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1.AbstractAnthropogenic activity is threatening ecosystem multifunctionality, i.e. the ability of ecosystems to provide multiple functions and services which are vital for human well-being. Here we assess how multifunctionality of agroecosystems in Central Germany depends on land-use type and climate change. Our analysis included 13 ecosystem functions in a large-scale field experiment with five different land-use types (three grassland and two farmland types either sustainably or intensively managed) under two different climate scenarios (ambient and future climate). We consider ecological measures of multifunctionality using averaging approaches with different weights, i.a. reflecting preferences of farmers and environmentalists, and assess an economic multifunctionality measure based on the total value of ecosystem services. Results show that intensive management and future climate decrease ecological multifunctionality for multiple weighting scenarios in both grassland and farmland. Only under a weighting according to farmers’ preferences, intensively-managed grassland shows higher multifunctionality as compared to sustainably-managed grassland. The economic multifunctionality measure, which includes economic benefits for society at large, reveals a multifunctionality about ∼1.7 times higher for sustainable compared to intensive management for both grassland and farmland. Above-belowground biodiversity correlates positively with ecosystem multifunctionality and is expected to be one of its main drivers. Based on these findings, we suggest to promote and economically incentivise sustainable land management that enhances both ecological and economic multifunctionality, also under future climatic conditions.

Pathogens have the potential to shape plant community structure, and thus, it is important to understand the factors that determine pathogen diversity and infection in communities. The abundance, origin, and evolutionary relationships of plant hosts are all known to influence pathogen patterns and are typically studied separately. We present an observational study that examined the influence of all three factors and their interactions on the diversity of and infection of several broad taxonomic groups of foliar, floral, and stem pathogens across three sites in a temperate grassland in the central United States. Despite that pathogens are known to respond positively to increases in their host abundances in other systems, we found no relationship between host abundance and either pathogen diversity or infection. Native and exotic plants did not differ in their infection levels, but exotic plants hosted a more generalist pathogen community compared to native plants. There was no phylogenetic signal across plants in pathogen diversity or infection. The lack of evidence for a role of abundance, origin, and evolutionary relationships in shaping patterns of pathogens in our study might be explained by the high generalization and global distributions of our focal pathogen community, as well as the high diversity of our plant host community. In general, the community‐level patterns of aboveground pathogen infections have received less attention than belowground pathogens, and our results suggest that their patterns might not be explained by the same drivers., We investigated the effects of plant abundance, origin, and phylogenetic community context on the diversity and infection levels of aboveground pathogens in a temperate grassland in the central United States. We found no relationship between host abundance, plant origin or phylogeny, and our observed infection levels. However, exotic host species harbored a more generalist pathogen community.

Ensuring ecosystem resilience is an intuitive approach to safeguard the functioning of ecosystems and hence the future provisioning of ecosystem services (ES). However, resilience is a multi-faceted concept that is difficult to operationalize. Focusing on resilience mechanisms, such as diversity, network architectures or adaptive capacity, has recently been suggested as means to operationalize resilience. Still, the focus on mechanisms is not specific enough. We suggest a conceptual framework, resilience trinity, to facilitate management based on resilience mechanisms in three distinctive decision contexts and time-horizons: i) reactive, when there is an imminent threat to ES resilience and a high pressure to act, ii) adjustive, when the threat is known in general but there is still time to adapt management, and iii) provident, when time horizons are very long and the nature of the threats is uncertain, leading to a low willingness to act. Resilience has different interpretations and implications at these different time horizons, which also prevail in different disciplines. Social ecology, ecology, and engineering are often implicitly focussing on provident, adjustive, or reactive resilience, respectively, but these different notions and of resilience and their corresponding social, ecological, and economic trade-offs need to be reconciled. Otherwise, we keep risking unintended consequences of reactive actions, or shying away from provident action because of uncertainties that cannot be reduced. The suggested trinity of time horizons and their decision contexts could help ensuring that longer-term management actions are not missed while urgent threats to ES are given priority.

Litter decomposition is a key ecosystem function in forests and varies in response to a range of climatic, edaphic, and local stand characteristics. Disentangling the relative contribution of these factors is challenging, especially along large environmental gradients. In particular, knowledge of the effect of management options, such as tree planting density and species composition, on litter decomposition would be highly valuable in forestry. In this study, we made use of 15 tree diversity experiments spread over eight countries and three continents within the global TreeDivNet network. We evaluated the effects of overstory composition (tree identity, species/mixture composition and species richness), plantation conditions (density and age), and climate (temperature and precipitation) on mass loss (after 3 months and 1 year) of two standardized litters: high-quality green tea and low-quality rooibos tea. Across continents, we found that early-stage decomposition of the low-quality rooibos tea was influenced locally by overstory tree identity. Mass loss of rooibos litter was higher under young gymnosperm overstories compared to angiosperm overstories, but this trend reversed with age of the experiment. Tree species richness did not influence decomposition and explained almost no variation in our multi-continent dataset. Hence, in the young plantations of our study, overstory composition effects on decomposition were mainly driven by tree species identity on decomposer communities and forest microclimates. After 12 months of incubation, mass loss of the high-quality green tea litter was mainly influenced by temperature whereas the low-quality rooibos tea litter decomposition showed stronger relationships with overstory composition and stand age. Our findings highlight that decomposition dynamics are not only affected by climate but also by management options, via litter quality of the identity of planted trees but also by overstory composition and structure.

Symbiotic foliar fungal endophytes can have beneficial effects on host trees and might alleviate climate-induced stressors. Whether and how the community of foliar endophytes is dependent on the tree neighborhood is still under debate with contradicting results from different tree diversity experiments. Here, we present our finding regarding the effect of the tree neighborhood from the temperate, densely planted and 12-years-old Kreinitz tree diversity experiment. We used linear models, redundancy analysis, Procrustes analysis and Holm-corrected multiple t-tests to quantify the effects of the plot-level tree neighborhood on the diversity and composition of foliar fungal endophytes in Fagus sylvatica, Quercus petraea and Picea abies. Against our expectations, we did not find an effect of tree diversity on endophyte diversity. Endophyte composition, however, was driven by the identity of the host species. Thirteen endophytes where overabundant in tree species mixtures, which might indicate frequent spillover or positive interactions between foliar endophytes. The independence of the diversity of endophytes from the diversity of tree species might be attributed to the small plot size and the high density of tree individuals. However, the mechanistic causes for these cryptic relationships still remain to be uncovered.

Climate change has the potential to alter plant reproductive success directly and indirectly through disruptions in animal pollination. Climate models project altered seasonal precipitation patterns, and thus, the effects of climate change on available resources and pollination services will depend on the season. Plants have evolved reproductive strategies to so they are not limited by either pollen or water availability in their reproductive success, and therefore, we expect that the disruption of climate change might cause plants to be more pollen limited in seasons that become wetter than they were historically. In this study, we conducted a pollen supplementation experiment within the Global Change Experiment Facility (GCEF) in Central Germany. The GCEF experimentally manipulates future climate based on a realistic scenario of climate change for the region (drier summers and wetter springs and falls) in a native grassland ecosystem. We quantified seed production of two perennial species Dianthus carthusianorum and Scabiosa ochroleuca in response to pollination treatments (control, supplement), climate treatments (ambient and future) and season (summer and fall). Dianthus carthusianorum produced more seeds in future climate conditions independent of the season, but only when given supplemental pollen. Both species showed an increased reproduction in summer compared with the fall. We did not find evidence for our specific expectation of higher pollen limitation in the future climate and fall season (i.e., no three‐way interaction pollination × season × climate), which might be explained by the high‐drought tolerance and generalized pollination of our focal plant species. We conclude that plant reproductive success has the potential to change with changing climates and that this change will depend on how pollinator services change in the future. We offer many suggestions for future studies that are necessary to understand the context dependence and underlying mechanisms of plant reproductive responses to climate., In this study, we conduct pollen supplementation experiments on two plant species within a climate change experiment in which precipitation is manipulated in the context of a regional climate change scenario. Dianthus carthusianorum produced more seeds in future climate conditions independent of the season, but only when given supplemental pollen. Both species showed an increased reproduction in summer compared with the fall, but we did not find any evidence for our expectation of higher pollen limitation in the future climate and fall season.

Litter decomposition is a key process determining the cycling of nutrients in ecosystems. Soil fauna plays an essential role in this process, e.g., by fragmenting and burrowing surface litter material, and thereby enhancing microbial decomposition. However, soil fauna-mediated decomposition might be influenced by interacting factors of environmental changes. Here we used a large-scale global change field experiment to test potential interacting effects between land-use type (croplands and grasslands differing in management intensity) and projected climate change on litter decomposition rates over a period of two years. For that, climate and land-use treatments were orthogonally crossed: (1) two climate scenarios: ambient vs. future; and (2) five land-use regimes: conventional farming, organic farming, intensively used meadow, extensively used meadow, and extensively used pasture. Litterbags with two mesh sizes (5 mm and 0.02 mm) were used to differentiate contributions of microbes and fauna to the mass loss of standardized crop residues. Soil fauna accounted for more than 68% of surface litter mass loss. Future climate treatment decreased decomposition rates as a result of reduced precipitation and elevated temperature during summer months. Litter decomposition and the contribution of soil fauna to it were significantly higher in croplands than in grasslands, but did not differ due to management intensity within these land-use types. In grasslands, faunal contribution to decomposition decreased under future climate. There were no interacting effects between climate change and land use on decomposition rates. These findings indicate that predicted changes in precipitation patterns and temperature will consistently decelerate litter decomposition across land-used types via both microbial and faunal effects.

Anthropogenic global change alters the activity and functional composition of soil communities that are responsible for crucial ecosystem functions and services. Two of the most pervasive global change drivers are drought and nutrient enrichment. However, the responses of soil organisms to interacting global change drivers remain widely unknown. We tested the interactive effects of extreme drought and fertilization on soil biota ranging from microbes to invertebrates across seasons. We expected drought to reduce the activity of soil organisms and fertilization to induce positive bottom-up effectsviaincreased plant productivity. Furthermore, we hypothesized fertilization to reinforce drought effects through enhanced plant growth, resulting in even dryer soil conditions. Our results revealed that drought had detrimental effects on soil invertebrate feeding activity and simplified nematode community structure, whereas soil microbial activity and biomass were unaffected. Microbial biomass increased in response to fertilization, whereas invertebrate feeding activity substantially declined. Notably, these effects were consistent across seasons. The dissimilar responses suggest that soil biota differ vastly in their vulnerability to global change drivers. As decomposition and nutrient cycling are driven by the interdependent concurrence of microbial and faunal activity, this may imply far-reaching consequences for crucial ecosystem processes in a changing world.

Seed dispersal limitation, which can be exacerbated by a number of anthropogenic causes, can result in local communities having fewer species than they might potentially support, representing a potential diversity deficit. The link between processes that shape natural variation in diversity, such as dispersal limitation, and the consequent effects on productivity is less well known. Here, we synthesised data from 12 seed addition experiments in grassland communities to examine the influence of reducing seed dispersal limitation (from 1 to 60 species added across experiments) on species richness and productivity. For every 10 species of seed added, we found that species richness increased by about two species. However, the increase in species richness by overcoming seed limitation did not lead to a concomitant increase in above-ground biomass production. This highlights the need to consider the relationship between biodiversity and ecosystem functioning in a pluralistic way that considers both the processes that shape diversity and productivity simultaneously in naturally assembled communities.

Global environmental change is strongly altering biodiversity and ecosystem functioning. Antagonistic biotic interactions affect the diversity and functioning of plant communities but are notoriously context dependent and are therefore likely to be altered by global change drivers. Global change can directly affect biotic interactions and can also indirectly alter the abundance, diversity and composition of plant enemy communities, via changes to plant productivity, diversity and functional composition. Changes in the enemy community feedback to alter the plant community. However, we lack predictions for how different global change drivers may alter enemy communities and their impact on plant communities. In this review we summarize current knowledge on the impact of invertebrate herbivores and fungal pathogens on plant productivity, diversity and community composition, and outline theory and expectations on how important global change drivers – nitrogen enrichment, warming and elevated CO2, as well as the loss of plant and insect diversity, may affect the impact of plant-enemies on plant communities.

Land management is known to have consequences for biodiversity; however, our synthetic understanding of its effects is limited due to highly variable results across studies, which vary in the focal taxa and spatial grain considered, as well as the response variables reported. Such synthetic knowledge is necessary for management of agroecosystems for high diversity and function.To fill this knowledge gap, we investigated the importance of scale‐dependent effects of land management (LM) (pastures vs. meadows), on plant and soil microbe diversity (fungi and bacteria) across 5 study sites in Central Germany. Analyses included diversity partitioning of species richness and related biodiversity components (i.e., density of individuals, species‐abundance distribution, and spatial aggregation) at two spatial grains (α‐ and γ‐scale, 1 m2 and 16 km2, respectively).Our results show scale‐dependent patterns in response to LM to be the norm rather than the exception and highlight the importance of measuring species richness and its underlying components at multiple spatial grains.Our outcomes provide new insight to the complexity of scale‐dependent responses within and across taxonomic groups. They suggest that, despite close associations between taxa, LM responses are not easily extrapolated across multiple spatial grains and taxa. Responses of biodiversity to LM are often driven by changes to evenness and spatial aggregation, rather than by changes in individual density. High‐site specificity of LM effects might be due to a variety of context‐specific factors, such as historic land management, identity of grazers, and grazing regime. Synthesis and applications: Our results suggest that links between taxa are not necessarily strong enough to allow for generalization of biodiversity patterns. These findings highlight the importance of considering multiple taxa and spatial grains when investigating LM responses, while promoting management practices that do the same and are tailored to local and regional conditions., We investigated the occurrence of scale‐dependent impacts of land management on above‐ and belowground biodiversity within managed grassland. Our results showed scale‐dependent patterns in response to land management to be the norm rather than the exception and highlight the importance of measuring species richness and its underlying components at multiple spatial grains. Outcomes provide new insight to the complexity of scale‐dependent responses within and across taxonomic groups.

AimSoil microorganisms are essential for the functioning of terrestrial ecosystems. Although soil microbial communities and functions may be linked to the tree species composition and diversity of forests, there has been no comprehensive study of how general potential relationships are and if these are context-dependent. A global network of tree diversity experiments (TreeDivNet) allows for a first examination of tree diversity-soil microbial function relationships across environmental gradients.LocationGlobalMajor Taxa StudiedSoil microorganismsMethodsSoil samples collected from eleven tree diversity experiments in four biomes across four continents were used to measure soil basal respiration, microbial biomass, and carbon use efficiency using the substrate-induced respiration method. All samples were measured using the same analytical device in the same laboratory to prevent measurement bias. We used linear mixed-effects models to examine the effects of tree species diversity, environmental conditions, and their interactions on soil microbial functions.ResultsAcross biodiversity experiments, abiotic drivers, mainly soil water content, significantly increased soil microbial functions. Potential evapotranspiration (PET) increased, whereas soil C-to-N ratio (CN) decreased soil microbial functions under dry soil conditions, but high soil water content reduced the importance of other abiotic drivers. Tree species richness and phylogenetic diversity had overall similar, but weak and context-dependent (climate, soil abiotic variables) effects on soil microbial respiration. Positive tree diversity effects on soil microbial respiration were most pronounced at low PET, low soil CN, and high tree density. Soil microbial functions increased with the age of the experiment.Main conclusionsOur results point at the importance of soil water content for maintaining high levels of soil microbial functions and modulating effects of other environmental drivers. Moreover, overall tree diversity effects on soil microbial functions seem to be negligible in the short term (experiments were 1-18 years old). However, context-dependent tree diversity effects (climate, soil abiotic variables) have greater importance at high tree density, and significant effects of experimental age call for longer-term studies. Such systematic insights are key to better integrate soil carbon dynamics into the management of afforestation projects across environmental contexts, as today’s reforestation efforts remain focused largely on aboveground carbon storage and are still dominated by less diverse forests stands of commercial species.

The research of a generation of ecologists was catalysed by the recognition that the number and identity of species in communities influences the functioning of ecosystems. The relationship between biodiversity and ecosystem functioning (BEF) is most often examined by controlling species richness and randomising community composition. In natural systems, biodiversity changes are often part of a bigger community assembly dynamic. Therefore, focusing on community assembly and the functioning of ecosystems (CAFE), by integrating both species richness and composition through species gains, losses and changes in abundance, will better reveal how community changes affect ecosystem function. We synthesise the BEF and CAFE perspectives using an ecological application of the Price equation, which partitions the contributions of richness and composition to function. Using empirical examples, we show how the CAFE approach reveals important contributions of composition to function. These examples show how changes in species richness and composition driven by environmental perturbations can work in concert or antagonistically to influence ecosystem function. Considering how communities change in an integrative fashion, rather than focusing on one axis of community structure at a time, will improve our ability to anticipate and predict changes in ecosystem function. ISSN:1461-023X ISSN:1461-0248

Background Aquatic plants are an important component of aquatic ecosystems. They are valuable for the oxygen and carbon dioxide household and generate habitats especially for small fish and other small organisms. However, problems for the maintenance of water bodies can result from mass occurrences of these plants. Invasive neophytes - such as members of the Elodea genus - are particularly problematic in this regard. Aquatic plants need to be harvested regularly to ensure that water bodies remain usable and to safeguard flood protection for flowing water bodies. Energy can be produced from the harvested material by anaerobic digestion in biogas plants. Therefore, it is beneficial to know the best time for harvesting in this context. Methods To identify the best time for harvesting, samples of the Elodea stock in the river Parthe in Leipzig-Schönefeld were taken each week over the course of the two hydrological years 2015 and 2016. The composition of these samples was analyzed in the laboratory. In the second hydrological year, three samples from surface areas of 1 m2 were also harvested once each month in order to determine the biomass yield per unit area. Results The best harvesting time for energy production from Elodea biomass in Germany is in the summer months (June to September). During this period, the specific yield of 0.5–0.7 kg VS/m2 is relatively high and the Elodea biomass contains the highest fractions of volatile solids (80.1 ± 2.3%), high contents of plant nutrients (N 35.9 ± 4.0 g/kg TS; P 6.1 ± 1.4 g/kg TS; and K 47.7 ± 8.0 g/kg TS), and low concentrations of heavy metals (Cr ≤8.9 mg/kg TS, Cd ≤0.9 mg/kg TS, Cu ≤120 mg/kg TS, Ni ≤30 mg/kg TS, Pb ≤8.6 mg/kg TS, and Zn ≤439 mg/kg TS). Conclusions Energy production from Elodea biomass is feasible. This biomass also provides the nutrients and trace elements necessary for the digestion in the anaerobic process.

The enemy-release hypothesis is one of the most popular but also most discussed hypotheses to explain invasion success. However, there is a lack of explicit, experimental tests of predictions of the enemy-release hypothesis (ERH), particularly regarding the effects of above- and belowground herbivory. Long-term studies investigating the relative effect of herbivores on invasive vs. native plant species within a community are still lacking. Here, we report on a long-term field experiment in an old-field community, invaded by Solidago canadensis s. l., with exclusion of above- and belowground insect herbivores. We monitored population dynamics of the invader and changes in the diversity and functioning of the plant community across eight years. Above- and belowground insects favoured the establishment of the invasive plant species and thereby increased biomass and decreased diversity of the plant community. Effects of invertebrate herbivores on population dynamics of S. canadensis appeared after six years and increased over time, suggesting that long-term studies are needed to understand invasion dynamics and consequences for plant community structure. We suggest that the release from co-evolved trophic linkages is of importance not only for the effect of invasive species on ecosystems, but also for the functioning of novel species assemblages arising from climate change.

In their response to our letter, De Boek et al. (2019) and Muller, Ballhausen, Lakovic, and Rillig (2019) argue that our conclusion that we need more realistic climate change experiments is too "gloomy" and that we need a plurality of experiments including extremes and multifactorial approaches. We agree that a diversity of experimental approaches is required in order to anticipate the consequences for plant communities of alternative future environmental conditions. However, we argue that "realistic" experiments are underrepresented in the portfolio of previous experiments, and are urgently needed to understand how species communities of the future will look like and how they will function. This article is a response to Muller et al., 26, e4-e5 and De Boeck et al., 26, e6-e7.

Aim: Understanding the forces that drive range shifts in forest landscapes is imperative for predicting species distributions under anthropogenic climate and land use change. However, empirical studies exploring how these components jointly influence critical early life stages of mountain tree species across environmental gradients are scarce. We used the high mountain tree Polylepis australis as model species to investigate the relative importance of altitude and associated climatic conditions, land use for livestock and microsite characteristics on early life performance. Location: Córdoba Sierras, central Argentina. Methods: We set up an extensive in situ sowing experiment with a robust split-plot design that integrated spatial scales ranging from 0.4 m2 subplots at the microsite level (associated with vegetative and microtopographic structures), to livestock exclosure and enclosure plots of several hectares, to an altitudinal gradient of 1,000 m. Components of early life performance were monitored across two subsequent growing seasons. Results: Microsite characteristics played a fundamental role in P. australis establishment, whereby interactions with altitude and/or land use suggested alternate mechanisms: facilitation (likely reduced desiccation) dominated at low altitude while at high altitude, abiotic stress (likely intensive frost and radiation) overruled any microsite effects. At mid-altitude, benefits of competition release prevailed over facilitation and microsite effects gained importance under livestock presence. Inconsistencies between pre- and post-emergence responses illustrated potential trade-offs between beneficial and detrimental effects of microsite conditions upon performance throughout early life: a favourable location for seeds may abruptly turn adverse for seedlings. Main conclusions: We unravel how changes in altitude, anthropogenic disturbances and microsite characteristics jointly modulate P. australis performance across stages of early establishment. Such information is fundamental when categorizing specific microhabitats as “safe sites” for tree regeneration especially in mountain environments with high spatio-temporal heterogeneity. Fil: Cáceres, Yolanda. German Centre For Integrative Biodiversity Research.; Alemania. Martin Luther Universität Halle Wittenberg; Alemania Fil: Schrieber, Karin. Universitat Bielefeld; Alemania. Martin Luther Universität Halle Wittenberg; Alemania Fil: Lachmuth, Susanne. Martin Luther Universität Halle Wittenberg; Alemania. German Centre For Integrative Biodiversity Research.; Alemania Fil: Auge, Harald. Helmholtz Centre for Environmental Research; Alemania. German Centre For Integrative Biodiversity Research.; Alemania Fil: Argibay, Daihana Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Ecología y Recursos Naturales Renovables; Argentina Fil: Renison, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Ecología y Recursos Naturales Renovables; Argentina Fil: Hensen, Isabell. Martin Luther Universität Halle Wittenberg; Alemania. German Centre For Integrative Biodiversity Research.; Alemania

Experiments that alter local climate and measure community- and ecosystem-level responses are an important tool for understanding how future ecosystems will respond to climate change. Here, we synthesized data from 76 studies that manipulated climate and measured plant community responses, and found that most climate change experiments do not correspond to model-projected climate scenarios for their respective regions. This mismatch constrains our ability to predict responses of plant biodiversity and ecosystem functions to climate change, and we conclude with suggestions for a way forward. See also the Commentary on this article by Muller et al., 26, e4-e5 and De Boeck et al.,26, e6-e7.

Ensuring ecosystem resilience is an intuitive approach to safeguard future provisioning of ecosystem services (ES). However, resilience is an ambiguous concept and difficult to operationalize. Focusing on resilience mechanisms, such as diversity, network architectures or adaptive capacity, has recently been suggested as means to operationalize resilience. Still, the focus on mechanisms is not specific enough because the usefulness of a mechanism is context-dependent. We suggest a conceptual framework, resilience trinity, to facilitate management of resilience mechanisms in three distinctive decision contexts and time-horizons. i) reactive, when there is an imminent threat to ES resilience and a high pressure to act, ii) adjustive, when the threat is known in general but there is still time to adapt management, and iii) provident when time horizons are very long and the nature of the threats is uncertain, leading to a low willingness to act. This emphasizes that resilience has different interpretations and implications at different time horizons which however need to be reconciled. The inclusion of time into resilience thinking ensures that longer-term management actions are not missed while urgent threats to ES are given priority.

The local invasion success of invasive plants can be strongly influenced by reduced antagonist pressure and changes in resistance-mediating traits, but information about comprehensive metabolic backgrounds of native versus invasive populations and their functions is lacking. We examined the defence potential of ten native (Chinese) and ten invasive (European) populations of the shrub Buddleja davidii (Scrophulariaceae) grown in a common garden in the invasive range. We compared the chemical defence arsenal of these plant populations, scored their herbivore damage in the field and determined effects on a generalist herbivore species in the laboratory. Moreover, we isolated compounds that mediate resistance against two potential generalist herbivore species and a pathogenic fungus using bioassay-guided fractionation. Metabolic fingerprinting revealed that invasive populations were chemically very similar to one native population (Mupingzhen, Sichuan Province), which may indicate the geographic region from where the species was introduced. Herbivore damage and herbivore performance were reduced on plants of invasive populations. Different chemical compounds provided distinct resistance against the herbivore and fungus species. Based on our results we suggest that the diverse cocktail of chemical compounds, potentially together with physical leaf features, may provide this plant species with an effective defence arsenal against antagonists. In particular, advantageous pre-adaptations and/or shifted profiles of the chemical bouquet may contribute to the success of invasive plants.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A conversion from permanently flooded rice cropping systems to crop rotations that include non-flooded upland crops is heavily promoted in tropical regions to meet the challenges of sustainable food production while reducing water consumption and trace gas emissions. Shorter periods of flooding and manipulation of fertilizer inputs affect belowground community composition, biomass and functioning. However, there have been no previous studies of how such shifts in rice field management might affect soil biota and decomposition. Our objective was to examine how crop diversification, which demands different moisture regimes and nitrogen inputs, influences belowground invertebrate assemblages and their contribution to the decomposition of crop residues. We conducted a litterbag experiment in lowland paddy fields at the experimental field sites of the DFG-ICON project (Laguna, the Philippines) that were either continuously flooded, had seasonally alternating wet and dry periods, or were continuously dry. Additionally, subplot treatments within these crop rotations included different N fertilizer management practices. At a total of 36 plots we used litterbags with two different mesh sizes to assess decomposition with and without fauna over a period of 72 days. Furthermore, we sampled soil microfauna and mesofauna in both the wet (rainy) and dry seasons. Although we found no correlation between faunal abundance and the contribution by invertebrates to rice straw decomposition, we found that soil water content was the decisive factor determining the activity of decomposer invertebrates as well as the composition and abundance of the soil fauna in fields with alternating cropping regimes. The impact of invertebrates on rice straw decomposition was higher under anaerobic than aerobic soil conditions which compensated for reduced microbial decay rates during periods of flooding. In contrast, microbial decomposition rates were higher under aerobic conditions, whereas invertebrates had no apparent effects on the mass loss of rice straw despite their higher abundance in dry fields. Our results demonstrate that invertebrates are essential for the effective decay of rice straw residues under flooded soil conditions, and therefore play an important role in supplying nutrients to flooded rice.

Sustainable management of agricultural systems includes promoting nutrient cycles, which can reduce the need for application of fertilizer. As rice is one of the most important food resources in the world, sustainable management of rice paddies is increasingly in demand. However, little is known about the influence of invertebrates on decomposition processes in these ecosystems. We hypothesized that invertebrates contribute significantly to the decomposition of rice straw in paddies and that their relative contribution is affected by the distance to other landscape structures within fields. We placed rice straw in litterbags of two different mesh sizes which prevent (20 μm × 20 μm) or allow (5 mm × 5 mm) access of invertebrates in six irrigated rice fields for 84 days. In each field, bags were set on three transects running from the bund to the center of the field. Invertebrates significantly increased total rice straw litter mass loss by up to 45% (total decomposition: fine-meshed bags 64%; coarse-meshed bags 83%). Litter mass loss in bags accessed by invertebrates decreased with increasing distance from the bund. Such a spatial trend in litter mass loss was not observed in bags accessed only by microbes. Our results indicated that invertebrates can contribute to soil fertility in irrigated rice fields by decomposing rice straw, and that the efficiency of decomposition may be promoted by landscape structures around rice fields.

Species’ responses to antagonists, such as fungal pathogens and insect herbivores, are part of a species’ niche and are thought to contribute to species coexistence. In theory, coexistence is supposed to be maintained by the effects of equalizing mechanisms that reduce fitness differences among species, and stabilizing mechanisms that are the result of niche differences. The presence of stabilizing niche differences is hallmarked by negative frequency-dependent per capita rates of increase. However, rigorous experimental testing of how insect herbivores and fungal pathogens contribute to negative frequency dependence among co-occurring plant species, in particular in the context of biological invasions, is scarce. We present an experimental study in a grassland in central Germany, in which we established native and exotic-dominated communities on 1 m²-plots, and reduced above- and belowground fungal pathogens and insect herbivores by applying pesticides. We manipulated the frequencies of six native and six exotic focal species, in order to assemble one dominant and five rare species per community. We quantified productivity and diversity for each community, and recorded data on per capita rates of increase and other fitness components for two native and two exotic focal species over three years. We found that native and exotic-dominated communities did not differ in their productivity and diversity. Reduction of fungi and insects increased productivity but the effect was similar for both species origins, suggesting that effects of enemy release are transitory or not existent. Negative frequency-dependence was common in our species, but could not be linked to interactions with antagonists. Although focal species responded to the reduction of antagonists, these effects were only present at low frequency, suggesting a greater importance of intraspecific competition, e.g. for resources, in explaining the observed stabilizing niche differences. Offsetting responses of the two exotic focal species to both antagonist groups highlight the significance of equalizing mechanisms among native and exotic species at the community level. Our study demonstrates the importance of both equalizing and stabilizing mechanisms in the context of biological invasions and differential contributions of antagonistic interactions to these mechanisms.

Herbivory and disturbance are major drivers of biological invasions, but it is unclear how they interact to determine exotic vs. native seedling recruitment and what consequences arise for biodiversity and ecosystem functioning. Previous studies neglected the roles of different, potentially interacting, guilds of generalist herbivores such as rodents and gastropods. We therefore set up a full-factorial rodent exclusion x gastropod exclusion x disturbance x seed-addition experiment in a grassland community in Central Germany and measured early seedling recruitment, as well as species richness, species composition and aboveground biomass. Gastropod herbivory reduced the positive effect of disturbance on seedling recruitment, particularly for exotic species. Rodent herbivory had weak positive effects on seedling recruitment at undisturbed sites, irrespective of species origin. This effect was likely driven by their strong negative effect on productivity. Interactive effects between both herbivore guilds became only evident for species richness and composition. How many species established themselves depended on disturbance, but was independent of species origin. The fewer exotic species that established themselves increased productivity to a stronger extent compared to native species. Our study highlights that joint effects of disturbance, herbivory and species origin shape early recruitment, while they only weakly affect biodiversity and ecosystem functioning.

International audience; TreeDivNet is the largest network of biodiversity experiments worldwide, but needs to expand. We encourage colleagues to establish new experiments on the relation between tree species diversity and forest ecosystem functioning, and to make use of the platform for collaborative research.