Biodiversity-ecosystem Function Relationships Research Articles

Spatiotemporal dynamics of abiotic and biotic properties explain biodiversity–ecosystem‐functioning relationships

AbstractThere is increasing evidence that spatial and temporal dynamics of biodiversity and ecosystem functions play an essential role in biodiversity–ecosystem‐functioning (BEF) relationships. Despite the known importance of soil processes for forest ecosystems, belowground functions in response to tree diversity and spatiotemporal dynamics of ecological processes and conditions remain poorly described. We propose a novel conceptual framework integrating spatiotemporal dynamics in BEF relationships and hypothesized a positive tree species richness effect on soil ecosystem functions through the spatial and temporal stability of biotic and abiotic soil properties based on species complementarity and asynchrony. We tested this framework within a long‐term tree diversity experiment in Central Germany by assessing soil ecosystem functions (soil microbial properties and litter decomposition) and abiotic variables (soil moisture and surface temperature) for two consecutive years in high spatial and temporal resolution. Tree species richness and identity had significant effects on soil properties (e.g., soil microbial biomass). Structural equation modeling revealed that overall soil microbial biomass was partly explained by (1) enhanced temporal stability of soil surface temperature and (2) decreased spatial stability of soil microbial biomass. Overall, spatial stability of soil microbial properties was positively correlated with their temporal stability. These results suggest that spatiotemporal dynamics are indeed crucial determinants in BEF relationships and highlight the importance of vegetation‐induced microclimatic conditions for stable provisioning of soil ecosystem functions and services.

Belowground facilitation and trait matching: two or three to tango?

High biodiversity increases ecosystem functions; however, belowground facilitation remains poorly understood in this context. Here, we explore mechanisms that operate via 'giving-receiving feedbacks' for belowground facilitation. These include direct effects via root exudates, signals, and root trait plasticity, and indirect biotic facilitation via the effects of root exudates on soil biota and feedback from biota to plants. We then highlight that these two- or three-way mechanisms must affect biodiversity-ecosystem function relationships via specific combinations of matching traits. To tango requires a powerful affinity and harmony between well-matched partners, and such matches link belowground facilitation to the effect of biodiversity on function. Such matching underpins applications in intercropping, forestry, and pasture systems, in which diversity contributes to greater productivity and sustainability.

Richness and antagonistic effects co-affect plant growth promotion by synthetic microbial consortia

Plant-related microbial communities are essential to plant growth and development, and empirical evidence suggests that inoculation with a synthetic microbial consortium can enhance plant performance; however, to manipulate the functions of these communities, we require a better understanding of the influencing factors. Here, we used the biodiversity ecosystem function (BEF) framework to specifically test the impact of community richness (1, 2, 4, or 8 strains per community) and antagonistic intensity on plant growth promotion in two kinds of nutritional environments. We found that increasing the richness of microbes can improve the accumulation of plant biomass, revealing that diversity effects were stronger than single-strain effects. The intensity of antagonism between highly diverse microbes may have a consistent negative effect on plant growth in comparison with the effects of communities with the same richness; intriguingly, this negative effect did not change positive BEF relationships. These results suggested that high diversity in the synthetic microbial consortia harboured stable and effective plant growth promotion capability and, in turn, also increased susceptibility to the negative effects of antagonism among microbial strains.

Soil multitrophic network complexity enhances the link between biodiversity and multifunctionality in agricultural systems.

Belowground biodiversity supports multiple ecosystem functions and services that humans rely on. However, there is a dearth of studies exploring the determinants of the biodiversity-ecosystem function (BEF) relationships, particularly in intensely managed agricultural ecosystems. Here, we reported significant and positive relationships between soil biodiversity of multiple organism groups and multiple ecosystem functions in 228 agricultural fields, relating to crop yield, nutrient provisioning, element cycling, and pathogen control. The relationships were influenced by the types of organisms that soil phylotypes with larger sizes or at higher trophic levels, for example, invertebrates or protist predators, appeared to exhibit weaker or no BEF relationships when compared to those with smaller sizes or at lower trophic levels, for example, archaea, bacteria, fungi, and protist phototrophs. Particularly, we highlighted the role of soil network complexity, reflected by co-occurrence patterns among multitrophic-level organisms, in enhancing the link between soil biodiversity and ecosystem functions. Our results represent a significant advance in forecasting the impacts of belowground multitrophic organisms on ecosystem functions in agricultural systems, and suggest that soil multitrophic network complexity should be considered a key factor in enhancing ecosystem productivity and sustainability under land-use intensification.

Ecosystem functions are related to tree diversity in forests but soil biodiversity in open woodlands and shrublands

Abstract Millions of trees are expected to be planted in forested and non‐forested ecosystems during the United Nations Decade of Restoration. Trees and soil organisms are known to interact, and are both crucial for maintaining multiple ecosystem functions. However, little is known about how the bidirectional relationships among above‐ and below‐ground diversity and ecosystem functions differ across forested and non‐forested ecosystems. We collected data from 126 sites from humid to arid areas in eastern Australia to explore bidirectional relationships among above‐ground (richness of trees and other plants) and below‐ground (richness of bacteria, fungi, invertebrate, protist) diversity and multiple ecosystem functions (multifunctionality, litter and labile carbon storage, nutrient pools, decomposition, groundstorey plant biomass production, soil stability) in forested (tree cover >10%) and non‐forested (tree cover ≤10%, open woodlands, shrublands) systems. We found that the relative importance of above‐ and below‐ground diversity differed among forested and non‐forested systems. Ecosystem functions, such as litter and labile carbon storage and soil stability, were associated mainly with tree richness in forested systems. By comparison, ecosystem functions of non‐forests were related to the richness of soil organisms. Such bidirectional biodiversity–ecosystem function relationships varied with the target function, and the relationships among ecosystem functions and the relative abundance of species varied with tree and soil taxa. The richness of other plants (i.e. all plants excluding trees) and soil organisms was positively coupled in forests only, but there were no linkages among above‐ and below‐ground diversity and ecosystem functions in non‐forests for groundstorey plant biomass production. Furthermore, increases in aridity and soil pH further weakened the biodiversity–ecosystem function relationships in forested and non‐forested systems, by suppressing above‐ground diversity and bacterial richness, respectively. Synthesis. Our study provides strong empirical evidence that the bidirectional relationships among above‐ and below‐ground diversity and ecosystem functions are highly variable across ecosystem and function types. Moreover, our study demonstrates that soil biodiversity is relatively more important than tree diversity in supporting ecosystem functions in non‐forested systems. This suggests that conservation of soil biodiversity is critical for maintaining the functioning of open woodland and shrubland systems.

Facilitation enhances ecosystem function with non‐random species gains

Facilitation, an ecological interaction assembling plant communities worldwide, has been shown to modulate both species richness and ecosystem functions. Such a biodiversity–ecosystem functioning (BEF) relationship can be decomposed into different components not only related to species losses and gains but also to the identity of the species and the context in which they live. Using an extension of the classical BEF approach named CAFE (community assembly and the functioning of ecosystems), we quantified the contribution of these components to the BEF relationship in a Spanish semiarid plant community shaped by facilitation. We used species richness as a measure for biodiversity and plant cover as a proxy of multiple ecosystem functions including plant productivity, soil protection, soil fertility and microbial productivity. Nurse plants doubled the number of species that live beneath them relative to open ground, but caused a five‐fold increase in plant cover. The disproportionate increase of plant cover was a consequence of the identity of the species enhanced by nurse plants, which were more productive than the average. We discuss these results in terms of sampling effects (i.e. the higher probability of richer communities to harbour hyperproductive species) and complementary effects (i.e. richer communities enhancing productivity through resource partitioning, abiotic facilitation or biotic feedbacks). The enhancement of ecosystem functions that plant facilitation produces by incorporating species with high functional values to the community may reverberate among other trophic levels and propagate beyond the local scale where the ecological interaction is produced.

Fungal-fungal and fungal-bacterial interactions in aquatic decomposer communities: bacteria promote fungal diversity.

Fungi produce a variety of extracellular enzymes, making recalcitrant substrates bioavailable. Thus, fungi are central for the decomposition of dead organic matter such as leaf litter. Despite their ecological importance, our understanding of relationships between fungal species diversity and ecosystem functioning is limited, especially with regard to aquatic habitats. Moreover, fungal interactions with other groups of microorganisms such as bacteria are rarely investigated. This lack of information may be attributed to methodological limitations in tracking the biomass of individual fungal species in communities, impeding a detailed assessment of deviations from the overall performance expected from the sum of individual species' performances, so-called net diversity effects (NDEs). We used fungal species-specific biomolecular tools to target fungal-fungal and fungal-bacterial interactions on submerged leaves using four cosmopolitan aquatic fungal species and a stream microbial community dominated by bacteria. In microcosms, we experimentally manipulated fungal diversity and bacterial absence/presence and assessed functional performances and fungal community composition after 14d of incubation. Fungal community data were used to evaluate NDEs on leaf colonization. The individual fungal species were functionally distinct and fungal cultures were on average more efficient than the bacterial culture. In absence of bacteria, NDEs correlated with growth rate (negatively) and genetic divergence (positively), but were predominantly negative, suggesting that higher fungal diversity led to a lower colonization success (niche overlap). In both absence and presence of bacteria, the overall functional performances of the communities were largely defined by their composition (i.e., no interactions at the functional level). In the presence of bacteria, NDEs correlated with genetic divergence (positively) and were largely positive, suggesting higher fungal diversity stimulated colonization (niche complementarity). This stimulation may be driven by a bacteria-induced inhibition of fungal growth, alleviating competition among fungi. Resulting feedback loops eventually promote fungal coexistence and synergistic interactions. Nonetheless, overall functional performances are reduced compared to bacteria-free cultures. These findings highlight the necessity to conduct future studies, investigating biodiversity-ecosystem functioning relationships using artificial systems, without exclusion of key organisms naturally co-occurring in the compartment of interest. Otherwise, study outcomes might not reflect true ecological relationships and ultimately misguide conservation strategies.

Revisiting the link between cereal diversity and production in Ethiopia

AbstractStudies show that cereal diversity positively affects mean yields, suggesting increased crop diversity as a means of increasing production (Di Falco and Chavas 2009, Baumgärtner and Quaas 2010). In practice though, agricultural development has relied on nondiverse systems. Using the Ethiopian Rural Household Survey panel, we revisit this paradox and disentangle the effects of agroecological zones and composition of crop diversity. We find a positive effect of greater cereal diversity on cereal production, but mostly in specific agroecological zones and for households who diversify away from a particular low-productivity crop: teff. These results indicate that the scope of cereal diversity to drive increases in output may be limited. Similar to recent studies of biodiversity—ecosystem function relationships (e.g. Jochum et al. 2020), the results suggest that the composition of diverse systems can be more important than the measured diversity itself. In the case of cereal crops in Ethiopia, differences in the yields of particular cereals in the crop mix explain the diversity effect, rather than diversity alone. Since some combinations of crops add to productivity but others do not, productivity-related crop choice may not guarantee in situ conservation of crop diversity on its own. Alternative conservation solutions may well be needed for that.

Relationships between biodiversity and ecosystem functioning proxies strengthen when approaching chemosynthetic deep-sea methane seeps.

As biodiversity loss accelerates globally, understanding environmental influence over biodiversity–ecosystem functioning (BEF) relationships becomes crucial for ecosystem management. Theory suggests that resource supply affects the shape of BEF relationships, but this awaits detailed investigation in marine ecosystems. Here, we use deep-sea chemosynthetic methane seeps and surrounding sediments as natural laboratories in which to contrast relationships between BEF proxies along with a gradient of trophic resource availability (higher resource methane seep, to lower resource photosynthetically fuelled deep-sea habitats). We determined sediment fauna taxonomic and functional trait biodiversity, and quantified bioturbation potential (BPc), calcification degree, standing stock and density as ecosystem functioning proxies. Relationships were strongly unimodal in chemosynthetic seep habitats, but were undetectable in transitional ‘chemotone’ habitats and photosynthetically dependent deep-sea habitats. In seep habitats, ecosystem functioning proxies peaked below maximum biodiversity, perhaps suggesting that a small number of specialized species are important in shaping this relationship. This suggests that absolute biodiversity is not a good metric of ecosystem ‘value’ at methane seeps, and that these deep-sea environments may require special management to maintain ecosystem functioning under human disturbance. We promote further investigation of BEF relationships in non-traditional resource environments and emphasize that deep-sea conservation should consider ‘functioning hotspots' alongside biodiversity hotspots.

Structural diversity and tree density drives variation in the biodiversity-ecosystem function relationship of woodlands andsavannas.

Positive biodiversity-ecosystem function relationships (BEFRs) have been widely documented, but it is unclear if BEFRs should be expected in disturbance-driven systems. Disturbance may limit competition and niche differentiation, which are frequently posited to underlie BEFRs. We provide the first exploration of the relationship between tree species diversity and biomass, one measure of ecosystem function, across southern African woodlands and savannas, an ecological system rife with disturbance from fire, herbivores and humans. We used > 1000 vegetation plots distributed across 10 southern African countries and structural equationmodelling to determine the relationship between tree species diversity and above-ground woody biomass, accounting for interacting effects of resource availability, disturbance by fire, tree stem density and vegetation type. We found positive effects of tree species diversity on above-ground biomass, operating via increased structural diversity. The observed BEFR was highly dependent on organismal density, with a minimum threshold of c. 180 mature stems ha-1 . We found that water availability mainly affects biomass indirectly, via increasing species diversity. The study underlines the close association between tree diversity, ecosystem structure, environment and function in highly disturbed savannas and woodlands. We suggest that tree diversity is an under-appreciated determinant of wooded ecosystem structure and function.

Noncommercial forests need type- and age-differentiated conservation measures: A case study based on 600 plots in Zhejiang Province in eastern China

Global climate change and unprecedented human activities have significantly endangered forest biodiversity and productivity. Understanding the biodiversity-ecosystem functioning (BEF) relationship is the basis for forest management and the formulation of biodiversity conservation strategies. Forest productivity is one of the most important ecosystem functions. In this study, multiple stepwise linear regression methods were used to model the biomass and environment factors of 600 plots in the Qiantang River Basin in eastern China. We used seven types of linear models to simulate the BEF relationships with three age stages (age stage 1:<20 yr old, age stage 2:20–60 yr old, and age stage 3:>60 yr old) of pine forests, mixed forests and broad-leaved forests. Our results showed that the biomass of pine and mixed forests was significantly correlated with elevation and canopy density, and that of broad-leaved forest was correlated with canopy density. Furthermore, we found that the BEF relationships of pine forests and mixed forests are positive, while that of broad-leaved forests are negative, especially in old-growth broad-leaved forests. Thus, our results recommend some differentiated management plans: for pine forests and mixed forests, positive management is recommended, such as replanting some broadleaf species, while for those broad-leaved forests, keeping them maintaining natural succession state (avoid any management measures) is recommended. Our study provides more detailed data and references for carbon storage capacity and management of subtropical forests.

Linking Terrestrial and Aquatic Biodiversity to Ecosystem Function Across Scales, Trophic Levels, and Realms

Global declines in biodiversity have the potential to affect ecosystem function, and vice versa, in both terrestrial and aquatic ecological realms. While many studies have considered biodiversity-ecosystem function (BEF) relationships at local scales within single realms, there is a critical need for more studies examining BEF linkages among ecological realms, across scales, and across trophic levels. We present a framework linking abiotic attributes, productivity, and biodiversity across terrestrial and inland aquatic realms. We review examples of the major ways that BEF linkages form across realms–cross-system subsidies, ecosystem engineering, and hydrology. We then formulate testable hypotheses about the relative strength of these connections across spatial scales, realms, and trophic levels. While some studies have addressed these hypotheses individually, to holistically understand and predict the impact of biodiversity loss on ecosystem function, researchers need to move beyond local and simplified systems and explicitly investigate cross-realm and trophic interactions and large-scale patterns and processes. Recent advances in computational power, data synthesis, and geographic information science can facilitate studies spanning multiple ecological realms that will lead to a more comprehensive understanding of BEF connections.

A conceptual framework and experimental design for analysing the relationship between biodiversity and ecosystem functioning (BEF) in agroforestry systems

There is compelling evidence for positive effects of plant diversity on the functioning of forests and agroecosystems. This information is increasingly used to optimize production systems that provide a wide range of ecosystem services. While agroforestry is actively promoted for the sustainable intensification of agriculture and restoration of degraded landscapes, there is a paucity of knowledge on Biodiversity Ecosystem Functioning (BEF) relationships in agroforestry systems. Since BEF-relationships in agroforestry might be shaped by combinations of different life-forms (e.g. trees, shrubs, herbs) and their interactions, experiences from grassland and forest experiments cannot be readily transferred to agroforestry. This highlights the need for a new type of experiments in agroforestry to advance our understanding of the role of biodiversity for the functioning of these systems. Therefore, our aim was to develop a conceptual framework for analysing BEF-relationships in agroforestry systems and to present an exemplary design for this purpose, which we placed in a (sub)tropical context. Based on designs used in tree diversity experiments, we suggest four major design principles: 1) a trait-based approach for selecting tree and crop species, 2) the integration of trees and crops along a gradient of functional diversity, 3) maintaining constant density across different combinations of life-forms in agroforests through the concept of “growing-patch-density”, and 4) disentangling a priori the effects of species diversity on ecosystem functioning from those of structural and functional diversity, defined here as the variation in structural attributes such as plant dimensions and in plant functional traits, respectively. Our conceptual design and the embedded principles offer a promising avenue to identify important drivers of specific BEF-relationships and to quantify management influences on these. This design can support new research projects that aim at improving ecosystem functioning of agroforestry with the view of optimizing the provision of ecosystem services and facilitation of ecosystem restoration.

Biodiversity and ecosystem functioning: Have our experiments and indices been underestimating the role of facilitation?

Abstract After 25 years of biodiversity experiments, it is clear that higher biodiversity (B) plant communities are usually more productive and often have greater ecosystem functioning (EF) than lower diversity communities. However, the mechanisms underlying this positive biodiversity–ecosystem functioning (BEF) relationship are still poorly understood. The vast majority of past work in BEF research has focused on the roles of mathematically partitioned complementarity and selection effects. While these mathematical approaches have provided insights into underlying mechanisms, they have focused strongly on competition and resource partitioning. Importantly, mathematically partitioned complementarity effects include multiple facilitative mechanisms, including dilution of species‐specific pathogens, positive changes in soil nutrient cycling, associational defence and microclimate amelioration. Synthesis. This Special Feature takes an experimental and mechanistic approach to teasing out the facilitative mechanisms that underlie positive BEF relationships. As an example, we demonstrate diversity‐driven changes in microclimate amelioration. Articles in this Special Feature explore photoinhibition, experimental manipulations of microclimate, lidar examinations of plant canopy effects and higher‐order trophic interactions as facilitative mechanisms behind classic BEF processes. We emphasize the need for future BEF experiments to disentangle the facilitative mechanisms that are interlinked with niche complementarity to better understand the fundamental processes by which diversity regulates life on Earth.

Multiple diversity facets of crucial microbial groups in biological soil crusts promote soil multifunctionality

AbstractAimMicrobial diversity is one of the most important factors for maintaining the performance of multiple functions in soils (multifunctionality). However, existing studies typically consider the taxonomic richness or Shannon diversity of the entire community. We know little about the connection network of taxonomic and phylogenetic facets of diversity and their collective impact on multifunctionality. In this study, the linkages of effects of diversity within functional groups were disentangled in drylands.LocationThe central Tibetan Plateau.Time periodPresent.Major taxa studiedPhototrophs and diazotrophs (mainly cyanobacteria).MethodsGiven the carbon‐ and nitrogen‐limited nature of drylands, we conducted a high‐throughput sequencing of C/N‐fixing functional groups from biocrusts and evaluated multiple facets of diversity (i.e., richness, evenness and phylogeny‐related trait dissimilarity), together with seven crucial variables of soil functioning to calculate multifunctionality. The relationships between multifaceted diversity and abundance with individual functions and multifunctionality were validated by a set of solid statistical analyses.ResultsWe found that the integrated biodiversity index was a stronger predictor of multifunctionality than richness. The divergent performance of different facets of diversity determined the idiosyncratic effect of each functional group on soil multifunctionality. Moreover, the evaluation of functional significance at the species level gave important clues on the trade‐offs and redundancy in each functional group, explaining the distinct patterns of effects of diversity. Richness was the dominant factor for diazotrophs to maximize multifunctionality, whereas phylogenetic dissimilarity was the essential one for phototrophs.Main conclusionsOur study demonstrated that multiple facets of diversity should be considered when assessing the effects of biodiversity. In contrast to the community level, within‐functional group measures might adequately capture the features of diversity that are most correlated with soil multifunctionality. Our results provide a perspective to bridge the gap between taxonomic and trait‐based approaches for elucidating the biodiversity–ecosystem function relationship.

Physiological responses to light explain competition and facilitation in a tree diversity experiment

Abstract Ecologists often invoke interspecific facilitation to help explain positive biodiversity–ecosystem function relationships in plant communities, but seldom test how it occurs. One mechanism through which one species may facilitate another is by ameliorating abiotic stress. Physiological experiments show that a chronic excess of light can cause stress that depresses carbon assimilation. If shading by a plant's neighbours reduces light stress enough, it may facilitate that plant's growth. If light is instead most often a limiting factor for photosynthesis, shading may have an adverse, competitive effect. In a temperate tree diversity experiment, we measured stem growth rates and photosynthetic physiology in broadleaf trees across a gradient of light availability imposed by their neighbours. At the extremes, trees experienced nearly full sun (monoculture), or were shaded by nearby fast‐growing conifers (shaded biculture). Most species had slower growth rates with larger neighbours, implying a net competitive effect. On the other hand, the two most shade‐tolerant species (Tilia americana and Acer negundo) and the most shade‐intolerant one (Betula papyrifera) had faster stem growth rates with larger neighbours. The two shade‐tolerant species had the greatest increases in photoinhibition (reduced dark‐acclimated Fv/Fm) across the gradient of increasing light availability, which suggests they are more vulnerable to chronic light stress. While most species had lower carbon assimilation rates in the shaded biculture treatment, T. americana had rates up to 25% higher. T. americana also dropped its leaves 3–4 weeks earlier in monocultures, curtailing its growing season. We conclude that although large neighbours can cause light limitation in shade‐intolerant species, they can also increase growth through abiotic stress amelioration in shade‐tolerant species. Finally, in shade‐intolerant B. papyrifera, we find a pattern of stem elongation in trees with larger neighbours, which suggests that a shade avoidance response may account for the apparent positive trend in stem volume. Synthesis. Both positive and negative species interactions in our experiment can be explained in large part by the photosynthetic responses of trees to the light environment created by their neighbours. We show that photosynthetic physiology can help explain the species interactions that underlie biodiversity–ecosystem function relationships. The insights that ecologists gain by searching for such physiological mechanisms may help us forecast species interactions under environmental change.

Local Tree Diversity Suppresses Foliar Fungal Infestation and Decreases Morphological But Not Molecular Richness in a Young Subtropical Forest.

Leaf fungal pathogens alter their host species’ performance and, thus, changes in fungal species composition can translate into effects at the tree community scale. Conversely, the functional diversity of tree species in a host tree’s local neighbourhood can affect the host’s foliar fungal infestation. Therefore, understanding the factors that affect fungal infestations is important to advance our understanding of biodiversity-ecosystem functioning (BEF) relationships. Here we make use of the largest BEF tree experiment worldwide, the BEF-China experiment, where we selected tree host species with different neighbour species. Identifying fungal taxa by microscopy and by high-throughput DNA sequencing techniques based on the internal transcribed spacer (ITS) rDNA region, we analysed the fungal richness and infestation rates of our target trees as a function of local species richness. Based on the visual microscopic assessment, we found that a higher tree diversity reduced fungal richness and host-specific fungal infestation in the host’s local neighbourhood, while molecular fungal richness was unaffected. This diversity effect was mainly explained by the decrease in host proportion. Thus, the dilution of host species in the local neighbourhood was the primary mechanism in reducing the fungal disease severity. Overall, our study suggests that diverse forests will suffer less from foliar fungal diseases compared to those with lower diversity.

A combined microbial and ecosystem metric of carbon retention efficiency explains land cover-dependent soil microbial biodiversity–ecosystem function relationships

While soil organic carbon (C) is the foundation of productive and healthy ecosystems, the impact of the ecology of microorganisms on C-cycling remains unknown. We manipulated the diversity, applied here as species richness, of the microbial community present in similar soils on two contrasting land-covers—an adjacent pasture and forest—and observed the transformations of plant detritus and soil organic matter (SOM) using stable isotope (13C) tracing coupled with a novel nuclear magnetic resonance (NMR) experiment. The amount of detritus-C degraded was not affected by the microbial diversity (p > 0.05), however the fate of detritus- and SOM-C across the diversity gradient was complex and land cover-dependent. For example, in the pasture soil, higher diversity led to lower CO2 production (p = 0.001), a trend driven solely by SOM-C mineralization. There was no relationship between diversity and detritus-C mineralization or production of new mineral-associations after one year (p > 0.05). In contrast, in the forest soil higher diversity resulted in increased detritus-C (p = 0.01) and SOM-C (p = 0.0008) mineralization and decreased mineral-associated organic matter formation (p = 0.02). In both land cover types, retention efficiency—a measure that integrates both microbial physiology and the ability of the ecosystem to retain C—explained C loss and transformation trends. Overall, this demonstrates that the trajectory of C gained and lost is altered by land management-induced changes to microbial communities, soil structure, and chemical characteristics underlying SOM persistence.

Facilitation and biodiversity–ecosystem function relationships in crop production systems and their role in sustainable farming

Abstract We review the need for increasing agricultural sustainability, how this can in part be delivered by positive biodiversity–ecosystem function (BEF) effects, the role within these of plant–plant facilitation, and how a better understanding of this role may help to deliver sustainable crop (particularly arable) production systems. Major challenges facing intensive arable production include overall declines in biodiversity, poor soil structure and health, nutrient and soil particle run‐off, high greenhouse gas emissions, and increasing costs of synthetic inputs including herbicides, pesticides and fertilisers. Biodiversity–ecosystem function effects have the potential to deliver win–wins for arable food production, whereby enhanced biodiversity is associated with ‘good outcomes’ for farming sustainability, albeit sometimes through negative BEF effects for some components of the system. Although it can be difficult to separate explicitly from niche differentiation, evidence indicates facilitation can be a key component of these BEF effects. Explicit recognition of facilitation's role brings benefits to developing sustainable crop systems. First, it allows us to link fundamental ecological studies on the evolution of facilitation to the selection of traits that can enhance functioning in crop mixtures. Second, it provides us with analytical frameworks which can be used to bring structure and testable hypotheses to data derived from multiple (often independent) crop trials. Before concrete guidance can be provided to the agricultural sector as to how facilitation might be enhanced in crop systems, challenges exist with respect to quantifying facilitation, understanding the traits that maximise facilitation and integrating these traits into breeding programmes, components of an approach we suggest could be termed ‘Functional Ecological Selection’. Synthesis. Ultimately, better integration between ecologists and crop scientists will be essential in harnessing the benefits of ecological knowledge for developing more sustainable agriculture. We need to focus on understanding the mechanistic basis of strong facilitative interactions in crop systems and using this information to select and breed for improved combinations of genotypes and species as part of the Functional Ecological Selection approach.

Neighborhood effects and environmental variables drive sapling growth in a young subtropical tree plantation

We established a forest biodiversity and ecosystem functioning experiment in southern China by planting 20,480 saplings of eight subtropical tree species in 320 plots in monocultures and mixtures of two, four and eight species to explore the biodiversity-ecosystem functioning (BEF) relationships and the underlying coexistence determinants. In this study, we aimed to report the growth of these planted saplings and explore its abiotic and biotic driving factors. Specifically, we analyzed the relative importance of sapling species identity, initial size, neighborhood interactions, neighborhood diversity, and environmental factors to sapling growth in the early stage of our BEF experiment. We found that the species of Ilex rotunda, Pinus massoniana and Elaeocarpus sylvestris grew much faster than other five species, followed by Castanopsis carlesii, Cinnamomum camphora and Schima superba. Erythrophleum fordii and Castanopsis fissa had the lowest growth rates in ground diameter and height. In addition, the relative growth rates of saplings were positively related to the neighborhood interactions, neighborhood diversity and soil nutrients, but were negatively related to initial size. Our study stresses the importance of better understanding the effects of environmental and local neighborhood conditions on initial growth of subtropical forest tree species in a mixed plantation, and provides reference for other BEF experiments in China and elsewhere.