Thinning counteracts drought-induced reduction in soil interception capacity during heavy rainfall in a larch plantation

Forest management and climate change critically shape forest ecosystem functions. The efficacy of thinning in mitigating drought impacts on forest soil–water conservation remains uncertain. In this study, hydrogen stable isotopes were used to quantify the contribution of rainfall to soil water (CRSW) under a four-year experiment combining precipitation reduction (−30%), thinning (45% of trees removed), and their interaction in a Larix kaempferi plantation. We found that prolonged precipitation reduction significantly reduced the contribution of heavy rainfall to soil water (CHRSW) by 8.15%–9.88%. However, thinning alone or combined with precipitation reduction significantly increased CHRSW by 11.47%–13.27% and 6.52%–8.77%, respectively. Additionally, the influence of canopy, understory vegetation, and litter on CHRSW declined with soil depth, while soil and root properties persistently affected CHRSW across 0–40 ​cm depths. Crucially, the positive effects of thinning on these variables consistently outweighed the negative impacts of precipitation reduction, resulting in a net increase in CHRSW. Therefore, thinning effectively mitigates drought-associated declines in soil interception capacity during heavy rainfall, indicating its potential as a climate-adaptive management strategy for sustaining soil–water conservation functions in managed forests.