滇南热带季节雨林和橡胶林对降雨侵蚀力的减缓效应

降雨是影响土壤侵蚀的主要因素,降雨侵蚀力通常用降雨动能和一段时间的最大雨强的乘积表示,简化的计算也可用日降雨量估算。本文选取昆-曼国际大通道滇南段旷地4个气象站(勐腊、勐仑、景洪、思茅)以及1个人工林(橡胶林)和1个热带季节雨林的日降雨量资料,计算了降雨侵蚀力以及随季节变化的规律,比较了森林破坏对降雨侵蚀力的影响。结果表明,昆-曼国际大通道滇南段旷地的降雨侵蚀力干季均较小,雨季逐渐增大,在7、8月达最大;旷地的降雨侵蚀力明显大于橡胶林和热带季节雨林,其差值在干季较小,雨季显著;旷地的年降雨侵蚀力可达到橡胶林的1.8倍以上,是热带季节雨林的2.3倍以上;而月降雨侵蚀力差异最大可达6~7倍;此外橡胶林和热带季节雨林降雨侵蚀力干季相差不大,而雨季橡胶林降雨侵蚀力明显大于热带季节雨林。说明了水土保持效果橡胶林和热带季节雨林比旷地要好,而热带季节雨林的效果要比橡胶林好;森林破坏将极大地增加降雨侵蚀力,加速水土流失。

Release effects of tropical seasonal rain forest and rubber forest on rainfall erosivity in South Yunnan

Rainfall is a main factor affecting soil erosion.Its erosivity is usually estimated by the product of rain kinetic energy times the biggest rain density during a certain period,and also,can be determined by the daily rainfall amount.With the daily rainfall data collected from four meteorological stations(Mengla,Menglun,Jinghong and Simao) and from tropical seasonal rain forest and rubber forest,this paper analyzed the rainfall erosivity and its seasonal variation in Xishuangbanna,and studied the effects of deforestation on the rainfall erosivity.The results showed that the rainfall erosivity in Xishuangbanna was smaller in dry season(November-April),but increased gradually in rainy season and got its maximum in July and August.The rainfall erosivity was bigger in four meteorological stations than in tropical seasonal rain forest and rubber forest,and bigger in rubber forest than in tropical season rain forest,which was more notable in rainy season than in dry season.The results obtained in this study could be served as the scientific basis for the further research on water and soil loss due to deforestation.