Ecosystems are projected to experience altered precipitation patterns associated with climate change, with some areas becoming wetter and others drier. Both above‐ and belowground communities will be impacted by such rainfall changes, yet research has predominantly focused on the flora and fauna aboveground. Still, there is a growing body of literature for the effects of altered precipitation on soil fauna. Nematodes are diverse and abundant in most soils, represent multiple trophic levels, and influence essential soil processes, making this group a good proxy for broader impacts on soil food webs. Hence, we assessed the effects of increased and reduced rainfall amount on total and trophic‐level abundances of nematodes using a meta‐analytical approach based on 46 independent observations from 37 field studies and tested whether effects differed among ecosystem types and with treatment duration (1 year, long term). Overall, total and trophic group's abundances, except fungal feeders, were negatively impacted by reduced rainfall irrespectively of treatment duration. Increased rainfall had a positive effect on total abundances and plant parasitic nematodes, but only in longer term studies (>1 year). The impacts of altered rainfall were consistent across the ecosystems studied; however, most studies focus on grasslands and deserts, making it difficult to draw broad generalizations. Reductions in rainfall are therefore likely to decrease soil nematode abundance, with less pronounced effects on fungal feeders. Increased rainfall, on the other hand, may favor plant parasites, likely due to increased plant productivity. Hence, projections of reduced rainfall will have significant negative impacts on nematode abundances, at least in grasslands and deserts, with cascading effects on soil processes.

Background: Climate change is expected to affect plant–soil feedbacks (PSFs, i.e., the effects of a plant on the growth of another plant or community grown in the same soil via changes in soil abiotic and biotic properties), influencing plant community dynamics and, through this, ecosystem functioning. However, our knowledge of the effects of climate changes on the magnitude and direction of PSFs remains limited, with considerable variability between studies. We quantified PSFs associated with common climate change factors, specifically drought and warming, and their corresponding ambient (control) conditions using a meta-analytical approach. We investigated whether drought and warming effects on PSFs were consistent across functional groups, life histories (annual versus perennial) and species origin (native versus non-native), planting (monoculture, mixed culture) and experimental (field, greenhouse/laboratory) conditions. Results: PSFs were negative (a mechanism that encourage species co-existence) under drought and neutral under corresponding ambient conditions, whereas PSFs were negative under both ambient and elevated temperatures, with no apparent difference in effect size. The response to drought was largely driven by stronger negative PSFs in grasses, indicating that grasses are more likely to show stronger negative PSFs than other functional groups under drought. Moreover, non-native species showed negative drought-induced PSFs while native species showed neutral PSFs under drought. By contrast, we found the opposite in pattern in response to warming for native and non-native species. Perennial herbs displayed stronger drought-induced negative PSFs than annual herbs. Mixed species communities displayed more negative PSFs than monocultures, independent of climate treatment. Finally, warming and drought treatment PSF effect sizes were more negative in experiments performed in the field than under controlled conditions. Conclusions: We provide evidence that drought and warming can induce context-specific shifts in PSFs, which are dependent on plant functional groups, life history traits and experimental conditions. These shifts would be expected to have implications for plant community dynamics under projected climate change scenarios.

Background and aims: Both soil properties and plant traits shape the diversity, composition and functions of plant-associated soil microbial communities. However, the relative influence of these factors is poorly understood, as are interactive effects between factors and the degree to which their influence varies among climate zones. Methods: To address this gap, we compared the diversity and composition of soil microbial communities associated with co-occurring C₃ and C₄ grasses from arid and mesic environments, and plant traits influencing them. Results: Climate emerged as the main determinant of plant traits and microbial community properties. Within each climatic region, above- and below-ground traits and soil properties differentially affected microbial community composition, and their relative influence varied among communities. In both mesic and arid environments aboveground traits related to quantity and quality of leaf litter (e.g., specific leaf area, leaf C content) and nutrient availability were the most influential variables for community composition. However, in arid regions, belowground traits (i.e., root tissue density and specific root area) significantly contributed to structure the eukaryotic community, supporting the role of roots as important driver of eukaryotic differentiation in constrained environments. Further, the presence of C₄ plants in the arid region resulted in higher relative abundance of ciliate protists and higher recruitment of potentially beneficial microbial community members from green algae mediated by drought adaptation traits (e.g. decreased abundance of fine roots). Conclusions: Overall, our study revealed a differential response of microbial communities to environmental conditions, suggesting that soil microbial community composition is influenced by trade-offs between host adaptive traits across distinct climatic regions.

Drought may impact plant–soil biotic interactions in ways that modify aboveground herbivore performance, but the outcomes of such biotic interactions under future climate are not yet clear. We performed a growth chamber experiment to assess how long‐term, drought‐driven changes in belowground communities influence plant growth and herbivore performance using a plant–soil feedback experimental framework. We focussed on two common pasture legumes—lucerne, Medicago sativa L., and white clover, Trifolium repens L. (both Fabaceae)—and foliar herbivores—cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), and two‐spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Soil was collected from a field facility where rainfall had been manipulated for 6 years, focussing on treatments representing ambient rainfall and prolonged drought (50% reduction relative to ambient), to consider the effects of biological legacies mediated by the prolonged drought. All soils were sterilized and re‐inoculated to establish the respective home (i.e. where a given plant is cultivated in its own soil) and away (i.e. where a given plant is cultivated in another species' soil) treatments in addition to a sterile control. We found that the relative growth rate (RGR) and relative consumption of larvae were significantly lower on lucerne grown in soil with ambient rainfall legacies conditioned by white clover. Conversely, the RGR of insect larvae was lower on white clover grown in soil with prolonged drought legacies conditioned by lucerne. Two‐spotted spider mite populations and area damage (mm²) were significantly reduced on white clover grown in lucerne‐conditioned soil in drought legacies. The higher number of nodules found on white clover in lucerne‐conditioned soil suggests that root–rhizobia associations may have reduced foliar herbivore performance. Our study provides evidence that foliar herbivores are affected by plant–soil biotic interactions and that prolonged drought may influence aboveground–belowground linkages with potential broader ecosystem impacts.