The role of clipping and burning in modulating soil organic carbon stability in karst ecosystems of southwest China: A stoichiometric analysis

Clipping and burning is a traditional land reclamation practice used in forest plantations commonly employed for site preparation and plant disease control. While effective in these roles, it can severely degrade soil mineral properties, soil nutrients, and microbial traits, affecting soil organic carbon (SOC) dynamics. However, its specific impacts on the physical fractions of SOC in the karst landscapes of southwest China is still largely unexplored. Understanding these impacts could offer valuable insights into enhancing SOC stability in such fragile ecosystems. This study intended to evaluate the putative regulatory mechanisms governing physical fractions and stability of SOC by analyzing the impact of five different "clipping and burning" management practices that include high-intensity fire (HIF), low-intensity fire (LIF), clipping and fire (CF), clipping (CP), and an unmanipulated control (CK). To better understand the general constraints of physical fractionation and SOC stability in the karst land, labile particulate organic carbon (POC) and stable mineral associated organic carbon (MAOC) were determined. Our findings suggest that both SOC and MAOC declined to (34 % and 49 %) under HIF relative to CK, while POC was increased by 20 % in CF. These results suggest that SOC and its fractions appear partially sensitive to clipping-and-burning. The MAOC:SOC ratios were significantly (p < 0.05) elevated in CF, with a value of 0.57, compared to all other treatments. While MAOC:POC ratio was reduced significantly (p < 0.05) compared to CK. The increased MAOC:SOC ratio in CF treatment suggests that clipping-and-burning enhances the stabilization of SOC, likely by promoting the formation of more stable MAOC, while microbial activity and enzyme activity were more pronounced under CP treatment, likely reflecting a shift toward microbial-driven decomposition of organic matter. Additionally, structural equation modeling (SEM) and the Random Forest (RF) model revealed that soil nutrients and microbial activity directly influence SOC fractions, while soil minerals showed a stronger link to MAOC:SOC. These highlight the role of clipping-and-burning in shaping SOC stability in karst soils and offer important insights for managing carbon storage in the karst landscapes of southwest China.