Environmental filtering mediates grassland community assembly following restoration with soil carbon additions

The application of carbon (C) substrates has been viewed as a promising tool for lowering soil nitrogen (N) availability in grassland restoration. However, experimental evidence shows that C additions can enhance, suppress, or have no effect on native species productivity, making it difficult to predict the effects of C‐additions on plant communities. We used a community assembly approach to test the roles of environmental filtering and competition on community structure after C‐additions. We applied 3 recalcitrant C‐additions (wood chips, shavings, mixed chips + shavings), monitored temporal changes in soil N and P availability and species' abundances, and used phylogenetic tools to examine changes in community structure. All 3 soil C‐additions produced significant reductions in soil N and P fertility that, in turn, were correlated with increases in taxonomic species richness, diversity, and evenness, as well as shifts in community structure. In control and C‐amended plots, however, communities were composed of taxa that were more closely related than expected by chance (phylogenetically clustered); this pattern occurred across all C‐additions and years, and in both plot level and species pair‐wise metrics. In nonamended plots, phylogenetic clustering was correlated with soil N availability, consistent with environmental filtering. In C‐addition plots, biotic (clade specialization in different C additions) and abiotic factors (soil P variability) were important in structuring the community. These findings suggest that C‐additions create a different set of environmental filters and that variations in ecological traits among phylogenetically close species may be important in understanding and predicting the effects of C‐additions.     

Short-term invasibility patterns in burnt and unburnt experimental Mediterranean grassland communities of varying diversities

This paper reports the findings of a short-term natural invasibility field study in constructed Mediterranean herbaceous communities of varying diversities, under a fire treatment. Three components of invasibility, i.e. species richness, density and biomass of invaders, have been monitored in burnt and unburnt experimental plots with resident diversity ranging from monocultures to 18-species mixtures. In general, species richness, density and biomass of invaders decreased significantly with the increase of resident species richness. Furthermore, the density and biomass of invading species were significantly influenced by the species composition of resident communities. Although aboveground biomass, leaf area index, canopy height and percent bare ground of the resident communities explained a significant part of the variation in the success of invading species, these covariates did not fully explain the effects of resident species richness. Fire mainly influenced invasibility via soil nutrient levels. The effect of fire on observed invasibility patterns seems to be less important than the effects of resident species richness. Our results demonstrate the importance of species richness and composition in controlling the initial stages of plant invasions in Mediterranean grasslands but that there was a lack of interaction with the effects of fire disturbance.     

Ecological strategies in California chaparral: interacting effects of soils,climate, and fire on specific leaf area

Background: High values of specific leaf area (SLA) are generally associated with high maximal growth rates in resource-rich conditions, such as mesic climates and fertile soils. However, fire may complicate this relationship since its frequency varies with both climate and soil fertility, and fire frequency selects for regeneration strategies (resprouting versus seeding) that are not independent of resource-acquisition strategies. Shared ancestry is also expected to affect the distribution of resource-use and regeneration traits.

Aims: We examined climate, soil, and fire as drivers of community-level variation in a key functional trait, SLA, in chaparral in California.

Methods: We quantified the phylogenetic, functional, and environmental non-independence of key traits for 87 species in 115 plots.

Results: Among species, SLA was higher in resprouters than seeders, although not after phylogeny correction. Among communities, mean SLA was lower in harsh interior climates, but in these climates it was higher on more fertile soils and on more recently burned sites; in mesic coastal climates, mean SLA was uniformly high despite variation in soil fertility and fire history.

Conclusions: We conclude that because important correlations exist among both species traits and environmental filters, interpreting the functional and phylogenetic structure of communities may require an understanding of complex interactive effects.     

Environmental determinants of leaf litter ant community composition along an elevational gradient

Ant communities are extremely diverse and provide a wide variety of ecological functions in tropical forests. Here, we investigated the abiotic factors driving ant composition turnover across an elevational gradient at Mont Itoupé, French Guiana. Mont Itoupé is an isolated mountain whose top is covered by cloud forests, a biogeographical rarity that is likely to be threatened according to climate change scenarios in the region. We examined the influence of six soil, climatic, and LiDAR‐derived vegetation structural variables on leaf litter ant assembly (267 species) across nine 0.12‐ha plots disposed at three elevations (ca. 400, 600, and 800m asl). We tested (a) whether species cooccurring within a same plot or a same elevation were more similar in terms of taxonomic, functional, and phylogenetic composition, than species from different plots/elevations, and (b) which environmental variables significantly explained compositional turnover among plots. We found that the distribution of species and traits of ant communities along the elevational gradient was significantly explained by a turnover of environmental conditions, particularly in soil phosphorus and sand content, canopy height, and mean annual relative humidity of soil. Our results shed light on the role exerted by environmental filtering in shaping ant community assembly in tropical forests. Identifying the environmental determinants of ant species distribution along tropical elevational gradients could help predicting the future impacts of global warming on biodiversity organization in vulnerable environments such as cloud forests.     

Landscape‐ and small‐scale determinants of grassland species diversity: direct and indirect influences

Species richness is influenced both by mechanisms occurring at landscape scales, such as habitat availability, and local‐scale processes, that are related to abiotic conditions and plant–plant interactions. However, it is rarely tested to what extent local species richness can be explained by the combined effect of factors measured at multiple spatial scales. In this study, we quantified the simultaneous influence of historical landscape‐scale factors (past human population density, and past habitat availability – an index combining area and connectivity) and small‐scale environmental conditions (shrub cover, and heterogeneity of light, soil depth, and other soil environmental variables) on plant species richness in dry calcareous grasslands (alvars). By applying structural equation modelling (SEM) we found that both landscape conditions and local environmental factors had significant direct and indirect (i.e. through the modification of another factor), effects on species richness. At the landscape scale, we found a direct positive influence of historical habitat availability on species richness, and indirect positive influence of past human population (via its effects on historical habitat availability). At small scales, we found a positive direct influence of light heterogeneity and shrub cover on species richness. Conversely, we found that small‐scale soil environmental heterogeneity, which was mainly determined by soil depth heterogeneity, had a negative effect on species richness. Our study indicates that patterns of species richness in alvar grasslands are positively influenced by the anthropogenic management regime that maintained the landscape habitat conditions in the past. However, the abandonment of management, leading to shrub invasion and increased competition for light resources also influenced species richness. In contrast to the positive heterogeneity–diversity relationship we found that soil heterogeneity reduced species richness. Environmental heterogeneity, occurring at the plant neighbourhood scale (i.e. centimetres), can increase the isolation among suitable soil patches and thus hinder the normal functioning of populations. The combination of previous knowledge of the system with new ecological theories facilitates disentangling how species richness responds to complex relationships among factors operating at multiple scales.     

Biotic and Abiotic Properties Mediating Plant Diversity Effects on Soil Microbial Communities in an Experimental Grassland

Plant diversity drives changes in the soil microbial community which may result in alterations in ecosystem functions. However, the governing factors between the composition of soil microbial communities and plant diversity are not well understood. We investigated the impact of plant diversity (plant species richness and functional group richness) and plant functional group identity on soil microbial biomass and soil microbial community structure in experimental grassland ecosystems. Total microbial biomass and community structure were determined by phospholipid fatty acid (PLFA) analysis. The diversity gradient covered 1, 2, 4, 8, 16 and 60 plant species and 1, 2, 3 and 4 plant functional groups (grasses, legumes, small herbs and tall herbs). In May 2007, soil samples were taken from experimental plots and from nearby fields and meadows. Beside soil texture, plant species richness was the main driver of soil microbial biomass. Structural equation modeling revealed that the positive plant diversity effect was mainly mediated by higher leaf area index resulting in higher soil moisture in the top soil layer. The fungal-to-bacterial biomass ratio was positively affected by plant functional group richness and negatively by the presence of legumes. Bacteria were more closely related to abiotic differences caused by plant diversity, while fungi were more affected by plant-derived organic matter inputs. We found diverse plant communities promoted faster transition of soil microbial communities typical for arable land towards grassland communities. Although some mechanisms underlying the plant diversity effect on soil microorganisms could be identified, future studies have to determine plant traits shaping soil microbial community structure. We suspect differences in root traits among different plant communities, such as root turnover rates and chemical composition of root exudates, to structure soil microbial communities.     

Differential responses of soil bacteria,fungi, archaea and protists to plant species richness and plant functional group identity

Plants are known to influence belowground microbial community structure along their roots, but the impacts of plant species richness and plant functional group (FG) identity on microbial communities in the bulk soil are still not well understood. Here, we used 454‐pyrosequencing to analyse the soil microbial community composition in a long‐term biodiversity experiment at Jena, Germany. We examined responses of bacteria, fungi, archaea, and protists to plant species richness (communities varying from 1 to 60 sown species) and plant FG identity (grasses, legumes, small herbs, tall herbs) in bulk soil. We hypothesized that plant species richness and FG identity would alter microbial community composition and have a positive impact on microbial species richness. Plant species richness had a marginal positive effect on the richness of fungi, but we observed no such effect on bacteria, archaea and protists. Plant species richness also did not have a large impact on microbial community composition. Rather, abiotic soil properties partially explained the community composition of bacteria, fungi, arbuscular mycorrhizal fungi (AMF), archaea and protists. Plant FG richness did not impact microbial community composition; however, plant FG identity was more effective. Bacterial richness was highest in legume plots and lowest in small herb plots, and AMF and archaeal community composition in legume plant communities was distinct from that in communities composed of other plant FGs. We conclude that soil microbial community composition in bulk soil is influenced more by changes in plant FG composition and abiotic soil properties, than by changes in plant species richness per se.     

Wood trait-environment relationships in a secondary forest succession in South-East China

Concerning forest communities, not much is known about the relationship between wood traits and environmental conditions. Using a succession series, we analyzed which wood anatomical traits were correlated with successional stage and asked which traits and which environmental factors were particularly important for the trait–environment relationship. An extensive dataset of 11 groups of wood traits was generated for 93 woody species that occurred in 27 permanent plots in a secondary subtropical secondary broadleaved forest in Zhejiang Province (SE-China) and subjected to Fourth Corner Analyses, using different permutation models. We encountered a strong relationship of wood porosity, visibility of growth rings and vessel arrangement to the successional gradient. Compared to biotic community characteristics such as density of plants, abiotic environmental variables such as soil characteristics, aspect and inclination of the plots showed only marginal correlations to wood anatomical traits. Furthermore, the link between environment and species composition of the forest communities was found to be more important in explaining the trait–environment relationship than between the communities and species wood traits. In addition, our results support the idea that most of the species in the subtropical forest might be functionally equivalent.     

Plant functional traits along environmental gradients in seasonally dry and fire‐prone ecosystem

Questions: How does the abundance and richness of plant assemblages with different functional (regeneration and nutrient acquisition) traits vary with fire regime, moisture availability and substrate fertility? What is the role of different functional traits in maintaining plant diversity under changing environmental conditions in seasonally dry and fire‐prone environments? Location: Southwest Western Australia. Methods: Plant species abundance and soil nutrients were determined at 16 forest sites with variable fire histories across an aridity gradient. All plant species were classified based on their functional traits as (1) perennial or annual, (2) ectomycorrhizal, arbuscular mycorrhizal, ericoid mycorrhizal, orchid mycorrhizal, proteoid or other non‐mycorrhizal, (3) resprouters or seeder, and (4) nitrogen fixer or non‐fixer. We used a multivariate (fourth‐corner) technique to simultaneously test the significance and direction of the relationship between each of these traits and fire frequency, fire interval length, aridity, and soil N, P and C fractions. Results: The functional response of the vegetation to fire regime was minor and restricted to annual species, which comprised only ～4% of taxa. Proteoid and ectomycorrhizal species dominated over species with arbuscular and orchid mycorrhizal roots, N‐fixers dominated over non‐fixers, and seeders dominated over resprouters when N fertility was low but organic labile P was high. Further, proteoid and ectomycorrhizal species richness increased with aridity, while arbuscular mycorrhizal species richness decreased. Conclusions: While the functional composition of southwest Australian vegetation is largely insensitive to changes in fire regime, nutrient acquisition and, to a lesser extent, regeneration traits provide mechanisms for the vegetation community to adjust to changes in resource availability. Thus, diversity responses to environmental change in seasonally dry and fire‐prone ecosystems are likely to be primarily mediated by the composition of nutrient acquisition traits in the vegetation community.     

Experimental evidence that soil heterogeneity enhances plant diversity during community assembly

Aims Environmental heterogeneity is a primary mechanism explaining species coexistence and extant patterns of diversity. Despite strong theoretical support and ample observational evidence, few experimental studies in plant communities have been able to demonstrate a causal link between environmental heterogeneity and plant diversity. This lack of experimental evidence suggests that either fine-scale heterogeneity has weak effects on plant diversity or previous experiments have been unable to effectively manipulate heterogeneity. Here, we utilize a unique soil manipulation to test whether fine-scale soil heterogeneity will increase plant richness through species sorting among experimental patch types.Methods This experiment was conducted in the tallgrass prairie region of south-central Kansas, USA. We utilized the inherent variation found in the vertical soil profile, which varied in both biotic and abiotic characteristics, and redistributed these strata into either homogeneous or heterogeneous spatial arrangements in 2.4×2.4 m plots. After the soil manipulation, 34 native prairie species were sown into all plots. We conducted annual censuses at peak biomass to quantify species composition and plant density by species within the experimental communities.Important findings After 2 years, species richness was significantly higher in heterogeneous relative to homogeneous plots and this pattern was independent of total plant density. In the heterogeneous plots, 13 species had higher establishment in a specific patch type representing one of the three soil strata. Conversely, no species had greater establishment in the mixed stratum, which comprised the homogeneous plots, relative to the heterogeneous strata. These species sorting patterns suggest that fine-scale heterogeneity creates opportunities for plant establishment due to niche differences, which translates into increased plant diversity at the plot scale. Species richness was more strongly related to plant density among patches comprising homogenous plots—where fine-scale heterogeneity was minimized, but weak in heterogeneous plots. This pattern is consistent with the idea that richness–density relationships dominate when neutral processes are important but are weak when niche processes operate. Unlike many previous attempts, our results provide clear, experimental evidence that fine-scale soil heterogeneity increases species richness through species sorting during community assembly.     

Constraints on trait combinations explain climatic drivers of biodiversity: the importance of trait covariance in community assembly

Trade‐offs maintain diversity and structure communities along environmental gradients. Theory indicates that if covariance among functional traits sets a limit on the number of viable trait combinations in a given environment, then communities with strong multidimensional trait constraints should exhibit low species diversity. We tested this prediction in winter annual plant assemblages along an aridity gradient using multilevel structural equation modelling. Univariate and multivariate functional diversity measures were poorly explained by aridity, and were surprisingly poor predictors of community richness. By contrast, the covariance between maximum height and seed mass strengthened along the aridity gradient, and was strongly associated with richness declines. Community richness had a positive effect on local neighbourhood richness, indicating that climate effects on trait covariance indirectly influence diversity at local scales. We present clear empirical evidence that declines in species richness along gradients of environmental stress can be due to increasing constraints on multidimensional phenotypes.     

Diversity of the Western Carpathian flysch grasslands: Do extremely species-rich plant communities coincide with a high diversity of snails?

Upland fringes of the White Carpathians (Czech Republic) are known to support grasslands with the world’s highest local plant species richness. We investigated whether this unusually high plant richness has a parallel in snail communities, whether patterns of species composition of snail and plant communities in grasslands co-vary and how they are affected by local environment and landscape history. We compared plant and snail communities of dry to mesic grasslands in three neigh bouring regions: (1) hilly lowland of the Central Moravian Carpathians, (2) upland fringes and (3) upland of the White Carpathians. Both snail and plant communities exhibited a strong gradient in species composition associated with altitude, annual temperature and precipitation, soil calcium and pH. However, there was no correlation between local species richness of plants and snails in individual plots. The upland fringes of the White Carpathians were richest in snail species, probably due to intermediate environmental conditions, supporting the occurrence of species with contrasting environmental requirements. The highest local numbers of plant species were also recorded there, although differences among regions were not significant. The regional species richness of plants was also highest in the upland fringes, whereas that of snails was highest in the hilly lowland. Similarities in the diversity patterns of plants and snails among regions suggest the importance of regional factors for local richness, although local abiotic factors, which are partly correlated with the three regions, also influence local species composition and richness.     

Similarity of plant functional traits and aggregation pattern in a subtropical forest

The distribution of species and communities in relation to environmental heterogeneity is a central focus in ecology. Co‐occurrence of species with similar functional traits is an indication that communities are determined in part by environmental filters. However, few studies have been designed to test how functional traits are selectively filtered by environmental conditions at local scales. Exploring the relationship between soil characteristics and plant traits is a step toward understanding the filtering hypothesis in determining plant distribution at local scale. Toward this end, we mapped all individual trees (diameter >1 cm) in a one‐ha subtropical forest of China in 2007 and 2015. We measured topographic and detailed soil properties within the field site, as well as plant leaf functional traits and demographic rates of the seven most common tree species. A second one‐ha study plot was established in 2015, to test and validate the general patterns that were drawn from first plot. We found that variation in species distribution at local scale can be explained by soil heterogeneity and plant functional traits. (From first plot). (1) Species dominant in habitats with high soil ammonium nitrogen and total phosphorus tended to have high specific leaf area (SLA) and relative growth rate (RGR). (2) Species dominant in low‐fertility habitats tended to have high leaf dry matter content (LDMC), ratio of chlorophyll a and b (ratioab), and leaf thickness (LT). The hypothesis that functional traits are selected in part by environmental filters and determine plant distribution at local scale was confirmed by the data of the first plot and a second regional site showed similar species distribution patterns.     

Dissecting NDVI–species richness relationships in Hawaiian dry forests

Aim A growing body of research has used the normalized difference vegetation index (NDVI) as a proxy for productivity to predict species richness. Yet the mechanisms that produce the relationship between NDVI and species richness remain unclear because of correlated biotic and abiotic factors that influence NDVI. In this study we investigated different biotic and abiotic effects that potentially drive plant species richness–productivity relationships. Location Hawaiian Islands, USA. Methods We quantified woody plant species richness, structure (density, basal area and canopy height), and species composition along a precipitation gradient of 14 Hawaiian dry forest plots. We then used structural equation models combined with 10 years of satellite data to disentangle the effects of precipitation, structure and NDVI‐estimated productivity on species richness. Results Underlying the simple correlation between NDVI and species richness was the indirect effect of precipitation and direct effect of forest structure. The best‐fit model showed there was no direct effect of NDVI on species richness. Main conclusions Our results demonstrate that complex relationships drive simple correlations between species richness and productivity. Considering the mechanisms and underlying factors driving NDVI–species richness relationships could improve predictions of species diversity as satellite measures of productivity have an increasingly important role in habitat mapping, species distribution modelling and predictions for global change.     

Spatial patterns of herbivory by gall-forming insects: a test of the soil fertility hypothesis in a Mexican tropical dry forest

It has been proposed that fertile soils reduce the incidence of gall-forming insect (GFI) species in plant communities. This is known as the soil fertility hypothesis. The main objective of this study was to analyze the spatial distribution of GFI species under different habitats in a tropical dry forest at the Chamela-Cuixmala Biosphere Reserve, Mexico. Eight habitats which differ in soil type, topography, nutrient availability and vegetation were chosen. We found that 38 GFI species specialize on their host plant species. GFI species richness was negatively correlated with phosphorous and nitrogen availability. Using phosphorous as an indicator of soil fertility, we found low frequency and density of GFI on fertile soils. Our study indicates that soil fertility is one of the factors that negatively affects the patterns of spatial distribution of species richness, incidence and abundance of GFI at the community level in two different ways: i) indirectly affecting GFI species richness in plants adapted to infertile soils and ii) directly affecting GFI responses to plant traits of hosts found in a fertility gradient.     

Vegetation responses to different spatial patterns of soil disturbance in burned and unburned tallgrass prairie

Pocket gopher (Geomyidae) disturbances are created in spatiallypredictable patterns. This may influence resource heterogeneity and affectgrassland vegetation in a unique manner. We attempt to determine the extent towhich density and spatial pattern of soil disturbances influence tallgrassprairie plant community structure and determine how these disturbances interactwith fire. To investigate the effects of explicit disturbance patterns we createdsimulated pocket gopher burrows and mounds in various spatial patterns.Simulated burrows were drilled into the soil at different densities inreplicated plots of burned and unburned prairie. Separate plots of simulatedmounds were created in burned and unburned prairie at low, medium, or high mounddensities in clumped, uniform, or random spatial dispersions. In both burned and unburned plots, increased burrow density decreasedgraminoid biomass and increased forb biomass. Total-plant and graminoid biomasswere higher in burned than unburned plots while forb biomass was higher inunburned plots. Total-plant species richness was not significantly affected byburrow density or burning treatments, but graminoid species richness increasedin unburned plots and forb species richness increased in burned plots. Plant species richness was temporarily reduced directly on mounddisturbances compared to undisturbed prairie. Over time and at larger samplingscales, the interaction of fire and mound disturbance patterns significantlyaffected total-plant and graminoid species richness. The principal effect inburned and unburned prairie was decreased total-plant and graminoid speciesrichness with increased mound disturbance intensity. Although species richness at small patch scales was not increased by anyintensity of disturbance and species composition was not altered by theestablishment of a unique guild of disturbance colonizing plants, our studyrevealed that interactions between soil disturbances and fire alter the plantcommunity dominance structure of North American tallgrass prairie primarily viachanges to graminoids. Moreover, these effects become increasingly pronouncedover time and at larger spatial sampling scales.     

Fine-scale spatial variation in plant species richness and its relationship to environmental conditions in coastal marshlands

Previous studies have shown that variations in environmental conditions play a major role in explaining variations in plant species richness at community and landscape scales. In this study, we considered the degree to which fine-scale spatial variations in richness could be related to fine-scale variations in abiotic and biotic factors. To examine spatial variation in richness, grids of 1 m² plots were laid out at five sites within a coastal riverine wetland landscape. At each site, a 5 × 7 array of plots was established adjacent to the river’s edge with plots one meter apart. In addition to the estimation of species richness, environmental measurements included sediment salinity, plot microelevation, percent of plot recently disturbed, and estimated community biomass. Our analysis strategy was to combine the use of structural equation modeling (path modeling) with an assessment of spatial association. Mantel’s tests revealed significant spatial autocorrelation in species richness at four of the five sites sampled, indicating that richness in a plot correlated with the richness of nearby plots. We subsequently considered the degree to which spatial autocorrelations in richness could be explained by spatial autocorrelations in environmental conditions. Once data were corrected for environmental correlations, spatial autocorrelation in residual species richness could not be detected at any site. Based on these results, we conclude that in this coastal wetland, there appears to be a fine-scale mapping of diversity to microgradients in environmental conditions.     

Relationships between spatial environmental heterogeneity and plant species diversity on a limestone pavement

No empirical studies have examined the relationship between diversity and spatial heterogeneity across unimodal species richness gradients. We determined the relationships between diversity and environmental factors for 144 0.18 m² plots in a limestone pavement alvar in southern Ontario, Canada, including within-plot spatial heterogeneity in soil depth, microtopography and microsite composition. Species richness was unimodally related to mean soil depth and relative elevation. Microsite heterogeneity and soil depth heterogeneity were positively correlated with species richness, and the richness peaks of the unimodal gradients correspond to the maximally spatially heterogeneous plots. The best predictive models of species richness and evenness, however, showed that other factors, such as ramet density and flooding, are the major determinants of diversity in this system. The findings that soil depth heterogeneity had effects on diversity when the effects of mean soil depth were factored out, and that unimodal richness peaks were associated with high spatial heterogeneity in environmental factors represent significant contributions to our understanding of how spatial heterogeneity might contribute to diversity maintenance in plant communities.     

Eurosiberian meadows at their southern edge: patterns and phytogeography in the NW Tien Shan

Question: What are the community types, underlying gradients and phytogeographical affinities of montane meadows in the western Tien Shan? Location: Aksu‐Jabagly Nature Reserve, South Kazakhstan, Middle Asia. Methods: Species composition, structural and environmental variables were studied in 98 plots. Species composition was classified by cluster analysis and gradients explored using NMDS. Relationships between species richness, environmental and structural variables were investigated with regression analysis. Phytogeographic patterns were assessed by examining species distribution types. Results: Seven community types were distinguished by cluster analysis. Three axes of the NMDS explained 77% of the variation, showing different overlap of communities with environmental and structural properties. Species richness showed linear relationships with pH, altitude, heat load, soil skeletal content and structural variables. Middle Asian and Eurosiberian species constituted the majority of the species pool and cover. Conclusion: The studied communities represent a unique mixture of Middle Asian and Eurosiberian species that exhibit structural and environmental similarities to Eurosiberian meadows. The Tien Shan mountain meadows can thus be considered an endemic‐rich southern outlier of the broader Eurosiberian meadow formation. Shifts in land‐use patterns pose a potential threat that deserves more attention from conservationists.     

Phylogeny, traits, environment, and space in cerrado plant communities at Emas National Park (Brazil)

Soil, drought, and fire are abiotic factors that may act as environmental filters in the cerrado, the Brazilian savanna. We used a framework to analyze environmental filtering in geographic and phylogenetic context, sampling woody species in one of the largest cerrado reserves. In 100 quadrats, we measured 10 functional traits on each woody individual. We also measured several soil variables, altitude and slope as a rough surrogate of water availability, interval between fires, and time since last fire. Almost all environmental variables were spatially auto-correlated. We found an overall trait clustering, but not an overall phylogenetic clustering. Nevertheless, we found a phylogenetic signal for some traits. Linking phylogeny, traits, environment, and space, we were able to detect a major dichotomy between two geomorphological units. The flat tableland was positively related with altitude, fire frequency, and nutrient-richer soil. Environmental filtering caused by water availability and fire lead to trait clustering, with smaller shrubs and trees that presented thicker barks, denser woods, sclerophyllous leaves, highlighted by the prevalance of Myrtaceae. The other geomorphological unit, hilly terrain, was positively related with slope, low fire frequency, and nutrient-poorer soil. Environmental filtering was caused especially by nutrient-poor soil that lead to trait clustering, assembling taller trees, with thinner barks, lighter woods, and compound, large, tender, nutrient-richer leaves, distributed across many lineages, including Fabaceae. Hence, the high environmental variability in space with different environmental filters assembled different combination of plant traits and lineages, increasing the overall diversity in cerrado.