mitigate ecological effects from anthropic changes in the Amazon and other high diverse tropical rivers. PubDate: 2023-01-18
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Abstract: Abstract Microphytobenthos (MPB) is one of the most important primary producers in coastal and estuarine ecosystems, where it plays a substantial role in many ecological functions. Although the influence of several environmental factors on MPB biomass and productivity is well documented, the effects of macrofaunal bioturbation remain poorly assessed. The purpose of this study was to experimentally quantify the influence of sediment bioturbation processes (that is, sediment reworking and bioirrigation) on biogeochemical fluxes across the sediment–water interface and MPB biomass and photosynthetic capacities. Two infaunal deposit feeders (the polychaete Hediste diversicolor and the bivalve Scrobicularia plana) exhibiting contrasting bioturbation modes and rates were studied as model organisms. They differently affected MPB biomass and photosynthetic performance. Hence, through an intense bioirrigation activity and the stimulation of nutrient fluxes (NH4+ , NOx, PO42− and dSi) at the sediment surface, H. diversicolor enhanced MPB growth, which seemed to compensate for its direct consumption. Conversely, high sediment reworking rates generated by S. plana, associated with an extensive grazing pressure, drastically limited the development of MPB at the sediment surface. The negative impact of bivalves on MPB biomass increased with increasing density, whereas there was no significant relationship with polychaete density, possibly due to trophic competition. This study demonstrates that macrofaunal bioturbation is a key factor regulating MPB dynamics, with complex interactions that can result in a net either positive or negative effect depending on dominant species functional traits and abundances. This may, in particular, explain the strong spatial and temporal variability of the microbenthic primary productivity in intertidal mudflats. PubDate: 2023-01-17
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Abstract: Abstract The extensive coastal forests in eastern southern Africa persist as a putative alternative stable state in an open ecosystem mosaic that includes grassland and savanna. We examine two current hypotheses of the state-transition origins of these forests: (1) facilitation—where light-demanding pioneer cohorts facilitate establishment by species that tolerate shade and whose functional traits align with forest; and (2) nucleation—where tree species of savanna origin establish on fire refugia in grassland, and where forest develops from the coalescence of these bush-clumps. We compared tree species diversity and composition on old-lands colonized by the savanna pioneer Vachellia kosiensis, with bush-clumps established on old-lands and on untransformed grassland, to determine their resemblance to intact coastal forest. The facilitation pathway in V. kosiensis woodland comprised impoverished tree assemblages differing markedly in richness, diversity, and composition from the nucleation pathway. By contrast, the bush-clump nucleation pathway comprised random assemblages of savanna species. Overlap in savanna tree composition between the bush-clump pathway and forest was notable. A suite of functional traits related to growth, reproduction and dispersal revealed that the life histories of most coastal forest tree species (~ 88%, n = 83 species) correspond with those expected from savanna. A combination of shade intolerance, multi-stemmed architecture, and growth form plasticity indicate species origins and persistence under frequent fire and variable light regimes typical of savanna environments. While these coastal woody formations satisfy the structural definition of forest, their constituents are clearly derived from savanna and questions the efficacy of their management as successional forest. PubDate: 2023-01-09 DOI: 10.1007/s10021-022-00814-0
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Abstract: Abstract Soil functioning is closely linked to the interactions between biological communities with the physical environment. Yet, the impact of plant community attributes on metabolic processes promoting soil nutrient cycling remains largely unknown. We hypothesized that the plant community acts as a regulating agent of nutrient mobilization in soils according to the phylogenetic and morpho-functional traits of plant species of which it is composed. Rhizosphere soils were collected in autumn and spring under 32 tree and shrub species in two Mediterranean mixed forests (four plots in each) located in southern Spain, and nine soil enzymatic activities related to C, N and P mobilization were assessed. Phylogeny and morpho-functional traits of plant species were recorded and their imprint in soil enzymatic activities across forests was determined. The results showed a plant phylogenetic signal for N mobilization in both forests, while it varied across forests for non-labile C and P mobilization. The plant phylogenetic signals were primarily driven by lineages that diversified through the Miocene, about 25 Myr ago. In addition, leaf traits and plant’s mycorrhizal type explained soil enzymatic activities independently from phylogeny. C and P mobilization increased under ectomycorrhizal plants, whilst enhanced N mobilization did occur under arbuscular mycorrhizal ones. The plant community composition led to a different carbon and nutrient mobilization degree, which in turn was mediated by distinct microbial communities mirroring differentiated resource-acquisition strategies of plants. Our results highlight the role of plant traits and mycorrhizal interactions in modulating carbon and nutrient cycling in Mediterranean mixed forest soils. PubDate: 2023-01-05 DOI: 10.1007/s10021-022-00815-z
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Abstract: Abstract We used a long-term herbivore removal experiment where paired exclosure–open treatments were established at the Mpala Research Centre, Laikipia, Kenya, in 1999 to examine changes in soil nitrogen (N) at nutrient-rich glades and adjacent nutrient-poor bushland sites after almost two decades of herbivore removal. Glades in this landscape are created by large inputs of dung and urine from previous long-term corralling of cattle in an otherwise nutrient-poor matrix of woodland (bushland). We predicted (1) a net gain of soil nutrients at bushland sites (that is, inputs of nutrients > losses) and (2) a net loss of soil nutrients at glade sites (that is, inputs of nutrients < losses) following herbivore exclusion. As expected, soil N increased (by 28% after 17 years) with herbivore removal, but remained largely unchanged in the presence of herbivores at low-nutrient bushland sites. However, contrary to our expectations, soil total N in nutrient-rich glades also increased (+ 18%) when herbivores were removed, but declined when grazed (− 11%). Although the underlying mechanisms are unclear, we suggest that increased N fixation by Acacia spp., combined with increased canopy cover and associated tree leaf litter, resulted in elevated soil N following browser removal in low-nutrient bushland sites, while grazer-induced increases in the rate of N transformations between organic and mineral forms resulted in a more “open” N cycle (as evidenced by higher N mineralization rates and foliar N), with increased potential for N loss in gaseous forms, in grazed nutrient-rich glade sites. Grazers and browsers thus appear to affect the N cycle and create and reinforce heterogeneity in unique ways. PubDate: 2023-01-01
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Abstract: Abstract Recurrent fires can impede the spontaneous recruitment capacity of pine forests. Empirical studies have suggested that this can lead to a prolonged replacement of pine forest by shrubland, especially if shrub species are pyrophytic. Model-based studies, however, have suggested that post-fire succession of pine forest under current climatic conditions will eventually tend towards the dominance of oaks under high fire severity and recurrence. These previous modelling studies did not address the role of the various post-fire regeneration traits of the understory shrub species. Considering the dichotomy of obligate seeder vs. resprouter species, either obligate or facultative resprouter, we hypothesized that when the shrubs present are post-fire seeders, the oaks steadily occupy the forest, whereas resprouter shrub species might compete with oaks and delay or arrest post-fire succession. To test this hypothesis, we developed a dynamic, cellular automaton model for simulating post-fire successional transitions in pine forests, including shrubs, pines and oaks, and stochastic fires of regular frequency. Our results showed a strong tendency towards oak dominance as final model state and a very reduced role of fire recurrence in this final state, with low yearly acorn input delaying oak dominance. Most relevantly, and in line with our hypothesis, the trend towards oak dominance depended markedly on the two types of shrub species, being delayed by resprouter species, which extended the shrub-dominated succession stage for several centuries. Our simulation results supported the view that the type of understorey species should be a key consideration in post-fire restoration strategies aiming to enhance fire resilience. PubDate: 2023-01-01
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