Abstract: To understand the spatial-temporal dynamics of soil water content under precipitation fluctuations especially extreme precipitations in tropical seasonal rainforest, we analyzed 15 years (2006-2020) data of soil water content at different depths (up to 110 cm) and precipitations in a tropical seasonal rainforest of Xishuangbanna. We found that the annual average soil water content remained stable over the 15 years with a relatively low interannual coefficient of variation (CV). But we detected a pattern of obvious seasonal dynamic because CV of the rainy season was significantly higher than that of the dry season. In addition, soil water content generally followed a “C” shape pattern along the soil vertical profile. Specifically, soil water contents in both shallow and deep depths were significantly higher than that in middle depths. In recent years, extreme precipitation events occurred frequently in Xishuangbanna, with increasing precipitation fluctuation. However, changes of soil water content did not follow the trend of precipitation but rather remained relatively stable through the spatio-temporal dynamic balance of soil water loss and recharge across seasons and soil depths. Our results highlight that the tropical seasonal rainforest in Xishuangbanna could maintain soil water content under fluctuation of precipitations, even extreme ones. Xishuangbanna tropical seasonal rainforest shows a strong ability to regulate soil water content and therefore to conserve water resources. This study provides empirical support for understanding the important ecological functions of tropical seasonal rainforests.

Key words: soil water content, precipitation, tropical forest, water conservation, climate change