金沙江干热河谷典型区(云南省)土壤退化机理研究 Ⅱ 土壤水分与土壤退化

MECHANISMS INVOLVED IN SOIL DEGRADATION IN DRY ANDHOT VALLEYS IN JINSHAJIANG RIVER AREA,YUNNAN PROVINCE:Ⅱ SOIL WATER AND SOIL DEGRADATION

在金沙江干热河谷地区 ,存在以土壤退化为主要形式的土地荒漠化和水资源匮乏这两大生态环境问题。试比较不同退化程度土壤在土壤水分及特性方面产生的差异 ,研究土壤水分特性对土壤退化的作用机理。通过对金沙江干热河谷典型区 (云南省 )不同退化程度的燥红土水分特性的对比研究 ,发现退化土壤 PWP(凋萎湿度 )增加 ,而 FC(田间持水量 )和 BCM(毛管联系断裂含水量 )降低 ,使植物可利用的有效水范围变窄 ;退化土壤的入渗速率减小 ,渗透性减弱 ,在降雨入渗 90 min后 ,未退化燥红土的入渗速率降低 5 4 % ,而退化的燥红变性土却下降了 94 %。因土壤的水分蒸发量和蒸发速度加快 ,导致土壤持水能力降低和抗旱性显著减弱。未退化燥红土在有效水的两个蒸发阶段 ,土壤含水量降低速度小于退化燥红土 ,有效水蒸发历时达 82 .5 h,表蚀燥红土仅有 4 5 .9h,同时 ,未退化燥红土的水容量在低吸力阶段高于退化燥红土 ,但在水分蒸发阶段失水比却低于退化燥红土。由于有效含水量的降低 ,退化土壤即使雨季处于水分亏缺时期也超过 4 5 d。

The eco-environmental land desertification,as predominated by soil degradation,and shortage of water resources have been the serious problems in the dry and hot valleys of Jinshajiang River Area. The disparities in water property in soils of different degradation degrees have been investigated in relation to the mechanisms of soil degradation.By comparing the soil water properties of dry red soils in different degradations in Jinshajiang River Area, Yunnan Province,it is found that in degraded soil the PWP increases,and the FC and BCM decrease.The range of water available for plants also becomes narrower in the degraded soil.The permeability of degraded soil declines because of the reduction of the soil infiltration rate.Moreover,the increase of the soil water evaporation rate further incuces the water holding capabilities in the soil.It is predicted that the time of water efficiency may exceed 45 days even in rain season,duo to the reduction of available soil water.Thus,the inferiority of the soil water property in this area may result in the occurrence or aggravation of soil degradation.