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Artificial light at night (ALAN) is increasing worldwide, but its effects on the soil system have not yet been investigated. We tested the influence of experimental manipulation of ALAN on two taxa of soil communities (microorganisms and soil nematodes) and three aspects of soil functioning (soil basal respiration, soil microbial biomass and carbon use efficiency) over four and a half months in a highly controlled Ecotron facility. We show that during peak plant biomass, increasing ALAN reduced plant biomass and was also associated with decreased soil water content. This further reduced soil respiration under high ALAN at peak plant biomass, but microbial communities maintained stable biomass across different levels of ALAN and times, demonstrating higher microbial carbon use efficiency under high ALAN. While ALAN did not affect microbial community structure, the abundance of plant-feeding nematodes increased and there was homogenization of nematode communities under higher levels of ALAN, indicating that soil communities may be more vulnerable to additional disturbances at high ALAN. In summary, the effects of ALAN reach into the soil system by altering soil communities and ecosystem functions, and these effects are mediated by changes in plant productivity and soil water content at peak plant biomass. This article is part of the theme issue 'Light pollution in complex ecological systems'. [ABSTRACT FROM AUTHOR]

Aim: Soil microorganisms are essential for the functioning of terrestrial ecosystems. Although soil microbial communities and functions are linked to tree species composition and diversity, there has been no comprehensive study of the generality or context dependence of these relationships. Here, we examine tree diversity–soil microbial biomass and respiration relationships across environmental gradients using a global network of tree diversity experiments. Location: Boreal, temperate, subtropical and tropical forests. Time period: 2013. Major taxa studied: Soil microorganisms. Methods: Soil samples collected from 11 tree diversity experiments were used to measure microbial respiration, biomass and respiratory quotient using the substrate‐induced respiration method. All samples were measured using the same analytical device, method and procedure to reduce measurement bias. We used linear mixed‐effects models and principal components analysis (PCA) to examine the effects of tree diversity (taxonomic and phylogenetic), environmental conditions and interactions on soil microbial properties. Results: Abiotic drivers, mainly soil water content, but also soil carbon and soil pH, significantly increased soil microbial biomass and respiration. High soil water content reduced the importance of other abiotic drivers. Tree diversity had no effect on the soil microbial properties, but interactions with phylogenetic diversity indicated that the effects of diversity were context dependent and stronger in drier soils. Similar results were found for soil carbon and soil pH. Main conclusions: Our results indicate the importance of abiotic variables, especially soil water content, for maintaining high levels of soil microbial functions and modulating the effects of other environmental drivers. Planting tree species with diverse water‐use strategies and structurally complex canopies and high leaf area might be crucial for maintaining high soil microbial biomass and respiration. Given that greater phylogenetic distance alleviated unfavourable soil water conditions, reforestation efforts that account for traits improving soil water content or select more phylogenetically distant species might assist in increasing soil microbial functions. [ABSTRACT FROM AUTHOR]

There 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. [ABSTRACT FROM AUTHOR]

Diversity loss has been shown to change the soil community; however, little is known about long-term consequences and underlying mechanisms. Here, we investigated how nematode communities are affected by plant species richness and whether this is driven by resource quantity or quality in 15-year-old plant communities of a long-term grassland biodiversity experiment. We extracted nematodes from 93 experimental plots differing in plant species richness, and measured above- and belowground plant biomass production and soil organic carbon concentrations (Corg) as proxies for resource quantity, as well as C/Nleaf ratio and specific root length (SRL) as proxies for resource quality. We found that nematode community composition and diversity significantly differed among plant species richness levels. This was mostly due to positive plant diversity effects on the abundance and genus richness of bacterial-feeding, omnivorous, and predatory nematodes, which benefited from higher shoot mass and soil Corg in species-rich plant communities, suggesting control via resource quantity. In contrast, plant-feeding nematodes were negatively influenced by shoot mass, probably due to higher top–down control by predators, and were positively related to SRL and C/Nleaf, indicating control via resource quality. The decrease of the grazing pressure ratio (plant feeders per root mass) with plant species richness indicated a higher accumulation of plant-feeding nematodes in species-poor plant communities. Our results, therefore, support the hypothesis that soil-borne pathogens accumulate in low-diversity communities over time, while soil mutualists (bacterial-feeding, omnivorous, predatory nematodes) increase in abundance and richness in high-diversity plant communities, which may contribute to the widely-observed positive plant diversity–productivity relationship. [ABSTRACT FROM AUTHOR]

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

The magnitude and frequency of extreme weather events are predicted to increase in the future due to ongoing climate change. In particular, floods and droughts resulting from climate change are thought to alter the ecosystem functions and stability. However, knowledge of the effects of these weather events on soil fauna is scarce, although they are key towards functioning of terrestrial ecosystems. Plant species richness has been shown to affect the stability of ecosystem functions and food webs. Here, we used the occurrence of a natural flood in a biodiversity grassland experiment that was followed by a simulated summer drought experiment, to investigate the interactive effects of plant species richness, a natural flood, and a subsequent summer drought on nematode communities. Three and five months after the natural flooding, effects of flooding severity were still detectable in the belowground system. We found that flooding severity decreased soil nematode food-web structure (loss of K-strategists) and the abundance of plant feeding nematodes. However, high plant species richness maintained higher diversity and abundance of higher trophic levels compared to monocultures throughout the flood. The subsequent summer drought seemed to be of lower importance but reversed negative flooding effects in some cases. This probably occurred because the studied grassland system is well adapted to drought, or because drought conditions alleviated the negative impact of long-term soil waterlogging. Using soil nematodes as indicator taxa, this study suggests that high plant species richness can maintain soil food web complexity after consecutive environmental perturbations. [ABSTRACT FROM AUTHOR]

Earthworms drive important ecosystem functions like decomposition and nutrient mineralization in many terrestrial ecosystems, which is why factors controlling their mass gain are of great scientific interest. We conducted a microcosm experiment using two common endogeic earthworm species ( Aporrectodea caliginosa and Octolasion tyrtaeum) and two different soils (one from a beech-dominated forest and one from a mixed tree species forest in Germany) to test litter quality (different nutrient concentrations) and soil quality effects (low and high) on relative mass gain of earthworms. We hypothesized that mass gain of endogeic earthworms is driven by both soil and litter quality. Soil pH, carbon (C) and nitrogen (N) concentrations were used to characterize soil quality, while leaf litter N, phosphorus (P), calcium (Ca), and magnesium (Mg) concentrations were used as proxies for leaf litter quality. Forest soils were incubated with leaf litter of six common tree species in Central Europe ( Fagus sylvatica , Acer platanoides , Acer pseudoplatanus , Carpinus betulus , Tilia spp., and Fraxinus excelsior) that span a gradient in leaf litter quality. In addition, we determined soil microbial biomass C as a potential food source of endogeic earthworms. After three months, relative earthworm mass gain of A. caliginosa and O. tyrtaeum was significantly higher in soil from the mixed tree species forest (high quality soil: +218% and +240%, respectively) compared to soil from the beech-dominated forest (low quality soil: +160% and +162%, respectively). Relative mass gain of A. caliginosa increased significantly with all leaf litter nutrients in low quality soil, whereas in high quality soil only leaf litter Ca positively affected relative mass gain. Similarly, relative mass gain of O. tyrtaeum increased significantly with increasing concentrations of leaf litter N, Mg, and Ca in the low quality soil. In the high quality soil, only leaf litter Mg significantly increased relative mass gain. Overall, our results indicate that leaf litter quality effects on endogeic earthworm mass gain were more important in low quality soil for both earthworm species. Notably, microbial biomass was significantly higher in high quality soil (506 ± 135 μg C g −1 soil dw) compared to low quality soil (217 ± 64 μg C g −1 soil dw), but microbial biomass was not significantly affected by leaf litter type and was a poor predictor of relative earthworm mass gain. This finding indicates that endogeic earthworms did not significantly depend on soil microbial biomass, but rather on the quality of dead organic material in the soil and surface leaf litter. As earthworms may prefer feeding on certain microbial taxa, and we only measured total soil microbial biomass, future studies could investigate if leaf litter quality effects on earthworms are mediated by changes in soil microbial community structure, micronutrients, and organic compounds. [ABSTRACT FROM AUTHOR]

Earthworms are invading soil communities worldwide, and their actions as decomposers and ecosystem engineers are vastly impacting many ecosystem functions. In the northern regions of North America, invasive earthworms are often functionally distinct from the native invertebrate fauna and, thus, typically occupy empty trophic niches in soil food webs. Nevertheless, they can affect the co-occurring soil invertebrate communities in multiple indirect ways. Particularly, the redistribution and removal of litter resources can affect feeding interactions of soil biota that channel up to higher trophic levels, such as predators, causing shifts across all components of the soil food web, which are hard to investigate. To study trophic shifts in earthworm-invaded soil communities, we used ground predators as model organisms since they occupy high trophic levels and connect different energy channels in soil food webs. We used stable isotope (13C and 15N) and fatty acid analyses as complementary tools to describe the trophic levels and basal resources of consumers that were impacted by earthworm invasion, specifically examining the trophic niches and resources available to ground-dwelling invertebrates of a northern aspen forest. The distinct trophic niches of invertebrate species were affected significantly by earthworm invasion. Shifts in neutral lipid fatty acid profiles as well as decreases in animal Δ13C and Δ15N signatures indicated changes in basal resources and trophic levels, respectively. Furthermore, we observed a trend of greater intra-specific and less inter-specific variation in fatty acid profiles of soil organisms following earthworm invasion. Notably, shifts in marker fatty acids of ground-dwelling invertebrates were opposite to the changes observed in soil microbial communities, suggesting de-coupling of soil microbial and ground arthropod food-web compartments. Overall, our study revealed a systemic effect of invasive earthworms on ground-dwelling invertebrates. Earthworms presumably consumed a considerable amount of resources, such as litter and, thus, incorporated them in the soil food web, which was, as a basal resource, not available in the food web free of earthworms. Overall, the ground-dwelling invertebrates have adapted (changed their trophic function) which could explain the balancing of potential environmental changes that are caused by invasive earthworms. This observation potentially explains why these species are dominant in the studied forest and resist earthworm invasion. Future studies should investigate if altered litter availability also causes shifts in soil biodiversity in invaded forests, which is assumed but rarely directly tested to date. • Earthworms are invading soil communities worldwide with vast impacts on ecosystems. • We investigated trophic niches in soil communities with earthworm invasion. • We combined stable isotope and fatty acid analyses as complementary tools. • We found that earthworms incorporated litter resources in the soil food web. • Intra-specific variation in niches increased and inter-specific variation decreased. [ABSTRACT FROM AUTHOR]

Soils store ∼80% of global terrestrial organic carbon and alterations in fluxes into and out of this pool may interact with ongoing climate change. Belowground food webs drive soil C dynamics, but little is known about their responses to co-occurring global change agents. We investigated open-air experimental grassland communities at ambient and elevated atmospheric CO 2 concentration, ambient and enriched nitrogen input, and ambient and reduced summer precipitation to evaluate how these agents interactively affect soil nematodes, which are often used as an indicator group for soil food web structure and soil health. The aim of the study was to elucidate the response of the functional diversity of soil nematodes to changing environmental conditions by using nematode functional guilds and indices as indicators. The results suggest that nematode functional guilds surpass nematode trophic groups as soil indicators, suggesting that more detailed data on nematode community structure is essential to capture functional changes in response to environmental change. For instance, the density of opportunistic fungal feeders increased due to N addition with the response being more pronounced at elevated CO 2 , whereas densities of sensitive fungal-feeders were increased at ambient N and elevated CO 2 , illustrating opposing responses within one trophic group. Opportunistic bacterial feeders increased at elevated N, but did not respond to other environmental factors studied. Root-feeding Longidoridae were significantly reduced at elevated CO 2 and elevated N compared to ambient conditions, whereas other plant feeders were little affected by the manipulations. Predacious nematodes were less abundant at elevated N, and the Structure Index (which indicates food web structure) suggested reduced top-down forces and simplified soil food webs, although omnivores did not vary significantly. Elevated CO 2 buffered the effect of reduced precipitation on the Enrichment Index (which indicates increased resource availability) and the Channel Index (which indicates changes in decomposition channel) probably due to reduced stomatal conductance at elevated CO 2 . Further, the results suggest that the decomposer community switched from a bacterial-dominated to a fungal-dominated system at elevated N, indicating shifts in the microbial community as well as in the functioning of belowground food webs. Overall, the studied global change agents interactively and differentially affected functional guilds of soil nematodes, suggesting complex changes in soil processes. We highlight that detailed information on the functional guilds of nematodes is likely necessary to fully understand alterations in soil food webs and related processes due to global environmental change. [ABSTRACT FROM AUTHOR]

One of the challenges in soil ecology is to determine which organisms utilise stable forms of carbon in soil. Recent studies have indicated that endogeic earthworms are able to mobilise such stable carbon compounds. However, it remains unclear which particular compounds of stabilised carbon in soil are utilised by earthworms. Furthermore, current knowledge on ecological groups and food resources of earthworms is mainly based on direct observations, hence only reflecting what was ingested but not what was actually assimilated. We analysed seven earthworm species in beech and spruce forests and the associated litter, earthworm middens and soils, and employed compound-specific 13C stable isotope analysis of fatty acids (FAs) to identify the origins of carbon resources of the earthworms. To relate food resources to carbon compounds of different stability, we analysed 13C signatures of FAs of different particle size fractions. FA δ13C profiles of epigeic and endogeic earthworm species indicated assimilation of recently-fixed and recalcitrant carbon resources, respectively, whereas anecic earthworms assimilated a mixture of resources of different stability. Utilisation of carbon resources did not differ between beech and spruce forests. Endogeic species were associated with neutral lipids of soil particle size fractions with δ13C signatures of the bacterial marker a15:0 in earthworms resembling those of the clay fraction. This suggests that they assimilated carbon associated with small particle size fractions attached to clay-humus complexes. The results showed that earthworms of different ecological groups utilise carbon pools of different origin and stability. As indicated by neutral lipids of bacterial origin, physically-stabilised organic matter appears to contribute to the nutrition of endogeic earthworms in forest systems. [ABSTRACT FROM AUTHOR]

Abstract: Human activities, such as land use change, cause severe land degradation in many ecosystems around the globe with potential impacts on soil processes. Restoration practices aim at reverting such impacts and reconstituting the biotic composition and functioning of an ecosystem to its initial condition. The aim of this study was to monitor soil microbial properties in degraded lands in Northeast Brazil and to compare those with land under restoration. Soil samplings were conducted in 2009, 2010 and 2011 in two different seasons (wet and dry season) at sites differing in degradation status: native vegetation (NAT), moderately degraded land (MDL), highly degraded land (HDL), and land under restoration for four years (RES). Soil microbial properties showed pronounced fluctuations between seasons with higher levels of functioning in the wet than in the dry season. Soil microbial biomass and enzymes had significantly higher values under native vegetation than in degraded land, while restored land mostly corresponded to native vegetation. Soil microbial biomass, respiratory quotient and enzyme activities were more strongly affected by land degradation than soil chemical properties. Soil microbial properties varied more between seasons and years in highly degraded land than under native vegetation suggesting a buffering effect of the native vegetation on soil microbial processes. However, land degradation effects on soil microbial properties were significant in both seasons. Moreover, our results indicate that the land restoration practice applied here shifted soil microbial community composition as indicated by soil microbial stoichiometry. Our results indicate that land degradation strongly deteriorates soil microbial properties and their stability in time, but that land restoration practices likely are successful in promoting the recovery of some soil microbial functions, even after only four years. However, shifts in soil microbial community composition in restored lands may have significant feedback effects on element cycles. [Copyright &y& Elsevier]

Abstract: Positive relationships between biodiversity and ecosystem functioning are reported in many studies. The underlying mechanisms are, however, only little understood, likely due to the focus on the aboveground system and neglecting species-specific traits. We used different clusters of tree species composition to investigate how tree species diversity and tree species identity affect belowground nematode communities. Since soil nematodes comprise different trophic groups and are strongly linked to the microbial community, results can provide insight on how soil food webs are structured. In addition, data on leaf litter and fine root biomass were included to account for different effects of aboveground and belowground resources. Clusters of three trees of one, two and three species were identified within a temperate deciduous forest. Target tree species were European beech (Fagus sylvatica), common ash (Fraxinus excelsior) and lime (Tilia cordata, T. platyphyllos) differing in physiology, leaf litter quality and type of mycorrhiza. Tree species identity strongly affected nematode trophic structure, whereas tree species diversity had no impact. Ash beneficially affected bacterial-feeding nematodes, whereas fungal feeders were suppressed, likely caused by ash litter increasing soil pH. Fostering of the bacterial food chain by ash additionally could be related to rhizodeposition gaining importance after disappearance of high quality ash litter in spring, highlighting seasonal shifts in root and leaf litter-derived resources. The negative effect of ash on fungal-feeding nematodes is suggested to be due to the lack of ectomycorrhizal fungi as ash roots only form arbuscular mycorrhiza. In contrast, beech benefited fungal feeders and detrimentally affected bacterial feeders due to more acidic soil conditions that increase the competitive strength of fungi. Lime tended to negatively impact total nematode density but positively influenced plant-feeding nematodes. Generally, beech and ash strongly but opposingly influenced the trophic structure of nematode communities suggesting that changes in tree species identity result in major shifts in the channeling of energy through decomposer food webs. The results indicate that the structure of soil food webs varies markedly with tree species and point to the importance of basal resources, i.e., leaf litter and rhizodeposits. This suggests bottom-up forces mediated by individual tree species to control major decomposition pathways rather than tree diversity. [Copyright &y& Elsevier]

Abstract: Knowledge about the influence of living roots on decomposition processes in soil is scarce but is needed to understand carbon dynamics in soil. We investigated the effect of dominant deciduous tree species of the Central European forest vegetation, European beech (Fagus sylvatica L.) and European ash (Fraxinus excelsior L.), on soil biota and carbon dynamics differentiating between root- and leaf litter-mediated effects. The influence of beech and ash seedlings on carbon and nitrogen flow was investigated using leaf litter enriched in 13C and 15N in double split-root rhizotrons planted with beech and ash seedlings as well as a mixture of both tree species and a control without plants. Stable isotope and compound-specific fatty acid analysis (13C-PLFA) were used to follow the incorporation of stable isotopes into microorganisms, soil animals and plants. Further, the bacterial community composition was analyzed using pyrosequencing of 16S rRNA gene amplicons. Although beech root biomass was significantly lower than that of ash only beech significantly decreased soil carbon and nitrogen concentrations after 475 days of incubation. In addition, beech significantly decreased microbial carbon use efficiency as indicated by higher specific respiration. Low soil pH probably increased specific respiration of bacteria suggesting that rhizodeposits of beech roots induced increased microbial respiration and therefore carbon loss from soil. Compared to beech δ13C and δ15N signatures of gamasid mites in ash rhizotrons were significantly higher indicating higher amounts of litter-derived carbon and nitrogen to reach higher trophic levels. Similar δ13C signatures of bacteria and fine roots indicate that mainly bacteria incorporated root-derived carbon in beech rhizotrons. The results suggest that beech and ash differentially impact soil processes with beech more strongly affecting the belowground system via root exudates and associated changes in rhizosphere microorganisms and carbon dynamics than ash. [Copyright &y& Elsevier]

The world's ecosystems are subjected to various anthropogenic global change agents, such as enrichment of atmospheric CO2 concentrations, nitrogen ( N) deposition, and changes in precipitation regimes. Despite the increasing appreciation that the consequences of impending global change can be better understood if varying agents are studied in concert, there is a paucity of multi-factor long-term studies, particularly on belowground processes. Herein, we address this gap by examining the responses of soil food webs and biodiversity to enrichment of CO2, elevated N, and summer drought in a long-term grassland study at Cedar Creek, Minnesota, USA (Bio CON experiment). We use structural equation modeling ( SEM), various abiotic and biotic explanatory variables, and data on soil microorganisms, protozoa, nematodes, and soil microarthropods to identify the impacts of multiple global change effects on drivers belowground. We found that long-term (13-year) changes in CO2 and N availability resulted in modest alterations of soil biotic food webs and biodiversity via several mechanisms, encompassing soil water availability, plant productivity, and - most importantly - changes in rhizodeposition. Four years of manipulation of summer drought exerted surprisingly minor effects, only detrimentally affecting belowground herbivores and ciliate protists at elevated N. Elevated CO2 increased microbial biomass and the density of ciliates, microarthropod detritivores, and gamasid mites, most likely by fueling soil food webs with labile C. Moreover, beneficial bottom-up effects of elevated CO2 compensated for detrimental elevated N effects on soil microarthropod taxa richness. In contrast, nematode taxa richness was lowest at elevated CO2 and elevated N. Thus, enrichment of atmospheric CO2 concentrations and N deposition may result in taxonomically and functionally altered, potentially simplified, soil communities. Detrimental effects of N deposition on soil biodiversity underscore recent reports on plant community simplification. This is of particular concern, as soils house a considerable fraction of global biodiversity and ecosystem functions. [ABSTRACT FROM AUTHOR]

Summary: Understanding the complex interactions between trees and fungi is crucial for forest ecosystem management, yet the influence of tree mycorrhizal types, species identity, and diversity on tree‐tree interactions and their root‐associated fungal communities remains poorly understood.Our study addresses this gap by investigating root‐associated fungal communities of different arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) tree species pairs (TSPs) in a subtropical tree diversity experiment, spanning monospecific, two‐species, and multi‐species mixtures, utilizing Illumina sequencing of the ITS2 region.The study reveals that tree mycorrhizal type significantly impacts the alpha diversity of root‐associated fungi in monospecific stands. Meanwhile, tree species identity's influence is modulated by overall tree diversity. Tree‐related variables and spatial distance emerged as major drivers of variations in fungal community composition. Notably, in multi‐species mixtures, compositional differences between root fungal communities of AM and EcM trees diminish, indicating a convergence of fungal communities irrespective of mycorrhizal type. Interestingly, dual mycorrhizal fungal communities were observed in these multi‐species mixtures.This research underscores the pivotal role of mycorrhizal partnerships and the interplay of biotic and abiotic factors in shaping root fungal communities, particularly in varied tree diversity settings, and its implications for effective forest management and biodiversity conservation. [ABSTRACT FROM AUTHOR]

Artificial light at night (ALAN) is predicted to have far-reaching consequences for natural ecosystems given its influence on organismal physiology and behaviour, species interactions and community composition. Movement and predation are fundamental ecological processes that are of critical importance to ecosystem functioning. The natural movements and foraging behaviours of nocturnal invertebrates may be particularly sensitive to the presence of ALAN. However, we still lack evidence of how these processes respond to ALAN within a community context. We assembled insect communities to quantify their movement activity and predation rates during simulated Moon cycles across a gradient of diffuse night-time illuminance including the full range of observed skyglow intensities. Using radio frequency identification, we tracked the movements of insects within a fragmented grassland Ecotron experiment. We additionally quantified predation rates using prey dummies. Our results reveal that even low-intensity skyglow causes a temporal shift in movement activity from day to night, and a spatial shift towards open habitats at night. Changes in movement activity are associated with indirect shifts in predation rates. Spatio-temporal shifts in movement and predation have important implications for ecological networks and ecosystem functioning, highlighting the disruptive potential of ALAN for global biodiversity and the provision of ecosystem services. This article is part of the theme issue 'Light pollution in complex ecological systems'. [ABSTRACT FROM AUTHOR]

Artificial light at night (ALAN) affects many areas of the world and is increasing globally. To date, there has been limited and inconsistent evidence regarding the consequences of ALAN for plant communities, as well as for the fitness of their constituent species. ALAN could be beneficial for plants as they need light as energy source, but they also need darkness for regeneration and growth. We created model communities composed of 16 plant species sown, exposed to a gradient of ALAN ranging from 'moonlight only' to conditions like situations typically found directly underneath a streetlamp. We measured plant community composition and its production (biomass), as well as functional traits of three plant species from different functional groups (grasses, herbs, legumes) in two separate harvests. We found that biomass was reduced by 33% in the highest ALAN treatment compared to the control, Shannon diversity decreased by 43% and evenness by 34% in the first harvest. Some species failed to establish in the second harvest. Specific leaf area, leaf dry matter content and leaf hairiness responded to ALAN. These responses suggest that plant communities will be sensitive to increasing ALAN, and they flag a need for plant conservation activities that consider impending ALAN scenarios. This article is part of the theme issue 'Light pollution in complex ecological systems'. [ABSTRACT FROM AUTHOR]

Knowledge from agriculture and ecological field studies suggests that plant monocultures lose productivity over time, but the drivers underlying the long‐term performance of monocultures of grassland species are not completely understood. We examined the performance of 60 grassland species growing in monoculture for 12 years in a biodiversity experiment (Jena Experiment) and studied three groups of biotic drivers potentially affecting plant performance in monocultures over time: 1) soil biota (nematode communities, arbuscular mycorrhizal fungi), 2) leaf traits related to leaf economics spectrum, and 3) plant life‐cycle characteristics related to buffered population growth (viable seeds in topsoil, seedling density, seed survival). Monocultures of 15 out of 60 species increased productivity, while monocultures of the remaining 45 species showed slight to strong losses of productivity over time, resulting in zero biomass in 15 species. All three biotic drivers were related to the varying long‐term performance of monocultures. Their combined influence on monoculture performance could be interpreted as a tradeoff between 'fast' versus 'slow' life strategies. 'Fast' species showed rapid resource use and little buffering of population growth through a viable seed bank, which led to high biomass production in young monocultures but a consecutive loss of biomass production over time. 'Slow' species were characterized by positive nematode effects (high abundance of predatory nematodes), conservative use of resources, and a viable seed bank with high recruitment success resulting in gradually increasing productivity over time. In summary, our study highlights the importance of studying long‐term field monocultures to investigate the complex role of different biotic drivers responsible for productivity changes over time. These insights provide an essential baseline for estimating biodiversity effects on productivity as well as to understand and predict long‐term performance of plant populations. [ABSTRACT FROM AUTHOR]

Ecological communities are increasingly confronted with multiple global change factors, which can have wide-ranging consequences for ecosystem structure and functions. Yet, we lack studies on the interacting effects of multiple global change factors on ecological communities – particularly long-term studies in field settings. Here, using a grassland field experiment in temperate North America, we report the interactive effects of four of the most common and pressing global change factors of the Anthropocene (elevated CO 2 , elevated nitrogen, warming, and summer drought) on soil microbial and free-living soil nematode communities, which together form an extensive share of terrestrial biodiversity. In addition, we measured microbial mass-specific soil enzyme activities related to carbon, nitrogen, and phosphorus cycles. Our results showed that mass-specific soil enzyme activities and their stoichiometry were strongly affected by higher-order interactions among the global change factors. In particular, the three-way interaction among elevated CO 2 , reduced precipitation, and warming decreased the ratio of carbon-to phosphorus-acquiring enzymes as well as nitrogen-to phosphorus-acquiring enzymes in the soil, indicating a relative increase in the breakdown of organic phosphorus in the soil. We also found that the three-way interaction among elevated CO 2 , reduced precipitation, and warming altered the predominant decomposition pathway in the soil (towards a bacterial-dominated energy channel in future environments), indicated by the Channel Index of nematode communities. Further, the three-way interaction among nitrogen fertilization, reduced precipitation, and warming enhanced acid phosphatase (related to the P cycle). Nematode density increased at elevated nitrogen and ambient CO 2 as well as at ambient nitrogen and elevated CO 2, whereas it did not differ from controls at elevated nitrogen and elevated CO 2. Changes in microbial biomass were mainly driven by the additive effects of elevated CO 2 and temperature. Our results reveal various ways in which global change factors affect (both additively and interactively) soil biotic responses mainly via altering nutrient demands of soil microorganisms and changing soil community structure and energy channels. • Effects of CO 2 , nitrogen, warming and drought on soil biota and processes were investigated. • Higher-order interactions among global change drivers changed soil enzyme production. • Elevated CO 2 and warming changed microbial biomass C over the four year period. • Nematode density increased at elevated nitrogen and ambient CO 2. • Elevated CO 2 , precipitation, and temperature altered the decomposition pathway. [ABSTRACT FROM AUTHOR]

Forest ecosystems are critical for their carbon sequestration potential. Increasing tree diversity has been shown to enhance both forest productivity and litter decomposition. Litter diversity increases litter decomposability by increasing the diversity of substrates offered to decomposers. However, the relative importance of litter decomposability and decomposer community in mediating tree diversity effects on decomposition remains unknown. Moreover, tree diversity modulation of litterfall spatial distribution, and consequently litter decomposition, has rarely been tested. We studied tree diversity effects on leaf litter decomposition and its mediation by the amount of litterfall, litter species richness and decomposability, and soil microorganisms in a large‐scale tree diversity experiment in subtropical China. Furthermore, we examined how litter functional identity and diversity affect leaf litter decomposability. Finally, we tested how leaf functional traits, tree biomass, and forest spatial structure drive the litterfall spatial distribution. We found evidence that tree species richness increased litter decomposition by increasing litter species richness and the amount of litterfall. We showed that soil microorganisms in this subtropical forest perform 84–87% of litter decomposition. Moreover, changes in the amount of litterfall and microbial decomposition explained 19–37% of the decomposition variance. Additionally, up to 20% of the microbial decomposition variance was explained by litter decomposability, while litter decomposability itself was determined by litter functional identity, diversity, and species richness. Tree species richness increased litter species richness and the amount of litterfall (+200% from monoculture to eight‐species neighborhood). We further demonstrated that the amount of species‐specific litterfall increased with increasing tree proximity and biomass, and was modulated by leaf functional traits. These litterfall drivers increased the spatial heterogeneity of litter distribution, and thus litter decomposition. We highlighted multiple biomass‐ and diversity‐mediated effects of tree diversity on ecosystem properties driving forest nutrient cycling. We conclude that considering spatial variability in biotic properties will improve our mechanistic understanding of ecosystem functioning. [ABSTRACT FROM AUTHOR]

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

Forests are ecosystems critical to understanding the global carbon budget, due to their carbon sequestration potential in both aboveground and belowground compartments, especially in species‐rich forests. Soil carbon sequestration is strongly linked to soil microbial communities, and this link is mediated by the tree community, likely due to modifications of microenvironmental conditions (i.e., biotic conditions, soil properties, and microclimate). We studied soil carbon concentration and the soil microbial biomass of 180 local neighborhoods along a gradient of tree species richness ranging from 1 to 16 tree species per plot in a Chinese subtropical forest experiment (BEF‐China). Tree productivity and different tree functional traits were measured at the neighborhood level. We tested the effects of tree productivity, functional trait identity, and dissimilarity on soil carbon concentrations, and their mediation by the soil microbial biomass and microenvironmental conditions. Our analyses showed a strong positive correlation between soil microbial biomass and soil carbon concentrations. In addition, soil carbon concentration increased with tree productivity and tree root diameter, while it decreased with litterfall C:N content. Moreover, tree productivity and tree functional traits (e.g., fungal root association and litterfall C:N ratio) modulated microenvironmental conditions with substantial consequences for soil microbial biomass. We also showed that soil history and topography should be considered in future experiments and tree plantations, as soil carbon concentrations were higher at sites where historical (i.e., at the beginning of the experiment) carbon concentrations were high, themselves being strongly affected by the topography. Altogether, these results implied that the quantification of the different soil carbon pools is critical for understanding microbial community–soil carbon stock relationships and their dependence on tree diversity and microenvironmental conditions. [ABSTRACT FROM AUTHOR]

Aims: Recent studies in experimental grasslands indicated that declining plant species diversity negatively affects soil microbial communities. Here, we assessed if plant diversity effects also occur in 'real-world' grasslands. Methods: We studied the influence of fertilization, soil, and plant community characteristics on soil microbial activity (microbial biomass carbon, basal respiration) in 12 managed temperate grasslands of varying plant species richness in two subsequent years. Results: The most important variable explaining variation in microbial activity was soil water content, while positive effects of other soil characteristics (organic carbon and nitrogen concentrations) and fertilization became more important in one study year with generally moister soil conditions. Under moister conditions, fertilization also indirectly influenced soil microbial biomass C via negative effects on plant species richness, which itself increased soil microbial biomass C. Conclusion: Our results show that variation in soil microbial activity in managed grasslands involves direct effects of fertilization as well as indirect effects through changes in plant diversity and the amount of carbon and nitrogen stored in plants and soil. These results emphasize that increased nutrient inputs in grasslands entail complex changes in ecosystem processes and indicate that mechanisms driving soil microbial activity in experimental grasslands also apply to 'real-world' grasslands. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The relationship between species' body masses and densities is strongly conserved around a three‐quarter power law when pooling data across communities. However, studies of local within‐community relationships have revealed major deviations from this general pattern, which has profound implications for their stability and functioning. Despite multiple contributions of soil communities to people, there is limited knowledge on the drivers of body mass–abundance relationships in these communities. We compiled a dataset comprising 155 soil–animal communities across four countries (Canada, Germany, Indonesia, USA), all sampled using the same methodology. We tested if variation in local climatic and edaphic conditions drives differences in local body mass–abundance scaling relationships. We found substantial variation in the slopes of this power‐law relationship across local communities. Structural equation modeling showed that soil temperature and water content have a positive and negative net effect, respectively, on soil communities. These effects are mediated by changes in local edaphic conditions (soil pH and carbon content) and the body‐mass range of the communities. These results highlight ways in which alterations of soil climatic and edaphic conditions interactively impact the distribution of abundance between populations of small and large animals. These quantitative mechanistic relationships facilitate our understanding of how global changes in environmental conditions, such as temperature and precipitation, will affect community–abundance distributions and thus the stability and functioning of soil–animal communities. [ABSTRACT FROM AUTHOR]

In a recent Forum paper, Wardle ( Journal of Vegetation Science, 2016) questions the value of biodiversity-ecosystem function ( BEF) experiments with respect to their implications for biodiversity changes in real world communities. The main criticism is that the previous focus of BEF experiments on random species assemblages within each level of diversity has 'limited the understanding of how natural communities respond to biodiversity loss.' He concludes that a broader spectrum of approaches considering both non-random gains and losses of diversity is essential to advance this field of research. Wardle's paper is timely because of recent observations of frequent local and regional biodiversity changes across ecosystems. While we appreciate that new and complementary experimental approaches are required for advancing the field, we question criticisms regarding the validity of BEF experiments. Therefore, we respond by briefly reiterating previous arguments emphasizing the reasoning behind random species composition in BEF experiments. We describe how BEF experiments have identified important mechanisms that play a role in real world ecosystems, advancing our understanding of ecosystem responses to species gains and losses. We discuss recent examples where theory derived from BEF experiments enriched our understanding of the consequences of biodiversity changes in real world ecosystems and where comprehensive analyses and integrative modelling approaches confirmed patterns found in BEF experiments. Finally, we provide some promising directions in BEF research. [ABSTRACT FROM AUTHOR]

Abstract: The understanding of belowground biodiversity is still rather incomplete and interactions between above- and belowground systems have rarely been looked at when explaining belowground biodiversity patterns. The present study presents results of the influence of tree species diversity on the earthworm community in a central European deciduous mixed forest. Within the Hainich National Park three replicate sites were chosen within three levels of tree diversity ranging from one species (beech, DL1) to three species (beech, lime, ash, DL2) to five species stands (beech, lime, ash, hornbeam, maple, DL3). Earthworms were extracted by heat from soil and litter samples at four sampling dates at each site. In addition, in spring four samples per site were sorted by hand and identified to species level. Generally, earthworm densities were positively correlated with tree diversity in May and November but negatively in February. Sites with low tree species diversity had earthworm populations which were more stable due to a more permanent and deeper litter layer. Increasing proportions of high quality litter in DL2 und DL3 were correlated with higher densities of both epigeic and endogeic earthworm species, while litter in DL1 sites was mainly inhabited by epigeic species. Generally, there was a positive correlation between earthworm and tree species diversity indicating the importance of diverse food qualities for the decomposer fauna at the local scale especially in springtime. [Copyright &y& Elsevier]

1. Understanding how ecosystem multifunctionality is maintained in naturally assembled communities is crucial, because human activities benefit from multiple functions and services of various ecosystems. However, the effects of aboveand below-ground biodiversity on ecosystem multifunctionality in alpine and boreal moorland ecosystems remain unclear despite their potential as global carbon sinks. 2. Here we evaluated how ecosystem multifunctionality related to primary production and carbon sequestration, which are crucial for global climate regulation, is maintained in natural systems. We disentangled the relationships between diversity and composition of plants and soil microbes (fungi and bacteria) and ecosystem multifunctionality in subalpine moorlands in northern Japan. 3. We found that microbial composition primarily regulated carbon sequestration, whereas plant taxonomic and functional composition were related to all functions considered. Plant and microbial α diversity (diversity within local communities) were not generally related to any single function, highlighting the important roles of specific plant and microbial taxa in determining ecosystem functioning. When single functions were aggregated to ecosystem multifunctionality within local communities, plant and microbial community composition rather than diversity regulated ecosystem multifunctionality. We further found that plant and bacterial taxonomic β diversity (taxonomic turnover between local communities) primarily regulated the dissimilarity of ecosystem multifunctionality between local communities. 4. Synthesis. We provide observational evidence that plant and microbial community composition rather than diversity are essential for sustaining subalpine moorland multifunctionality. Furthermore, plant and bacterial β diversity enhance the dissimilarity of moorland multifunctionality. Our study provides novel insights into biodiversity–ecosystem multifunctionality relationships occurring in nature, and helps to sustain desirable ecosystem functioning to human society. [ABSTRACT FROM AUTHOR]

Summary: There is limited knowledge on how the association of trees with different mycorrhizal types shapes soil microbial communities in the context of changing tree diversity levels. We used arbuscular (AM) and ectomycorrhizal (EcM) tree species as con‐ and heterospecific tree species pairs (TSPs), which were established in plots of three tree diversity levels including monocultures, two‐species mixtures and multi‐tree species mixtures in a tree diversity experiment in subtropical China. We found that the tree mycorrhizal type had a significant effect on fungal but not bacterial alpha diversity. Furthermore, only EcM but not AM TSPs fungal alpha diversity increased with tree diversity, and the differences between AM and EcM TSPs disappeared in multi‐species mixtures. Tree mycorrhizal type, tree diversity and their interaction had significant effects on fungal community composition. Neither fungi nor bacteria showed any significant compositional variation in TSPs located in multi‐species mixtures. Accordingly, the most influential taxa driving the tree mycorrhizal differences at low tree diversity were not significant in multi‐tree species mixtures. Collectively, our results indicate that tree mycorrhizal type is an important factor determining the diversity and community composition of soil microbes, and higher tree diversity levels promote convergence of the soil microbial communities. Significance statement: More than 90% of terrestrial plants have symbiotic associations with mycorrhizal fungi which could influence the coexisting microbiota. Systematic understanding of the individual and interactive effects of tree mycorrhizal type and tree species diversity on the soil microbiota is crucial for the mechanistic comprehension of the role of microbes in forest soil ecological processes. Our tree species pair (TSP) concept coupled with random sampling within and across the plots, allowed us the unbiased assessment of tree mycorrhizal type and tree diversity effects on the tree‐tree interaction zone soil microbiota. Unlike in monocultures and two‐species mixtures, we identified species‐rich and converging fungal and bacterial communities in multi‐tree species mixtures. Consequently, we recommend planting species‐rich mixtures of EcM and AM trees, for afforestation and reforestation regimes. Specifically, our findings highlight the significance of tree mycorrhizal type in studying 'tree diversity – microbial diversity – ecosystem function' relationships. [ABSTRACT FROM AUTHOR]

Human activities are causing climatic changes and alter the composition and biodiversity of ecosystems. Climate change has been and will be increasing the frequency and severity of extreme climate events and natural disasters like floods in many ecosystems. Therefore, it is important to investigate the effects of disturbances on ecosystems and identify potential stabilizing features of ecological communities. In this study, soil microbial and nematode communities were investigated in a grassland biodiversity experiment after a natural flood to investigate if plant diversity is able to attenuate or reinforce the magnitude of effects of the disturbance on soil food webs. In addition to community analyses of soil microorganisms and nematodes, the stability indices proportional resilience, proportional recovery, and proportional resistance were calculated. Generally, soil microbial biomass decreased significantly due to the flood with the strongest reduction in gram-negative bacteria, while gram-positive bacteria were less affected by flooding. Fungal biomass increased significantly three months after the flood compared to few days before the flood, reflecting elevated availability of dead plant biomass in response to the flood. Similar to the soil microbial community, nematode community structure changed considerably due to the flood by favoring colonizers (in the broadest sense r-strategists; c–p 1, 2 nematodes), particularly so at high plant diversity. None of the soil microbial community stability indices and few of the nematode stability indices were significantly affected by plant diversity, indicating limited potential of plant diversity to buffer soil food webs against flooding disturbance. However, plant diversity destabilized colonizer populations, while persister populations (in the broadest sense K-strategists; c–p 4 nematodes) were stabilized, suggesting that plant diversity can stabilize and destabilize populations depending on the ecology of the focal taxa. The present study shows that changes in plant diversity and subsequent alterations in resource availability may significantly modify the compositional shifts of soil food webs in response to disturbances. [ABSTRACT FROM AUTHOR]

Background and Aims: Litter decomposition is a major determinant of carbon (C) and nutrient cycling in ecosystems, and contributes to soil organic carbon (SOC) formation. Ongoing global changes are exacerbating biodiversity loss, potentially elevating foliar fungal pathogen infections and consequently impacting litter quality and quantity. However, the potential interplay between biodiversity loss and fungal pathogen infection on litter decomposition and SOC formation remains largely unknown.We collected leaf litter with different fungal pathogen infection levels across various tree species richness (TSR) stands within a subtropical forest biodiversity-ecosystem functioning experiment in China. We conducted a 383-day incubation experiment using these litter samples and measured initial litter quality, litter mass loss, and incubation-induced changes in mineral-associated soil C and nitrogen (N).We found that litter from higher richness plots exhibited lower N concentration and higher carbon to nitrogen ratio (C:N). Moreover, TSR exerted control over the effects of fungal pathogen infection on litter quality, decomposition, and N turnover. Under higher richness, litter with higher fungal infection levels tended to have higher N concentration and lower C:N, thus leading to faster decomposition rates and more soil N loss. Meanwhile, litter with elevated fungal infection levels contributed more to litter C retained in soil.Our findings indicate that changes in litter chemistry and fungal pathogen infection rates induced by biodiversity loss could affect decomposition and the extent of C stabilized in soil, highlighting the significance of considering fungal pathogen infection in studies related to biodiversity and biogeochemical cycles.Methods: Litter decomposition is a major determinant of carbon (C) and nutrient cycling in ecosystems, and contributes to soil organic carbon (SOC) formation. Ongoing global changes are exacerbating biodiversity loss, potentially elevating foliar fungal pathogen infections and consequently impacting litter quality and quantity. However, the potential interplay between biodiversity loss and fungal pathogen infection on litter decomposition and SOC formation remains largely unknown.We collected leaf litter with different fungal pathogen infection levels across various tree species richness (TSR) stands within a subtropical forest biodiversity-ecosystem functioning experiment in China. We conducted a 383-day incubation experiment using these litter samples and measured initial litter quality, litter mass loss, and incubation-induced changes in mineral-associated soil C and nitrogen (N).We found that litter from higher richness plots exhibited lower N concentration and higher carbon to nitrogen ratio (C:N). Moreover, TSR exerted control over the effects of fungal pathogen infection on litter quality, decomposition, and N turnover. Under higher richness, litter with higher fungal infection levels tended to have higher N concentration and lower C:N, thus leading to faster decomposition rates and more soil N loss. Meanwhile, litter with elevated fungal infection levels contributed more to litter C retained in soil.Our findings indicate that changes in litter chemistry and fungal pathogen infection rates induced by biodiversity loss could affect decomposition and the extent of C stabilized in soil, highlighting the significance of considering fungal pathogen infection in studies related to biodiversity and biogeochemical cycles.Results: Litter decomposition is a major determinant of carbon (C) and nutrient cycling in ecosystems, and contributes to soil organic carbon (SOC) formation. Ongoing global changes are exacerbating biodiversity loss, potentially elevating foliar fungal pathogen infections and consequently impacting litter quality and quantity. However, the potential interplay between biodiversity loss and fungal pathogen infection on litter decomposition and SOC formation remains largely unknown.We collected leaf litter with different fungal pathogen infection levels across various tree species richness (TSR) stands within a subtropical forest biodiversity-ecosystem functioning experiment in China. We conducted a 383-day incubation experiment using these litter samples and measured initial litter quality, litter mass loss, and incubation-induced changes in mineral-associated soil C and nitrogen (N).We found that litter from higher richness plots exhibited lower N concentration and higher carbon to nitrogen ratio (C:N). Moreover, TSR exerted control over the effects of fungal pathogen infection on litter quality, decomposition, and N turnover. Under higher richness, litter with higher fungal infection levels tended to have higher N concentration and lower C:N, thus leading to faster decomposition rates and more soil N loss. Meanwhile, litter with elevated fungal infection levels contributed more to litter C retained in soil.Our findings indicate that changes in litter chemistry and fungal pathogen infection rates induced by biodiversity loss could affect decomposition and the extent of C stabilized in soil, highlighting the significance of considering fungal pathogen infection in studies related to biodiversity and biogeochemical cycles.Conclusions: Litter decomposition is a major determinant of carbon (C) and nutrient cycling in ecosystems, and contributes to soil organic carbon (SOC) formation. Ongoing global changes are exacerbating biodiversity loss, potentially elevating foliar fungal pathogen infections and consequently impacting litter quality and quantity. However, the potential interplay between biodiversity loss and fungal pathogen infection on litter decomposition and SOC formation remains largely unknown.We collected leaf litter with different fungal pathogen infection levels across various tree species richness (TSR) stands within a subtropical forest biodiversity-ecosystem functioning experiment in China. We conducted a 383-day incubation experiment using these litter samples and measured initial litter quality, litter mass loss, and incubation-induced changes in mineral-associated soil C and nitrogen (N).We found that litter from higher richness plots exhibited lower N concentration and higher carbon to nitrogen ratio (C:N). Moreover, TSR exerted control over the effects of fungal pathogen infection on litter quality, decomposition, and N turnover. Under higher richness, litter with higher fungal infection levels tended to have higher N concentration and lower C:N, thus leading to faster decomposition rates and more soil N loss. Meanwhile, litter with elevated fungal infection levels contributed more to litter C retained in soil.Our findings indicate that changes in litter chemistry and fungal pathogen infection rates induced by biodiversity loss could affect decomposition and the extent of C stabilized in soil, highlighting the significance of considering fungal pathogen infection in studies related to biodiversity and biogeochemical cycles. [ABSTRACT FROM AUTHOR]

There is mounting evidence that the functioning of an ecosystem is highly connected to the diversity of its biota. However, the influence of biodiversity on ecosystem functions in terrestrial ecosystems has mainly been investigated in grassland. In contrast, forests have long been neglected in this context, though their functional relevance is undoubted. This study investigated the effects of different tree diversity indices (species richness, species evenness, functional diversity) and of tree species identity on earthworm communities in three distinct eight to ten years-old tree diversity experiments. Consistently in all three experiments we found no significant relationships between tree diversity indices and earthworms, whereas they were significantly affected by tree species identity. European larch ( Larix decidua ) and Norway spruce ( Picea abies ) had strong and consistent negative effects on earthworms, while the presence of oak ( Quercus petraea and Quercus robur ) and Scots pine ( Pinus sylvestris ) increased earthworm abundance and biomass significantly, but effects were inconsistent. Soil pH was only a poor explanatory variable for tree identity effects. The results indicate that tree identity, but not tree diversity drives earthworm communities in young tree stands. The negative effects of larch and spruce may be due to rather low palatability of their litter and to the dense canopy structure reducing soil moisture and temperature, while we found limited support for soil acidification effects. Future studies should consider litter and root traits of trees, and both the effects of trees and herbaceous plants in the understory to explain variations in ecological communities and ecosystem processes. [ABSTRACT FROM AUTHOR]

• SIP (13CO2 and 18O water) revealed impacts of soil fauna on microbial functioning. • Nematode grazing increased net assimilation of plant derived C in microbial biomass. • Bacterivore nematodes impacted directly bacteria and indirectly saprophytic fungi. • Grazing activated bacterial taxa typical for the rhizosphere microbiome. • Grazing enhances allocation of plant C and thus energy to the soil food web. Microbially driven soil processes are crucial for ecosystem functions such as soil carbon storage and nutrient cycling. The functioning of the microbial community, in turn, largely depends on plant-derived carbon inputs. However, besides the energy supply by plants, the microbial community also underlies a top-down control by higher trophic levels, which has often not been considered when investigating soil microbial processes. Here we investigated the impact of bacterivore and fungivore-grazing nematodes on the net assimilation of carbon into the bacterial and fungal biomass in a microcosm experiment. We manipulated bacterivorous or fungivorous nematodes to obtain different grazing densities. In combination with a 13CO 2 pulse labelling we traced the carbon flow from plants into the soil microbial community using PLFA biomarkers. Furthermore, we investigated if nematode grazing, independent of the carbon flow, shifted the active bacterial community using H 2 18O DNA stable isotope probing. We found that the microbial biomass was unaffected by nematode grazers. However, bacterivore nematodes stimulated the incorporation of the 13C label directly into biomarkers of bacteria groups and indirectly into biomarkers of saprophytic fungi. The nematode grazing furthermore enhanced the activity of bacterial taxa typically for the rhizosphere microbiome that utilize mainly root deposits, while bacterial groups that degrade already stored soil organic matter were inhibited. We conclude that grazing of higher trophic levels impacts soil processes and likely the entire soil biota via two mechanisms: firstly, through the constant grazing on soil microorganisms and their constant regrowth, the allocation of plant-derived carbon that enters the soil food web increases; and secondly, it preferentially activates bacteria of the rhizosphere microbiome that putatively contribute to soil organic matter storage. [ABSTRACT FROM AUTHOR]

Recent metaanalyses suggest biodiversity loss affects the functioning of ecosystems to a similar extent as other global environmental change agents. However, the abundance and functioning of soil organisms have been hypothesized to be much less responsive to such changes, particularly in plant diversity, than aboveground variables, although tests of this hypothesis are extremely rare. We examined the responses of soil food webs (soil microorganisms, nematodes, microarthropods) to 13-y manipulation of multiple environmental factors that are changing at global scales-specifically plant species richness, atmospheric CO2, and N deposition-in a grassland experiment in Minnesota. Plant diversity was a strong driver of the structure and functioning of soil food webs through several bottom-up (resource control) effects, whereas CO2 and N only had modest effects. We found few interactions between plant diversity and CO2 and N, likely because of weak interactive effects of those factors on resource availability (e.g., root biomass). Plant diversity effects likely were large because high plant diversity promoted the accumulation of soil organic matter in the site's sandy, organic matter-poor soils. Plant diversity effects were not explained by the presence of certain plant functional groups. Our results underline the prime importance of plant diversity loss cascading to soil food webs (density and diversity of soil organisms) and functions. Because the present results suggest prevailing plant diversity effects and few interactions with other global change drivers, protecting plant diversity may be of high priority to maintain the biodiversity and functioning of soils in a changing world. [ABSTRACT FROM AUTHOR]

Aim: Quantify direct and indirect relationships between soil microbial community properties (potential basal respiration, microbial biomass) and abiotic factors (soil, climate) in three major land‐cover types. Location: Europe. Time period: 2018. Major taxa studied: Microbial community (fungi and bacteria). Methods: We collected 881 soil samples from across Europe in the framework of the Land Use/Land Cover Area Frame Survey (LUCAS). We measured potential soil basal respiration at 20 ºC and microbial biomass (substrate‐induced respiration) using an O2‐microcompensation apparatus. Soil and climate data were obtained from the same LUCAS survey and online databases. Structural equation models (SEMs) were used to quantify relationships between variables, and equations extracted from SEMs were used to create predictive maps. Fatty acid methyl esters were measured in a subset of samples to distinguish fungal from bacterial biomass. Results: Soil microbial properties in croplands were more heavily affected by climate variables than those in forests. Potential soil basal respiration and microbial biomass were correlated in forests but decoupled in grasslands and croplands, where microbial biomass depended on soil carbon. Forests had a higher ratio of fungi to bacteria than grasslands or croplands. Main conclusions: Soil microbial communities in grasslands and croplands are likely carbon‐limited in comparison with those in forests, and forests have a higher dominance of fungi indicating differences in microbial community composition. Notably, the often already‐degraded soils of croplands could be more vulnerable to climate change than more natural soils. The provided maps show potentially vulnerable areas that should be explicitly accounted for in future management plans to protect soil carbon and slow the increasing vulnerability of European soils to climate change. [ABSTRACT FROM AUTHOR]

Current analyses and predictions of spatially explicit patterns and processes in ecology most often rely on climate data interpolated from standardized weather stations. This interpolated climate data represents long‐term average thermal conditions at coarse spatial resolutions only. Hence, many climate‐forcing factors that operate at fine spatiotemporal resolutions are overlooked. This is particularly important in relation to effects of observation height (e.g. vegetation, snow and soil characteristics) and in habitats varying in their exposure to radiation, moisture and wind (e.g. topography, radiative forcing or cold‐air pooling). Since organisms living close to the ground relate more strongly to these microclimatic conditions than to free‐air temperatures, microclimatic ground and near‐surface data are needed to provide realistic forecasts of the fate of such organisms under anthropogenic climate change, as well as of the functioning of the ecosystems they live in. To fill this critical gap, we highlight a call for temperature time series submissions to SoilTemp, a geospatial database initiative compiling soil and near‐surface temperature data from all over the world. Currently, this database contains time series from 7,538 temperature sensors from 51 countries across all key biomes. The database will pave the way toward an improved global understanding of microclimate and bridge the gap between the available climate data and the climate at fine spatiotemporal resolutions relevant to most organisms and ecosystem processes. [ABSTRACT FROM AUTHOR]

Empirical evidence suggests that the rich set of ecosystem functions and nature's contributions to people provided by forests depends on tree diversity. Biodiversity–ecosystem functioning research revealed that not only species richness per se but also other facets of tree diversity, such as tree identity, have to be considered to understand the underlying mechanisms. One important ecosystem function in forests is the decomposition of deadwood that plays a vital role in carbon and nutrient cycling and is assumed to be determined by above‐ and belowground interactions. However, the actual influence of tree diversity on wood decay in forests remains inconclusive. Recent studies suggest an important role of microclimate and advocate a systematical consideration of small‐scale environmental conditions. We studied the influence of tree species richness, tree species identity, and microclimatic conditions on wood decomposition in a 12‐year‐old tree diversity experiment in Germany, containing six native species within a tree species richness gradient. We assessed wood mass loss, soil microbial properties, and soil surface temperature in high temporal resolution. Our study shows a significant influence of tree species identity on all three variables. The presence of Scots pine strongly increased wood mass loss, while the presence of Norway spruce decreased it. This could be attributed to structural differences in the litter layer that were modifying the capability of plots to hold the soil surface temperature at night, consequently leading to enhanced decomposition rates in plots with higher nighttime surface temperatures. Therefore, our study confirmed the critical role of microclimate for wood decomposition in forests and showed that soil microbial properties alone were not sufficient to predict wood decay. We conclude that tree diversity effects on ecosystem functions may include different biodiversity facets, such as tree identity, tree traits, and functional and structural diversity, in influencing the abiotic and biotic soil properties. [ABSTRACT FROM AUTHOR]

Human activities are accelerating global biodiversity change and have resulted in severely threatened ecosystem services. A large proportion of terrestrial biodiversity is harbored by soil, but soil biodiversity has been omitted from many global biodiversity assessments and conservation actions, and understanding of global patterns of soil biodiversity remains limited. In particular, the extent to which hotspots and coldspots of aboveground and soil biodiversity overlap is not clear. We examined global patterns of these overlaps by mapping indices of aboveground (mammals, birds, amphibians, vascular plants) and soil (bacteria, fungi, macrofauna) biodiversity that we created using previously published data on species richness. Areas of mismatch between aboveground and soil biodiversity covered 27% of Earth's terrestrial surface. The temperate broadleaf and mixed forests biome had the highest proportion of grid cells with high aboveground biodiversity but low soil biodiversity, whereas the boreal and tundra biomes had intermediate soil biodiversity but low aboveground biodiversity. While more data on soil biodiversity are needed, both to cover geographic gaps and to include additional taxa, our results suggest that protecting aboveground biodiversity may not sufficiently reduce threats to soil biodiversity. Given the functional importance of soil biodiversity and the role of soils in human well‐being, soil biodiversity should be considered further in policy agendas and conservation actions by adapting management practices to sustain soil biodiversity and considering soil biodiversity when designing protected areas. Article impact statement: Given the importance of soil biodiversity for human well‐being, it should be considered in conservation policy and actions. [ABSTRACT FROM AUTHOR]

Concern about human modification of Earth's ecosystems has recently motivated ecologists to address how global change drivers will impact the simultaneous provisioning of multiple functions, termed ecosystem multifunctionality (EMF). However, metrics of EMF have often been applied in global change studies with little consideration of the information they provide beyond single functions, or how and why EMF may respond to global change drivers. Here, we critically review the current state of this rapidly expanding field and provide a conceptual framework to guide the effective incorporation of EMF in global change research. In particular, we emphasize the need for a priori identification and explicit testing of the biotic and abiotic mechanisms through which global change drivers impact EMF, as well as assessing correlations among multiple single functions because these patterns underlie shifts in EMF. While the role of biodiversity in mediating global change effects on EMF has justifiably received much attention, empirical support for effects via other biotic and physicochemical mechanisms are also needed. Studies also frequently stated the importance of measuring EMF responses to global change drivers to understand the potential consequences for multiple ecosystem services, but explicit links between measured functions and ecosystem services were missing from many such studies. While there is clear potential for EMF to provide novel insights to global change research, predictive understanding will be greatly improved by insuring future research is strongly hypothesis‐driven, is designed to explicitly test multiple abiotic and biotic mechanisms, and assesses how single functions and their covariation drive emergent EMF responses to global change drivers. The use of ecosystem multifunctionality (EMF) is quickly proliferating in global change research, but with little consideration of its added value for understanding patterns of ecological change. Here, we conduct an extensive literature review and identify the potential pitfalls and benefits of integrating EMF into global change studies. Furthermore, we propose a framework that clearly defines a niche for ecosystem multifunctionality in global change research to guide a more informative, hypothesis‐driven trajectory for this rapidly expanding field. [ABSTRACT FROM AUTHOR]

Abstract Extensive biodiversity conservation efforts in Europe resulted in the recent establishment of the ecological network of protected areas Natura 2000. However, it remains unclear how such protected areas reflect the distribution of soil biodiversity, which represents a substantial fraction of terrestrial biodiversity and drives a plethora of ecosystem services. Here we analyzed and compared different metrics of soil nematode taxonomic diversity, i.e., taxon richness, Shannon Diversity Index, Shannon Evenness (all based on supraspecific diversity), and functional diversity, i.e., Maturity Index (environmental disturbance), Structure Index (food web complexity), Enrichment Index (system enrichment), and Channel Index (dominant decomposition pathway of soil organic matter) in 16 grasslands assigned to two Natura 2000 priority habitat types and 14 grasslands assigned to five Natura 2000 non-priority habitat types in Romania. Nematode communities consisted of a total of 123 taxa (115 genera and 8 suprageneric taxa). We found no significant difference in nematode taxonomic and functional diversity between grasslands assigned to Natura 2000 priority and non-priority habitats, suggesting that this categorization does not reflect nematode diversity patterns. [ABSTRACT FROM AUTHOR]

The article focuses on impacts of human development and the benefits of nature conservation for oceans and aboveground terrestrial organisms and majority of terrestrial biodiversity that is unseen and living in the soil. It mentions Soil biodiversity and its ecosystem functions thus require explicit consideration when establishing nature protection priorities and post-2020 discussions of the Convention on Biological Diversity (CBD).

Climate change can alter soil communities and functions, but the consequences are uncertain for most ecosystems. We assessed the impacts of climate change on soil nematodes in a semiarid grassland using a 7-year, factorial manipulation of temperature and [CO 2 ]. Elevated CO 2 and warming decreased the abundance of plant-feeding nematodes and nematodes with intermediate to high values on the colonizer-persister scale (cp3-5), including predators and omnivores. Thus, under futuristic climate conditions, nematode communities were even more dominated by r- strategists (cp1-2) that feed on bacteria and fungi. These results indicate that climate change could alter soil functioning in semiarid grasslands. For example, the lower abundance of plant-feeding nematodes could facilitate positive effects of elevated CO 2 and warming on plant productivity. The effects of elevated CO 2 and warming on nematode functional composition were typically less than additive, highlighting the need for multi-factor studies. [ABSTRACT FROM AUTHOR]

Intensive land use of the Brazilian Atlantic Forest accelerated with the rise of sugar cane plantations in the northeastern part of Brazil. Consequently, many ecosystems were destroyed, including riparian forests. The number of studies of riparian restoration has increased but comparative studies on the belowground effects of common reforestation strategies are rare. Here, we compared soil microbial properties among four different land use types: native rainforest, sugar cane plantation, single species reforestation, and mixed species reforestation, each replicated at two spatially independent sites. Soil samples were taken in 2013 and 2014, that is 2 and 3 years after reforestation, respectively. In both years, land use types had a significant effect on basal respiration, microbial biomass, and specific respiration (whereas specific respiration was marginally affected in 2014). In 2013, basal respiration in sugar cane plantations was significantly lower (−65%) when compared to native forests. In 2014, basal respiration (+60%) and soil microbial biomass (+90%) were significantly higher in mixed species reforestation compared to sugar cane, whereas single species reforestation had comparable values as in sugar cane plantations. Our results indicate that soil microbial biomass and activity respond rapidly to land use change when mixed species reforestation is used. Thus, using mixed species reforestation may enhance the provisioning of ecosystem services already in the short term. [ABSTRACT FROM AUTHOR]

Soil food webs comprise a multitude of trophic interactions that can affect the composition and productivity of plant communities. Belowground predators feeding on microbial grazers like Collembola could decelerate nutrient mineralization by reducing microbial turnover in the soil, which in turn could negatively influence plant growth. However, empirical evidences for the ecological significance of belowground predators on nutrient cycling and plant communities are scarce. Here, we manipulated predator density ( Hypoaspis aculeifer: predatory mite) with equal densities of three Collembola species as a prey in four functionally dissimilar plant communities in experimental microcosms: grass monoculture ( Poa pratensis), herb monoculture ( Rumex acetosa), legume monoculture ( Trifolium pratense), and all three species as a mixed plant community. Density manipulation of predators allowed us to test for density-mediated effects of belowground predators on Collembola and lower trophic groups. We hypothesized that predator density will reduce Collembola population causing a decrease in nutrient mineralization and hence detrimentally affect plant growth. First, we found a density-dependent population change in predators, that is, an increase in low-density treatments, but a decrease in high-density treatments. Second, prey suppression was lower at high predator density, which caused a shift in the soil microbial community by increasing the fungal: bacterial biomass ratio, and an increase of nitrification rates, particularly in legume monocultures. Despite the increase in nutrient mineralization, legume monocultures performed worse at high predator density. Further, individual grass shoot biomass decreased in monocultures, while it increased in mixed plant communities with increasing predator density, which coincided with elevated soil N uptake by grasses. As a consequence, high predator density significantly increased plant complementarity effects indicating a decrease in interspecific plant competition. These results highlight that belowground predators can relax interspecific plant competition by increasing nutrient mineralization through their density-dependent cascading effects on detritivore and soil microbial communities. [ABSTRACT FROM AUTHOR]

Rapid ecosystem assessments are needed for large-scale ecotoxicological studies and coordinated distributed experiments. Bait-lamina stripes are commonly used as a standardized method to assess decomposer activity, but it is often difficult to distinguish bait substrate from soil. In the present study our aim was to identify a dyeing method that improves the precision of visual assessment of decomposition rates, while having negligible side effects. We compared five different dyes (food dye, Easter Grass, organic textile dye, ink, and wall paint) with control substrate in microcosms containing either acidic or alkaline soil with two introduced Collembola species (Folsomia candida and Sinellacoeca). Organic textile dye showed the highest precision of visual assessment, and had no detectable side effects on decomposition rates, soil microbial activity (biomass and respiration), or Collembola densities. We recommend using organic textile dye to improve the bait-lamina test due to the high precision and the ease of preparation. [ABSTRACT FROM AUTHOR]

Anthropogenic changes in biodiversity and atmospheric temperature significantly influence ecosystem processes. However, little is known about potential interactive effects of plant diversity and warming on essential ecosystem properties, such as soil microbial functions and element cycling. We studied the effects of orthogonal manipulations of plant diversity (one, four, and 16 species) and warming (ambient, +1.5°C, and +3°C) on soil microbial biomass, respiration, growth after nutrient additions, and activities of extracellular enzymes in 2011 and 2012 in the BAC (biodiversity and climate) perennial grassland experiment site at Cedar Creek, Minnesota, USA. Focal enzymes are involved in essential biogeochemical processes of the carbon, nitrogen, and phosphorus cycles. Soil microbial biomass and some enzyme activities involved in the C and N cycle increased significantly with increasing plant diversity in both years. In addition, 16-species mixtures buffered warming induced reductions in topsoil water content. We found no interactive effects of plant diversity and warming on soil microbial biomass and growth rates. However, the activity of several enzymes (1,4-ß-glucosidase, 1,4-ß-N-acetylglucosaminidase, phosphatase, peroxidase) depended on interactions between plant diversity and warming with elevated activities of enzymes involved in the C, N, and P cycles at both high plant diversity and high warming levels. Increasing plant diversity consistently decreased microbial biomass-specific enzyme activities and altered soil microbial growth responses to nutrient additions, indicating that plant diversity changed nutrient limitations and/or microbial community composition. In contrast to our expectations, higher plant diversity only buffered temperature effects on soil water content, but not on microbial functions. Temperature effects on some soil enzymes were greatest at high plant diversity. In total, our results suggest that the fundamental temperature ranges of soil microbial communities may be sufficiently broad to buffer their functioning against changes in temperature and that plant diversity may be a dominant control of soil microbial processes in a changing world. [ABSTRACT FROM AUTHOR]

Global climate warming is one of the key forces driving plant community shifts, such as range shifts of temperate species into boreal forests. As plant community shifts are slow to observe, ecotones, boundaries between two ecosystems, are target areas for providing early evidence of ecological responses to warming. The role of soil fauna is poorly explored in ecotones, although their positive and negative effects on plant species can influence plant community structure. We studied nematode communities in response to experimental warming (ambient, +1.7, +3.4 °C) in soils of closed and open canopy forest in the temperate-boreal ecotone of Minnesota, USA and calculated various established nematode indices. We estimated species-specific coverage of understory herbaceous and shrub plant species from the same experimental plots and tested if changes in the nematode community are associated with plant cover and composition. Individual nematode trophic groups did not differ among warming treatments, but the ratio between microbial-feeding and plant-feeding nematodes increased significantly and consistently with warming in both closed and open canopy areas and at both experimental field sites. The increase in this ratio was positively correlated with total cover of understory plant species, perhaps due to increased predation pressure on soil microorganisms causing higher nutrient availability for plants. Multivariate analyses revealed that temperature treatment, canopy conditions and nematode density consistently shaped understory plant communities across experimental sites. Our findings suggest that warming-induced changes in nematode community structure are associated with shifts in plant community composition and productivity in the temperate-boreal forest ecotones. [ABSTRACT FROM AUTHOR]

The interactions between earthworms and soil microbial communities have attracted a lot of scientific attention, but if and how important soil invertebrates may modulate climate effects on soil microorganisms in different land-use types is less clear. Here we collected earthworm casts as an indicator of earthworm effects on soil microbial communities and bulk soil from the Global Change Experiment Facility (GCEF) situated at Bad Lauchstädt, Germany. We tested the interactive effect of two climate treatments (ambient and future), land-use type (conventional farming, organic farming, and extensively used meadows), and sample type (cast and bulk soil) on the soil microbial community. The biomass and community composition of the bacterial and fungal communities were assessed by fatty acid analysis. Climate, alone and in interaction with land-use type, had no significant effects on the biomass and composition of soil microorganisms in bulk soil and casts produced by earthworms. The biomasses of almost all microbial markers (except for 18:2ω6t and 18:1ω9t) were significantly higher in the cast than in bulk soil in all land-use types (+185%), with the most substantial impact on all other fungal makers in soil. However, the land-use effect was significantly modulated by soil type, i.e., earthworms. Mainly extensively managed meadows had more than double (+237%) the microbial biomass in casts than in bulk soil, whereas in the other land-use types, the positive effect of cast soil was much smaller (conventional farming: +166%; organic farming: +123%). The microbial community composition showed no difference between the two cropping systems (conventional farming and organic farming). Here, bulk soil was more associated with fungal biomarkers, whereas casts were more dominated by bacterial markers; however, this effect was rather weak. Extensively managed meadows showed strong differences to both cropping systems, mainly due to higher microbial biomass and a more heterogeneous association of either more fungal or bacterial communities. We suggest that the main factors that led to differences between land-use types were a more diverse plant community in meadows and the less intensive management regime with undisturbed soils. The conditions in extensively managed meadows allowed earthworms to strongly amplify those positive effects in casts, suggesting that earthworms can act as important biotic filters modulating land-use effects on soil microbes across climate treatments. • We explored climate and land-use effects on soil microbial communities in bulk soil and earthworm casts. • Extensive land use enhanced soil microbial biomass, while climate had no significant effects. • Microbial biomass was significantly higher in earthworm casts than in bulk soil. • Extensively managed meadows had more than double the microbial biomass in casts than in bulk soil • Earthworms intensified beneficial effects of extensive land use on soil microbial communities. [ABSTRACT FROM AUTHOR]

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 effects via increased plant productivity. Furthermore, we hypothesized fertilization to reinforce drought effects through enhanced plant growth, resulting in even drier 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. Thus, important ecosystem processes like decomposition and nutrient cycling, which are driven by the interdependent activity of soil microorganisms and invertebrates, may be disrupted under future conditions. [ABSTRACT FROM AUTHOR]