金沙江干热河谷人工植被土壤水环境

金沙江干热河谷异常干热的气候特点，普遍存在水分亏缺问题，人工植被土壤水环境问题比其它干旱、半干旱地区更加突出．在干热河谷典型地段——元谋的试验观测表明，现有的乔木林明显表现出“土壤干化”的特点，土壤水分持续长时间亏缺，雨季结束之后的11月份。2m土层内的土壤含水量只有15％(相当于田间持水量的35％)左右，之后持续下降，直到5月份达到最低点(9％左右)，几乎接近林木的凋萎湿度(元谋表蚀燥红壤的凋萎湿度为9．O％)．由此而导致林木生长缓慢．车桑子(Radonaea wiscosa)灌木林同层土壤含水率相对比乔木林高42．68％，自然草坡的土壤水分明显优于乔木和灌木林，分别比乔木林和灌木林高34．36％和22．22％．这种人工乔木林的“土壤干化”问题在干热河谷地区的植被恢复中还没有引起重视，将极大地制约人工植被的可持续发展．

Soil water environment of artificial vegetation in Jinshajiang dry-hot volley

Jinshajiang dry-hot volley has the characteristics of extremely hot and dry climate due to its specific local climate,where universally exists moisture deficit and the problem of soil water environment of artificial vegetation becomes more serious than other arid and semi-arid areas.The environmental determination in the typical sector of dry-hot volley Yuanmou showed that the existed arboreous forests evidently showed the characteristics of soil drying.Soil was short of moisture for a long term.In November after the rain season was over,soil water content in two-meter-deep soil layer was only 15% (equal to 35% of field capacity).Later on,soil water content continued decreasing and reached the lowest point in May (9%),which was near to wilting moisture of trees (the wilting moisture of surface eroded dry red soil of Yuanmou was 9.0%).As a result,trees grew slowly.As for Radonaea wiscosa shrubbery,its soil water content at the same layer was relatively 42.68% higher than that of arboreous trees.The soil moisture of natural grass slope was evidently better than that of arboreous trees and shrubbery,and was 34.36% and 22.22% higher,respectively.This kind of soil drying problem didn't come into notice in the vegetation restoration of Jinshajiang dry-hot volley,which would greatly restrict the sustainable development of artificial vegetation.