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440 results for “community changes”
Data from: Forest structure determines spatial changes in avian community along an elevational gradient in tropical Africa
Aim To test if tree species richness and forest structure drive spatial variation in avian communities along a tropical elevation gradient and to present information about the role of detailed forest parameters. Location A 2000-m long elevational gradient of tropical forest on Mt. Cameroon, west-central Africa. Taxon Birds and trees. Methods We performed bird censuses and vegetation mapping at the same plots across six forested sites at elevations of 350, 650, 1,100, 1,500, 1,850, and 2,200 m a.s.l., with 16 plots per elevation. We tested the effects of elevation, forest structure and tree diversity on the species richness, functional diversity and β-diversity of birds (Bray-Curtis dissimilarity). We used conditional inference trees based on random forests (RF) to investigate these relationships across all elevation sites as well as within elevations. Results Both tree and bird species richness declined monotonically with elevation. Vegetation structure correlated with elevation, and all vegetation attributes significantly differed among elevations. The RF explained 70% of the variance in avian species richness, with the most important predictors being elevation, proportion of dead trees, tree species richness and herb layer coverage. We found that elevation (and shrub layerE2) was a particularly important predictor of avian functional diversity. We identified no important predictor of bird species richness after standardization within elevations, and the proportion of dead trees was the sole important predictor of functional diversity. Within-elevation β-diversity in avian community composition was determined by the dissimilarity of the tree community and differences in leaf area index, solar radiation and spatial distance. The functional dissimilarity was best explained by leaf area index. Main conclusions Apart from elevation itself, spatial distance even within elevations correlated with compositional and functional variation among avian assemblages. Forest structural traits can have a significant influence on distribution of birds. Thus, gaps in the spatial distribution of species such as along elevations might be caused by fine-scale recognition of suitable habitats.
Data from: Plant community dynamics and carbon sequestration in Sphagnum-dominated peatlands in the era of global change
<p>Aim: Hydroclimatic shift and anthropogenic-driven nitrogen deposition are major outcomes of global change that could compromise the functioning of many peatlands as a carbon sink. For Sphagnum-dominated peatlands, an emerging hypothesis is that the change could be triggered by shifts in competitive dominance among plant functional groups, specifically from the currently predominant decay-resistant Sphagnum to the more decomposable vascular plants. However, the relationship between Sphagnum and vascular plant occurrence is notably complex and also includes facilitative interactions that are crucial to the productivity of Sphagnum and therefore carbon sequestration.</p> <p>Location: Global</p> <p>Taxa: Northern peatlands—Sphagnum moss and vascular plants</p> <p>Methods: We use a conceptual review to examine underlying mechanisms for the competitive exclusion hypothesis and the nature of facilitative interactions between Sphagnum and vascular plants under the potential global change conditions. We complement the review with an empirical study of peatlands with contrasting hydrology to provide some critical insights into the potential effects of change in plant communities on carbon sequestration. We also propose a conceptual model that presents probable combinations of global change factors and their implications for carbon sequestration.</p> <p>Results: Vegetation structure in Sphagnum-dominated peatland appears to be driven largely by hydrology, rather than competition among plant functional groups. The peat deposit also exerts some controls (e.g., nutrient immobilization) on biotic structure, thereby acting as resistance against an abrupt shift in plant communities.<br> Main conclusions: Peatland controls that constrain vegetation shifts have developed over a millennial timescale in many peatlands, and the pace of climate change may not allow enough time for the establishment of those mechanisms in younger peatlands. Thus, the persistence of a given peatland as a carbon sink also likely depends on the successional stage of the peatland.</p>
Data from: Fire history and plant community composition outweigh decadal multi-factor global change as drivers of microbial composition in an annual grassland
Soil microbial communities regulate and respond to key biogeochemical cycles and influence plant community patterns. However, microbial communities also respond to disturbance events, motivating an assessment of the relative roles of decadal multi-factor global change, disturbance, and plant community structure on microbial community responses. We used high-throughput amplicon sequencing to characterize the diversity and composition of bacterial and fungal communities in bulk soil (0–7 cm) collected in 2014 from the Jasper Ridge Global Change Experiment, a full-factorial field experiment in which ambient and elevated levels of nitrogen deposition (+7 g N m-2 yr-1 calcium nitrate), CO2 concentration (+275 ppm), temperature (+1–2 ºC), and precipitation (+50% volume with +3 weeks duration) were applied to a California annual grassland from 1998 to 2014. We used linear mixed-effects modeling to test for the effects of global change on microbial diversity (observed richness, Shannon index). We also used generalized dissimilarity modeling (GDM) to study controls on compositional dissimilarity in fungal and bacterial communities. Bacterial community composition was best explained by exposure to fires in 2003 and 2011, whereas fungal community composition was best explained by plant community composition. The richness of fungi increased under elevated nitrogen deposition; bacterial diversity metrics decreased under warmer temperatures. Interactions between global change factors were statistically insignificant or weak. Synthesis. Our results indicate that even on decadal timescales, the effects of fire history and plant community composition on bacterial and fungal community composition, respectively, outweigh the effects of multi-factor global change. Furthermore, global change factors have mostly additive effects on microbial diversity patterns. Our results show that highly variable mediators such as fire history and plant community composition limit the generalizability of soil microbial responses to long-term global change.
Data for Body mass-related changes in mammal community assembly patterns during the late Quaternary of North America
<p>The late Quaternary of North America was marked by prominent ecological changes, including the end-Pleistocene megafaunal extinction, the spread of human settlements, and the rise of agriculture. Here we examine the mechanistic reasons for temporal changes in mammal species association and body size during this time period. Building upon the co-occurrence results from Lyons et al. (2016) – wherein each species pair was classified as spatially aggregated, segregated, or random – we examined body mass differences (BMD) between each species pair for each association type and time period (Late Pleistocene: 40,000 14C - 11,700 14C ybp, Holocene: 11,700 14C - 50 ybp, and Modern: 50 - 0 yrs). In the Late Pleistocene and Holocene, the BMD of both aggregated and segregated species pairs was significantly smaller than the BMD of random pairs. These results are consistent with environmental filtering and competition as important drivers of community structure in both time periods. Modern assemblages showed a breakdown between BMD and co-occurrence patterns: the average BMD of aggregated, segregated, and random species pairs did not differ from each other. Collectively, these results indicate that the late Quaternary mammalian extinctions not only eliminated many large- bodied species but were followed by a re-organization of communities that altered patterns of species coexistence and associated differences in body size.</p>
FIGURE 2 in Abundance changes in orb-weaver spider communities at the edge of the Argiope bruennichi expansion range
FIGURE 2. Scatter plots and Spearman rank-order correlation (RS) between Argiope bruennichi and Araneus quadratus in the three regions of Poland.
FIGURE 1 in Abundance changes in orb-weaver spider communities at the edge of the Argiope bruennichi expansion range
FIGURE 1. Comparison of densities of Argiope bruennichi (Ab) and Araneus quadratus (Aq) in three regions of Poland during 2009–2012. Points are means, boxes are SEs, and whiskers are SDs.
Data from: Wintering bird communities are tracking climate change faster than breeding communities
<p><span>1. Global climate change is driving species' distributions towards the poles and mountain tops during both non-breeding and breeding seasons, leading to changes in the composition of natural communities. However, the degree of season differences in climate-driven community shifts has not been thoroughly investigated at large spatial scales. </span></p> <p><span>2. We compared the rates of change in the community composition during both winter (non-breeding season) and summer (breeding) and their relation to temperature changes.</span></p> <p><span>3. Based on continental-scale data from Europe and North America, we examined changes in bird community composition using the community temperature index (CTI) approach and compared the changes with observed regional temperature changes during 1980–2016.</span></p> <p><span>4. CTI increased faster in winter than in summer. This seasonal discrepancy is probably because individuals are less site-faithful in winter, and can more readily shift their wintering sites in response to weather in comparison to the breeding season. Regional long-term changes in community composition were positively associated with regional temperature changes during both seasons, but the pattern was only significant during summer due to high annual variability in winter communities. Annual changes in community composition were positively associated with the annual temperature changes during both seasons. </span></p> <p><span>5. Our results were broadly consistent across continents, suggesting some climate-driven restructuring in both European and North American avian communities. Because community composition has changed much faster during the winter than during the breeding season, it is important to increase our knowledge about climate-driven impacts during the less-studied non-breeding season.</span></p>
Diversity and phylogenetic community structure across elevation during climate change in a family of hyperdiverse neotropical beetles (Staphylinidae)
<p>Environmental stress from abiotic conditions imposes physiological limits on individuals within communities, and these stressful conditions can act as a filter on the species present in any given environment. Such abiotic stressors can reduce a community's diversity and make its composition more phylogenetically clustered. Using a decade of staphylinid beetle (Staphylinidae, Coleoptera, rove beetles) collections made across a 1,500 m elevation gradient in northwestern Costa Rica (2008-2017) we asked what species lived there, how large and overlapping were the communities across this gradient, and what relationship was there between elevation and diversity. Using DNA barcodes for identification and phylogenetic estimates of community structure, we found high turnover across elevation, and that staphylinid diversity increased linearly with elevation. Because of this, we found staphylinid diversity was negatively related to surface area and temperature, and positively with precipitation. We suggest that historical biogeography and contemporary environmental stress have combined to produce these observed patterns. The forests in which these beetles are found are heating and drying rapidly and our finding that diversity increases with elevation suggests that there will be catastrophic biodiversity loss in the coming decades.</p>
Contrasting responses of different functional groups stabilise community responses to a dominant shrub under global change
<p>1. Changes in precipitation regimes and nitrogen deposition levels due to global change are altering terrestrial ecosystems worldwide. Most attempts at understanding how biotic interactions affect plant species and community responses to global change have focused on biotic interactions measured at the community-level. However, these approaches ignore that communities include functionally dissimilar species that might respond differently to changes in the effects of dominant neighbours along environmental gradients. We test the hypothesis that plant species with differences in functional traits may exhibit contrasting interactions with a dominant shrub species within a single community, thereby stabilizing community-level responses to the effects of global change.</p> <p>2. We manipulated water and nitrogen applications in a semi-arid dune community in northern China, quantified the biomass of herbaceous species occurring below the dominant shrub, <i>Artemisia ordosica</i>, and in adjacent open patches (without the shrub), and measured herbaceous species height and leaf dry matter content. The effects of <i>A. ordosica</i> were quantified at the species, group, and community levels using the relative interaction index (<i>RII</i>). Redundancy analysis was performed on species traits and the <i>RII</i> values to assess the relationships between functional differences in species and plant-plant interactions. Species were then grouped using a cluster analysis and the <i>RII</i> values were recalculated at the group level.</p> <p>3. The redundancy analysis showed that species height and leaf dry matter content were significantly correlated to the changes in species' responses to the effect of <i>A. ordosica</i> along treatments. The four groups of species identified by the cluster analysis showed contrasting variations in competitive or facilitative responses depending on species traits and environmental treatments. However, the interactions measured at the group level balanced the community-level responses, as we found no significant changes in the effects of <i>A. ordosica</i> along treatments for community biomass, richness, and functional diversity indices.</p> <p>4. Synthesis. Our findings indicate that species with different functional strategies within a community exhibit contrasting responses to a dominant shrub along environmental gradients. These contrasting changes in plant-plant interactions of functionally different species may balance the responses of community-level metrics. This suggests that functional differences between species groups and the balance of plant-plant interactions stabilize community responses to global change.</p>
Projected effects of climate change on boreal bird community accentuated by anthropogenic disturbances in western boreal forest, Canada
<p><b>Aim</b></p> <p>Climate change<b> </b>is expected to influence boreal bird communities significantly, notably through changes in forest habitat (composition and age structure),<b> </b>in the coming decades. How these changes will accumulate and interact with anthropogenic disturbances remains an open question for most species.</p> <p><b>Location</b></p> <p>Northeastern Alberta, Canada.</p> <p><b>Methods </b></p> <p>We used the LANDIS-II forest landscape model to project changes in forest landscapes, and associated bird populations (72 passerine species), according to three climatic scenarios (baseline, RCP 4.5, RCP 8.5) and three forest harvesting scenarios of differing intensity.</p> <p><b>Results</b></p> <p>Both forest harvesting and climate-related drivers were projected to have large impacts on bird communities in this region. As a result of climate-induced increases in fire activity as well as decreased conifer productivity, our simulations projected that an important proportion of Alberta's boreal forests would transition to treeless habitat (i.e. grass-, or shrub-dominated vegetation) while many conifer-dominated stands would likely be replaced by broadleaf tree cover. Consequently, the abundance of bird species associated with open and deciduous habitats were projected to increase. With a strong anthropogenic climate forcing scenario (RCP 8.5), sharp declines in abundance of coniferous trees were also projected, particularly in mature and old forest stands, triggering major declines for bird species associated with coniferous and mixedwood forest types.</p> <p><b>Main Conclusions</b></p> <p><a>As the most comprehensive simulation of climate change and harvesting impacts on avian habitats in the North American boreal region to date</a>, our study <a>reveals</a> the importance of considering key habitat characteristics like forest age structure and composition through forest landscape modeling, and identifies 18 bird species particularly sensitive to climate change. Our simulations suggest that a change in forest management practices could play an important role in the conservation of boreal bird species vulnerable to climate change. The intensive forest harvesting simulated accelerated declines in bird abundance compared to a "no harvesting" scenario.</p> <div> <div> <div class="msocomtxt"> </div> </div> </div>
Data from: Demographic traits improve predictions of spatiotemporal changes in community resilience to drought
<ol> <li>Communities are increasingly threatened by extreme weather events. The cumulative effects of such events are typically investigated by assessing community resilience,<i> i.e.</i>, the extent to which affected communities can achieve pre-event states. However, a mechanistic understanding of the processes underlying resilience is frequently lacking and requires linking various measures of resilience to demographic responses within natural communities.</li> <li>Using 13 years of data from a shrub community that experienced a severe drought in 2005, we use generalized additive models to investigate temporal changes in three measures of resilience. We assess whether community-weighted, species-specific demographic traits such as longevity and reproductive output can predict changes in resilience and how the performance of these traits compares to more commonly used plant functional traits such as leaf area or root dry-matter content.</li> <li>We find significant spatiotemporal variation in community dynamics after the drought. Overall, demographic traits are better at predicting absolute and relative resilience in total plant cover, but functional traits outperform demographic traits when resilience in community composition is assessed. All resilience measures show non-linear and context-specific responses to demographic and functional traits; and these responses depend strongly on the severity of initial drought impact.</li> <li> <i>Synthesis</i>: Our work demonstrates that a full picture of the mechanisms underlying community responses to drought requires the assessment of numerous species-specific characteristics (including demographic and functional traits) and how these characteristics differentially affect complementary measures of community changes through time. </li> </ol>
Data from: Changes in soil microbial communities in post mine ecological restoration: implications for monitoring using high throughput DNA sequencing
<p>The ecological restoration of ecosystem services and biodiversity is a key intervention used to reverse the impacts of anthropogenic activities such as mining. Assessment of the performance of restoration against completion criteria relies on biodiversity monitoring. However, monitoring usually overlooks soil microbial communities (SMC), despite increased awareness of their pivotal role in many ecological functions. Recent advances in cost, scalability and technology has led to DNA sequencing being considered as a cost-effective biological monitoring tool, particularly for otherwise difficult to survey groups such as microbes. However, such approaches for monitoring complex restoration sites such as post-mined landscapes have not yet been tested. Here we examine bacterial and fungal communities across chronosequences of mine site restoration at three locations in Western Australia to determine if there are consistent changes in SMC diversity, community composition and functional capacity. Although we detected directional changes in community composition indicative of microbial recovery, these were inconsistent between locations and microbial taxa (bacteria or fungi). Assessing functional diversity provided greater understanding of changes in site conditions and microbial recovery than could be determined through assessment of community composition alone. These results demonstrate that <span>high-throughput amplicon sequencing of environmental DNA (eDNA)</span> is an effective approach for monitoring the complex changes in SMC following restoration. Future monitoring of mine site restoration using eDNA should consider archiving samples to provide improved understanding of changes in communities over time. Expansion to include other biological groups (e.g. soil fauna) and substrates would also provide a more holistic understanding of biodiversity recovery. </p>
Changes in tree community structures in defaunated forests are not driven only by dispersal limitation
<p>1. Bushmeat hunting has reduced population sizes of large frugivorous vertebrates throughout the tropics, thereby reducing the dispersal of seeds. This is believed to affect tree population dynamics, and therefore community composition, because the seed dispersal of large-seeded trees depends upon large-bodied vertebrates.</p> <p>2. We report on a long-running study of the effect of defaunation on a tropical tree community. In three censuses over 11 years, we compared sapling recruitment between a hunted and a nonhunted site, which are nearby and comparable to one another, to determine the extent to which species composition has changed through time following defaunation. We expected to find a reduced abundance of tree species that rely on large frugivores for dispersal at the hunted site, and altered community structure as a consequence.</p> <p>3. Although community composition at the hunted site diverged from that at the nonhunted site, the changes were independent of dispersal syndrome, with no trend towards a decline in species that are dispersed by large, hunted vertebrates. Moreover, the loss of large-bodied dispersers did not generate the changes in tree community composition that we hypothesised. Some species presumed to rely on large-bodied frugivores for dispersal are effectively recruiting despite the absence of their dispersers.</p> <p>4. Synthesis: The presumption that forests depleted of large-bodied dispersers will experience rapid, directional compositional change is not fully supported by our results. Altered species composition in the sapling layer at the hunted site, however, indicates that defaunation may be connected with changes to the tree community, but that the nature of these changes are not unidirectional as previously assumed. It remains difficult to predict how defaunation will affect tree community composition without a deeper understanding of the driving mechanisms at play.</p>
Data from: Plant-driven changes in soil microbial communities influence seed germination through negative feedbacks
1. Plant-soil feedbacks (PSFs) drive plant community diversity via interactions between plants and soil microbes. However, we know little about how frequently PSFs affect plants at the seed stage, and the compositional shifts in fungi that accompany PSFs on germination. 2. We conducted a pairwise PSF experiment to test whether seed germination was differentially impacted by conspecific versus heterospecific soils for seven grassland species. We used metagenomics to characterize shifts in fungal community composition in soils conditioned by each plant species. To investigate whether changes in the abundance of certain fungal taxa were associated with multiple PSFs, we assigned taxonomy to soil fungi and identified putative pathogens that were significantly more abundant in soils conditioned by plant species that experienced negative or positive PSFs. 3. We observed negative, positive, and neutral PSFs on seed germination. Although conspecific and heterospecific soils for pairs with significant PSFs contained host-specialized soil fungal communities, soils with specialized microbial communities did not always lead to PSFs. The identity of host-specialized pathogens, i.e. taxa uniquely present or significantly more abundant in soils conditioned by plant species experiencing negative PSFs, overlapped among plant species, while putative pathogens within a single host plant species differed depending on the identity of the heterospecific plant partner. Finally, the magnitude of feedback effects on germination were not related to the degree of fungal community differentiation between species pairs involved in negative PSFs. 4. Synthesis. Our findings reveal the potential importance of PSFs at the seed stage. Although plant species developed host-specialized fungal communities in rhizosphere soil, pathogens were not strictly host-specific, and varied not just between plant species, but according to the identity of plant partner. These results illustrate the complexity of microbe-mediated interactions between plants at different life stages that next-generation sequencing can begin to unravel.
Data from: Deer-mediated changes in environment compound the direct impacts of herbivory on understory plant communities
1. In forests of eastern North America, white-tailed deer (Odocoileus virginianus) can directly affect, via herbivory, the presence, abundance, and reproductive success of many plant species. In addition, deer indirectly influence understory communities by altering environmental conditions. 2. To examine how deer indirectly influence understory plants via environmental modification, we sampled vegetation and environmental variables in- and outside deer exclosures (10-20 years old) located in temperate forests in northern Wisconsin and the Upper Peninsula of Michigan, USA. We assessed how excluding deer affected understory community composition and structure, the soil and light environment, and relationships between direct and indirect effects using non-metric multidimensional scaling (NMDS), mixed linear models and non-parametric multiplicative regression (NPMR). 3. Excluding deer altered sapling communities and several aspects of the understory environment. Excluding deer from plots with lower overstory basal area increased sapling abundance, decreasing the amount of light available to groundlayer plants. Exclusion also reduced soil compaction and the thickness of the soil E horizon. 4. The composition of understory communities and the frequencies of various species and groups covaried in apparent response to the environmental factors affected by exclusion. In several common species and groups, E horizon thickness, compaction, openness, and/or total (sapling and overstory) basal area were significant predictors of plant frequency. 5. Complementary analyses revealed that deer exclusion also altered the frequency distributions of several species and groups across environmental space. Synthesis: Deer alter many facets of the understory environment, such as light availability, soil compaction and depth of the soil E horizon, which, in turn, appear to mediate variation in plant communities. Those environmental modifications likely compound direct impacts of herbivory as drivers of understory community change, having important implications for forest composition. Thus, we suggest a reexamination of the common assumption that understory community shifts stem primarily from tissue removal.
Data from: Individual-level trait diversity concepts and indices to comprehensively describe community change in multidimensional trait space
Global environmental change can influence ecosystem processes directly or through changes in the trait composition of natural communities. Traits are individual-level features of organisms, and theory predicts that diversity in traits should relate to ecosystem processes. Validated indices that account for both intra- and interspecific trait variation in multidimensional trait space are lacking. In this article, we highlight how an individual-level perspective requires new concepts for trait diversity (TD) and we validate a set of measures suitable to study trait richness, evenness and divergence at the individual scale. First, we tested a selection of multivariate indices for trait richness, evenness and divergence from the literature (FRic, FEve, FDis and the Rao coefficient) using simulated and real individual-level data. We compared the observed changes in the tested indices with those predicted from their expected/required behaviour (i.e. increase or decrease under specific manipulation of community trait structure) and found unsatisfactory results only for FRic and FEve, whereas FDis and the Rao coefficient showed the expected changes. Therefore, we propose two novel concepts and related indices for individual-level trait richness (TOP = trait onion peeling) and evenness (TED = trait even distribution). TOP represents the sum of all successive convex hull areas touching all individuals (points) within a multidimensional trait distribution. TED is a measure of how evenly distributed are individuals within the multidimensional trait space. It is calculated comparing the probability distributions of pairwise distances between individuals and between points of a perfectly even reference distribution. We tested TOP and TED on the same simulated and real data as above, and results indicated appropriate behaviour for TOP (trait richness) and TED (trait evenness). By validating TD indices in an individual-level context, this study contributes to the expansion of functional ecology towards individual-level dynamics. Future comprehensive investigations of individual trait differences in natural communities may improve our understanding of the pathways by which environmental changes affect ecosystem functioning through biodiversity change.
Data from: Contemporary land change alters fish communities in a San Francisco Bay drainage, California, U.S.A.
Urbanization is one of the leading threats to freshwater biodiversity, and urban regions continue to expand globally. Here we examined the relationship between recent urbanization and shifts in stream fish communities. We sampled fishes at 32 sites in the Alameda Creek Watershed, near San Francisco, California, in 1993–1994 and again in 2009, and we quantified univariate and multivariate changes in fish communities between the sampling periods. Sampling sites were classified into those downstream of a rapidly urbanizing area ("urbanized sites"), and those found in less impacted areas ("low-impacted sites"). We calculated the change from non-urban to urban land cover between 1993 and 2009 at two scales for each site (the total watershed and a 3km buffer zone immediately upstream of each site). Neither the mean relative abundance of native fish nor nonnative species richness changed significantly between the survey periods. However, we observed significant changes in fish community composition (as measured by Bray-Curtis dissimilarity) and a decrease in native species richness between the sampling periods at urbanized sites, but not at low-impacted sites. Moreover, the relative abundance of one native cyprinid (Lavinia symmetricus) decreased at the urbanized sites but not at low-impacted sites. Increased urbanization was associated with changes in the fish community, and this relationship was strongest at the smaller (3km buffer) scale. Our results suggest that ongoing land change alters fish communities and that contemporary resurveys are an important tool for examining how freshwater taxa are responding to recent environmental change.
Data from: Environmental degradation results in contrasting changes in the assembly processes of stream bacterial and fungal communities
Environmental degradation may have strong effects on community assembly processes. We examined the assembly of bacterial and fungal communities in anthropogenically altered and near-pristine streams. Using pyrosequencing of bacterial and fungal DNA from decomposed alder Alnus incana leaves, we specifically examined if environmental degradation deterministically decreases or increases the compositional turnover of bacterial and fungal communities. Our results showed that near-pristine streams and anthropogenically altered streams supported distinct fungal and bacterial communities. The mechanisms assembling these communities were different in near-pristine and altered environments. Environmental disturbance homogenized bacterial communities, whereas fungal communities were more dissimilar in disturbed sites than in near-pristine sites. Compositional variation of both bacteria and fungi was related to water chemistry variables in disturbed sites, further implying the influence of environmental degradation on community assembly. Bacterial and fungal communities in near-pristine streams were weakly controlled by environmental factors, suggesting that the relative importance of niche-based versus neutral processes in assembling microbial communities may strongly depend on the spatial scale and local environmental context. Our results thus suggest that environmental degradation may strongly affect the composition and β-diversity of stream microbial communities colonizing leaf litter, and that the direction of the change can be different between bacteria and fungi. A better understanding of the environmental tolerances of microbes and the mechanisms assembling microbial communities in natural environmental settings is needed to predict how environmental alteration is likely to affect microbial communities.
Data from: Belowground-mediated and phase-dependent processes drive nitrogen-evoked community changes in grasslands
<ol> <li>Enhanced deposition of atmospheric nitrogen (N) leads to loss of plant diversity in grassland ecosystems. Numerous theories have provided potential explanations for the negative effects of N enrichment on plant diversity. However, the relative importance of each mechanism and the time scales of responses for the different functional groups remain unclear.</li> <li>We investigated the temporal responses of plant community in a temperate steppe to N enrichment by linking aboveground to belowground processes using a series of field N-addition and greenhouse experiments.</li> <li>The N enrichment-induced declines in plant diversity of grasslands were phase-based, functional group-dependent, and driven by three belowground processes. The rapid accumulation of NH<sub>4</sub><sup>+</sup>-N by N addition inhibited photosynthetic rates of broad-leaf-non-rhizomatous forbs, contributing to loss of these N-sensitive species during early phase of N enrichment (≤3 years). The N-induced changes in this phase were independent of soil pH as evidenced by results from application lime to mitigate N-evoked soil acidification. With progression of N addition, manganese (Mn) toxicity to narrow-leaf-non-rhizomatous forbs due to soil acidification-induced Mn<sup>2+</sup> mobilization in soil accounted for their loss in the second phase of N enrichment (~ 4-9 years). When N addition proceeded longer than ~10 years, N enrichment stimulated belowground meristem differentiation and rhizome growth of the rhizomatous species, leading to the dominance by rhizomatous sedges/grasses in the community at later phase of N enrichment.</li> </ol> <p>Synthesis: The hierarchical mechanisms not only provide a comprehensive explanation for the N enrichment-induced diversity decline in grasslands, but can also facilitate us to understand the differential sensitivities of ecosystems to chronic N enrichment, and predict future ecosystem dynamics.</p>
Data from: Snowbeds are more affected than other subalpine-alpine plant communities by climate change in the Swiss Alps
While the upward shift of plant species has been observed on many alpine and nival summits, the reaction of the subalpine and lower alpine plant communities to the current warming and lower snow precipitation has been little investigated so far. To this aim, 63 old, exhaustive plant inventories, distributed along a subalpine–alpine elevation gradient of the Swiss Alps and covering different plant community types (acidic and calcareous grasslands; windy ridges; snowbeds), were revisited after 25–50 years. Old and recent inventories were compared in terms of species diversity with Simpson diversity and Bray–Curtis dissimilarity indices, and in terms of community composition with principal component analysis. Changes in ecological conditions were inferred from the ecological indicator values. The alpha-diversity increased in every plant community, likely because of the arrival of new species. As observed on mountain summits, the new species led to a homogenization of community compositions. The grasslands were quite stable in terms of species composition, whatever the bedrock type. Indeed, the newly arrived species were part of the typical species pool of the colonized community. In contrast, snowbed communities showed pronounced vegetation changes and a clear shift toward dryer conditions and shorter snow cover, evidenced by their colonization by species from surrounding grasslands. Longer growing seasons allow alpine grassland species, which are taller and hence more competitive, to colonize the snowbeds. This study showed that subalpine–alpine plant communities reacted differently to the ongoing climate changes. Lower snow/rain ratio and longer growing seasons seem to have a higher impact than warming, at least on plant communities dependent on long snow cover. Consequently, they are the most vulnerable to climate change and their persistence in the near future is seriously threatened. Subalpine and alpine grasslands are more stable, and, until now, they do not seem to be affected by a warmer climate.
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Allen Brain Atlas
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Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
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OpenNeuro
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