西双版纳热带季节雨林土壤含水量的时空格局及其与降水的关联

Spatial-temporal pattern of soil water content and its response to precipitation in a tropical seasonal rain-forest in Xishuangbanna

以云南省西双版纳热带季节雨林为研究对象,基于2006—2020年国家野外科学观测站土壤含水量及降水量的动态监测数据,分析在极端降水加剧背景下土壤水分的时空动态特征,从土壤含水量的角度探究热带季节雨林涵养水源的机制。结果表明:2006—2020年西双版纳热带季节雨林年平均土壤含水量总体保持稳定,其年际变异系数较低,但具有明显的季节动态变化规律,雨季显著高于旱季;土壤含水量沿土壤垂直剖面呈“C”型格局,即中层土壤含水量较低,而表层与深层土壤含水量明显高于中层;近年来,西双版纳地区极端降水事件频发,降水量波动增大,但该地区热带季节雨林的土壤含水量的变化明显滞后于降水变化,且能通过不同季节、不同层土壤水分散失和补给的时空动态平衡保持土壤含水量的相对稳定。本研究解析了西双版纳热带季节雨林土壤含水量的时空演变特征及其与降水的关系,证明了在降水不稳定性加剧的气候背景下热带季节雨林仍能保持土壤含水量稳定,即热带季节雨林具有较强的调蓄降水、涵养水源的能力,这为认识热带季节雨林的重要生态功能提供了数据支撑。

To understand the spatial-temporal dynamics of soil water content under precipitation fluctuations espe-cially 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 sea-son 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.Xishuang-banna 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 sea-sonal rainforests.