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Abstract Covering approximately 40% of land surfaces, grasslands provide critical ecosystem services that rely on soil organisms. However, the global determinants of soil biodiversity and functioning remain underexplored. In this study, we investigate the drivers of soil microbial and detritivore activity in grasslands across a wide range of climatic conditions on five continents. We apply standardized treatments of nutrient addition and herbivore reduction, allowing us to disentangle the regional and local drivers of soil organism activity. We use structural equation modeling to assess the direct and indirect effects of local and regional drivers on soil biological activities. Microbial and detritivore activities are positively correlated across global grasslands. These correlations are shaped more by global climatic factors than by local treatments, with annual precipitation and soil water content explaining the majority of the variation. Nutrient addition tends to reduce microbial activity by enhancing plant growth, while herbivore reduction typically increases microbial and detritivore activity through increased soil moisture. Our findings emphasize soil moisture as a key driver of soil biological activity, highlighting the potential impacts of climate change, altered grazing pressure, and eutrophication on nutrient cycling and decomposition within grassland ecosystems.

Tree pathogens threaten the survival of many forest foundation tree species worldwide. However, there is limited knowledge of how dieback of foundation tree species may threaten other components of forest ecosystems, such as soil biodiversity and associated ecosystem functions. Kauri (Agathis australis), threatened by the root-borne pathogen Phytophthora agathidicida, are culturally and ecologically significant tree species that exert great influence on soil properties. We aimed to characterise soil mesofauna community structure and energy fluxes in kauri forests and assess the potential threat that tree pathogens such as P. agathidicida pose to belowground ecosystems. We sampled soil mesofauna communities and identified specimens to functional feeding groups at 24 pairs of kauri and adjacent broadleaf trees in sites across the Waitākere Ranges Regional Park, Aotearoa – New Zealand. We attributed kauri canopy health scores, measured tree diameter, slope, forest floor depth, and soil carbon dioxide efflux. We also analysed soil samples for P. agathidicida presence, total carbon, and total nitrogen. We constructed soil mesofauna food webs associated with kauri and broadleaf trees, and assessed the uniqueness of food webs associated with kauri and the impacts of P. agathidicida on density, biomass, mean body mass, and energy fluxes of mesofauna taxonomic and trophic groups. We found omnivores with larger body mass at kauri where P. agathidicida was detected (i.e., P. agathidicida-positive soils). Compared to broadleaf trees, mesofauna density and biomass were lower in soils under kauri, and body masses of Symphyla and omnivores were smaller in soils under kauri. Differences in mesofauna community response variables between tree types were mainly modulated by the soil C:N ratio, which had positive effects under broadleaf and neutral to negative effects under kauri. Energy fluxes to detritivores and fungivores were greater under larger trees, regardless of tree type or P. agathidicida detection status. Our findings suggest that kauri support soil mesofauna food webs that are distinctly different from those found under broadleaf trees in the same habitat. A decreased presence of this foundation species may be linked to future impacts on soil mesofauna in this forest ecosystem with increasingly advanced stages of kauri dieback.

Abstract Soils provide essential ecosystem functions that are threatened by climate change and intensified land use. We explore how climate and land use impact multiple soil function simultaneously, employing two datasets: (1) observational – 456 samples from the European Land Use/Land Cover Area Frame Survey; and (2) experimental – 80 samples from Germany’s Global Change Experimental Facility. We aim to investigate whether manipulative field experiment results align with observable climate, land use, and soil multifunctionality trends across Europe, measuring seven ecosystem functions to calculate soil multifunctionality. The observational data showed Europe-wide declines in soil multifunctionality under rising temperatures and dry conditions, worsened by cropland management. Our experimental data confirmed these relationships, suggesting that changes in climate will reduce soil multifunctionality across croplands and grasslands. Land use changes from grasslands to croplands threaten the integrity of soil systems, and enhancing soil multifunctionality in arable systems is key to maintain multifunctionality in a changing climate.

Abstract Global change is affecting soil biodiversity and functioning across all terrestrial ecosystems. Still, much is unknown about how soil biodiversity and function will change in the future in response to simultaneous alterations in climate and land use, as well as other environmental drivers. It is crucial to understand the direct, indirect and interactive effects of global change drivers on soil communities and ecosystems across environmental contexts, not only today but also in the near future. This is particularly relevant for international efforts to tackle climate change like the Paris Agreement, and considering the failure to achieve the 2020 biodiversity targets, especially the target of halting soil degradation. Here, we outline the main frontiers related to soil ecology that were presented and discussed at the thematic sessions of the World Biodiversity Forum 2022 in Davos, Switzerland. We highlight multiple frontiers of knowledge associated with data integration, causal inference, soil biodiversity and function scenarios, critical soil biodiversity facets, underrepresented drivers, global collaboration, knowledge application and transdisciplinarity, as well as policy and public communication. These identified research priorities are not only of immediate interest to the scientific community but may also be considered in research priority programmes and calls for funding.

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

Abstract Global change alters ecological communities with consequences for ecosystem processes. Such processes and functions are a central aspect of ecological research and vital to understanding and mitigating the consequences of global change, but also those of other drivers of change in organism communities. In this context, the concept of energy flux through trophic networks integrates food‐web theory and biodiversity‐ecosystem functioning theory and connects biodiversity to multitrophic ecosystem functioning. As such, the energy‐flux approach is a strikingly effective tool to answer central questions in ecology and global‐change research. This might seem straight forward, given that the theoretical background and software to efficiently calculate energy flux are readily available. However, the implementation of such calculations is not always straight forward, especially for those who are new to the topic and not familiar with concepts central to this line of research, such as food‐web theory or metabolic theory. To facilitate wider use of energy flux in ecological research, we thus provide a guide to adopting energy‐flux calculations for people new to the method, struggling with its implementation, or simply looking for background reading, important resources, and standard solutions to the problems everyone faces when starting to quantify energy fluxes for their community data. First, we introduce energy flux and its use in community and ecosystem ecology. Then, we provide a comprehensive explanation of the single steps towards calculating energy flux for community data. Finally, we discuss remaining challenges and exciting research frontiers for future energy‐flux research.

Human-induced global environmental change is predicted to alter the stability and functioning of ecosystems worldwide. Most research in recent decades has focused on studying climate-change effects on aboveground systems, causing a poor understanding of belowground responses. However, gaining knowledge on environmental-change effects on soil biota is of crucial importance, as soil-ecosystem services are indispensable for human well-being and contribute fundamentally to the functioning of terrestrial ecosystems. Nematode communities play a central role in various soil ecosystem processes and are therefore commonly used as biological indicators to assess soil conditions and soil health. While causing overall shifts in community composition patterns, which are most often examined, climate change might also alter nematode population dynamics and the sex ratio (number of males per female). Previous studies on plant-parasitic nematode species suggest that changes to unfavorable environmental conditions trigger reduced development of females and favor sexual rather than parthenogenetic reproduction. Therefore, we are presenting the working hypothesis that predicted climate change causing reduced resource availability and enhanced environmental stress will lead to an increased proportion of males in soil nematode communities. Our systematic literature review revealed that climate- and environmental change effects on the sex ratio of free-living soil nematode populations are inconsistent, but heavily understudied. Data on sex ratios have been treated mostly as additional information, presented without any underlying theory and hypotheses, as well as limited discussion. In this perspective paper, we thus propose that future studies should include clear hypotheses and test if the sex ratio of free-living nematodes increases with climate change due to more stressful environmental conditions and low resource availability. Furthermore, we conclude that experimental studies investigating the specific roles of male and female nematodes are needed to better predict the implications of a changing climate on soil ecosystem functioning.