Responses of soil C pools to combined warming and altered precipitation regimes: A meta‐analysis

Abstract

AimGlobal warming and altered precipitation substantially affect soil carbon (C) pools and can, in turn, feed back into climate change. However, how soil C pools respond to the combined effects of warming and altered precipitation remains unclear.LocationGlobal.Time period1996–2021.Major taxa studiedSoil organic C pools.MethodA meta‐analysis was performed using 657 observations obtained from 34 published articles that focused on both individual and combined effects of warming and altered precipitation on soil organic C (SOC), dissolved organic C (DOC) and microbial biomass C (MBC) to quantify the responses of soil C pools.ResultsAcross all combined warming and increased precipitation experiments, SOC and MBC increased by an average of 4.0% and 15.4%, respectively. In contrast, warming combined with decreased precipitation led to a substantial decline in SOC and MBC by an average of 8.2% and 12.3%, respectively. The responses of DOC to combined warming and altered precipitation were marginal. The direction and magnitude of the responses to the combined treatment were more similar to those in the individual altered precipitation treatment than to those in the individual warming treatment. Furthermore, these combined effects were substantially influenced by altered precipitation magnitudes. Combined warming and altered precipitation had greater impacts on soil C pools than their individual treatments but were not substantially different from the sum of their respective individual effects, showing overall additive effects. The responses of soil C pools to combined warming and altered precipitation were observed to be more pronounced in grasslands than in forests.Main conclusionThe results demonstrated that altered precipitation regimes often dominated over warming in regulating soil C pools under combined warming and altered precipitation and improved our understanding of soil C cycles under climate change scenarios.

Responses of Soil Nitrogen Pools to Litter Input Under Nitrogen Addition: A Meta‐Analysis

“…Compared to the individual effects of litter input and N addition on soil N pools, we observed greater and additive effects of combined litter input and N addition (Figure 5). These findings align with a broader body of work suggesting that additive effects of multiple global change factors on terrestrial ecosystem functions were more prevalent than synergistic or antagonistic effects (Peng et al., 2022; Wei et al., 2023; Yue et al., 2017). The positive responses of N addition on litter decomposition are noteworthy, as it promotes soil N and P cycling within natural ecosystems, consequently enhancing soil nutrient pools (Pei et al., 2020; J. Wu et al., 2023).…”

Field experiments have enhanced our understanding of drought impacts on terrestrial ecosystems—But where do we go from here?

“…This level of interest is consistent with observations that extreme reductions in vegetation growth globally are commonly linked to extreme reductions in soil water availability (Yang et al., 2023)—a manifestation of drought. Drought experiments are so numerous that they have been subjected to multiple meta‐analyses (from Wu et al., 2011 to Wei et al., 2023) particularly in the last 5 years (Table S1). But what have these collective experiments taught us about ecosystem responses to drought?…”