Community-weighted Mean Research Articles

Functional Traits Drive the Changes in Diversity and Composition of Benthic Invertebrate Communities in Response to Hydrological Regulation

Of all the environmental elements that influence the biological communities of rivers, water flow characteristics are undoubtedly the most important. Unfortunately, natural hydrological characteristics are increasingly threatened by human activities, especially in alpine or high mountain areas where there are numerous hydropower plants. In this study, we analysed the impact of hydrological alterations on the macroinvertebrate community of a lowland river in NW Italy. Specifically, we analysed the macroinvertebrate communities of an unaffected site by comparing them with those of a site subject to hydrological alteration. We adopted an approach that is not only taxonomic but also functional, allowing us to study a component of biodiversity that is generally less known. Our results show that the flow-altered site hosted a benthic community with lower species and functional diversity than the control site. Interestingly, we also detected a number of significant differences between the summer and autumn samples. In particular, examination of community-weighted mean (CWM) trait values reveals significant variation in body size, voltinism, substrate, locomotion, feeding habits and other traits between sites and seasons. The integration of taxonomic and functional approaches provides a comprehensive understanding of how human-induced hydrological variations can affect aquatic biodiversity and ecological functions.

Trees diversity explains variations in biodiversity-ecosystem function relationships across environmental gradients and conservation status in riparian corridors

Riparian ecosystems are recognized as large reservoirs of biodiversity providing important ecosystem services. However, the relationship between tree species diversity and ecosystem functions and the underlying ecological mechanisms have less been studied in riparian corridors. This study assessed the effect of tree diversity (taxonomic, functional, and phylogenetic) on riparian ecosystem functions (habitat quality–HbQ and aboveground carbon–AGC) across environmental gradients (distances to stream bed) and conservation status. Data were collected from 96 inventory plots installed in a 1 km buffer zone on either side of permanent streams in the Upper Ouémé watershed in northern Benin. We employed linear mixed effects models and structural equation modeling to analyze the data. We found that ecosystem functions (HbQ, AGC) and diversity attributes including species richness (SR), Faith’s phylogenetic diversity index (PD) and community-weighted mean of maximum height (CWMHmax) were significantly lower away from the streambed than nearby. The correlation between SR and ecosystem functions was significant and positive across and within the distance gradient and conservation status. We also found that the CWMHmax was the best predictor of both ecosystem functions, and that PD mediated the effect of SR on AGC and HbQ in areas close to the streambed and in unprotected areas, respectively. Our study reveals the influence of human activities on biodiversity and ecosystem functioning relationships in riparian corridors and provides new insights into the importance of tall stature trees and species with distant lineages for the functioning of these ecosystems. Based on the variables measured and tested in this study, we argue that riparian corridor management policies should consider plant traits and phylogeny and promote wider riparian buffers for the co-benefits of biodiversity conservation and climate change mitigation.

Taxonomic and functional-trait metrics track recovery of demersal fish and shrimp communities following system collapse

Monitoring programs that integrate both structural and functional ecosystem components play integral roles in ecosystem management and conservation planning. In the early 1990’s, the marine ecosystem of the waters surrounding Newfoundland and Labrador (NL) underwent a regime shift. Several demersal and pelagic fish stocks collapsed simultaneously, and this had significant ecological and socioeconomic consequences. As this regime shift impacted numerous commercial and non-commercial species, assessments based on individual species would be insufficient. We explored a variety of metrics that capture different facets of diversity across multiple species to provide a more robust ecosystem assessment. These were species richness, evenness, community-weighted means of maximum body length and trophic level (i.e., the mean maximum body size or trophic level of the species present in a community), and functional dispersion (FDis). The objectives of this study were 1) to assess trends in community structure of the NL demersal community during the post-collapse period (1995-2018), 2) explore how the various community-level metrics differ or are redundant, and 3) investigate how these metrics are associated with important covariates. Several metrics were redundant and displayed strongly positive, temporal trends being consistent with expectations for a recovery encompassing the entire demersal community. In particular, unweighted community-weighted means of body length and trophic level displayed nearly equal temporal patterns, showing increasing trends throughout the study period which were most prominent in the northern study area and within a limited depth range at the upper shelf break. Corresponding biomass-weighted metrics were also correlated with each other but only showed similar increasing tendencies after the first decade. In contrast, species richness did not show any temporal increase. Evenness and biomass-weighted FDis showed similar temporal patterns, decreasing during the first decade followed by strong increases during subsequent years, patterns that were directly linked to variation in Northern shrimp and Atlantic cod biomass. This study demonstrates how a variety of community metrics can provide insight into different aspects of the post-collapse recovery of the demersal community and help us better understand the complexity of the changes the ecosystem is undergoing.

Changes in taxonomic and functional composition of subalpine plant communities in response to climate change under contrasting conditions of bedrock and snow cover duration

AbstractQuestionsWe assessed interactions between climate change, bedrock types and snow cover duration on the trajectories of taxonomic and functional composition of subalpine plant communities. We predict (i) an increase in species richness on siliceous bedrock due to a reduced competition and a decrease in richness on calcareous bedrock due to increasing drought stress; (ii) decreasing snow cover duration should induce a higher shrub encroachment in hollows as compared to ridges; and (iii) increasing growing season temperature should induce taller sizes and more conservative growth traits, in particular in hollows.LocationSubalpine belt of the Grandes Rousses mountain range, southwestern Alps (France).Methods189 vegetation plots were sampled in 1997 and 2017–2018. The duration of snow cover was assessed during two years in 1995–1997 and five functional traits were measured on 108 species in 2021. We performed multivariate analyses, quantified community‐weighted means (CWM) of traits and used ANOVAs to detect responses to local‐scale factors and changes in snow cover, temperature and precipitation since 1997 according to a nearby meteorological station.ResultsOverall, taxonomic composition weakly changed and changes were more dependent on the position of communities along the snow cover duration gradient than on their bedrock type. The abundance of drought‐tolerant species increased at the border of hollows and there was, over all communities, a slight increase in the abundance of dwarf shrubs and tall herbaceous species, a strong decrease in short herbaceous species and, thus, an overall decrease in species richness. There were important overall changes in CWM of size traits, in particular leaf area which increased the most in hollows irrespective of bedrock types.ConclusionIn this subalpine site the effects of decreasing snow cover duration overwhelmed the effects of bedrocks, which may explain the overall increase in competitive species and decrease in species richness.

Bornean tropical forests recovering from logging at risk of regeneration failure.

Active restoration through silvicultural treatments (enrichment planting, cutting climbers and liberation thinning) is considered an important intervention in logged forests. However, its ability to enhance regeneration is key for long-term recovery of logged forests, which remains poorly understood, particularly for the production and survival of seedlings in subsequent generations. To understand the long-term impacts of logging and restoration we tracked the diversity, survival and traits of seedlings that germinated immediately after a mast fruiting in North Borneo in unlogged and logged forests 30-35 years after logging. We monitored 5119 seedlings from germination for ~1.5 years across a mixed landscape of unlogged forests (ULs), naturally regenerating logged forests (NR) and actively restored logged forests via rehabilitative silvicultural treatments (AR), 15-27 years after restoration. We measured 14 leaf, root and biomass allocation traits on 399 seedlings from 15 species. Soon after fruiting, UL and AR forests had higher seedling densities than NR forest, but survival was the lowest in AR forests in the first 6 months. Community composition differed among forest types; AR and NR forests had lower species richness and lower evenness than UL forests by 5-6 months post-mast but did not differ between them. Differences in community composition altered community-weighted mean trait values across forest types, with higher root biomass allocation in NR relative to UL forest. Traits influenced mortality ~3 months post-mast, with more acquisitive traits and relative aboveground investment favoured in AR forests relative to UL forests. Our findings of reduced seedling survival and diversity suggest long time lags in post-logging recruitment, particularly for some taxa. Active restoration of logged forests recovers initial seedling production, but elevated mortality in AR forests lowers the efficacy of active restoration to enhance recruitment or diversity of seedling communities. This suggests current active restoration practices may fail to overcome barriers to regeneration in logged forests, which may drive long-term changes in future forest plant communities.

Precipitation and plant community-weighted mean traits determine total transpirable soil water in a desert grassland

The desert grassland has low precipitation, high evaporation and a limited soil water supply. Thus the tension between water shortage and sustainable vegetation restoration is increasingly evident. Change in total transpirable soil water (TTSW) reflects the water utilization and extraction capacity of plant communities, which are the basis for maintaining productivity and stability in communities, as well as the key ecological processes alleviating the above tension. Change in TTSW is influenced by precipitation, vegetation and soil. Quantifying the relative contribution of these factors to change in TTSW is key to the sustainable restoration of desert grassland. However, the current understanding of such effects remains limited. This study examined four typical plant communities in the Ningxia desert grassland, monitoring soil water content and evaluating plant community characteristics and diversity over three consecutive years. Using redundancy analysis and hierarchical partitioning methods, the influence of annual precipitation, vegetation (functional and species diversity, community characteristics) and soil physical properties on TTSW variation were investigated. Findings revealed: (1) The factors contributing to TTSW variation were annual precipitation (41 %-68 %,), vegetation (29 %-45 %), and soil physical properties (0 %-6.7 %). Specifically, community-weighted mean traits (CWM) and functional diversity (FD) explained TTSW variation by 24–37 % and 0.25–11 % respectively. In Gramineae communities, the influence of annual precipitation and vegetation on TTSW variation was consistent across soil depths. However, in degraded Sophora alopecuroides + Artemisia scoparia (SA) communities, the influence of vegetation (CWM, FD, community composition and community function) on TTSW variation was more pronounced in shallow soils (45 %) than in deeper soils (33 %), while annual precipitation effects were more substantial in the deep soil layers (66 %) than in the shallow soil layers (42 %). (2) Annual precipitation and CWM were the main biological and abiotic factors affecting TTSW. Interestingly, increased annual precipitation was negatively correlated with TTSW. Similarly, the primary controlling factor, CWM, also showed a significant negative relationship with TTSW. This relationship varied across community types and could be linear or quadratic, highlighting the need to understand the selection effects mediated by CWM in ensuring sustainable vegetation restoration. This research offers insights into the relationship between plant functional diversity and soil water retention function.

Influence of surface water and groundwater on functional traits and trade-off strategies of oasis communities at the end of the Keriya River, China.

Plant functional traits reflect the capacity of plants to adapt to their environment and the underlying optimization mechanisms. However, few studies have investigated trade-off strategies for functional traits in desert-wetland ecosystems, the mechanisms by which surface water disturbance and groundwater depth drive functional trait variation at the community scale, and the roles of intraspecific and interspecific variation. Therefore, this study analyzed specific differences in community-weighted mean traits among habitat types and obtained the relative contribution of intraspecific and interspecific variation by decomposing community-weighted mean traits, focusing on the Daliyabuyi Oasis in the hinterland of the Taklamakan Desert. We also explored the mechanisms by which surface water and groundwater influence different sources of variability specifically. The results showed that plant height, relative chlorophyll content, leaf thickness, leaf nitrogen content, and nitrogen-phosphorus ratio were the key traits reflecting habitat differences. As the groundwater depth becomes shallower and surface water disturbance intensifies, plant communities tend to have higher leaf nitrogen content, nitrogen-phosphorus ratio, and relative chlorophyll content and lower height. Surface water, groundwater, soil water content, and total soil nitrogen can influence interspecific and intraspecific variation in these traits through direct and indirect effects. As arid to wet habitats change, plant trade-off strategies for resources will shift from conservative to acquisitive. The study concluded that community functional traits are mainly contributed by interspecific variation, but consideration of intraspecific variation and the covariation effects that exist between it and interspecific variation can help to further enhance the understanding of the response of community traits in desert-wetland ecosystems to environmental change. Surface water disturbance has a non-negligible contribution to this adaptation process and plays a higher role than groundwater depth.

Body size induced changes in metabolic carbon of soil nematodes under N deposition and precipitation regime change in a temperate grassland

Abstract Background Global climate change has resulted in precipitation regimes exhibiting an increasing trend in rainfall intensity but a reduction in its frequency. Nitrogen (N) deposition is a crucial component of the global N cycling. Nematode body size is a trait that responds to climate change and is used as a standard trait-based indicator in soil community analysis. Variations in body size influence metabolic carbon (C). We examined the ways by which body size and metabolic C of nematodes respond to changing precipitation regimes and how N deposition regulates these responses by an 8-year manipulative experiment. Methods Nematode body size was indicated by the community-weighted mean (CWM) mass. We quantified C metabolism components of soil nematodes including production C, respiration C, and corresponding C use efficiency (CUE) under different precipitation intensities and N addition in a semi-arid steppe on the Mongolian Plateau. The Mantel test was used to determine the correlations between CWM, CUE and environmental factors. The partial least squares path modeling (PLS-PM) was conducted to quantify direct or indirect contributions among latent variables. Results We found that heavy precipitation intensity increased the CWM mass of total nematodes and omnivores-predators without N addition. N addition decreased CWM mass of bacterivores across all the precipitation intensity treatments. Stronger precipitation intensities might be favorable for nematode production and respiration C. Variations in the nematode CWM mass drove the CUE to change with N addition. Conclusions Our findings provide new insights into the mechanisms underlying nematode body size and C metabolism, and highlight that explorative studies, such as manipulative experiments, are needed to identify traits underlying size-related effects and to investigate how they affect CUE of nematodes. These efforts may increase our understanding of how changes in precipitation regimes and N deposition may alter soil nematode communities in grassland ecosystems.

Vascular plant communities and biocrusts act as controlling factors in mitigating soil erosion on the Great Wall in a semi-humid area of Northwestern China

The Great Wall, a World Heritage Site and a vertical wall habitat, is under threat of soil erosion. The role of vascular plants and biocrust in controlling soil erosion has attracted attention, yet our knowledge of the underlying mechanism is limited, and there is a lack of systematic strategies for erosion prevention and control. In this study, we quantified the vascular plant community functional composition (including species diversity, functional diversity, and community-weighted mean), biocrust coverage, and soil erosion levels associated with seven different zones (lower, middle, and upper zones on East and West faces, plus wall crest) of the Great Wall. We then employed a combination of linear regression analysis, random forest model, and structural equation model to evaluate the individual and combined effects, as well as the direction and relative importance of these factors in reducing soil erosion. The results indicated that the vascular plant species richness, species diversity, functional richness, community-weighted mean, and moss crust coverage decreased significantly from the crest to the lower zone of the Great Wall (P < 0.05), and were negatively correlated with the soil erosion area and depth on both sides of the Great Wall (P < 0.05). This suggests that higher zones on the wall favored the colonization and growth of biocrusts and vascular plants and that biocrusts and vascular plants reduced soil erosion on the wall. Based on these findings, we propose a “restoration framework” for managing soil erosion on walls, based on biocrust and vascular plant communities (namely target species selection, plant community construction, biocrust inoculation, and maintenance of community stability), which aims to address the urgent need for more effective soil erosion prevention and control strategies on the Great Wall and provide practical methods that practitioners can utilize.

Climate regulation processes are linked to the functional composition of plant communities in European forests, shrublands, and grasslands.

Terrestrial ecosystems affect climate by reflecting solar irradiation, evaporative cooling, and carbon sequestration. Yet very little is known about how plant traits affect climate regulation processes (CRPs) in different habitat types. Here, we used linear and random forest models to relate the community-weighted mean and variance values of 19 plant traits (summarized into eight trait axes) to the climate-adjusted proportion of reflected solar irradiation, evapotranspiration, and net primary productivity across 36,630 grid cells at the European extent, classified into 10 types of forest, shrubland, and grassland habitats. We found that these trait axes were more tightly linked to log evapotranspiration (with an average of 6.2% explained variation) and the proportion of reflected solar irradiation (6.1%) than to net primary productivity (4.9%). The highest variation in CRPs was explained in forest and temperate shrubland habitats. Yet, the strength and direction of these relationships were strongly habitat-dependent. We conclude that any spatial upscaling of the effects of plant communities on CRPs must consider the relative contribution of different habitat types.

Trait-related functional changes in understory forest community after invasion are driven by complementarity rather than displacement

Forests support a variety of functions essential for the provisioning of ecosystem services. However, invasive plants can disrupt forest functioning, particularly in temperate forest understories that commonly experience invasive plant encroachment, by altering community-level trait distributions. Invasive plants, frequently characterized by acquisitive traits such as higher specific leaf area and nitrogen content, may either outcompete native species with different trait values (displacement), or add trait values to the existing community (complementarity). Therefore, complementarity may still allow restoration of the original community function by removing invasive species, and consequently the added provision of function when compared to the natives, but displacement may not. While understanding which process occurs is critical in managing ecosystem functionality, little is known about the impact of invasion on the co-occurring native community trait distributions. To address this knowledge gap, we leveraged survey data on temperate forest understories that varied in their degree of invasion (i.e., gradient of invasion). We calculated the community-weighted mean of three leaf traits: leaf nitrogen, specific leaf area, and leaf dry matter content – traits strongly linked to invasion, sensitive to environmental changes, and that affect ecosystem functions. Our findings show that increasing invasion had a significant positive effect on total (native and invasive) community leaf nitrogen, but did not alter native community trait distributions. This suggests that potential impacts on ecosystem functions, such as increased primary productivity and nitrogen cycling, would be primarily driven by trait complementarity and not displacement. We did not find any significant differences in the total or native communities with respect to specific leaf area or leaf dry matter content. Differentiating trait displacement from trait complementarity contributes to our understanding of how invasion affects functionality of understory plant communities in forests. Additionally, it provides a valuable framework to facilitate evidence-based decisions for the management of ecosystem functionality.

Contrasting roles of fungal and oomycete pathogens in mediating nitrogen addition and winter grazing effects on biomass.

Both bottom-up and top-down processes modulate plant communities. Fungal and oomycete pathogens are most common in global grasslands, and due to differences in their physiology, function, host range, and life cycles, they may differentially affect plants (in both intensity and direction). However, how fungal and oomycete pathogens regulate bottom-up and top-down effects on plant community biomass remains unclear. To this end, we conducted a 3-year field experiment in an alpine meadow incorporating mammalian herbivore exclosure, fungicide/oomyceticide application, and nitrogen addition treatments. We arranged 12 blocks with half randomly assigned to be mammalian herbivore exclosures (fenced to exclude grazing sheep), and the other half were fenced most of the year but not in winter (winter grazing control). Six 2.5 × 2.5 m square plots were established in each block, with each of the six plots assigned as control, nitrogen addition, fungicide application, oomyceticide application, nitrogen addition + fungicide application, and nitrogen addition + oomyceticide application. We found that fungicide application significantly increased plant community biomass (mainly Poaceae species) under nitrogen addition and promoted the bottom-up effect of nitrogen addition on plant community biomass by altering the community-weighted mean of plant height (via species turnover). Meanwhile, oomyceticide application significantly increased plant community biomass (mainly Poaceae species) when mammalian herbivores were excluded and weakened the top-down effect of winter grazing on plant community biomass by driving intraspecific variation in plant height. Our results highlight that fungal and oomycete pathogens play important (but differing) roles in mediating the effects of nutrient availability and higher trophic levels on plant community biomass. Mechanistically, we demonstrated that plant pathogen-related modulation of plant community biomass is achieved by alterations to plant height. Overall, this study combines both community and disease ecology to reveal complex interactions among higher trophic levels and their potential impacts on terrestrial ecosystem functioning under human disturbance.

Trophic niches of Collembola communities change with elevation, but also with body size and life form

Climate change will likely increase habitat loss of endemic tree species and drives forest conversion in mountainous forests. Elevation gradients provide the opportunity to predict possible consequences of such changes. While species compositions of various taxa have been investigated along elevation gradients, data on trophic changes in soil-dwelling organisms are scarce. Here, we investigated trophic changes of the Collembola communities along the northern slope of Changbai Mountain, China. We sampled Collembola in primary forests at seven elevations (800–1700 m asl). We measured individual body lengths and bulk stable isotopes on species level. We further categorized Collembola species into life forms. The community-weighted means of Δ15N and Δ13C values as well as minimum Δ15N values and isotopic uniqueness of Collembola communities increased with increasing elevation, while the range of Δ15N values decreased. Maximum and minimum of Δ13C values differed between elevations but showed no linear trend. Further, Δ15N values of Collembola species occurring across all elevations increased with elevation. Changes in Δ15N values with elevation were most pronounced in hemiedaphic species, while Δ13C values increased strongest with elevation in euedaphic species. Δ15N values increased with decreasing body size in hemiedaphic and euedaphic species. Overall, the results suggest that Collembola species functioning as primary decomposers at lower elevations shift towards functioning as secondary decomposers or even predators or scavengers at higher elevation forests. The results further indicate that access to alternative food resources depends on Collembola life form as well as body size and varies between ecosystems.

Food budget ratio as an equitable metric for food affordability and insecurity: a population-based cohort study of 121 remote Indigenous communities in Canada

BackgroundFood insecurity is a public health issue for many regions globally, and especially Indigenous communities. We propose food budget ratio (FBR)—the ratio of food spending to after-tax income—as an affordability metric that better aligns with health equity over traditional price-focused metrics. Existing census and inflation monitoring programs render FBR an accessible tool for future affordability research.MethodsPublic census and food pricing datasets from 2011 to 2021 were analyzed to evaluate food affordability for a cohort of 121 remote Indigenous communities in Canada (n = 80,354 persons as of March 2021). Trends in population-weighted versus community-weighted averages, inflation-adjusted mean price of the Revised Northern Food Basket (RNFB), and distributions of FBR, per-capita price of food, and per-capita after-tax income were calculated and compared to Canada at large.ResultsPopulation-weighted versus community-weighted mean price of the RNFB differed by < 5% for most points in time, peaking at 17%. Mean raw price of the RNFB was relatively stable, while mean inflation-adjusted price of the RNFB decreased 19%. Mean and standard deviation in FBR trended downwards from (0.40; 0.21) in 2011 to (0.25; 0.10) in 2021, while the mean for Canada held stable at 0.10 ± 0.01. Mean and standard deviation in inflation-adjusted per-capita price of food fell from ($5,621; $493) to ($4,510; $243), while the Canada-wide mean rose from $2,189 to $2,567; values for per-capita after-tax income increased from ($17,384; $7,816) to ($21,661; $9,707), while the Canada-wide mean remained between $24,443 and $26,006. Current Nutrition North Canada (NNC) subsidy rates correlate closely with distance to nearest transportation hub (σXY = 0.68 to 0.70) whereas food pricing, after-tax income, and FBR correlate poorly with distance (σXY = -0.22 to 0.03).ConclusionsThe FBR approach yields greater insights on food affordability compared to price-based results, while using readily available public datasets. Whereas 19% reductions in RNFB per-capita food price were observed, FBR decreased 63% yet remained 2.5 times the Canada-wide FBR. The reduction in FBR was driven both by the reduced price of food and a 25% increase in after-tax income. It is recommended that NNC consider FBR for performance measurement and setting subsidy rates.

Stand age-driven tree size variation and stand type regulate aboveground biomass in alpine-subalpine forests, South Korea

Alpine and subalpine forests in mountains worldwide are ecologically significant because of their unique biodiversity and increased vulnerability to climate change. This study was conducted to explore the possibilities and ways to preserve the ecological diversity of alpine-subalpine forests and their function as important carbon sinks. In this study, data from 664 plots (400 m2) were collected in the alpine-subalpine zones above 1000 m elevation in South Korea, we divided 664 plots into four stand types: conifer, conifer-dominant mixed, broadleaved-dominant mixed, and broadleaved stands. Abiotic drivers and forest successional stage-related factor including topographic, climatic drivers and stand age class were used. Biotic drivers including taxonomic, phylogenetic, functional, stand structural diversity, and community-weighted mean of functional traits were used to find independent variables controlling aboveground biomass (AGB) for each stand type. We employed multi-model averaging approach as well as piecewise structural equation modeling (pSEM) for the identification of the most influential variables affecting AGB in each stand type of alpine-subalpine forests and to quantify their interrelationships and strengths. The main results showed that tree size variation (i.e., DBH STD) induced by stand age had direct effects on AGB, with varying degrees of significance (β) ranging from 0.146 to 0.241 across all stand types in alpine-subalpine forests. Following these results, as forest succession progresses, tree species adapted to the specific environmental conditions, such as topography and climate, become dominant by creating their own niche, which increases AGB in each stand type. Additionally, climatic and topographic conditions played an important role in controlling biotic drivers depending on the stand type. In this study, we suggest that AGB should be managed and conserved depending on forest stand types according to forest succession. Furthermore, increasing size variation among tree individuals through proper forest treatments is important for increasing AGB in alpine-subalpine forests.

Management of grassland: A necessary tool to maintain plant and earthworm diversity

In temperate grassland, earthworms contribute to the major soil processes which determine most of the ecosystem services. The characteristics of plant communities in grassland are key factors in maintaining earthworm communities, however effects of different herbage management on earthworms remain largely unknown. In this context, the aim of the present study was to determine the long-term effects of herbage management on grassland plant and earthworm communities. Plants and earthworms were sampled in a 14-years-old experiment in upland grasslands (Massif central, France). Abandoned grasslands were compared with mowed grasslands and with pastures grazed by cattle (at low or high intensities) or grazed by sheep (at low intensity). Compared to abandoned grassland, herbage management by grazing or by mowing display higher leguminous plant, community-weighted mean Ellenberg light values as well as plant richness while they display lower percentage of plant litter and community-weighted mean Ellenberg nitrogen values. The differences in plant richness were associated with a significant change in plant community structure. Compared to the abandoned grassland, herbage management by grazing or mowing significantly display higher earthworm biomass and total richness. Except for pastures grazed by cattle at high intensity, earthworm abundance was at least twice that in the grassland at low grazing intensity or mowing compared to the abandoned grassland. Earthworm communities were significantly different between grazed and mown treatments notably due to changes within Aporrectodea anecic and endogeic earthworm species. Overall, herbage management by animals or by mechanical export is beneficial for plant and earthworm diversity although no clear differences between management practices for earthworm richness, total biomass or total abundance were observed. Our results highlight that abandonment does not preserve biodiversity (plant, soil macrofauna) while management of grassland by grazing or mowing is a necessary tool for biodiversity conservation and improvement.

Grassland sensitivity to drought is related to functional composition across East Asia and North America.

Plant traits can be helpful for understanding grassland ecosystem responses to climate extremes, such as severe drought. However, intercontinental comparisons of how drought affects plant functional traits and ecosystem functioning are rare. The Extreme Drought in Grasslands experiment (EDGE) was established across the major grassland types in East Asia and North America (six sites on each continent) to measure variability in grassland ecosystem sensitivity to extreme, prolonged drought. At all sites, we quantified community-weighted mean functional composition and functional diversity of two leaf economic traits, specific leaf area and leaf nitrogen content, in response to drought. We found that experimental drought significantly increased community-weighted means of specific leaf area and leaf nitrogen content at all North American sites and at the wetter East Asian sites, but drought decreased community-weighted means of these traits at moderate to dry East Asian sites. Drought significantly decreased functional richness but increased functional evenness and dispersion at most East Asian and North American sites. Ecosystem drought sensitivity (percentage reduction in aboveground net primary productivity) positively correlated with community-weighted means of specific leaf area and leaf nitrogen content and negatively correlated with functional diversity (i.e., richness) on an intercontinental scale, but results differed within regions. These findings highlight both broad generalities but also unique responses to drought of community-weighted trait means as well as their functional diversity across grassland ecosystems.

Asymmetric environmental selection on intraspecific body size in Collembola communities along an elevational gradient in northern Japan

Body size is a crucial functional trait that influences the environmental filtering processes of animal communities. However, the role of intraspecific variations in soil invertebrate communities remains poorly understood. In this study, we investigated the influence of environmental changes on intraspecific body size variations in Collembola communities along an elevational gradient in northern Japan, using potential body length in the literature cited and realized body length actually measured. Our hypothesis posits that environmental conditions selectively filtered out smaller nymphs while sparing larger adults of Collembola, as stress tolerance, survival and mortality are directly influenced by body size in response to environmental severity. Calculating size quantiles based on observed realized individual body lengths, we found a stable size hierarchy among species across elevational sites. Species composition was significantly related with elevational gradient, with community-weighted means of smaller quantiles in body length increasing at higher elevations, while those of larger quantiles and adult body size remained unaffected. This suggests that environmental filtering predominantly influences the body size of smaller individuals, such as nymphs, but not larger adults within species. Our findings reveal asymmetric size selection among different life stages in soil animal communities.

Integrating field- and remote sensing data to perceive species heterogeneity across a climate gradient.

Tropical forests exhibit significant diversity and heterogeneity in species distribution. Some tree species spread abundantly, impacting the functional aspects of communities. Understanding how these facets respond to climate change is crucial. Field data from four protected areas (PAs) were combined with high-resolution Airborne Visible/InfraRed Imaging Spectrometer-Next Generation (AVIRIS-NG) datasets to extract large-scale plot data of abundant species and their functional traits. A supervised component generalized linear regression (SCGLR) model was used to correlate climate components with the distribution of abundant species across PAs. The recorded rainfall gradient influenced the proportion of PA-specific species in the observed species assemblages. Community weighted means (CWMs) of biochemical traits showed better correlation values (0.85-0.87) between observed and predicted values compared to biophysical traits (0.52-0.79). The model-based projection revealed distinct distribution responses of each abundant species to the climate gradient. Functional diversity and functional traits maps highlighted the interplay between species heterogeneity and climate. The appearance dynamics of abundant species in dark diversity across PAs demonstrated their assortment strategy in response to the climate gradient. These observations can significantly aid in the ecological management of PAs exposed to climate dynamics.

Lianas shift towards larger sizes and more acquisitive trait values in an Asian tropical rainforest

AbstractGlobal change is impacting forests worldwide, leading to shifts in forest dynamics and functional composition. We evaluated the changes in the liana community and trait composition over a five‐year period (2014–2019) in a Chinese tropical rainforest and assessed the underlying putative mechanisms. We monitored &gt;20,000 lianas in a 20‐ha plot, and analyzed community changes for each of the 20 1‐ha plots. To identify the putative drivers underlying community change, we used community‐weighted mean (CWM) trait values of 18 functional traits that are important for liana performance. During the 5‐year period, liana density decreased by 12.6% because of the high mortality of small lianas, whereas liana basal area increased by 5.8% because of the high growth of large lianas. After 5 years, liana communities showed a shift in trait values indicating that they changed towards more large, acquisitive lianas with rapid water use. The temporal shift from slow to fast community trait spectra in carbon, nutrient, and water use was also supported by shifts in the individual CWM traits, from conservative tough leaves towards more acquisitive and water‐spending leaves with higher K concentration, leaf thickness, and vessel diameter. Overall, we found no support for a role of disturbances or drought as drivers of the observed changes in the studied liana community. Instead, our study implies that CO2 fertilization should be considered to better understand dynamics in liana communities in tropical forests.Abstract in Chinese is available with online material.