Responses of soil organic carbon to climate extremes under warming across global biomes

The impact of more extreme climate conditions under global warming on soil organic carbon (SOC) dynamics remains unquantified. Here we estimate the response of SOC to climate extreme shifts under 1.5 degrees C warming by combining a space-for-time substitution approach and global SOC measurements (0-30 cm soil). Most extremes (22 out of 33 assessed extreme types) exacerbate SOC loss under warming globally, but their effects vary among ecosystems. Only decreasing duration of cold spells exerts consistent positive effects, and increasing extreme wet days exerts negative effects in all ecosystems. Temperate grasslands and croplands negatively respond to most extremes, while positive responses are dominant in temperate and boreal forests and deserts. In tundra, 21 extremes show neutral effects, but 11 extremes show negative effects with stronger magnitude than in other ecosystems. Our results reveal distinct, biome-specific effects of climate extremes on SOC dynamics, promoting more reliable SOC projection under climate change. Warming temperatures associated with climate change are expected to impact soil carbon stocks, yet the effect of more frequent and intense extreme climate events on soil carbon is yet unclear. This study shows that most extremes enhance soil carbon loss globally, with variation across ecosystems.