Drought-induced soil carbon dynamics in subtropical forests: emergent divergence from model structures

Abstract. Accurately quantifying drought impacts on terrestrial carbon cycling is essential for advancing predictions of climate-carbon feedbacks. However, current biogeochemical models exhibit limited capability in simulating drought-induced transformations of soil organic carbon (SOC), particularly regarding microbial processes. Here, we conducted a systematic comparative evaluation of three prevailing SOC modeling structures, including conventional three-pool partitioning scheme (SM1), mineral and particulate- associated carbon partitioning scheme (SM2) and Michaelis-Menten regulated carbon-stabilization scheme (SM3), to elucidate their capacity in simulating soil carbon dynamics under decadal drought scenarios in a subtropical forest. We found divergent effects of drought in soil C input (SM1, 66 %; SM2, 10 %; SM3, −4 %) and mean residence time (MRT; SM1, −31 %; SM2, −14 %; SM3, 65 %), which lead to the predicted SOC substantial accumulation for both SM1 and SM3 (+39.5 % and +56.9 %, respectively) and moderate depletion (−6.1 %) for SM2. Drought leads to a decrease in microbial carbon and an increase in POC, while the responses of other carbon pools vary across different models