Effective management of understory vegetation is crucial for forest biodiversity conservation and ecosystem functions. However, the impact of various understory management practices on key ecosystem processes, such as soil nutrient cycling in tree crop plantations, remains poorly understood. This study quantified the 7-year cumulative effects on soil organic carbon (SOC) and total nitrogen (STN) stocks in rubber plantations under four understory management practices: (i) conventional management (RC) as the control, (ii) herbicide application (RH), (iii) natural regeneration (RN), and (iv) replacement with leguminous shrub (RA). Compared to RC, RN and RA increased the average number of native and invasive species and produced high above- and belowground biomass. Conversely, RH decreased the species number and belowground biomass. More SOC and STN were stored in 0.0–0.2 m topsoil in both RN (+ 9.6 Mg C ha^–1; + 0.7 Mg N ha^–1) and RA (+ 10.7 Mg C ha^–1; + 0.6 Mg N ha^–1) than RC, while they remained stable in RN but declined in RA from deeper layers of 0.2–1.0 m. Across the entire 1 m soil profile, the annual increment of SOC stocks in RN and RA reached 1.7 and 1.0 Mg C ha^–1 yr^–1, respectively, and of STN stocks reached 0.02 and − 0.14 Mg N ha^–1 yr^–1. However, RH decreased SOC and STN stocks and corresponding annual increments for the entire profile. The variations in SOC and STN stocks in the topsoil were attributed primarily to aboveground biomass and determined by belowground biomass in the deeper soil. Moreover, litter depth also effectively reflected SOC and STN dynamics. These results suggest that the implementation of natural regeneration and agroforestry system in the understory of rubber plantations offers significant potential for increasing soil C and N stocks. Our findings imply that sustainable understory management practices, especially natural regeneration and agroforestry system, will benefit for understory plants conservation and soil nutrient supply in tree crop plantations.

林下植被的有效管理对于森林生物多样性保护和生态系统功能至关重要。然而，各种林下管理实践对关键生态系统过程（例如木本作物种植园土壤养分循环）的影响仍然知之甚少。本研究量化了四种林下管理措施对橡胶园土壤有机碳 (SOC) 和总氮 (STN) 储量的 7 年累积影响：(i) 常规管理 (RC) 作为对照，(ii) 除草剂施用（ RH），（iii）自然更新（RN），以及（iv）豆科灌木替代（RA）。与 RC 相比，RN 和 RA 增加了本地和入侵物种的平均数量，并产生了较高的地上和地下生物量。相反，相对湿度降低了物种数量和地下生物量。^–1 ; + 0.7 Mg N ha ^–1 ) 和 RA (+ 10.7 Mg C ha ^–1 ; + 0.6 Mg N ha ^–1 ) 高于 RC，而它们在 RN 中保持稳定，但在 RA 中从 0.2-1.0 m 更深的层开始下降。在整个1 m土壤剖面上，RN和RA的SOC库年增量分别达到1.7和1.0 Mg C ha ^–1  yr ^–1，STN库的年增量分别达到0.02和− 0.14 Mg N ha ^–1  yr ^–1。然而，RH 降低了 SOC 和 STN 库存以及整个剖面的相应年度增量。表土中 SOC 和 STN 储量的变化主要归因于地上生物量，并由深层土壤中的地下生物量决定。此外，凋落物深度还有效地反映了SOC和STN动态。这些结果表明，在橡胶种植园林下实施自然更新和农林复合系统为增加土壤碳和氮储量提供了巨大潜力。我们的研究结果表明，可持续的林下管理实践，特别是自然更新和农林复合系统，将有利于林下植物保护和木本作物种植园的土壤养分供应。