ABSTRACT
The joint effects of simultaneous warming and precipitation shifts on soil organic carbon (SOC)—the largest terrestrial carbonpool—remain poorly understood across large spatial extents. By evaluating a global dataset of SOC measurements in the topmeter of soil through a space-for-change substitution approach, we show that, averaging across the globe, increased precipitationcompensates for warming-induced SOC reductions regardless of soil depth and vice versa. Although additive effects betweenthese two factors are predominant, negative interactive effects, which exacerbate SOC losses, are also common, particularly intropical and subtropical grasslands/savannas and Mediterranean/montane shrublands. SOC responses vary widely across theglobe, primarily correlated to baseline SOC content and local climatic conditions. Notably, SOC responses in tundra systems areopposite the responses in other ecosystems, showing positive and negative responses to warming and precipitation increases,respectively. Under a scenario of 2°C air warming with projected precipitation changes, global SOC stocks in the 0–1 m depth areprojected to decrease by 13.1% ± 6.6% (mean ± 95% confidence interval, or 351 ± 100 Pg C). These results demonstrate that accu-rately predicting SOC dynamics under climate change necessitates explicit consideration of local climatic conditions and existingSOC content in relation to concurrent precipitation shifts and warming.