Changes In Plant Community Composition Research Articles

To what extent can we predict variation of bryophyte and tracheophyte community composition at fine spatial scale along an elevation gradient?

Mounting evidence points to the need for high-resolution climatic data in biodiversity analyses under global change. As we move to finer resolution, other factors than climate, including other abiotic variables and biotic interactions play, however, an increasing role, raising the question of our ability to predict community composition at fine scales. Focusing on two lineages of land plants, bryophytes and tracheophytes, we determine the relative contribution of climatic, non-climatic environmental drivers, spatial effects, community architecture and composition of one lineage to predict community composition of the other lineage, and how our ability to predict community composition varies along an elevation gradient. The relationship between community composition of one lineage and 68 environmental variables at 2-25 m spatial resolution, architecture and composition of the other lineage, and spatial factors, was investigated by hierarchical and variance partitioning across 413 2x2m plots in the Swiss Alps. Climatic data, although significant, contributed less to the model than any other variable considered. Community composition of one lineage, reflecting both direct interactions and unmeasured (hidden) abiotic factors, was the best predictor of community composition of the other lineage. Total explained variance substantially varied with elevation, underlining the fact that the strength of the species composition-environment relationship varies depending on environmental conditions. Total variance explained increased towards high elevation up to 50 %, with an increasing importance of spatial effects and vegetation architecture, pointing to increasing positive interactions and aggregated species distribution patterns in alpine environments. In tracheophytes, an increase of the contribution of non-climatic environmental factors was also observed at high elevation, in line with the hypothesis of a stronger environmental control under harsher conditions. Further improvements of our ability to predict changes in plant community composition may involve the implementation of historical variables and higher-resolution climatic data to better describe the microhabitat conditions actually experienced by organisms.

Two decades of dune slack restoration in North Wales: diversity, community and habitat specialists

Humid dunes slacks are a highly threatened habitat, listed as vulnerable in the EU habitat red list. Accelerated successional processes in dune systems have resulted in the loss and degradation of ideal conditions for specialist dune slack species, hence the need for conservation management. We investigated the restoration of a dune slack in North Wales, UK, where vegetation and soil removal to 10 cm depth was undertaken to reinstate nutrient‐poor, open and damp conditions. We assessed the outcomes of the management for dune slack communities over the 18 years since restoration. We also assessed the differences between restored and unrestored areas of dune slacks. The dunes were restored in the winter of 2004/2005, after which we conducted vegetation surveys in fixed quadrats for most years in the restored and adjacent, un‐restored dune slacks. Species diversity and plant community composition changes over time were assessed using Shannon's index, multivariate analysis and indicator species analysis. Comparisons between the restored and unrestored areas of the dune slacks were also made. Ellenberg indicator values (EIVs) were examined to identify potential environmental drivers of post management successional changes. After 18 years the restored dune slacks developed a species‐rich and diverse community. compared to the unrestored slacks. The establishment of species occurred rapidly in the first three years, followed by continued but slower increases in species richness and diversity. This is due to the addition of new species without losses of established species. EIVs show no significant difference over time suggesting the restored areas are still at an early stage of succession. Distinct stages of community change since restoration are characterised by different indicator species. Plants are likely to be largely recruited from an existing seed bank. Restoration by turf removal may be suitable for other low nutrient, species rich habitats dependent upon fluctuating groundwater levels.

Pollinator-mediated effects of landscape-scale land use on grassland plant community composition and ecosystem functioning - seven hypotheses.

Environmental change is disrupting mutualisms between organisms worldwide. Reported declines in insect populations and changes in pollinator community compositions in response to land use and other environmental drivers have put the spotlight on the need to conserve pollinators. While this is often motivated by their role in supporting crop yields, the role of pollinators for reproduction and resulting taxonomic and functional assembly in wild plant communities has received less attention. Recent findings suggest that observed and experimental gradients in pollinator availability can affect plant community composition, but we know little about when such shifts are to be expected, or the impact they have on ecosystem functioning. Correlations between plant traits related to pollination and plant traits related to other important ecosystem functions, such as productivity, nitrogen uptake or palatability to herbivores, lead us to expect non-random shifts in ecosystem functioning in response to changes in pollinator communities. At the same time, ecological and evolutionary processes may counteract these effects of pollinator declines, limiting changes in plant community composition, and in ecosystem functioning. Despite calls to investigate community- and ecosystem-level impacts of reduced pollination, the study of pollinator effects on plants has largely been confined to impacts on plant individuals or single-species populations. With this review we aim to break new ground by bringing together aspects of landscape ecology, ecological and evolutionary plant-insect interactions, and biodiversity-ecosystem functioning research, to generate new ideas and hypotheses about the ecosystem-level consequences of pollinator declines in response to land-use change, using grasslands as a focal system. Based on an integrated set of seven hypotheses, we call for more research investigating the putative pollinator-mediated links between landscape-scale land use and ecosystem functioning. In particular, future research should use combinations of experimental and observational approaches to assess the effects of changes in pollinator communities over multiple years and across species on plant communities and on trait distributions both within and among species.

Climate change and plant-microbe interactions: Water-availability influences the effective specialization of a fungal pathogen

Through species-specific effects on plants, pathogens play a key role in structuring plant communities. A change in abiotic context, such as those mediated by climate change, may alter plant communities through changes in the specificity of plant-pathogen interactions. To test how water availability influenced the specificity of plant-pathogen interactions, we grew paired congeners of three native and three nonnative coastal prairie plant species with or without a pathogenic soil fungus, Fusarium incarnatum-equiseti species complex 6 b, under low, average, and high water treatments. Across the plant species tested, the Fusarium treatment had stronger negative and species-specific effects on plant biomass at high water availability than low water availability. If generalizable, our results suggest that stronger and more species-specific pathogen effects could drive changes in plant community composition in wetter conditions, but plant-pathogen interactions may be less important for plant community structure in drier conditions.

Assembly of typical steppe community and functional groups along the precipitation gradient from 1985 to 2022

Long-term observations have shown that structure and function of grasslands have changed due to climate change over the past decades. However, little is known about how grasslands respond to climate change along the precipitation gradient, and potential mechanisms remain elusive. Here, we utilize a long-term experiment in typical steppe to explore universal and differential mechanisms of community and functional groups assembly along the precipitation gradient. Our results indicated that the sensitivity of community and functional groups assembly to climate change was related to local precipitation. The strength of the positive effects of climate change on aboveground biomass, species richness, and their relationship of community decreased modestly with local precipitation. The mechanism behind this was the change in plant community composition of the precipitation-induced, annuals that was more responsive to climate change decreased as increased local precipitation. Furthermore, current and past climate both drove community and functional group assembly, and the role of past climate diminished with increasing local precipitation. Among them, climate fluctuation, average climate and current climate were the most critical climate indicators affecting community and functional groups assembly in low, medium and high precipitation sites, respectively. In conclusion, climatic change do not always exert identical effects on grasslands along the precipitation gradient. This could be critical importance for improving our ability to predict future changes in grassland ecosystems.

Biophysical effects of an old tundra fire in the Brooks Range Foothills of Northern Alaska, U.S.A

Our understanding of tundra fire effects in Northern Alaska is limited because fires have been relatively rare. We sampled a 70+ year-old burn visible in a 1948 aerial photograph for vegetation composition and structure, soil attributes, terrain rugosity, and thermokarst pit density. Between 1948 and 2017 the burn initially became wetter as ice wedges melted but then drained and dried as the troughs became hydrologically connected. The reference tundra has become wetter over the last few decades and appears to be lagging through a similar sequence. The burn averaged 2.5 °C warmer than the reference tundra at 30 cm depth. Thinning of organic soil following fire appears to dramatically accelerate the background degradation of ground-ice features in response to climate change and promotes a plant community that is distinct in terms of taxa and structure, dominated by tall willows and other competitive, rather than cold-tolerant, species. The cover of sedges and mosses is low while that of willows and grass is high relative to the reference tundra. The changes in plant community composition and structure, increasing ground temperature, and thermokarst lead us to expect the observed biophysical changes to the tundra will persist centuries into the future.

Experimental climate change in desert steppe reveals the importance of C4 plants for ecosystem carbon exchange

Global climate change has greatly altered plant community composition and affected ecosystem carbon exchange of grasslands. However, the influences of long-term increasing temperature and precipitation on the composition of plant community and the ecosystem carbon exchange in degraded desert steppe remain unclear. After seven years of simulated climate warming (ambient temperature, W0, 2 ℃ and 4 ℃ increase in temperature, W1 and W2) and increasing precipitation (plant growing season precipitation, P0, 25% and 50% increase in precipitation, P1 and P2), we recorded the composition of plant community, the moisture and temperature of soil and calculated net ecosystem CO2 exchange (NEE). Results showed that 1) long-term warming and increasing precipitation improved the cover and height of C4 plants in the plant community, while decreasing the cover and density of C3 plants. 2) Climate warming and increasing precipitation significantly increased NEE. Compared with W0P0, the mean NEE in the plant growing season increased by 115% in W2P2. 3) Redundancy analysis showed that soil moisture content and the height and density of C4 plants significantly explained ecosystem carbon exchange (P < 0.01), while the effect of C3 plants on ecosystem carbon exchange was insignificant (P > 0.01). Therefore, our research revealed that warming and increasing precipitation positively affected ecosystem carbon exchange in degraded desert steppe through changes in plant community composition, and C4 plants will play a vital role in ecosystem carbon exchange in desert steppe under climate change.

Diverging trends and drivers of Arctic flower production in Greenland over space and time

The Arctic is warming at an alarming rate. While changes in plant community composition and phenology have been extensively reported, the effects of climate change on reproduction remain poorly understood. We quantified multidecadal changes in flower density for nine tundra plant species at a low- and a high-Arctic site in Greenland. We found substantial changes in flower density over time, but the temporal trends and drivers of flower density differed both between species and sites. Total flower density increased over time at the low-Arctic site, whereas the high-Arctic site showed no directional change. Within and between sites, the direction and rate of change differed among species, with varying effects of summer temperature, the temperature of the previous autumn and the timing of snowmelt. Finally, all species showed a strong trade-off in flower densities between successive years, suggesting an effective cost of reproduction. Overall, our results reveal region- and taxon-specific variation in the sensitivity and responses of co-occurring species to shared climatic drivers, and a clear cost of reproductive investment among Arctic plants. The ultimate effects of further changes in climate may thus be decoupled between species and across space, with critical knock-on effects on plant species dynamics, food web structure and overall ecosystem functioning.

When the neighborhood matters: contextual selection on seedling traits in native and non-native California grasses.

Plants interact extensively with their neighbors, but the evolutionary consequences of variation in neighbor identity are not well understood. Seedling traits are likely to experience selection that depends on the identity of neighbors because they influence competitive outcomes. To explore this, we evaluated selection on seed mass and emergence time in two California grasses, the native perennial Stipa pulchra and the non-native annual Bromus diandrus, in the field with six other native and non-native neighbor grasses in single and mixed species treatments. We also quantified characteristics of each neighbor treatment to further investigate factors influencing their effects on fitness and phenotypic selection. Selection favored larger seeds in both focal species and this was largely independent of neighbor identity. Selection generally favored earlier emergence in both focal species, but neighbor identity influenced the strength and direction of selection on emergence time in S. pulchra but not B. diandrus. Greater light interception, higher soil moisture, and greater productivity of neighbors was associated with more intense selection for earlier emergence and larger seeds. Our findings suggest that changes in plant community composition can alter patterns of selection in seedling traits, and that these effects can be associated with measurable characteristics of the community.

Local-scale changes in plant community composition following succession of oak- hornbeam forest after grassland abandonment

In this local-scale synecological study, we investigated the changes in plant community composition throughout secondary succession occurring after cessation of agricultural land use (i.e. grassland abandonment). The successional sequence studied had the following pathway: Avenula pubescens (Huds.) Dumort. haypastures → Brachypodium pinnatum (L.) P.Beauv. successional grassland → Cornus sanguinea L. scrubs → late-successional Populus tremula L. forest → late-successional oak-hornbeam (Quercus-Carpinus) forest. The last forest stage was represented by the association Epimedio-Carpinetum betuli (Horvat 1938) Borhidi 1963. Occurrence of plant species throughout secondary succession was mostly stage-specific; only Fragaria vesca L., Ajuga reptans L., Cornus sanguinea, Prunus spinosa L., and Viola hirta L. showed survival ability throughout almost all stages.

Geographical variation in community‐wide herbivory matches patterns of intraspecific variation instead of species turnover

AbstractAimAttempts over the past 30 years to explain geographical variation in the strength of herbivore pressure have given rise to ecological hypotheses like the latitudinal herbivory hypothesis. This hypothesis, however, has rarely been tested using community‐level data. Therefore, the aim of our study was to examine the patterns and potential mechanisms underlying geographical variation in community‐wide herbivory.LocationThe Qinghai‐Tibetan Plateau.Time PeriodJuly 2021.Major Taxa StudiedPlants.MethodsWe selected 43 grassland sites along a 1500‐km latitudinal gradient (c. 27°N to 39°N) and a 2698‐m elevational gradient (1886–4584 m) on the Qinghai‐Tibetan Plateau. We evaluated geographical patterns in invertebrate herbivory pressure at the population and community levels, while also evaluating the importance of geographical variation in mediating the effects of abiotic and biotic factors on intraspecific variation (through changes in herbivory on component species) and species turnover effects (through changes in plant community composition).ResultsCommunity‐wide herbivory decreased with latitude, mirroring intraspecific variation, while species turnover effects did not vary along any tested geographical gradients. Furthermore, we found that geographical variation in community‐wide herbivory was strongly positively correlated with soil nitrogen content. We also found a positive effect of soil nitrogen content on intraspecific variation and a negative effect of plant community biomass on species turnover effects.Main ConclusionsThe latitudinal gradient in community‐wide herbivory was primarily mediated by intraspecific variation, which was in turn associated with a gradient in soil nitrogen content. Our findings highlight the need for community‐wide assessments of geographical variation in plant–herbivore interactions, decomposing community‐wide herbivory into intraspecific variation and species turnover effects.

Agroecosystem edge effects on vegetation, soil properties, and the soil microbial community in the Canadian prairie.

Edge effects resulting from adjacent land uses are poorly understood in agroecosystems yet understanding above and belowground edge effects is crucial for maintaining ecosystem function. The aim of our study was to examine impacts of land management on aboveground and belowground edge effects, measured by changes in plant community, soil properties, and soil microbial communities across agroecosystem edges. We measured plant composition and biomass, soil properties (total carbon, total nitrogen, pH, nitrate, and ammonium), and soil fungal and bacterial community composition across perennial grassland-annual cropland edges. Edge effects due to land management were detected both aboveground and belowground. The plant community at the edge was distinct from the adjacent land uses, where annual, non-native, plant species were abundant. Soil total nitrogen and carbon significantly decreased across the edge (P < 0.001), with the highest values in the perennial grasslands. Both bacterial and fungal communities were different across the edge with clear changes in fungal communities driven directly and indirectly by land management. A higher abundance of pathogens in the more heavily managed land uses (i.e. crop and edge) was detected. Changes in plant community composition, along with soil carbon and nitrogen also influenced the soil fungal community across these agroecosystems edges. Characterizing edge effects in agroecosystem, especially those associated with soil microbial communities, is an important first step in ensuring soil health and resilience in these managed landscapes.

Effects of the invasive leafy spurge (Euphorbia esula L.) on plant community structure are altered by management history

Invasive species threaten biodiversity and ecosystem functioning, often causing changes in plant community composition and, thus, the functional traits of that community. Quantifying changes in traits can help us understand invasive species impacts on communities; however, both the invader and the plant community may be responding to the same environmental drivers. In North America, leafy spurge (Euphorbia esula L.) is a problematic invader that reduces plant diversity and forage production for livestock. Its documented effects on plant communities differ amongst studies, however, potentially due to differences in productivity or land management. To identify the potential effects of leafy spurge on plant communities, we quantified leafy spurge abundance, plant species richness, forage production, functional group composition and community weighted mean traits, intensively at a single site and extensively across ten sites differing in management. We then tested how leafy spurge abundance related to these variables as a function of site management activities. Leafy spurge abundance was consistently associated with fewer plant species, reduced forage production and more invasive grass. Community-weighted specific root length also consistently increased with leafy spurge abundance, suggesting that belowground competition may be important in determining co-existence with leafy spurge. Other changes were dependent on management. Native forbs were excluded as leafy spurge became more abundant, but only in grazed sites as these species were already absent from ungrazed sites. Taller plants better persisted in dense leafy spurge patches, but only in grazed sites, consistent with either facilitation of taller species via associational defences or competitive exclusion of shorter species in ungrazed sites and dense leafy spurge patches. These results show that, despite some emergent properties of invasion, management context can alter invasion impacts by causing changes in the plant community and its interactions with the invader.

Plant C:N ratio predicts community composition changes under N addition in an alpine meadow

Abstract Plant functional traits play important roles in determining plant responses to environmental change and further shaping community composition, but the role of plant stoichiometry remains poorly understood in regulating community responses to continually increased nitrogen (N) deposition. In this paper, we used a 5‐year manipulative experiment with six N addition rates (Nrate) to explore how the N response of different plant functional groups including forbs, grasses, sedges and legumes links to above‐ground plant carbon‐to‐N ratio (C:N, related to N use strategies) in an alpine meadow. We found that plant C:N explained 45.8% and 42.6% of N response variation among functional groups in plant above‐ground net primary productivity (ANPP) and abundance. Over increasing Nrate, functional groups with higher C:N (grasses and sedges) tended to grow better and have greater abundance, yet those with lower C:N (forbs and legumes) were at risk of loss, subsequently mitigating the N‐caused decline in community‐level plant C:N. This was mainly due to that functional groups with higher C:N not only possessed higher N use efficiency but also had greater competitiveness for above‐ground light due to higher plant height. In addition, we also found that plant C:N differences among functional groups remained relatively constant over Nrate, suggesting that the ability of this trait to indicate functional group‐specific N responses was stable. Synthesis. Our results show that the N responses of different herbaceous plants can be well explained by plant C:N. Thus, we suggest the prediction of plant community composition changes under N deposition would be greatly improved by considering this easily measured stoichiometric trait.

Fifty years of reduction in sulphur deposition drives recovery in soil pH and plant communities

Abstract Sulphur deposition through rainfall has led to species loss and ecosystem degradation globally, and across Europe huge reductions in sulphur emissions since the 1970s were expected to promote the recovery of acidified ecosystems. However, the rate and ecological impact of recovery from acidification in terrestrial ecosystems is still unclear as is the influence of management and climate, as to date there has been no long‐term spatially extensive evaluation of these changes. Here, we present data from thousands of sites across Great Britain (pH range 3.3–8.7) surveyed repeatedly from 1978–2019 and assess change in soil pH and plant acidity preference (Ellenberg R) in response to atmospheric deposition of sulphur and nitrogen. We analyse change in grasslands managed for pasture, referred to as high‐intensity habitats, and compare to seminatural habitats comprising rough grassland, broadleaved woodland, bog and heathland, referred to as low‐intensity habitats. Soil pH increased from 1978 to 2007 but then decreased between 2007 and 2019, resulting in a net increase of ~0.2 pH units in low‐intensity habitats but no change in high‐intensity habitats. The community average Ellenberg R increased in seminatural habitats by ~0.2 units but remained stable in intensive grasslands. In seminatural habitats, but not intensive grasslands, these changes in plant community composition were associated with the soil pH changes which were in turn linked to decreasing sulphur deposition and differences in rainfall. Nitrogen deposition, which was relatively stable over the survey period, showed no additional effect upon soil acidity once sulphur deposition was accounted for. Synthesis: Our results provide conclusive evidence that reductions in acid emissions are stimulating the gradual recovery of chronically acidified terrestrial ecosystems at a whole‐country scale, while also suggesting this recovery is being compromised by changing climate and land management.

Transitional mire vegetation restoration: changing failure back to success, case study from Slovenia

In this article, we describe two restoration efforts (raising and lowering the water table) in a transitional mire and use vegetation survey data (from 1987, 1999, and 2015) to evaluate restoration success. We used historical and current vegetation relevés and vegetation maps to identify target plant communities and track changes in vegetation over time. Ordination plot (NMDS) and the Sankey diagram were used to detect changes in plant community composition and overall vegetation. The first restoration (1993) was not planned according to the standards and was unsuccessful because of a very rapid rise in the water level. It caused the destruction of bog and mire plant communities and the emergence of new wetland stands. Subsequent restoration (in 2000), with a gradual lowering of the water table, allowed natural restoration of mire communities, but certain species remain absent. Our study demonstrated the importance of careful restoration planning, selection of target plant communities, and the importance of vegetation survey for monitoring.

Hydrology regime and hydrology recruitment niche predict changes in plant community composition across a pond habitat

AbstractQuestionsNiche differentiation is widely accepted as a key mechanism important for species coexistence. Seed germination and seedling survival were recognized as important contributors to niche segregation and could be a crucial filter for determining species' distributions and community composition. Only a little is known about the direct relationship between hydrology recruitment niche, hydrology regimes, and community composition. Therefore, the main aim of this study is to identify the changes in the composition of a pond community with respect to the hydrological regime and predict them by the recruitment niche of species.LocationThe Gloggere pond in the Altdorfer forest (47.848 N, 9.698 E, Ravensburg vicinity, Upper Swabia, Baden‐Wuerttemberg, Germany).MethodsA transect with 46 permanent plots was established throughout the Gloggere pond, and species percentage cover was recorded in September 1992–1995, 2006, and 2017. Pond drawdown was implemented in 1993. Sediment samples were collected in March 1995 across the transect, and a pot germination experiment with six hydrological treatments was performed. The hydrology recruitment niche from the seed bank germination experiment was compared with the field hydrology niche to show the importance of the hydrology regime for community composition.ResultsThe hydrological regime determined the community composition in both the germination experiment and the field. Species‐specific hydrology niche from the field correlated with species‐specific recruitment niche measured in the germination experiment.ConclusionsOur results support the importance of recruitment niche as a driver of community composition for pond areas. For understanding and predicting changes in plant community composition, it is necessary to combine knowledge about the recruitment niche and the ability of seeds’ survival in the sediment along a hydrological gradient with knowledge about abiotic filters, biotic interactions, and species‐specific traits. Recognizing the recruitment niche is useful for better predicting the effect of future environmental changes, especially in the context of climate change and conservation management.

Peatland Plant Functional Type Effects on Early Decomposition Indicators are Non-Pervasive, but Microhabitat Dependent

Ombrotrophic peatlands are important long-term sinks for atmospheric carbon as plant productivity exceeds litter decomposition. Changes in plant community composition may alter decomposition rates through alterations in microbial communities and activity. Such plant community driven changes in decomposition rates may however differ between microhabitats. Nevertheless, the microhabitat-context-dependency of plant community composition effects on decomposition remains poorly understood. We used a long-term (> 10 year) plant removal experiment to study how vascular plant functional types (PFTs, i.e. graminoids and ericoids) influence decomposition processes in wet lawns and hummocks. We employed the Tea Bag Index (TBI) as an indicator for early litter decomposition and carbon stabilization and assessed the potential activity of five hydrolytic extracellular enzymes (EEAs) as indicators for microbial activity. PFT removal had no effect on the TBI decomposition rate constant (k), nor on the stabilization factor (S). Yet, k increased slightly when both PFTs were absent. In the lawns, we observed higher values of k and S as compared to hummocks. PFT composition influenced four out of five hydrolytic EEAs that can drive decomposition. Yet, this influence was non-pervasive and microhabitat dependent. In wet lawns, PFT removal generally increased enzyme activities, while opposite trends were detected in the hummocks. Our results suggest an important role for vegetation change, through their influence on enzyme activity, along the lawn-hummock gradient in regulating decomposition processes in northern peatlands. This implies that potential consequences of vegetation changes on organic matter turnover, hence the peatland carbon sink function, cannot be generalized across peatland microhabitats.

Soil fungal communities show more specificity than bacteria for plant species composition in a temperate forest in China

BackgroundSoil microbiome is an important part of the forest ecosystem and participates in forest ecological restoration and reconstruction. Niche differentiation with respect to resources is a prominent hypothesis to account for the maintenance of species diversity in forest ecosystems. Resource-based niche differentiation has driven ecological specialization. Plants influence soil microbial diversity and distribution by affecting the soil environment. However, with the change in plant population type, whether the distribution of soil microbes is random or follows an ecologically specialized manner remains to be further studied. We characterized the soil microbiome (bacteria and fungi) in different plant populations to assess the effects of phytophysiognomy on the distribution patterns of soil microbial communities in a temperate forest in China.ResultsOur results showed that the distribution of most soil microbes in different types of plant populations is not random but specialized in these temperate forests. The distribution patterns of bacteria and fungi were related to the composition of plant communities. Fungal species (32%) showed higher specialization than bacterial species (15%) for different types of plant populations. Light was the main driving factor of the fungal community, and soil physicochemical factors were the main driving factor of the bacterial community.ConclusionThese findings suggest that ecological specialization is important in maintaining local diversity in soil microbial communities in this forest. Fungi are more specialized than bacteria in the face of changes in plant population types. Changes in plant community composition could have important effects on soil microbial communities by potentially influencing the stability and stress resistance of forest ecosystems.

Small herbivores with big impacts: Tundra voles (Microtus oeconomus) alter post-fire ecosystem dynamics.

Fire is an important ecological disturbance that can reset ecosystems and initiate changes in plant community composition, ecosystem biogeochemistry, and primary productivity. As herbivores rely on primary producers for food, changes in vegetation may alter plant-herbivore interactions with important-but often unexplored-feedbacks to ecosystems. Here we examined the impact of post-fire changes in plant community composition and structure on habitat suitability and rodent herbivore activity in response to a large, severe, and unprecedented fire in northern Alaskan tundra. In moist acidic tundra where the fire occurred, tundra voles (Microtus oeconomus) are the dominant herbivore and rely on the tussock forming sedge Eriophorum vaginatum for both food and nesting material. Tundra voles were 10 times more abundant at the burned site compared with nearby unburned tundra 7-12 years after the fire. Fire increased the habitat suitability for voles by increasing plant productivity and biomass, food quality, and cover through both taller vegetation and increased microtopography. As a result of elevated vole abundance, Eriophorum mortality caused by vole herbivory was two orders of magnitude higher than natural mortality and approached the magnitude of the mortality rate resulting directly from the fire. These findings suggest that post-fire increases in herbivore pressure on Eriophorum could, in turn, disrupt graminoid recovery and enhance shrub encroachment. Tundra state transitions from graminoid to shrub dominated are also evident following other disturbances and fertilization experiments, suggesting that as Arctic temperatures rise, greater available nutrients and increased frequencies of large-scale disturbances may also alter plant-animal interactions with cascading impacts on plant communities and ecosystem function.