Characteristics and Associations of Nutrient Transport with Runoff in Plantation Forests of Xishuangbanna

Rainfall erosion significantly affects nutrient transport in plantation forests, but the internal nutrient-driven mechanism remains unclear. In this study, three types of plantation forests in the Xishuangbanna were selected to examine soil nutrient contents in erosion and deposition zones, nutrient concentration in runoff, and nutrient contents in litter, while the relationship among them was analyzed using the RDA method, aiming at exploring the internal driving mechanism of nutrient transport following erosion caused by the rainy season. The results show that, after the rainy season, the nutrient contents in the soil of all three forest types decreased in the erosion zone, with the most severe changes at the bottom of the slope. Furthermore, the C contents in litter from the three forest types decreased by 8.9% to 14.8% and the K contents decreased by 30.9% to 44.5%, while the N contents increased by 3.7% to 14.8% and the P contents increased in RF and TF but decreased in AF. Based on the RDA, the presence of 81.1% of nutrients in the runoff can be explained by changes in nutrient concentrations in the erosion zone and the nutrient content in the deposition zone. Among these, the contribution rates of D.P, D.K, and DOC were 76.9%, 17.1%, and 6%, respectively, which shows that runoff is the main factor influencing the changes in and deposition of soil nutrients on the slope. The results also attribute 47.57% of nutrients in the runoff to nutrient changes in the litter. This indicates that runoff is not the primary factor influencing nutrient changes in litter; the remaining explained variance may be related to factors such as litter quality, soil animals, microbial activity, and temperature.