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Soil fauna plays a key role in regulating biogeochemical cycles, but how multiple global change factors (GCFs) may affect faunal communities remains poorly studied. We conducted a meta‐analysis using 1154 observations to evaluate the individual and combined effects of elevated CO2, nitrogen (N) addition, warming, increased rainfall and drought on soil fauna density and diversity. Here we show that, overall, individual and combined effects of GCFs had negligible effects on soil fauna density and diversity, except that density was negatively affected by drought (−27.4%) and positively affected by increased rainfall individually (+24.9%) and in combination with N addition (+67.3%) or warming (+70.4%). GCF effects varied among taxonomic groups both in magnitude and direction. Variables such as latitude, elevation and experimental setting significantly impacted both individual and combined effects. Our results suggest that soil fauna density is affected by changed rainfall regimes, while diversity is resistant against individual and combined effects of multiple GCFs. [ABSTRACT FROM AUTHOR]

Aim: We sought to understand how the individual and combined effects of multiple environmental change drivers differentially influence terrestrial nitrogen (N) concentrations and N pools and whether the interactive effects of these drivers are mainly antagonistic, synergistic or additive. Location: Worldwide. Time period: Contemporary. Major taxa studied: Plants, soil, and soil microbes in terrestrial ecosystems. Methods: We synthesized data from manipulative field studies from 758 published articles to estimate the individual, combined and interactive effects of key environmental change drivers (elevated CO2, warming, N addition, phosphorus addition, increased rainfall and drought) on plant, soil, and soil microbe N concentrations and pools using meta‐analyses. We assessed the influences of moderator variables on these effects through structural equation modelling. Results: We found that (a) N concentrations and N pools were significantly affected by the individual and combined effects of multiple drivers, with N addition (either alone or in combination with another driver) showing the strongest positive effects; (b) the individual and combined effects of these drivers differed significantly between N concentrations and N pools in plants, but seldom in soils and microbes; (c) additive effects of driver pairs on N concentrations and pools were much more common than synergistic or antagonistic effects across plants, soils and microbes; and (d) environmental and experimental factors were important moderators of the individual, combined and interactive effects of these drivers on terrestrial N. Main conclusions: Our results indicate that terrestrial N concentrations and N pools, especially those of plants, can be significantly affected by the individual and combined effects of environmental change drivers, with the interactive effects of these drivers being mostly additive. Our findings are important because they contribute to the development of models to better predict how altered N availability affects ecosystem carbon cycling under future environmental changes. [ABSTRACT FROM AUTHOR]

Soil microbial diversity is one of the key factors affecting the structure and function of the belowground ecosystem; yet, little is known about the response of microbial diversity to multiple global change factors. Here, we conducted a global meta-analysis based on data collected from 237 published papers to explore the effect of multiple global change factors (elevated carbon dioxide (eCO 2), warming, elevated nitrogen addition (eN), wetting–drying cycle, drought, decreased precipitation (precipitation(−)), and increased precipitation (precipitation(+))) on microbial diversity (Shannon index) across different ecosystems (cropland, grassland, forest, shrubland, desert, wetland, and tundra). Global change decreased soil bacterial and fungal diversity by an average of 2.9% and 3.5%, respectively. For each global change factor, the effect sizes of precipitation(−), eN, wetting–drying cycle, and drought on soil microbial diversity were negative, whereas the effect sizes of eCO 2 , warming, and precipitation(+) were positive. This phenomenon was driven by changes in mean annual temperature (MAT) and edaphic factors (especially soil pH, bulk density and organic carbon content) rather than mean annual precipitation. Moreover, the effect size of soil microbial diversity linearly declined with increasing MAT, suggesting that microbial diversity was highly dependent on climate conditions at the global scale. In addition, two- and three-way interactions of global change factors aggravated the negative effects of individual effects. We suggest that it is essential to conduct long-term, multiple-factor experiments to assess the response of soil microbial diversity to global change because multiple global change factors often occur simultaneously. • Negative effect of global change on soil microbial diversity. • Soil fungal diversity was more sensitive to global change factors. • There were combined effects of global change factors on soil microbial diversity. • Soil microbial diversity highly depended on climate conditions. [ABSTRACT FROM AUTHOR]