Climate change-driven shifts in plant-soil feedbacks: a meta-analysis

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.