Search

Summary Multispecies planting is an important approach to deliver ecosystem functions in afforestation projects. However, the importance of species richness vs specific species composition in this context remains unresolved. To estimate species or functional group richness and compositional change between two communities, we calculated nestedness, where one community contains a subset of the species of another, and turnover, where two communities differ in species composition but not in species richness. We evaluated the effects of species/functional group nestedness and turnover on stand productivity using 315 mixed plots from a pool of 40 tree species in a large forest biodiversity experiment in subtropical China. We found that the greater the differences in species or functional group nestedness and turnover, the greater the differences in stand productivity between plots. Additionally, the strong effects of both nestedness and turnover on stand productivity developed over the 11‐yr observation period. Our results indicate that selection of specific tree species is as important as planting a large number of species to support the productivity function of forests. Furthermore, the selection of specific tree species should be based on functionality, because beneficial effects of functional group composition were stronger than those of species composition. [ABSTRACT FROM AUTHOR]

Long-term research in grassland biodiversity experiments has provided empirical evidence that ecological and evolutionary processes are intertwined in determining both biodiversity–ecosystem functioning (BEF) and biodiversity–stability relationships. Focusing on plant diversity, we hypothesize that multifunctional stability is highest in high-diversity plant communities and that biodiversity–stability relationships increase over time due to a variety of forms of ecological complementarity including the interaction with other biota above and below ground. We introduce the multiple-mechanisms hypothesis of biodiversity–stability relationships suggesting that it is not an individual mechanism that drives long-term biodiversity effects on ecosystem functioning and stability but that several intertwined processes produce increasingly positive ecosystem effects. The following six mechanisms are important. Low-diversity plant communities accumulate more plant antagonists over time (1), and use resources less efficiently and have more open, leaky nutrient cycles (2). Conversely, high-diversity plant communities support a greater diversity and activity of beneficial interaction partners across trophic levels (3); diversify in their traits over time and space, within and across species, to optimize temporal (intra- and interannual) and spatial complementarity (4), create a more stable microclimate (5), and foster higher top-down control of aboveground and belowground herbivores by predators (6). In line with the observation that different species play unique roles in ecosystems that are dynamic and multifaceted, the particular mechanism contributing most to the higher performance and stability of diverse plant communities might differ across ecosystem functions, years, locations, and environmental change scenarios. This indicates "between-context insurance" or "across-context complementarity" of different mechanisms. We introduce examples of experiments that will be conducted to test our hypotheses and which might inspire additional work. [ABSTRACT FROM AUTHOR]

Extreme climate events such as floods and droughts are becoming increasingly frequent and intense across the world. Future climate scenarios predict both an increase in individual extreme events, as well as chronic changes in climatic seasonality. Yet, the combined and relative effects of these pressures on ecosystems remain unknown. Concurrently, human-induced ecological disruption is accelerating species extinction rates, which are estimated to be 100 to 1000 times greater than pre-human levels. This is alarming as greater biological diversity is thought to buffer ecosystem functioning against extreme climate events, thereby safeguarding the provisioning of essential ecological services that contribute to human well-being. However, how and to what extent biodiversity buffers ecosystems against climate variability remains unclear. We recently constructed experimental grassland communities in a mesocosm-based field design representing a realistic gradient of plant diversity. Both extreme events (drought and flood) and a change in seasonality of precipitation are manipulated in a full factorial design to quantify the effects of future seasonal shifts and extremes in precipitation. We will: 1) determine to what extent higher biological diversity ensures that grasslands can continue to provide multiple ecosystem services even in the context of climate change and 2) unravel the fundamental mechanisms by which this is achieved including species asynchrony and positive species interactions. Results of our experimental approach will advance our understanding of the buffering potential of plant diversity and contribute to the development of strategies for sustainable service provisioning of our ecosystems in the face of climate change.

Long-term research in grassland biodiversity experiments has provided empirical evidence that ecological and evolutionary processes are intertwined in determining both biodiversity–ecosystem functioning (BEF) and biodiversity–stability relationships. Focusing on plant diversity, we hypothesize that multifunctional stability is highest in high-diversity plant communities and that biodiversity–stability relationships increase over time due to a variety of forms of ecological complementarity including the interaction with other biota above and below ground. We introduce the multiple-mechanisms hypothesis of biodiversity–stability relationships suggesting that it is not an individual mechanism that drives long-term biodiversity effects on ecosystem functioning and stability but that several intertwined processes produce increasingly positive ecosystem effects. The following six mechanisms are important. Low-diversity plant communities accumulate more plant antagonists over time (1), and use resources less efficiently and have more open, leaky nutrient cycles (2). Conversely, high-diversity plant communities support a greater diversity and activity of beneficial interaction partners across trophic levels (3); diversify in their traits over time and space, within and across species, to optimize temporal (intra- and interannual) and spatial complementarity (4), create a more stable microclimate (5), and foster higher top-down control of aboveground and belowground herbivores by predators (6). In line with the observation that different species play unique roles in ecosystems that are dynamic and multifaceted, the particular mechanism contributing most to the higher performance and stability of diverse plant communities might differ across ecosystem functions, years, locations, and environmental change scenarios. This indicates “between-context insurance” or “across-context complementarity” of different mechanisms. We introduce examples of experiments that will be conducted to test our hypotheses and which might inspire additional work.

Summary: Decades of studies have demonstrated links between biodiversity and ecosystem functioning, yet the generality of the relationships and the underlying mechanisms remain unclear, especially for forest ecosystems.Using 11 tree‐diversity experiments, we tested tree species richness–community productivity relationships and the role of arbuscular (AM) or ectomycorrhizal (ECM) fungal‐associated tree species in these relationships.Tree species richness had a positive effect on community productivity across experiments, modified by the diversity of tree mycorrhizal associations. In communities with both AM and ECM trees, species richness showed positive effects on community productivity, which could have resulted from complementarity between AM and ECM trees. Moreover, both AM and ECM trees were more productive in mixed communities with both AM and ECM trees than in communities assembled by their own mycorrhizal type of trees. In communities containing only ECM trees, species richness had a significant positive effect on productivity, whereas species richness did not show any significant effects on productivity in communities containing only AM trees.Our study provides novel explanations for variations in diversity–productivity relationships by suggesting that tree–mycorrhiza interactions can shape productivity in mixed‐species forest ecosystems. [ABSTRACT FROM AUTHOR]

The frequency of consecutive drought years is predicted to increase due to climate change. These droughts have strong negative impacts on forest ecosystems. Mixing tree species is proposed to increase the drought resistance and resilience of tree communities. However, this promising diversity effect has not yet been investigated under extreme drought conditions and in the context of complementary mycorrhizal associations and their potential role in improving water uptake.Here, we investigate whether tree diversity promotes growth resistance and resilience to extreme drought and whether drought responses are modulated by mycorrhizal associations. We used inventory data (2015–2021) from a young tree diversity experiment in Germany, manipulating tree species richness (1, 2 and 4 species) and mycorrhizal type (communities containing arbuscular mycorrhizal [AM] or ectomycorrhizal [EM] tree species, or both). For all tree communities, we calculated basal area increment in the periods before, during and after drought and used the concepts of resistance and resilience to quantify growth responses to drought.We found strong growth declines during the extreme 2018–2020 drought for most tree communities. Contrary to our hypothesis, we did not find that tree species richness per se can buffer the negative impacts of extreme drought on tree growth. However, while for EM communities, drought resistance and resilience decreased with tree species richness, they increased for AM communities and communities comprising both mycorrhizal types. We highlight that among various mixtures of tree species, only those with mixed mycorrhizal types outperformed their respective monocultures during and after drought. Furthermore, under extreme drought, the community tends to segregate into 'winner' and 'loser' tree species in terms of diversity, indicating a possible intensification of competition.While we cannot disentangle the underlying mechanisms or clarify the role of mycorrhiza during drought, our findings suggest that mixtures of mycorrhizal types within tree communities could help safeguard forests against increasing drought frequency.Synthesis. Drought resistance and resilience of tree communities depend on tree diversity and mycorrhizal association types. Mixing tree species with diverse mycorrhizal types holds promise for forest restoration in the face of climate change. [ABSTRACT FROM AUTHOR]

Increases in species richness with habitat area (species–area relationship, or SAR) and increases in ecosystem function with species richness (biodiversity–ecosystem functioning, or BEF) are widely studied ecological patterns. Incorporating functional trait analysis into assemblage datasets may help clarify interpretations of SAR and BEF relationships in natural ecological systems. For example, life history theory can be used to make predictions about what species are most important in generating ecosystem function given a certain set of environmental conditions. We used quantitative assemblage data for freshwater mussels at nine sites in western Alabama, USA, to test for SAR and BEF relationships. At each site, we calculated species richness, mussel assemblage density, and two fundamental metrics of ecosystem function: biomass and secondary production. We also tested whether the proportional biomass and production contributions from species belonging to each of three life history strategies—opportunistic strategists adapted to unstable or frequently disturbed habitats, periodic strategists adapted to habitats subject to predictable large‐scale disturbances, and equilibrium strategists adapted to stable habitats—varied longitudinally with stream drainage area, a proxy for habitat area. Species richness increased with stream size (SAR), and both biomass and production increased with species richness (BEF) and mussel density. There were few longitudinal changes in the proportional contributions of the different life history strategy classifications that we used, but the invasive clam Corbicula fluminea contributed proportionally more biomass and production at sites that had smaller drainage areas. This study provides further evidence for a clear longitudinal SAR in stream‐dwelling taxa. It also suggests BEF relationships for biomass and secondary production in natural assemblages but underscores the importance of assemblage density in BEF studies that use observational field data. Variation in proportional biomass and production contributions by different life history strategies was likely limited by the size of the stream size gradient in our study, as contributions were uniformly high for species with life history traits better adapted to stable and productive habitats such as mid‐sized rivers with low or predictable hydrologic disturbance frequencies. This highlights the need to understand how organisms' functional traits govern their relationships to the environment at different scales. [ABSTRACT FROM AUTHOR]

The capacity of forests to sequester carbon in both above‐ and belowground compartments is a crucial tool to mitigate rising atmospheric carbon concentrations. Belowground carbon storage in forests is strongly linked to soil microbial communities that are the key drivers of soil heterotrophic respiration, organic matter decomposition and thus nutrient cycling. However, the relationships between tree diversity and soil microbial properties such as biomass and respiration remain unclear with inconsistent findings among studies. It is unknown so far how the spatial configuration and soil depth affect the relationship between tree richness and microbial properties. Here, we studied the spatial distribution of soil microbial properties in the context of a tree diversity experiment by measuring soil microbial biomass and respiration in subtropical forests (BEF‐China experiment). We sampled soil cores at two depths at five locations along a spatial transect between the trees in mono‐ and hetero‐specific tree pairs of the native deciduous species Liquidambar formosana and Sapindus saponaria. Our analyses showed decreasing soil microbial biomass and respiration with increasing soil depth and distance from the tree in mono‐specific tree pairs. We calculated belowground overyielding of soil microbial biomass and respiration – which is higher microbial biomass or respiration than expected from the monocultures – and analysed the distribution patterns along the transect. We found no general overyielding across all sampling positions and depths. Yet, we encountered a spatial pattern of microbial overyielding with a significant microbial overyielding close to L. formosana trees and microbial underyielding close to S. saponaria trees. We found similar spatial patterns across microbial properties and depths that only differed in the strength of their effects. Our results highlight the importance of small‐scale variations of tree–tree interaction effects on soil microbial communities and functions and are calling for better integration of within‐plot variability to understand biodiversity–ecosystem functioning relationships. [ABSTRACT FROM AUTHOR]

Livestock overgrazing causes environmental degradation, species invasion, biodiversity loss, and productivity decline, with profound consequences for ecological sustainability and human livelihoods. Habitat protection can mitigate such impacts, but we know little about how the long‐term recovery of plant communities from livestock overgrazing depends on the presence of encroaching shrubs. Here, we explored how shrub encroachment mediates the effects of habitat protection (i.e., livestock exclusion and creation of UNESCO protected areas) on biodiversity recovery and ecosystem functioning (i.e., biomass productivity). We leveraged a long‐term (15–25 years) experiment of livestock exclusion and complemented it with the removal of an encroaching shrub species in pasture areas and protected areas. We reveal that habitat protection has positive effects on patterns of recovery. Yet, the effects of habitat protection are mediated by shrub encroachment. Encroaching shrubs have net positive effects on plant diversity in pasture areas but inhibit biodiversity recovery in protected areas. The combination of habitat protection and the removal of encroaching shrubs best enhances the recovery of plant diversity and biomass productivity. A potential underlying mechanism is the shift in plant interactions from facilitation for recruitment and associated resistance to competition for water. Understanding species interactions is key to guiding conservation and restoration actions which can turn degraded ecosystems back into functional, species‐rich communities. [ABSTRACT FROM AUTHOR]

The relationship between biodiversity and multitrophic ecosystem functions (BEF) remains poorly studied in forests. There have been inconsistent reports regarding the significance of tree diversity effects on ecosystem functions, which may be better understood by considering critical biotic interactions of trees.This study investigates the role of tree‐mycorrhizal associations that may shape forest BEF relationships across multiple ecosystem functions. We used a field experiment (MyDiv) that comprises 10 deciduous tree species associated with either arbuscular mycorrhizal (AM) or ectomycorrhizal (EcM) fungi to create gradients in species richness (1, 2, 4 species) and different mycorrhizal communities (only AM‐species [AM fungi associated tree species] or EcM‐species [EcM fungi associated tree species], or a combination of both). We investigated the effects of tree species richness and mycorrhizal types on crucial multitrophic ecosystem functions (foliage damage, predation [using artificial caterpillars] and soil fauna feeding activity [~0–10 cm]) and assessed how these effects were mediated by stand characteristics.Overall, we found that tree species richness and mycorrhizal types strongly affected multitrophic ecosystem functions. Compared to monocultures, 4‐species mixtures with both mycorrhizal types experienced significantly lower foliage damage. The mixtures of EcM‐species supported significantly higher predation (i.e. a greater proportion of artificial caterpillars being attacked), and this effect strengthened with tree species richness. The effects of tree species richness on soil fauna feeding activity were negative across all mycorrhizal types in the lower soil layer. Moreover, we showed that tree diversity effects were mediated by above‐ground tree biomass, vertical structural complexity and leaf quality, with the dominating mechanisms largely depending on the mycorrhizal types.Synthesis. Tree species richness affected multitrophic ecosystem functioning by (1) directly decreasing the proportion of foliage damage in the communities with both mycorrhizal types, where AM‐species benefited from mixing with EcM‐species, and (2) increasing predation rates via changes in the vertical structural complexity in mixtures of EcM‐species. Our results highlight the importance of considering mycorrhizal types for managing well‐functioning mixed‐species forests and contribute to broadening the mechanistic understanding of the context‐dependent BEF relationships in forests. [ABSTRACT FROM AUTHOR]

Abstract Increases in species richness with habitat area (species–area relationship, or SAR) and increases in ecosystem function with species richness (biodiversity–ecosystem functioning, or BEF) are widely studied ecological patterns. Incorporating functional trait analysis into assemblage datasets may help clarify interpretations of SAR and BEF relationships in natural ecological systems. For example, life history theory can be used to make predictions about what species are most important in generating ecosystem function given a certain set of environmental conditions. We used quantitative assemblage data for freshwater mussels at nine sites in western Alabama, USA, to test for SAR and BEF relationships. At each site, we calculated species richness, mussel assemblage density, and two fundamental metrics of ecosystem function: biomass and secondary production. We also tested whether the proportional biomass and production contributions from species belonging to each of three life history strategies—opportunistic strategists adapted to unstable or frequently disturbed habitats, periodic strategists adapted to habitats subject to predictable large‐scale disturbances, and equilibrium strategists adapted to stable habitats—varied longitudinally with stream drainage area, a proxy for habitat area. Species richness increased with stream size (SAR), and both biomass and production increased with species richness (BEF) and mussel density. There were few longitudinal changes in the proportional contributions of the different life history strategy classifications that we used, but the invasive clam Corbicula fluminea contributed proportionally more biomass and production at sites that had smaller drainage areas. This study provides further evidence for a clear longitudinal SAR in stream‐dwelling taxa. It also suggests BEF relationships for biomass and secondary production in natural assemblages but underscores the importance of assemblage density in BEF studies that use observational field data. Variation in proportional biomass and production contributions by different life history strategies was likely limited by the size of the stream size gradient in our study, as contributions were uniformly high for species with life history traits better adapted to stable and productive habitats such as mid‐sized rivers with low or predictable hydrologic disturbance frequencies. This highlights the need to understand how organisms' functional traits govern their relationships to the environment at different scales.

Abstract The capacity of forests to sequester carbon in both above‐ and belowground compartments is a crucial tool to mitigate rising atmospheric carbon concentrations. Belowground carbon storage in forests is strongly linked to soil microbial communities that are the key drivers of soil heterotrophic respiration, organic matter decomposition and thus nutrient cycling. However, the relationships between tree diversity and soil microbial properties such as biomass and respiration remain unclear with inconsistent findings among studies. It is unknown so far how the spatial configuration and soil depth affect the relationship between tree richness and microbial properties. Here, we studied the spatial distribution of soil microbial properties in the context of a tree diversity experiment by measuring soil microbial biomass and respiration in subtropical forests (BEF‐China experiment). We sampled soil cores at two depths at five locations along a spatial transect between the trees in mono‐ and hetero‐specific tree pairs of the native deciduous species Liquidambar formosana and Sapindus saponaria. Our analyses showed decreasing soil microbial biomass and respiration with increasing soil depth and distance from the tree in mono‐specific tree pairs. We calculated belowground overyielding of soil microbial biomass and respiration – which is higher microbial biomass or respiration than expected from the monocultures – and analysed the distribution patterns along the transect. We found no general overyielding across all sampling positions and depths. Yet, we encountered a spatial pattern of microbial overyielding with a significant microbial overyielding close to L. formosana trees and microbial underyielding close to S. saponaria trees. We found similar spatial patterns across microbial properties and depths that only differed in the strength of their effects. Our results highlight the importance of small‐scale variations of tree–tree interaction effects on soil microbial communities and functions and are calling for better integration of within‐plot variability to understand biodiversity–ecosystem functioning relationships.

The biodiversity-ecosystem functioning (BEF) relationship is a critical topic in ecological research, as it guides the maintenance of ecosystem functioning in the face of climate change and human disturbance. However, the BEF relationship is complicated by the fact that biodiversity has multiple dimensions, and in particular functional diversity may be strongly correlated with community productivity. But the understanding is still lacking about how different functional traits determine community productivity. The present study tested the relationship between biodiversity and community productivity empirically in a demersal fish community, based on continuous bottom trawl surveys in Haizhou Bay, China from 2013 to 2022. Structural equation modeling (SEM) with composite variables was used to evaluate the relationships among environmental factors, species diversity (SD), functional diversity (FD), community weighted mean traits (CWM), and community productivity (CP), and the roles of different aspects of functional traits were further compared. The results showed that there were considerable heterogeneities in the temporal and spatial distributions of CP, and PCA revealed that the CP was weakly correlated with both species and functional diversity. SEM showed that CWM had the greatest influences on CP (r = 0.63), followed by SD (r = 0.52), and FD had the least impact (r = -0.42). This finding supported the mass ratio hypothesis, indicating that functional traits of dominant species determined community productivity. Environmental factors showed no direct impacts on CP but had indirect effects through biodiversity. Regarding the role of different functional traits, the trait of locomotion was the most important driver of CP in terms of CWM, while the food acquisition was more important than other components in terms of FD. Our study can contribute to an improved comprehension of the BEF linkages in marine fish communities, and serve as a guideline for fisheries management and biodiversity protection in the face of climate changes.

The relationship between biodiversity and ecosystem function (BEF) captivates ecologists, but the factors responsible for the direction of this relationship remain unclear. While higher ecosystem functioning at higher biodiversity levels ('positive BEF') is not universal in nature, negative BEF relationships seem puzzlingly rare. Here, we develop a dynamical consumer‐resource model inspired by microbial decomposer communities in pitcher plant leaves to investigate BEF. We manipulate microbial diversity via controlled colonization and measure their function as total ammonia production. We test how niche partitioning among bacteria and other ecological processes influence BEF in the leaves. We find that a negative BEF can emerge from reciprocal interspecific inhibition in ammonia production causing a negative complementarity effect, or from competitive hierarchies causing a negative selection effect. Absent these factors, a positive BEF was the typical outcome. Our findings provide a potential explanation for the rarity of negative BEF in empirical data. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms underlying diversity–productivity relationships (DPRs) is crucial to mitigating the effects of forest biodiversity loss. Tree–tree interactions in diverse communities are fundamental in driving growth rates, potentially shaping the emergent DPRs, yet remain poorly explored. Here, using data from a large‐scale forest biodiversity experiment in subtropical China, we demonstrated that changes in individual tree productivity were driven by species‐specific pairwise interactions, with higher positive net pairwise interaction effects on trees in more diverse neighbourhoods. By perturbing the interactions strength from empirical data in simulations, we revealed that the positive differences between inter‐ and intra‐specific interactions were the critical determinant for the emergence of positive DPRs. Surprisingly, the condition for positive DPRs corresponded to the condition for coexistence. Our results thus provide a novel insight into how pairwise tree interactions regulate DPRs, with implications for identifying the tree mixtures with maximized productivity to guide forest restoration and reforestation efforts. [ABSTRACT FROM AUTHOR]

Biodiversity drives ecosystem processes, but its influence on deadwood decomposition is poorly understood. To test the effects of insect diversity on wood decomposition, we conducted a mesocosm experiment manipulating the species richness and functional diversity of beetles. We applied a novel approach using computed tomography scanning to quantify decomposition by insects and recorded fungal and bacterial communities. Decomposition rates increased with both species richness and functional diversity of beetles, but the effects of functional diversity were linked to beetle biomass, and to the presence of one large‐bodied species in particular. This suggests that mechanisms behind observed biodiversity effects are the selection effect, which is linked to the occurrence probability of large species, and the complementarity effect, which is driven by functional differentiation among species. Additionally, beetles had significant indirect effects on wood decomposition via bacterial diversity, fungal community composition, and fungal biomass. Our experiment shows that wood decomposition is driven by beetle diversity and its interactions with bacteria and fungi. This highlights that both insect and microbial biodiversity are critical to maintaining ecosystem functioning. [ABSTRACT FROM AUTHOR]

Diversity-biomass relationships (DBRs) in terrestrial ecosystems tend to vary across spatial scales, but, particularly in hyperdiverse forests, the mechanisms driving these trends remain uncertain. Until now, few have simultaneously investigated the connections between tree species diversity, stand structural diversity, mycorrhizal associations, and ecosystem functioning. In addition, DBRs have only been studied at limited spatial scales, with limited focus on the direct and indirect effects of environmental factors. We addressed these research gaps using a 30-ha forest dynamics plot located in Pu'er City, Southwest China. Through piecewise structural equation models, we quantified the direct effects of tree species diversity (α, β, γ), stand structural diversity, mycorrhizal associations (AM, EcM), and the environmental factors (soil fertility and topography), as well as the indirect effects of the environmental factors on aboveground tree biomass across spatial scales ranging from 400 to 230,400 ​m2. We hypothesized that complex interactions among these factors underpin the variation in DBRs in natural ecosystems across spatial scales. Our results showed that environmental conditions indirectly affected the tree biomass via changes in tree species diversity, and these effects became stronger as the spatial scale increased. At small to moderate spatial scales, environmental factors were more predictive of tree biomass than tree species diversity (or its components); the effects of stand structural diversity on biomass also gradually increased with spatial scale. Conversely, from the intermediate to the largest spatial scales, mycorrhizal associations gradually became the best predictors of DBR dynamics. Our research offers novel empirical evidence demonstrating the importance of environmental conditions, structural diversity, and mycorrhizal associations in shaping cross-scale DBRs. Future comprehensive studies should consider these factors to assess the mechanisms shaping scale-dependent DBRs in complex natural ecosystems.

An improved understanding of biodiversity-productivity relationships (BPRs) along environmental gradients is crucial for effective ecosystem management and biodiversity conservation. The stress-gradient hypothesis suggests that BPRs are stronger in stressful environments compared to more favorable conditions. However, there is limited knowledge regarding the variation of BPRs along elevational gradients and their generality across different landscapes. To study how BPRs change with elevation, we harnessed inventory data on 6,431 trees from 152 plots surveyed twice in eight to ten year intervals in mountain forests of temperate Europe and subtropical Asia. We quantified the relationship between aboveground productivity and different biodiversity measures, including taxonomic, functional, and phylogenetic diversity. To elucidate the processes underlying BPRs, we studied the variation of different functional traits along elevation across landscapes. We found no general pattern of BPRs across landscapes and elevations. Relationships were neutral for all biodiversity measures in temperate forests, and negative for taxonomic and functional diversity in subtropical forests. BPRs were largely congruent between taxonomic, functional and phylogenetic diversity. We found only weak support for the stress-gradient hypothesis, with BPRs turning from negative to positive (effect not significant) close to the tree line in subtropical forests. In temperate forests, however, elevation patterns were strongly modulated by species identity effects as influenced by specific traits. The effect of traits such as community-weighted mean of maximum plant height and wood density on productivity was congruent across landscapes. Our study highlights the context-dependence of BPRs across elevation gradients and landscapes. Species traits are key modulating factors of BPRs and should be considered more explicitly in studies of the functional role of biodiversity. Furthermore, our findings highlight that potential trade-offs between conserving biodiversity and fostering ecosystem productivity exist, which require more attention in policy and management.

Introduction: Climate change and mono-afforestation or mono-reforestation have continuously caused a decline in biodiversity and ecosystem services on forest plantations. Key plant functional traits in forests or plantations may affect ecosystem functions after forest management practices. Plant clonality, a key functional trait, frequently links to biodiversity and ecosystem functions and affects the biodiversity--ecosystem functioning relationship. However, little is known about how plant clonality affects ecosystem functions and services of plantations after forest management. Methods: We conducted a field experiment to discuss the diversity and proportion of clonal plants, plant diversity of the communities, and ecosystem service functions and their relationships under 10 years of close-to-nature (CTN) management, artificial gap management, and control (i.e., without management) in the three stages of C. Lanceolata plantations. Results: Our results showed that CTN and gap management modes significantly facilitated diversity of clonal plants, plant diversity of the communities, and parameters of ecosystem service functions in C. lanceolata plantations. Moreover, CTN management promoted plant community diversity, soil water conservation, and carbon storage the most in the earlier stand stages. Diversity of clonal plants was significantly positively correlated with ecosystem service functions after forest management. Structural equation modeling analysis indicated that forest gap or CTN management indirectly positively affected ecosystem service functions through increasing diversity of clonal woody plants and plant diversity of the communities. Conclusion: Our results indicate a highly positive effect of gap or CTN management on diversity and proportion of clonal plants and on plant diversity of the communities, which link to improvements in ecosystem service functions (i.e., water and soil conservation and carbon storage). The link between forest management, diversity, and ecosystem functions suggests that key functional traits or plant functional groups should be considered to underline the mechanism of traits--ecosystem functioning relationships and the restoration of degraded plantations. [ABSTRACT FROM AUTHOR]

The patterns of species diversity of plankton functional groups (PFGs) remain poorly understood although they matter greatly for marine ecosystem functioning. Here, we use an ensemble of empirical species distribution models for 845 plankton species to estimate the global species richness of three phytoplankton and 11 zooplankton functional groups as a function of objectively selected environmental predictors. The annual mean species richness of all PFGs decreases from the low to the high latitudes, but the steepness and the shape of this decrease vary significantly across PFGs. Pteropods, small copepods (Oithonids and Poecilostomatoids) and Salps have the steepest latitudinal gradients, whereas Amphipods and the three phytoplankton groups have the weakest ones. Temperature, irradiance and nutrient concentration are the first-order control on the latitudinal richness patterns, whilst the environmental conditions associated to upwelling systems, boundary currents and oxygen minimum zones modulate the position of the peaks and troughs in richness. The species richness of all PFGs increases with net primary production but decreases with particles size and the efficiency of the biological carbon pump. Our study puts forward emergent biodiversity–ecosystem functioning relationships and hypotheses about their underlying drivers for future field-based and modelling research. [ABSTRACT FROM AUTHOR]

Plant community productivity generally increases with biodiversity, but the strength of this relationship exhibits strong empirical variation. In meta‐food‐web simulations, we addressed if the spatial overlap in plants' resource access and animal space‐use can explain such variability. We found that spatial overlap of plant resource access is a prerequisite for positive diversity–productivity relationships, but causes exploitative competition that can lead to competitive exclusion. Space‐use of herbivores causes apparent competition among plants, resulting in negative relationships. However, space‐use of larger top predators integrates sub‐food webs composed of smaller species, offsetting the negative effects of exploitative and apparent competition and leading to strongly positive diversity–productivity relationships. Overall, our results show that spatial overlap of plants' resource access and animal space‐use can greatly alter the strength and sign of such relationships. In particular, the scaling of animal space‐use effects opens new perspectives for linking landscape processes without effects on biodiversity to productivity patterns. [ABSTRACT FROM AUTHOR]

Recent long‐term tree biodiversity experiments have shown that diversity effects on productivity tend to strengthen over time, as complementarity among constituent species increases over the course of forest development. However, these community‐level metrics only account for the net outcome of multiple interactions among species and, thus, do not inform about the individual species' responses to diversity.In this study, using 11 years of growth records from a large diversity experiment, we explored how species respond to diversity based on their functional traits and those of their heterospecific neighbours over time and analysed their contribution to the community‐level overyielding.We show species‐specific responses to diversity, with fast‐growing deciduous species rapidly performing better in mixtures relative to monocultures, than slow‐growing evergreen species. Moreover, we find that species productivity in mixtures enhances over time as the proportion of slow‐growing evergreen species in the heterospecific neighbourhood increases. These patterns of response of species scale up and explain community overyielding, which occurs primarily in deciduous‐evergreen mixtures and is explained by the overyielding of deciduous species overcompensating the poor performance of evergreen species.This study sheds light on the temporal dynamics of species responses to diversity, which together help improve our understanding of community‐level overyielding over the course of stand development. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Changes in biodiversity often affect ecosystem functioning. However, most previous biodiversity and ecosystem functioning (BEF) studies have generally been limited to very small spatial grains. Thus, knowledge regarding the biodiversity–ecosystem functioning relationships across spatial scales is lacking. Moreover, the multiscale nature of biodiversity, and specifically β diversity (i.e., spatial heterogeneity in species composition) was still largely missing in BEF studies. Here, using the vegetation and functional trait data collected from four 6‐ha forest dynamics plots (FDPs) in temperate and tropical forests in China, we examine the scale‐dependent relationships between tree diversity and the aboveground biomass (AGB), as well as the roles of species spatial heterogeneity in determining the AGB. In tropical forests, the effect of species richness on AGB decreased with spatial grains, while functional dominance played a stronger role at larger spatial grains. In temperate forests, positive relationship between diversity and AGB occurred at all spatial grains, especially on smaller scales. In both temperate and tropical forests, β diversity was positively correlated with AGB, but weaker than α diversity in determining AGB. Overall, complementarity and selection hypothesis play dominant role in determining AGB in temperate and tropical forests, respectively. The roles of these underlying mechanisms are more pronounced with increasing spatial scales. β diversity, a hitherto underexplored facet of biodiversity, is likely to increase ecosystem functions by species spatial turnover and should not be neglected in BEF explorations. Our findings have practical implications for forest management and demonstrate that biotic heterogeneity plays an important positive role in ecosystem functioning. [ABSTRACT FROM AUTHOR]

Summary: Resource complementarity can contribute to enhanced ecosystem functioning in diverse plant communities, but the role of facilitation in the enhanced complementarity is poorly understood.Here, we use leaf manganese concentration ([Mn]) as a proxy for rhizosheath carboxylate concentration to explore novel mechanisms of complementarity mediated by phosphorus (P) facilitation.In pot experiments, we showed that mixtures involving Carex korshinskyi, an efficient P‐mobilizing species, exhibited greater biomass and relative complementarity effect than combinations without C. korshinskyi on P‐deficient soils. Compared with monocultures, leaf [Mn] and [P] of species that are inefficient at P mobilization increased by 27% and 21% when grown with C. korshinskyi (i.e. interspecific P facilitation via carboxylates) rather than next to another inefficient P‐mobilizing species. This experimental result was supported by a meta‐analysis including a range of efficient P‐mobilizing species. Phosphorus facilitation enhanced the relative complementarity effect in low‐P environments, related to a greater change in several facilitated species of their root morphological traits relative to those in monoculture.Using leaf [Mn] as a proxy, we highlight a vital mechanism of interspecific P facilitation via belowground processes and provide evidence for the pivotal role of P facilitation mediated by the plasticity of root traits in biodiversity research. [ABSTRACT FROM AUTHOR]

There is increasing evidence that the strength of tree diversity effects on productivity varies considerably over the course of forest development. Evidence points to canopy closure and the subsequent self‐thinning as key phases of forest development during which positive diversity effects emerge. A number of studies have shown that self‐thinning can differ among species, and also in mixtures compared with monocultures. Yet, how diversity influences the process of canopy closure and self‐thinning remains poorly understood.In this study, using 11 years of growth and mortality records from a large diversity experiment, we fitted self‐thinning trajectories for 37 tree communities with equal initial densities and explored whether and how functional diversity and identity may affect these trajectories. We then examined whether the diversity effects on self‐thinning were influenced by differences in growth or in mortality.We found that tree communities' functional diversity and identity strongly influence the self‐thinning process. First, we observed that tree communities dominated by early successional species, and slow‐growing evergreens begin self‐thinning at a larger mean tree size. Second, we found that mixing species with contrasting resource‐use strategies, and the dominance of deciduous, fast‐growing species, reduce tree mortality rate in relation to mean tree size during self‐thinning (i.e. shallower self‐thinning slope). The lower rates of self‐thinning in these functionally diverse communities seem to be explained by both an increase in tree growth and a reduction in density‐related mortality simultaneously over time.Synthesis. Overall, this study highlights that increasing tree diversity has the potential to enhance forest productivity in the long term through a better performance during the self‐thinning process when competition for resources is most intense. [ABSTRACT FROM AUTHOR]

Functional trait distances between coexisting organisms reflect not only complementarity in the way they use resources, but also differences in their competitive abilities. Accordingly, absolute and relative trait distances have been widely used to capture the effects of niche dissimilarity and competitive hierarchies, respectively, on the performance of plants in competition. However, multiple dimensions of the plant phenotype are involved in these plant–plant interactions (PPI), challenging the use of relative trait distances to predict their outcomes. Furthermore, estimating the effects of competitive hierarchy on the performance of a group of coexisting plants remains particularly difficult since relative trait distances relate to the effects of a focal plant on another.We argue that trait distinctiveness, an emerging facet of functional diversity that characterizes the eccentric position of a species (or genotype) in a phenotypic space, can reveal the unique role played by a given individual plant in a group of competing plants. We used the model crop species Oryza sativa spp. japonica to evaluate the ability of trait distances and trait distinctiveness to predict the outcome of intraspecific PPI on the performance of single genotype and genotype mixtures. We performed a screening experiment to characterize the phenotypic space of 49 rice genotypes based on 11 above‐ground and root traits. We selected nine genotypes with contrasting positions in the phenotypic space and grew them in pots following a complete pairwise interaction design.Relative distances and distinctiveness based on traits associated with light competition were by far the best predictors of the performance of single genotypes—taller genotypes that acquired resource faster being the best competitors—while absolute trait distances had no effect. These results indicate that competitive hierarchy for light dominates PPI in this experiment. Consistently, trait distinctiveness in plant height and age at flowering had the strongest, positive effects on mixture performance, confirming that functional distinctiveness captures the effects of trait hierarchies and asymmetric PPI at this scale.Our findings shed new light on the role of trait diversity in regulating PPI and ecosystem processes and call for a greater consideration of functional distinctiveness in studies of coexistence mechanisms. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Abstract The relationships between biodiversity-ecosystem functioning (BEF) for microbial communities are poorly understood despite the important roles of microbes acting in natural ecosystems. Dilution-to-extinction (DTE), a method to manipulate microbial diversity, helps to fill the knowledge gap of microbial BEF relationships and has recently become more popular with the development of high-throughput sequencing techniques. However, the pattern of community assembly processes in DTE experiments is less explored and blocks our further understanding of BEF relationships in DTE studies. Here, a microcosm study and a meta-analysis of DTE studies were carried out to explore the dominant community assembly processes and their potential effect on exploring BEF relationships. While stochastic processes were dominant at low dilution levels due to the high number of rare species, the deterministic processes became stronger at a higher dilution level because the microbial copiotrophs were selected during the regrowth phase and rare species were lost. From the view of microbial functional performances, specialized functions, commonly carried by rare species, are more likely to be impaired in DTE experiments while the broad functions seem to be less impacted due to the good performance of copiotrophs. Our study indicated that shifts in the prokaryotic community and its assembly processes induced by dilutions result in more complex BEF relationships in DTE experiments. Specialized microbial functions could be better used for defining BEF. Our findings may be helpful for future studies to design, explore, and interpret microbial BEF relationships using DTE.

Abstract Changes in biodiversity often affect ecosystem functioning. However, most previous biodiversity and ecosystem functioning (BEF) studies have generally been limited to very small spatial grains. Thus, knowledge regarding the biodiversity–ecosystem functioning relationships across spatial scales is lacking. Moreover, the multiscale nature of biodiversity, and specifically β diversity (i.e., spatial heterogeneity in species composition) was still largely missing in BEF studies. Here, using the vegetation and functional trait data collected from four 6‐ha forest dynamics plots (FDPs) in temperate and tropical forests in China, we examine the scale‐dependent relationships between tree diversity and the aboveground biomass (AGB), as well as the roles of species spatial heterogeneity in determining the AGB. In tropical forests, the effect of species richness on AGB decreased with spatial grains, while functional dominance played a stronger role at larger spatial grains. In temperate forests, positive relationship between diversity and AGB occurred at all spatial grains, especially on smaller scales. In both temperate and tropical forests, β diversity was positively correlated with AGB, but weaker than α diversity in determining AGB. Overall, complementarity and selection hypothesis play dominant role in determining AGB in temperate and tropical forests, respectively. The roles of these underlying mechanisms are more pronounced with increasing spatial scales. β diversity, a hitherto underexplored facet of biodiversity, is likely to increase ecosystem functions by species spatial turnover and should not be neglected in BEF explorations. Our findings have practical implications for forest management and demonstrate that biotic heterogeneity plays an important positive role in ecosystem functioning.

Human actions are decreasing the diversity and complexity of forests, and a mechanistic understanding of how these changes affect predators is needed to maintain ecosystem services, including pest regulation. Using a large‐scale tree diversity experiment, we investigate how spiders respond to trees growing in plots of single or mixed species combinations (4 or 12) by repeatedly sampling 540 trees spanning 15 species. In 2019 (6 years post‐establishment), spider responses to tree diversity varied by tree species. By 2021, diversity had a more consistently positive effect, with trees in 4‐ or 12‐species plots supporting 23% or 50% more spiders, respectively, compared to conspecifics in monocultures. Spiders showed stronger tree species preferences in late summer, and the positive impact of plot diversity doubled. In early summer, the positive diversity effect was tied to higher canopy cover in diverse plots, leading to higher spider densities. This indirect path strengthened in late summer, with an additional direct effect of plot diversity on spiders. Prey availability was higher in diverse plots but was not tied to spider density. Overall, diverse plots supported more predators, partly by increasing available habitat. Adopting planting strategies focused on species mixtures may better maintain higher trophic levels and ecosystem functions. [ABSTRACT FROM AUTHOR]

Vegetation structural complexity (VSC)—the three‐dimensional distribution of plants within an ecosystem—is an important ecological trait. To date, research has focused primarily on the effects of VSC on ecological patterns and processes, but comparatively little is known about what drives variation in VSC.Recent advances in active remote sensing technology, particularly light detection and ranging and radio detection and ranging, have allowed the measurement of VSC at unprecedented spatial scales and resolutions. Out of this and earlier work has emerged evidence that VSC is typically associated with greater ecosystem functioning (especially microclimate regulation, productivity, faunal diversity and habitat provisioning), making restoration of vegetation complexity a potentially powerful restoration tool.Recent studies of VSC across natural and experimental gradients of plant diversity have also revealed that more diverse plant communities tend to be more structurally complex. However, the shape and generality of this relationship—and the mechanism(s) by which phytodiversity might contribute to structural complexity—remain poorly understood.Here, we review how active remote sensing has facilitated recent VSC research and shaped our understanding of the relationship between vegetation complexity and ecosystem function. We then present a theoretical framework for the relationship between phytodiversity and VSC based on classic biodiversity‐ecosystem functioning principles. Finally, we evaluate the evidence for the notion that diverse plant assemblages tend to be more structurally complex and explore the shape of the relationship between phytodiversity and VSC using data from 13 recent remote sensing studies.Synthesis. The relationship between phytodiversity and VSC appears to be almost universally positive. Preliminary evidence further suggests that the most common relationships between phytodiversity and VSC are linear or saturating, indicating that the extent of functional redundancy between species varies across plant communities and ecosystems. In contrast, we find little evidence for exponential or negative relationships between plant diversity and VSC, suggesting that even modest increases in plant diversity could markedly increase structural complexity. Additional investigations of phytodiversity‐VSC relationships are necessary to establish whether the observed positive relationships are causal (and, if so, in which direction) and to clarify the potential impact of plant community restoration on structural complexity and broader ecosystem function. [ABSTRACT FROM AUTHOR]

Ever-growing human population and nutritional demands, supply chain disruptions, and advancing climate change have led to the realization that changes in diversity and system performance are intimately linked. Moreover, diversity and system performance depend on heterogeneity. Mitigating changes in system performance and promoting sustainable living conditions requires transformative decisions. Here, we introduce the heterogeneity–diversity–system performance (HDP) nexus as the conceptual basis upon which to formulate transformative decisions. We suggest that managing the heterogeneity of systems will best allow diversity to provide multiple benefits to people. Based on ecological theory, we pose that the HDP nexus is broadly applicable across systems, disciplines, and sectors, and should thus be considered in future decision making as a way to have a more sustainable global future. [ABSTRACT FROM AUTHOR]

The stability of forest productivity can reflect the functioning of forest ecosystems. It is a crucial topic to understand the relationship between biodiversity and ecosystem functions in ecology. Although previous studies have made great progress in understanding the effects of diversity, species asynchrony, and other factors on community biomass and productivity, few studies have explored how these factors affect the temporal stability of productivity. In this study, we hypothesized that diversity, species asynchrony, and topography would directly or indirectly impact the temporal stability of productivity. To test this hypothesis, we used a multiple regression model and a piecewise structural equation model based on the inventory data over 20 years (5‐year intervals) from 1992 to 2012 at Jingouling Forest Farm in Northeast China. Our results showed that species asynchrony was the main driving factor affecting the temporal stability of productivity. Structural diversity significantly decreased community stability, while species diversity had a nonsignificant effect on it. We found the combination of a multiple regression model and a piecewise structural equation model is an effective method for evaluating the factors that influence community stability. The effect of species asynchrony is crucial for understanding the ecological mechanisms underlying the diversity–stability relationship in mixed forests. [ABSTRACT FROM AUTHOR]

Diversity–biomass relationships (DBRs) often vary with spatial scale in terrestrial ecosystems, but the mechanisms driving these scale‐dependent patterns remain unclear, especially for highly heterogeneous forest ecosystems. This study explores how mutualistic associations between trees and different mycorrhizal fungi, i.e., arbuscular mycorrhizal (AM) vs. ectomycorrhizal (EM) association, modulate scale‐dependent DBRs. We hypothesized that in soil‐heterogeneous forests with a mixture of AM and EM tree species, (i) AM and EM tree species would respond in contrasting ways (i.e., positively vs. negatively, respectively) to increasing soil fertility, (ii) AM tree dominance would contribute to higher tree diversity and EM tree dominance to greater standing biomass, and that as a result (iii) mycorrhizal associations would exert an overall negative effect on DBRs across spatial scales. To empirically test these hypotheses, we collected detailed tree distribution and soil information (e.g., nitrogen, phosphorus, organic matter, pH) from seven temperate and subtropical AM–EM mixed forest megaplots (16–50 ha). Using a spatial codispersion null model and structural equation modeling, we identified the relationships among AM or EM tree dominance, soil fertility, tree species diversity, and biomass and, thus, DBRs across 0.01‐ to 1‐ha scales. We found the first evidence overall supporting the three aforementioned hypotheses in these AM–EM mixed forests: (i) In most forests, with increasing soil fertility, tree communities changed from EM‐dominated to AM‐dominated; (ii) increasing AM tree dominance had an overall positive effect on tree diversity and a negative effect on biomass, even after controlling for soil fertility and number of trees. Together, (iii) the changes in mycorrhizal dominance along soil fertility gradients weakened the positive DBR observed at 0.01‐ to 0.04‐ha scales in nearly all forests and drove negative DBRs at 0.25‐ to 1‐ha scales in four out of seven forests. Hence, this study highlights a soil‐related mycorrhizal dominance mechanism that could partly explain why, in many natural forests, biodiversity–ecosystem functioning (BEF) relationships shift from positive to negative with increasing spatial scale. [ABSTRACT FROM AUTHOR]

Aim: Theoretical, experimental and observational studies have shown that biodiversity–ecosystem functioning (BEF) relationships are influenced by functional community structure through two mutually non‐exclusive mechanisms: (1) the dominance effect (which relates to the traits of the dominant species); and (2) the niche partitioning effect [which relates to functional diversity (FD)]. Although both mechanisms have been studied in plant communities and experiments at small spatial extents, it remains unclear whether evidence from small‐extent case studies translates into a generalizable macroecological pattern. Here, we evaluate dominance and niche partitioning effects simultaneously in grassland systems world‐wide. Location: Two thousand nine hundred and forty‐one grassland plots globally. Time period: 2000–2014. Major taxa studied: Vascular plants. Methods: We obtained plot‐based data on functional community structure from the global vegetation plot database "sPlot", which combines species composition with plant trait data from the "TRY" database. We used data on the community‐weighted mean (CWM) and FD for 18 ecologically relevant plant traits. As an indicator of primary productivity, we extracted the satellite‐derived normalized difference vegetation index (NDVI) from MODIS. Using generalized additive models and deviation partitioning, we estimated the contributions of trait CWM and FD to the variation in annual maximum NDVI, while controlling for climatic variables and spatial structure. Results: Grassland communities dominated by relatively tall species with acquisitive traits had higher NDVI values, suggesting the prevalence of dominance effects for BEF relationships. We found no support for niche partitioning for the functional traits analysed, because NDVI remained unaffected by FD. Most of the predictive power of traits was shared by climatic predictors and spatial coordinates. This highlights the importance of community assembly processes for BEF relationships in natural communities. Main conclusions: Our analysis provides empirical evidence that plant functional community structure and global patterns in primary productivity are linked through the resource economics and size traits of the dominant species. This is an important test of the hypotheses underlying BEF relationships at the global scale. [ABSTRACT FROM AUTHOR]

There is substantial evidence that biodiversity underpins ecosystem functioning, but it is unclear how these relationships change with multiple stressors in complex real-world settings. Coastal zones are affected by numerous stressors (for example, sediment input and nutrient runoff from land) and the cumulative effects of these stressors may result in pronounced and unexpected changes in the functioning of ecosystems. To investigate the cumulative effects of turbidity and elevated nutrients on coastal biodiversity-ecosystem functioning relationships, we performed a large-scale field experiment manipulating in situ sediment porewater ammonium concentrations and measured multiple ecosystem functions related to carbon fixation and mineralisation in 15 estuaries with varying levels of turbidity. The results indicated that the benthic macrofauna diversity (species richness, abundance, and functional richness) declined with increased porewater ammonium concentrations and there were clear thresholds in light levels at the seafloor in relation to the biodiversity-ecosystem function relationships. Multifunctionality indices (an integrated index of all measured functions) in moderately turbid and turbid estuaries (daily mean seafloor PAR < 420 µmol m−2 s−1) decreased with the loss of macrofauna biodiversity. Functioning in low-turbidity estuaries (daily mean PAR > 420 µmol m−2 s−1) however remained relatively constant, suggesting that they were more resilient against the nutrient-induced biodiversity loss. Our results demonstrate that ecosystems already stressed by stressors that alter functional performance (turbidity) may be more prone to loss of overall functioning if biodiversity is reduced by another stressor (nutrient enrichment), highlighting the potential snowballing effects of cumulative change. [ABSTRACT FROM AUTHOR]

The relationships between biodiversity-ecosystem functioning (BEF) for microbial communities are poorly understood despite the important roles of microbes acting in natural ecosystems. Dilution-to-extinction (DTE), a method to manipulate microbial diversity, helps to fill the knowledge gap of microbial BEF relationships and has recently become more popular with the development of high-throughput sequencing techniques. However, the pattern of community assembly processes in DTE experiments is less explored and blocks our further understanding of BEF relationships in DTE studies. Here, a microcosm study and a meta-analysis of DTE studies were carried out to explore the dominant community assembly processes and their potential effect on exploring BEF relationships. While stochastic processes were dominant at low dilution levels due to the high number of rare species, the deterministic processes became stronger at a higher dilution level because the microbial copiotrophs were selected during the regrowth phase and rare species were lost. From the view of microbial functional performances, specialized functions, commonly carried by rare species, are more likely to be impaired in DTE experiments while the broad functions seem to be less impacted due to the good performance of copiotrophs. Our study indicated that shifts in the prokaryotic community and its assembly processes induced by dilutions result in more complex BEF relationships in DTE experiments. Specialized microbial functions could be better used for defining BEF. Our findings may be helpful for future studies to design, explore, and interpret microbial BEF relationships using DTE. [ABSTRACT FROM AUTHOR]

Biodiversity and ecosystem functioning (BEF) relationships are important research issues in the context of biodiversity loss. However, most studies only explored BEF relationships using species richness as a proxy for biodiversity without considering the effects of species evenness and importance of functional diversity on ecosystem functioning. In the present study, we explored multiple relationships among in-stream environmental variables, species diversity (species richness and species evenness), functional diversity (functional richness, functional evenness and Rao’s quadratic entropy index) and biomass of benthic diatom communities from a Chinese mountainous river network. We tested two hypotheses: (1) species richness and evenness affect community biomass independently, and (2) species diversity directly affects community biomass and also indirectly affects community biomass by influencing functional diversity. We found that benthic diatom diversity and biomass were influenced by wetted width, conductivity, and pH. Species richness and evenness had positive and negative effects on community biomass, respectively; while, the effect of richness (with a pathway coefficient of 0.39) was stronger than that of evenness (−0.28). However, we have not found an interaction pathway between species richness and species evenness in structural equation models, indicating that the two effects on community biomass were independent of each other. Both functional richness and Rao’s quadratic entropy index had positive effects on community biomass, although effects of other variables blurred the relationship between functional richness and community biomass in structural equation modeling. Besides direct effects, species diversity also indirectly affected community biomass through influencing Rao’s quadratic entropy index, with direct effects (0.27) were more than twice stronger than indirect effects (0.12). Our findings imply that the selection effect played a dominant role in the relationship between diatom diversity and biomass, indicated by the negative species evenness and biomass relationship; meanwhile, the complementarity effect was also important. The inclusion of more diversity indices to explore the biodiversity-biomass relationship would help to provide a deeper and more comprehensive understanding of this relationship and its driving mechanisms. We suggest carrying out more studies on BEF relationships in streams and rivers to support protection practices for sustaining biodiversity and their ecosystem functions in natural lotic ecosystems.

Biodiversity drives the maintenance and stability of ecosystem functioning as well as many of nature’s benefits to people, yet people cause substantial biodiversity change. Despite broad consensus about a positive relationship between biodiversity and ecosystem functioning (BEF), the underlying mechanisms and their context-dependencies are not well understood. This proposal, submitted to the European Research Council (ERC), aims at filling this knowledge gap by providing a novel conceptual framework for integrating biotic interactions across guilds of organisms, i.e. plants and mycorrhizal fungi, to explain the ecosystem consequences of biodiversity change. The overarching hypothesis is that EF increases when more tree species associate with functionally dissimilar mycorrhizal fungi. Taking a whole-ecosystem perspective, we propose to explore the role of tree-mycorrhiza interactions in driving BEF across environmental contexts and how this relates to nutrient dynamics. Given the significant role that mycorrhizae play in soil nutrient and water uptake, BEF relationships will be investigated under normal and drought conditions. Resulting ecosystem consequences will be explored by studying main energy channels and ecosystem multifunctionality using food web energy fluxes and by assessing carbon storage. Synthesising drivers of biotic interactions will allow us to understand context-dependent BEF relationships. This interdisciplinary and integrative project spans the whole gradient from local-scale process assessments to global relationships by building on unique experimental infrastructures like the MyDiv Experiment, iDiv Ecotron and the global network TreeDivNet, to link ecological mechanisms to reforestation initiatives. This innovative combination of basic scientific research with real-world interventions links trait-based community ecology, global change research and ecosystem ecology, pioneering a new generation of BEF research and represents a significant step towards implementing BEF theory for human needs.

Abstract The stability of forest productivity can reflect the functioning of forest ecosystems. It is a crucial topic to understand the relationship between biodiversity and ecosystem functions in ecology. Although previous studies have made great progress in understanding the effects of diversity, species asynchrony, and other factors on community biomass and productivity, few studies have explored how these factors affect the temporal stability of productivity. In this study, we hypothesized that diversity, species asynchrony, and topography would directly or indirectly impact the temporal stability of productivity. To test this hypothesis, we used a multiple regression model and a piecewise structural equation model based on the inventory data over 20 years (5‐year intervals) from 1992 to 2012 at Jingouling Forest Farm in Northeast China. Our results showed that species asynchrony was the main driving factor affecting the temporal stability of productivity. Structural diversity significantly decreased community stability, while species diversity had a nonsignificant effect on it. We found the combination of a multiple regression model and a piecewise structural equation model is an effective method for evaluating the factors that influence community stability. The effect of species asynchrony is crucial for understanding the ecological mechanisms underlying the diversity–stability relationship in mixed forests.

Livestock grazing is the major land-use regime of grasslands, and affects ecosystem structure and functioning considerably. However, few studies have examined how grazing intensity impacts ecosystem multifunctionality (EMF) via biodiversity loss. We studied the responses of EMF to livestock grazing in a temperate grassland in Inner Mongolia, China. Four grazing intensities (i.e., no grazing (NG), light grazing (LG), moderate grazing (MG), and heavy grazing (HG)) were chosen based on the distance to the core zones, vegetation and soil indications of grazing, and suggestions from local guides. For each grazing intensity, three plots (10 m × 10 m) were placed randomly, and plants, soil, and four traits of the present species were sampled in three 1-m2 quadrats in each plot. We analyzed the responses of three biodiversity components (i.e., taxonomic diversity (TD), functional diversity (FD), and functional identity), multiple ecosystem functions (i.e., aboveground biomass, belowground biomass, soil water content, soil organic matter, soil total nitrogen, soil total phosphorus, soil available nitrogen, soil available phosphorus), and EMF (based on averaging approach and threshold-based approach) to different grazing intensities, and the relative importance of biodiversity components in regulating the effect of grazing intensity on EMF. Our results showed that the dominant species of the plant community shifted from slow-growing conservative traits to fast-growing acquisitive traits as grazing intensified, accompanied by a decline in Stipa baicalensis (the predominant native grass in NG), whereas Carex duriuscula became the dominant species in HG sites. TD, FD, EMF, as well as six of eight individual ecosystem functions, displayed a significant decrease trend along the grazing intensity gradient. According to Bayesian structural equation models (SEM), EMF was mainly driven by the indirect effects of grazing through TD reduction (direct effects: 0.45) and changes in functional identity (direct effects: − 0.67), but the direct effect of grazing was not significant. By using the threshold-based approach, we found TD, FD, and CWM have a prominent impact on the number of functions exceeding a threshold level of 63 %, 64 %, and 65 %, respectively. When the threshold increased to 90 %, the explanation of the SEM decreased to 41 %, and no significant direct and indirect effects of grazing on EMF were found. Our results highlighted the vital role of biodiversity in mediating the response of EMF to grazing and shed light on grassland biodiversity conservation and sustainability.

Tree species are known to predominantly interact either with arbuscular mycorrhizal (AM) or ectomycorrhizal (EM) fungi. However, there is a knowledge gap regarding whether these mycorrhizae differently influence biodiversity–ecosystem functioning (BEF) relationships and whether a combination of both can increase community productivity. In 2015, we established a tree‐diversity experiment by growing tree communities with varying species richness levels (one, two, or four species) and either with AM or EM tree species or a combination of both. We investigated basal area and annual basal area increment from 2015 to 2020 as proxies for community productivity. We found significant positive relationships between tree species richness and community productivity, which strengthened over time. Further, AM and EM tree species differently influenced productivity; however, there was no overyielding when AM and EM trees grew together. EM tree communities were characterized by low productivity in the beginning but an increase of increment over time and showed overall strong biodiversity effects. For AM tree communities the opposite was true. Although young trees did not benefit from the presence of the other mycorrhizal type, dissimilar mechanisms underlying BEF relationships in AM and EM trees indicate that maximizing tree and mycorrhizal diversity may increase ecosystem functioning in the long run. [ABSTRACT FROM AUTHOR]

Cryogenic soils are the most important terrestrial carbon reservoir on the planet. However, the relationship between soil microbial diversity and CO2 emission by cryogenic soils is poorly studied. This is especially important in the context of rising temperatures in the high Arctic which can lead to the activation of microbial processes in soils and an increase in carbon input from cryogenic soils into the atmosphere. Here, using high-throughput sequencing of 16S rRNA gene amplicons, we analyzed microbial community composition and diversity metrics in relation to soil carbon dioxide emission, water-extractable organic carbon and microbial biomass carbon in the soils of the Barents Sea archipelagos, Novaya Zemlya and Franz Josef Land. It was found that the highest diversity and CO2 emission were observed on the Hooker and Heiss Islands of the Franz Josef Land archipelago, while the diversity and CO2 emission levels were lower on Novaya Zemlya. Soil moisture and temperature were the main parameters influencing the composition of soil microbial communities on both archipelagos. The data obtained show that CO2 emission levels and community diversity on the studied islands are influenced mostly by a number of local factors, such as soil moisture, microclimatic conditions, different patterns of vegetation and fecal input from animals such as reindeer. [ABSTRACT FROM AUTHOR]

Biodiversity loss is altering key ecosystem processes as primary production and decomposition, however, the after-life effects of plant diversity (species-mixing effects) on instream organic matter (litter) decomposition is still under debate. Available evidence of litter species-mixing effect (or the lack of) comes from studies using dominant plant species, despite rare species comprising the majority of species in an ecosystem and can contribute to ecosystem functions or in the provisioning of essential elements. Here, we simulated different extinction scenarios of plant from rare species by incubating leaf litter in artificial channels located within a tropical stream. We thus, assessed whether the loss of litter from rare plant species alters functional diversity (resource dissimilarity) and litter quality (resource concentration) of species mixtures and change decomposition, N loss and fungal biomass production. We show that the loss of litter from rare plant species reduced the functional diversity of litter mixtures and consequently, reduced decomposition, N loss and fungal biomass production. Although species lost also changed the nutritional quality of litter mixtures (resource concentration), it did not affect decomposition or N loss but fungal biomass production. Also, when only similar rare species were present, processes were reduced to higher rates than in the scenario with only dissimilar rare species (except for N loss). Our findings reveal the relevance of litter from rare plant species to key ecosystem processes related to carbon and nutrient flow in tropical streams, especially when dissimilar traits are added to litter pools. [ABSTRACT FROM AUTHOR]

Any newly created area includes human-created habitats such as the mineral material of post-coal mining spoil heaps undergoing natural colonization and ecosystem development during the succession processes of vegetation colonization. The study of the factors that influence the succession dynamics, and the mechanisms behind this, have a long history (including the species-area relationship or Arrhenius equation). Nevertheless, the list of scientific questions is increasing. One of the significant issues in the study of these processes is the relationship between factors influencing the Biodiversity-Ecosystem Functioning (BEF) relationships. The main prerequisite is the relationships between the plant species' assemblage mechanisms including diversity and the variety of assembly rules concerning the environmental abiotic habitat processes and these properties are not straightforward. At the large scale, parameters such as age and area of the colonized sites are considered to be important. These relationships are more complicated in newly established post-mineral excavation habitats where novel ecosystems are developing. Regardless of the degree of disturbances, vegetation re-establishes in such environments, as a result of spontaneous succession, by the colonization and establishment of the best-adapted organisms. In the habitats of post-coal mining spoil heaps with pure oligotrophic mineral conditions, the non-analogous, newly formed composition of flora, fauna, and saprophytes has been stated in many previous field studies. This study aimed to explore the biodiversity versus area size relationships, in particular, it investigated the species composition and diversity found in the development of the spontaneous vegetation formed during primary succession on mineral substrate habitats of postcoal mining spoil heaps of different area sizes. We tested the hypothesis: species diversity of the vegetation patches on coal mine spoil heaps becomes more diverse on larger sites over time. These results indicate that the area size of the spoil heap significantly affects the diversity of the vegetation. Regardless of which of the characteristics of the vegetation type (dominant species) is compared, the vegetation on the heaps differs depending on its area size. [ABSTRACT FROM AUTHOR]

Abstract Climate change is one of the most pressing threats to humanity, inducing a global increase in temperatures and more frequent extreme climatic events. Considering this, global reforestation initiatives are proposed to capture carbon and mitigate climate change. Global restoration and reforestation programs and their targets have inspired both unparalleled enthusiasm worldwide and intense scientific criticism and debate regarding their feasibility and implementation. We agree that global reforestation forecasting and efforts require a nuanced discussion and approach. In that vein, we would like to emphasize the potential of increasing existing forest diversity to enhance climate change mitigation by increasing aboveground and belowground carbon storage. Moreover, we argue that focusing on planting diverse forests in reforestation efforts can help to reduce climate change effects on ecosystems: first, by increasing resistance and resilience to extreme climatic events, and second, by buffering microclimatic conditions in natural and urban areas. Diversifying forests plantations and reforestation projects may not always be feasible and cannot solve the climate crisis by itself. However, we highlight that a focus on diverse forests could maximize the benefits of reforestation programs by promoting sustainable land management.

ABSTRACT The presence of more species in the community of a sampling site (α diversity) typically increases ecosystem functions via nonrandom processes like resource partitioning. When considering multiple communities, we hypothesize that higher compositional difference (β diversity) increases overall functions of these communities. Further, we hypothesize that the β diversity effect is more positive when β diversity is increased by nonrandom assembly processes. To test these hypotheses, we collected bacterioplankton along a transect of 6 sampling sites in the southern East China Sea in 14 cruises. For any pairs of the 6 sites within a cruise, we calculated the Bray-Curtis index to represent β diversity and summed bacterial biomass as a proxy to indicate the overall function of the two communities. We then calculated deviation of observed mean pairwise phylogenetic similarities among species in two communities from random to represent the influences of nonrandom processes. The bacterial β diversity was found to positively affect the summed bacterial biomass; however, the effect varied among cruises. Cross-cruise comparison indicated that the β diversity effect increased with the nonrandom processes selecting for phylogenetically dissimilar species. This study extends biodiversity-ecosystem functioning research to the scale of multiple sites and enriches the framework by considering community assembly processes. IMPORTANCE The implications of our analyses are twofold. First, we emphasize the importance of studying β diversity. We expanded the current biodiversity-ecosystem functioning framework from single to multiple sampling sites and investigated the influences of species compositional differences among sites on the overall functioning of these sites. Since natural ecological communities never exist alone, our analyses allow us to more holistically perceive the role of biodiversity in natural ecosystems. Second, we took community assembly processes into account to attain a more mechanistic understanding of the impacts of biodiversity on ecosystem functioning.

Marine heatwaves (MHWs) are increasing in frequency and intensity due to climate change. Several well-documented effects of heatwaves on community structure exist, but examples of their effect on functioning of species, communities or ecosystems remain scarce. We tested the effects of short-term, moderate and strong MHWs on macrofauna bioturbation and associated solute fluxes as examples of ecosystem functioning. We also measured macrofaunal excretion rates to assess effects of temperature on macrofauna metabolism. For this experiment, we used unmanipulated sediment cores with natural animal communities collected from a muddy location at 32 m depth in the northern Baltic Sea. Despite the mechanistic effect of bioturbation remaining unchanged between the treatments, there were significant differences in oxygen consumption, solute fluxes and excretion. Biogeochemical and biological processes were boosted by the moderate heatwave, whereas biogeochemical cycling seemed to decrease under a strong heatwave. A prolonged, moderate heatwave could possibly lead to resource depletion if primary production cannot meet the demands of benthic consumption. By contrast, decreased degradation activities under strong heatwaves could lead to a build-up of organic material and potentially hypoxia. The strong variability and the complexity of the response highlight the context dependency of these processes complicating future predictions. [ABSTRACT FROM AUTHOR]

Relatively few studies have attempted to resolve the pathways through which the effects of biodiversity on ecosystem functioning cascade from one trophic level to another. Here, we manipulated the richness of habitat‐forming seaweeds in a western Atlantic estuary to explore how changes in foundation species diversity affect the structure and functioning of the benthic consumer communities that they support. Structural equation modeling revealed that macroalgal richness enhanced invertebrate abundance, biomass, and diversity, both directly by changing the quality and palatability of the foundational substrate and indirectly by increasing the total biomass of available habitat. Consumer responses were largely driven by a single foundational seaweed, although stronger complementarity among macroalgae was observed for invertebrate richness. These findings with diverse foundational phyla extend earlier inferences from terrestrial grasslands by showing that biodiversity effects can simultaneously propagate through multiple independent pathways to maintain animal foodwebs. Our work also highlights the potential ramifications of human‐induced changes in marine ecosystems. [ABSTRACT FROM AUTHOR]

While most studies yield positive relationships between biodiversity (B) and ecosystem functioning (EF), awareness is growing that BEF relationships can vary with ecological context. The awareness has led to increased efforts to understand how contemporary environmental context modifies BEF relationships, but the role of historical context, and the mechanisms by which it may influence biodiversity effects, remains poorly understood.We examined how historical context alters plant diversity–community productivity relationships via plant species interactions in alpine grassland. We also tested how historical context modifies interactions between plants and arbuscular mycorrhizal (AM) fungi, which can potentially mediate the above processes.We studied biodiversity effects on plant community productivity at two grassland sites with different histories related to grazing intensity—heavy versus light livestock grazing—but similar current management. We assembled experimental communities of identical species composition with plants from each of the two sites in disturbed soil from a contemporary heavily grazed grassland, ranging in species richness from one to two, three and six species. Moreover, we carried out a mycorrhizal hyphae‐exclusion experiment to test how plant interactions with AM fungi influence plant responses to historical context.We detected a significantly positive diversity–productivity relationship that was driven by complementarity effects in communities composed of plants from the site without heavy‐grazing history, but no such relationship in plant communities composed of plants from the site with heavy‐grazing history. Plants from the site with heavy‐grazing history had increased competitive ability and increased yields in low‐diversity communities but disrupted complementarity effects in high‐diversity communities. Moreover, plants of one species from the site with heavy‐grazing history benefitted more from AM fungal communities than did plants from the site without such history.Synthesis. Using the same experimental design and species, communities assembled by plants from two sites with different historical contexts showed different plant diversity–community productivity relationships. Our results suggest that historical context can alter plant diversity–community productivity relationships via plant species interactions and potentially plant–soil interactions. Therefore, considering historical contexts of ecological communities is of importance for advancing our understanding of long‐term impacts of anthropogenic disturbance on ecosystem functioning. [ABSTRACT FROM AUTHOR]

Land degradation can result in a loss of critical ecosystem services that we often seek to restore through re‐establishment of desired plant communities. Trait‐based approaches have the potential to target specific ecosystem services based on associations between the functional composition of plant communities and ecosystem properties that serve as indicators of those services.The effect of functional composition on ecosystem recovery may depend on the amount of restored plant biomass, itself a supporting service frequently targeted in restoration efforts. Yet, interactions between functional composition and biomass are not formally integrated into trait‐based analytical frameworks.We tested the hypothesis that functional composition of plant communities both drives, and interacts with, biomass production to influence indicators of soil functioning and weed suppression across a network of degraded dryland restoration experiments. This networked approach allowed us to identify generalized effects of functional composition on ecosystem recovery across a range of dryland climate conditions.Climate had a substantial effect on ecosystem indicators, with weed cover and soil surface stability increasing in more arid climates, water infiltration increasing with precipitation, and aggregate structure increasing with less freezing. After accounting for climate effects across study sites, we found significant effects of community‐weighted mean (CWM) trait values on biomass, particularly a positive effect of leaf carbon‐to‐nitrogen ratio, and of CWM‐biomass interactions on other ecosystem indicators. Cover of exotic species was reduced in restored communities with a combination of low leaf dry matter content and high biomass, soil water infiltration increased with lower specific root length and high biomass, and soil aggregate stability increased with higher root dry matter content and high biomass, among other effects. Functional diversity had no significant effects on any ecosystem indicators.Synthesis: The influence of community functional composition on ecosystem properties increases with community biomass, particularly in disturbed or low productivity systems. This suggests that active management should not only focus on trait values that optimize individual ecosystem indicators but also how those functional strategies are complementary or counter to those that increase biomass. Read the free Plain Language Summary for this article on the Journal blog [ABSTRACT FROM AUTHOR]