Positive Biodiversity Effects Research Articles

Biodiversity increases resistance of grasslands against plant invasions under multiple environmental changes.

Biodiversity often helps communities resist invasion. However, it is unclear whether this diversity-invasion relationship holds true under environmental changes. Here, we conduct a meta-analysis of 1010 observations from 25 grassland studies in which plant species richness is manipulated together with one or more environmental change factors to test invasibility (measured by biomass or cover of invaders). We find that biodiversity increases resistance to invaders across various environmental conditions. However, the positive biodiversity effect on invasion resistance is strengthened under experimental warming, whereas it is weakened under experimentally imposed drought. When multiple factors are imposed simultaneously, the positive biodiversity effect is strengthened. Overall, we show that biodiversity helps grassland communities resist plant invasions under multiple environmental changes. Therefore, investment in the protection and restoration of native biodiversity is not only important for prevention of invasions under current conditions but also under continued global environmental change.

Biodiversity and quality of urban green landscape affect mental restorativeness of residents in Multan, Pakistan

IntroductionThe influence of urban green spaces on public health is receiving unprecedented attention. Managing urban greenspaces sustainably requires an understanding of the mechanisms behind the positive effects of urban biodiversity on the wellbeing of residents. Urban parks could improve mental restoration of park users. The restoration potential may be influenced by the biophysical characteristics of the park.MethodsThis study aimed to understand two aspects of urban parks in Multan, Pakistan: (a) How does the perception of biodiversity and the quality of urban parks relate to mental restorativeness of park visitors? (b) What are the determinants of respondents' willingness to pay for the conservation and management of park biodiversity and quality in urban parks? Data were collected from October 2021 to December 2021 through a cross-sectional survey in which 550 park visitors were interviewed from six randomly selected urban parks in Multan. Multiple linear regression analysis, a binary logistic model, and a chi-square test were applied to analyze the data.Results and discussionThe study empirically highlights the positive contribution of park visits to mental restorativeness. Biodiversity and quality were positively correlated with the mental restorativeness of park visitors. Sixty-two percent (62%) of the visitors were reluctant to pay, whereas 38% were ready to pay between Rs. 850/3.7$ and Rs. 1,700/7.4$ each year. Education, occupation, and monthly income significantly positively affected the respondent's WTP attitudes. The study highlights the importance of using urban parks as tools to promote mental restorativeness, combat social stress, and increase urban vegetation cover.

No positive effects of biodiversity on ecological resilience of lake ecosystems

<p>Ecological resilience is critical for ecosystems to persist in the face of perturbations without shifting to a different state. Global biodiversity loss in multiple ecosystems is considered to be associated with decreasing ecological resilience and increasing the risk of ecosystem collapse. However, how temporal changes in biodiversity affect ecological resilience in natural ecosystems remains poorly elucidated. By analyzing subfossil records of diatoms, chironomids, and cladocerans from 53 lake sediment cores across the globe, we found that species richness showed an increasing trend with time, while beta diversity and ecological resilience presented a decreasing temporal trend when ecosystems are approaching the abrupt shift. Asynchronous fluctuations among species and temporal stability at species level are suggested to be the mechanisms that contribute to the maintenance of temporal community stability. We found species richness and beta diversity have positive effects on species asynchrony but negative effects on species stability. However, we found that species asynchrony and species stability had negative relationships with ecological resilience, with species richness and beta diversity overall having no positive effects on ecological resilience. We highlighted that biodiversity effects on ecological resilience are not only the role of species richness, but also the species assemblage and network complexity of species-species interactions. Our study indicates that increased species diversity and community heterogeneity may be not beneficial for the ecosystem to recover from disturbances at a lake ecosystem scale, which has great implications for the assessment of ecological resilience and predicting ecosystem collapse in future global environmental change scenarios.</p>

Hill-Chao numbers allow decomposing gamma multifunctionality into alpha and beta components.

Biodiversity-ecosystem functioning (BEF) research has provided strong evidence and mechanistic underpinnings to support positive effects of biodiversity on ecosystem functioning, from single to multiple functions. This research has provided knowledge gained mainly at the local alpha scale (i.e. within ecosystems), but the increasing homogenization of landscapes in the Anthropocene has raised the potential that declining biodiversity at the beta (across ecosystems) and gamma scales is likely to also impact ecosystem functioning. Drawing on biodiversity theory, we propose a new statistical framework based on Hill-Chao numbers. The framework allows decomposition of multifunctionality at gamma scales into alpha and beta components, a critical but hitherto missing tool in BEF research; it also allows weighting of individual ecosystem functions. Through the proposed decomposition, new BEF results for beta and gamma scales are discovered. Our novel approach is applicable across ecosystems and connects local- and landscape-scale BEF assessments from experiments to natural settings.

Increasing intraspecific diversity of wheat affects plant nutrient contents but not N recovery in the plant-soil system

Crop homogenization in conventional agriculture has been pervasive while ecology has shown positive effects of biodiversity on ecosystem functioning, that arise from complementarity/facilitation and sampling/selection effects. These effects are well documented for interspecific diversity in both natural ecosystems and agroecosystems but remain less documented at an intraspecific level, particularly for the rates of nutrient uptake by plants and nutrient losses from ecosystems. We conducted a field experiment with 88 experimental plots cultivated with 1, 2, 4 or 8 wheat varieties and 1, 2, 3 or 4 functional groups to assess the effects of the number of varietal and functional diversity of winter wheat on plant biomass production, plant nutrient contents (N, Ca, Cu, Fe, Mg, Mn, P, K, Na and Zn) and fertilizer N recovery in the plant-soil system using a 15N labeling method. We found both negative and positive effects of the number of varieties or number of functional groups on shoot Cu, Fe, Zn, Na and P contents, but no significant effects of intraspecific diversity on biomass production, N content and 15N recovery in the plant-soil system. Our results show differential responses to an increase of intraspecific diversity of wheat on the contents of several essential nutrients in plants and highlight the need to jointly analyze multiple nutrients. Our study also suggests that increasing intraspecific diversity had no overall negative effects on biomass production or N content. Using knowledge on variety functional traits to target specific complementarity mechanisms when designing variety mixtures could thus lead to a positive effect on nutrient absorption and biomass production.

High phytoplankton diversity in eutrophic states impedes lake recovery

AbstractAimThe widely observed positive response of productivity to biodiversity, known as the biodiversity‐productivity relationship (BPR), underpins nature‐based solutions for mitigating and adapting to global changes. Little is known of the role of such emergent processes in the restoration of damaged ecosystems. Here, we test for evidence of a BPR in degraded freshwater lakes, and its role in underpinning or undermining lake recovery from eutrophic states.LocationLower Yangtze and Huaihe river basins, China, East Asia.TaxaFreshwater phytoplankton; also macrophytes, fish, zooplankton and zoobenthos.MethodsA systematic review of biodiversity studies was conducted to enumerate freshwater biodiversity change during eutrophication, encompassing 572 samples from 155 lakes in East China. Empirical samples were then taken of 93 phytoplankton communities from 38 lakes in ecologically degraded states of eutrophication. Samples were analysed for niche overlap in relation to biodiversity and productivity, and metrics of network structure indicative of community stability.ResultsReviewed publications on eutrophication in East China lakes revealed losses in biodiversity of macrophytes, fishes, zooplankton and zoobenthos but not phytoplankton. Empirically sampled eutrophic lakes maintained high phytoplankton biodiversity through niche differentiation, and phytoplankton biodiversity correlated positively with biomass, in line with the expectations of BPR.ConclusionsThe positive effect of biodiversity on phytoplankton productivity in eutrophic lakes acts in opposition to the negative impacts on productivity induced by eutrophication‐management strategies of nutrient suppression. In degraded systems, the BPR contributes to sustaining productivity of lake phytoplankton communities, impeding recovery from a eutrophic state. This is a case of the BPR playing an undesirable role at the ecosystem level. Lake recovery programmes need to anticipate that the control of phytoplankton biomass will depend on reducing nutrients to a level sufficient to degrade the internal structure of the phytoplankton community.

Plant biodiversity offsets negative effects of metals and metalloids soil multi-contamination on ecosystem multifunctionality

Despite increasing metals and metalloids (MM) human-driven soil contamination, how it simultaneously alters biodiversity and ecosystem functioning remains unknown. We used a wide gradient of a 170-year-old MM soil multi-contamination in Mediterranean scrublands to assess the effects of soil multi-contamination on multiple plant biodiversity facets, microbial communities and ecosystem multifunctionality (EMF). We found an overall positive effect of plant biodiversity on EMF mediated by microbial communities, and allowing offsetting the negative impacts of MM soil multi-contamination, especially on soil water holding capacity and nitrogen content. The diversity of distant plant lineages was the key facet promoting EMF by enhancing microbial communities, whereas the subordinate species richness altered EMF. By developing a holistic approach of these complex relationships between soil multi-contamination, plant biodiversity, microbial communities and ecosystem functioning, our results reveal the potential of plant biodiversity, and especially the diversity of evolutionary distant species, to offset the alteration of ecosystem functioning by MM soil multi-contamination. In this worldwide decade of ecosystems restoration, our study helps to identify relevant facets of plant biodiversity promoting contaminated ecosystem functioning, which is crucial to guide and optimize management efforts aiming to restore ecosystems and preserve human health.

Diversity‐conditioned soil strengthens plant diversity–productivity relationship

Abstract How biodiversity affects terrestrial productivity is important to the maintenance of ecosystem services under global change. Although the crucial role of plant–soil feedbacks (PSF) in determining diversity–productivity relationship has been increasingly recognized in recent years, its legacy effects on subsequent diversity–productivity relationship are still unclear. We conducted a classic PSF experiment to assess how plant diversity‐conditioned soils influenced subsequent plant diversity–productivity relationships, where three plant diversity levels (1, 4 and 8 species) were planted in soils conditioned at three diversity levels (conditioned by 1, 4 and 8 species for 3 years). In addition, to test the role of soil microbial diversity in mediating the effects of soil conditioning diversity, the three plant diversity levels were planted with low, moderate and high soil biodiversity created by a soil inoculum dilution. The results showed that plant productivities were promoted by mixed‐conditioned soils (4 and 8 species) comparing to mono‐conditioned soils (1 species). Productivity was positively related to planted diversity in mixed‐conditioned soils, while showed no relation with planted diversity in mono‐conditioned soils. Productivity was promoted by soil biodiversity when 4 and 8 species were mixed planted, while did not change when 1 species was planted. Synthesis and applications . Our results highlight that PSF is crucial to strengthen the positive effects of biodiversity on productivity, implying that diversifying cropping systems should be encouraged in agroecosystem management to benefit from positive PSF effects. The importance of soil legacy for optimizing plant productivity is particularly important for conditioning soils with an intermediate number of plant species.

Multitrophic biodiversity enhances ecosystem functions, services and ecological intensification in agriculture

Abstract One central challenge for humanity is to mitigate and adapt to an ongoing climate and biodiversity crisis while providing resources to a growing human population. Ecological intensification (EI) aims to maximize crop productivity while minimizing impacts on the environment, especially by using biodiversity to improve ecosystem functions and services. Many EI measures are based on trophic interactions between organisms (e.g. pollination, biocontrol). Here, we investigate how research on multitrophic effects of biodiversity on ecosystem functioning could advance the application of EI measures in agriculture and forestry. We review previous studies and use qualitative analyses of the literature to test how important variables such as land-use parameters or habitat complexity affect multitrophic diversity, ecosystem functions and multitrophic biodiversity–ecosystem functioning relationships. We found that positive effects of biodiversity on ecosystem functions are prevalent in production systems, largely across ecosystem function dimensions, trophic levels, study methodologies and different ecosystem functions, however, with certain context dependencies. We also found strong impacts of land use and management on multitrophic biodiversity and ecosystem functions. We detected knowledge gaps in terms of data from underrepresented geographical areas, production systems, organism groups and functional diversity measurements. Additionally, we identified several aspects that require more attention in the future, such as trade-offs between multiple functions, temporal dynamics, effects of climate change, the spatial scale of the measures and their implementation. This information will be vital to ensure that agricultural and forest landscapes produce resources for humanity sustainably within the environmental limits of the planet.

Incorporated cover crop residue suppresses weed seed germination

AbstractCover crops have been shown to be important integrated weed management tools. In addition to directly competing with weeds, cover crops can provide weed suppressive effects following incorporation through release of allelopathic compounds and/or changes to nutrient availability. Incorporation of a cover crop mixture may provide a synergistic or antagonistic effect on weed suppression by further altering nutrient dynamics. To investigate this phenomenon, we evaluated the suppressive effects following incorporation of annual ryegrass, buckwheat, brown mustard, and phacelia sown with and without field pea on germination and growth of several pernicious weed species. Further, we used the additive partitioning model to determine if pea synergistically improved biomass production and weed suppression of cover crops. Our results demonstrate that following incorporation, cover crop residues suppress weed germination and weed biomass production. According to the additive partitioning model, the addition of pea had an antagonistic effect on buckwheat and brown mustard biomass production and decreased buckwheat weed suppression by 8%. In contrast, the addition of field pea greatly enhanced biomass production of phacelia at a reduced seeding rate suggesting a positive biodiversity effect. Limited evidence was found for changes to nutrient availability following cover crop incorporation, however, a dose‐dependent effect of cover crop residue on weed suppression suggests allelopathy and/or nutrient availability may have a role on weed seed germination success. Together, our results support the use of incorporated cover crop residues as an integrated weed management tool.

Environmental filtering drives biodiversity–spatial stability relationships in a large temperate forest region

Abstract The assumption that greater biodiversity enhances ecosystem stability, commonly known as ‘portfolio effect’, has attracted considerable research attention. However, the potential portfolio effects on spatial stability (the similarity of ecosystem functioning among forest communities) are still poorly examined especially at different spatial scales and under varying environmental stress conditions. Accordingly, this study investigates the biodiversity–spatial stability relationship among regional communities across different spatial scales and environmental conditions in a temperate forest region. We define spatial stability as the invariability of the productivity of woody plants among plots within a regional community. To test spatial stability, the N closest plots to a given plot were aggregated to form regional communities representing different spatial scales. Structural equation modelling was used to evaluate how biodiversity (including taxonomic [TD] and phylogenetic diversity [PD]) increases spatial stability via species asynchrony and/or population stability across spatial scales. Hierarchical Bayesian modelling was used to evaluate the environmental dependence of the portfolio effects on spatial stability. TD and PD both increased the spatial stability by increasing asynchrony, but decreased population stability. The portfolio effect of TD on spatial stability became stronger and reached saturation at the intermediate scale and then decreased as regional communities became larger. The portfolio effects of TD were weaker under the stressful conditions of drought, high precipitation seasonality and high elevation but unchanged across temperature seasonality and human disturbance. PD showed no discernable effect on spatial stability and did not change across spatial scale and environmental condition. Our results suggest that the positive effect of biodiversity on species asynchrony overcomes the negative biodiversity effect on population stability to buffer the spatial change in productivity in diverse communities. Future research of the biodiversity–spatial stability relationship may thus benefit from incorporating different spatial scales and environmental conditions into the analysis. Read the free Plain Language Summary for this article on the Journal blog.

Leaf nitrogen resorption is more important than litter nitrogen mineralization in mediating the diversity–productivity relationship along a nitrogen-limited temperate forest succession chronosequence

The resorption of nutrients by plants before litter fall and the mineralization of nutrients from plant litter by soil processes are both important pathways supporting primary productivity. While the positive relationship between plant biodiversity and primary productivity is widely accepted for natural ecosystems, the roles of nutrient resorption and mineralization in mediating that relationship remains largely unknown. Here, we quantified the relative importance of nitrogen (N) resorption and N mineralization in driving plant community N investment and the correlation between species diversity and community productivity along an N-limited successional chronosequence of the mixed broadleaved–Korean pine (Pinus koraiensis) forest in northeastern China. Leaf N resorption efficiency (NRE) at the community level increased significantly along the successional chronosequence, whereas litter N mineralization rate decreased significantly. Leaf NRE was more important than litter N mineralization rate in driving the diversity–productivity relationship. However, higher leaf NRE led to less N mineralization as succession progressed along the chronosequence. Our results highlight the importance of the N resorption pathway rather than the N mineralization pathway for forest N acquisition with community succession, and they provide mechanistic insights into the positive effects of biodiversity on ecosystem functioning. In future forest management practices, we recommend appropriate application of N fertilizer to mitigate the adverse effects of N-poor soil on seedling regeneration during late succession and thus maintain the sustainable development of temperate forest ecosystems.

Enhancing the structural diversity between forest patches-A concept and real-world experiment to study biodiversity, multifunctionality and forest resilience across spatial scales.

Intensification of land use by humans has led to a homogenization of landscapes and decreasing resilience of ecosystems globally due to a loss of biodiversity, including the majority of forests. Biodiversity-ecosystem functioning (BEF) research has provided compelling evidence for a positive effect of biodiversity on ecosystem functions and services at the local (α-diversity) scale, but we largely lack empirical evidence on how the loss of between-patch β-diversity affects biodiversity and multifunctionality at the landscape scale (γ-diversity). Here, we present a novel concept and experimental framework for elucidating BEF patterns at α-, β-, and γ-scales in real landscapes at a forest management-relevant scale. We examine this framework using 22 temperate broadleaf production forests, dominated by Fagus sylvatica. In 11 of these forests, we manipulated the structure between forest patches by increasing variation in canopy cover and deadwood. We hypothesized that an increase in landscape heterogeneity would enhance the β-diversity of different trophic levels, as well as the β-functionality of various ecosystem functions. We will develop a new statistical framework for BEF studies extending across scales and incorporating biodiversity measures from taxonomic to functional to phylogenetic diversity using Hill numbers. We will further expand the Hill number concept to multifunctionality allowing the decomposition of γ-multifunctionality into α- and β-components. Combining this analytic framework with our experimental data will allow us to test how an increase in between patch heterogeneity affects biodiversity and multifunctionality across spatial scales and trophic levels to help inform and improve forest resilience under climate change. Such an integrative concept for biodiversity and functionality, including spatial scales and multiple aspects of diversity and multifunctionality as well as physical and environmental structure in forests, will go far beyond the current widely applied approach in forestry to increase resilience of future forests through the manipulation of tree species composition.

Species choice and N fertilization influence yield gains through complementarity and selection effects in cereal-legume intercrops

Maintaining yield when reducing inputs is one prime objective of sustainable agriculture. In this context, cereal-legume intercropping is a practice that can achieve increased yield under low-input conditions through the complementary use of abiotic resources and facilitation mechanisms. Many management options exist to design cereal-legume intercropping systems, among which the choice of the species intercropped and the level of nitrogen (N) fertilization are essential. In this study, we collected the results of 35 field experiments across Europe of cereal-grain legume intercrops that combined various intercropped species and N fertilization levels. We first assessed the intensity of the biodiversity effect and its components in unfertilized intercrops. Then, we focused on a subset of systems to analyze how N fertilization influenced biodiversity effects on three intercrops (durum wheat/pea, soft wheat/pea, and durum wheat/faba bean). The biodiversity effect represents the gap between the observed and expected yields of a mixture. The complementarity effect is the performance of mixtures relative to the performance of the component monocultures. The selection effect captures the extent to which a species with a high monoculture yield dominates a mixture at the expense of the other intercropped species. Our results confirmed an overall positive biodiversity effect under unfertilized conditions and various climate conditions (0.86 ± 0.04 t.ha−1). Complementarity effect was the main driver as it represented 76% of the biodiversity effect, confirming intercropping as a useful practice in low-input systems. N fertilization lowered the complementarity effect in durum wheat/pea intercrops, did not influence these effects in soft wheat/pea intercrops, and increased only the selection effect in durum wheat/faba bean intercrops. These results highlight the need for a sufficiently competitive legume in intercrops when N fertilizers are applied in order to avoid too much disruption of plant–plant interactions.

Environmental self-identity partially mediates the effects of exposure and connection to nature on urban children's conservation behaviours

As crises of biodiversity loss and climate change have intensified, so too have efforts to promote human behaviours that ameliorate these global stressors. Leveraging people's connectedness with nature is proposed as a means of inspiring pro-nature behaviours at a personal and societal scale. However, it is only recently that studies have begun to characterise the specific mechanistic drivers of connectedness and its behavioural outcomes. A separate body of research shows that self-identities motivate pro-environmental behaviours. Here, we simultaneously investigate the effects of affective connection to nature and environmental self-identity on urban children's conservation behaviours. We also evaluate passive exposure, active learning, and nature-focused activities as predictors of connectedness. Using confirmatory composite analysis and path analysis in tandem, we analyse survey responses from 1037 children and adolescents attending 16 schools throughout Sydney, Australia. In this dataset, connection to nature had a large effect on commitment to conservation behaviours, half of which was mediated by environmental self-identity. Time spent in green and blue spaces had a weak direct effect on connection to nature. Most of its impact was mediated by regular engagement with nature-focused activities (e.g., looking for wild animals), which were the strongest predictors of connectedness alongside frequency of outdoor learning and reading about nature. Greenness of school catchment areas was negatively associated with connectedness, likely because children connect with nature at a finer scale and even indoors, as suggested by the moderate positive effect of household biodiversity on connectedness. Overall, we demonstrate that not all forms of contact with nature are equal when it comes to strengthening the kinds of affective bonds that lead urban children to identify with and act for nature.

Biodiversity promotes ecosystem functioning despite environmental change.

Three decades of research have demonstrated that biodiversity can promote the functioning of ecosystems. Yet, it is unclear whether the positive effects of biodiversity on ecosystem functioning will persist under various types of global environmental change drivers. We conducted a meta‐analysis of 46 factorial experiments manipulating both species richness and the environment to test how global change drivers (i.e. warming, drought, nutrient addition or CO2 enrichment) modulated the effect of biodiversity on multiple ecosystem functions across three taxonomic groups (microbes, phytoplankton and plants). We found that biodiversity increased ecosystem functioning in both ambient and manipulated environments, but often not to the same degree. In particular, biodiversity effects on ecosystem functioning were larger in stressful environments induced by global change drivers, indicating that high‐diversity communities were more resistant to environmental change. Using a subset of studies, we also found that the positive effects of biodiversity were mainly driven by interspecific complementarity and that these effects increased over time in both ambient and manipulated environments. Our findings support biodiversity conservation as a key strategy for sustainable ecosystem management in the face of global environmental change.

Using plant traits to understand the contribution of biodiversity effects to annual crop community productivity.

Increasing biodiversity generally enhances productivity through selection and complementarity effects not only in natural, but also in agricultural, systems. However, the quest to explain why diverse cropping systems are more productive than monocultures remains a central goal in agricultural science. In a mesocosm experiment, we constructed monocultures, two‐ and four‐species mixtures from eight crop species with or without fertilizer and both in temperate Switzerland and dry, Mediterranean Spain. We measured physical factors and plant traits and related these in structural equation models to selection and complementarity effects to explain seed yield differences between monocultures and mixtures. Increased crop diversity increased seed yield in Switzerland. This positive biodiversity effect was driven to almost the same extent by selection and complementarity effects, which increased with plant height and specific leaf area (SLA), respectively. Also, ecological processes driving seed yield increases from monocultures to mixtures differed from those responsible for seed yield increases through the diversification of mixtures from two to four species. Whereas selection effects were mainly driven by one species, complementarity effects were linked to larger leaf area per unit leaf weight. Seed yield increases due to mixture diversification were driven only by complementarity effects and were not mediated through the measured traits, suggesting that ecological processes beyond those measured in this study were responsible for positive diversity effects on yield beyond two‐species mixtures. By understanding the drivers of positive biodiversity–productivity relationships, we can improve our ability to predict species combinations that enhance ecosystem functioning and can promote sustainable agricultural production.

Phytoplankton diversity affects biomass and energy production differently during community development

Abstract Biodiversity determines the productivity and stability of ecosystems but some aspects of biodiversity–ecosystem functioning relationships remain poorly resolved. One key uncertainty is the inter‐relationship between biodiversity, energy and biomass production as communities develop over time. Energy production drives biomass accumulation but the ratio of the two processes can change during community development. How biodiversity affects these temporal patterns remains unknown. We empirically assessed how species diversity mediates the rates of increase and maximum values of biomass and net energy production in experimental phytoplankton communities over 10 days in the laboratory. We used five phytoplankton species to assemble three levels of diversity (monocultures, bicultures and communities) and we quantify their changes in biomass production and energy fluxes (energy produced by photosynthesis, consumed by metabolism, and net energy production as their difference) as the cultures move from a low density, low competition system to a high density, high competition system. We find that species diversity affects both biomass and energy fluxes but in different ways. Diverse communities produce net energy and biomass at faster rates, reaching greater maximum biomass but with no difference in maximum net energy production. Bounds on net energy production seem stronger than those on biomass because competition limits energy fluxes as biomass accumulates over time. In summary, diversity initially enhances productivity by diffusing competitive interactions but metabolic density dependence reduces these positive effects as biomass accumulates in older communities. By showing how biodiversity affects both biomass and energy fluxes during community development, our results demonstrate a mechanism that underlies positive biodiversity effects and offer a framework for comparing biodiversity effects across systems at different stages of development and disturbance regimes. A free Plain Language Summary can be found within the Supporting Information of this article.

Early positive biodiversity effects on total biomass in experimental tree seedling assemblages with and without water limitation

AbstractQuestionsWhile positive effects of tree diversity on tree community biomass have often been reported in mature stands, the debate on whether diversity effects may be detectable at the seedling level persists, with opposing outcomes found so far. We still lack a comprehensive evaluation of the biodiversity effects (so‐called ‘complementarity’ and ‘selection’ effects), as well as the phenotypic drivers at play, underlying early‐community biomass. Even less is known about whether such biodiversity effects may change under water‐limited conditions.LocationSeeds from four tree species coexisting in a Mediterranean forest (Spain).MethodsWe built experimental tree seedling assemblages with three diversity levels — monocultures, two‐species and four‐species mixtures — and under two soil moisture conditions. We quantified the extent to which species richness, species identity, community‐weighted mean (CWM) and functional dissimilarity (FD) influence complementarity and selection effects. We computed CWM and FD for seven functional traits related to water and light acquisition; and we calculated the complementarity and selection effects from above‐ and below‐ground biomass measures at the community level.ResultsOur results showed that complementarity drove the greater biomass in more diverse assemblages at the seedling stage. This pattern was largely favored by a particular species, Quercus faginea, with distinct phenotypic traits (great height, lateral ramification and root biomass with high dry matter content), which induced a positive effect of CWM on community biomass. Moreover, our study showed that the water deficit limited the production of above‐ground biomass without interacting with the community’s species richness.ConclusionOur study provides evidence that positive biodiversity effects on community biomass occur early, at the seedling stage, and it highlights the essential role that certain tree species play from their initial development stages by favoring spatial resource partitioning. Our work motivates future studies to apply integrated approaches in assessing both the community‐wide and species‐specific effects to understand the biodiversity–biomass relationship.

Biodiversity has a positive but saturating effect on imperiled coral reefs.

Species loss threatens ecosystems worldwide, but the ecological processes and thresholds that underpin positive biodiversity effects among critically important foundation species, such as corals on tropical reefs, remain inadequately understood. In field experiments, we manipulated coral species richness and intraspecific density to test whether, and how, biodiversity affects coral productivity and survival. Corals performed better in mixed species assemblages. Improved performance was unexplained by competition theory alone, suggesting that positive effects exceeded agonistic interactions during our experiments. Peak coral performance occurred at intermediate species richness and declined thereafter. Positive effects of coral diversity suggest that species’ losses on degraded reefs make recovery more difficult and further decline more likely. Harnessing these positive interactions may improve ecosystem conservation and restoration in a changing ocean.