黄土高原人工林对区域深层土壤水环境的影响

通过对典型黄土区 1 0m土层土壤水分的分析表明 :黄土高原土壤深层具有丰富的土壤水资源 ,3～ 1 0m土层内土壤水资源从南部的 1 0 86.8mm逐渐降低到北部的 5 2 4.1mm ,各地土壤水资源量约相当于当地多年平均降水量的 2倍。在 1 0m土壤水分剖面内 ,随土层深度的变化土壤含水量具有波动性和相对稳定性的特征。以荒坡地或低产农田为对照 ,通过对比分析发现 ,黄土高原目前主要的造林树种可利用 9～ 1 0m以下土层的土壤水资源。在黄土高原半干旱气候背景下 ,人工林植被的耗水主要使黄土区中北部地区 3～ 8m土层土壤含水量降低到长期接近或低于凋萎湿度 ,形成难以恢复的深厚土壤干层。人工林大量耗水形成的难以恢复的土壤干层是黄土高原特殊的生态水文现象 ,是目前区域人工植被生态系统不稳定性的体现。同时表明 ,黄土高原营造的人工林尚不能达到涵养水源之功能。

IMPACT OF ARTIFICIAL FOREST ON SOIL MOISTURE OF THE DEEP SOIL LAYER ON LOESS PLATEAU

By the analysis of soil moisture profile of 10 m deep it shown that there is very abundant soil water resources (SWR) on Loess Plateau, SWR amount in the 3~10 m depths is 1 086.8 mm in the south and 524.1 mm in the north on Loess Plateau. SWR amount of various sites is about two times of rainfall amount in the same sites. There was a fluctuation and relatively steady of soil moisture change with soil layer deep. By comparing soil moisture of the control sites with artificial forest land it was found that mainly artificial tree types in Loess Plateau could take up soil moisture from 9~10 m deep soil layer and caused the dried soil layer of 3~8 m soil layer, of which soil water content is nearly to or lower wilting point during longterm. Dried Soil layer was a special phenomenon of eco-hydrology and also was an indicator the instability of artificial forest vegetation on Loess Plateau. It shown that artificial forest vegetation did not currently has function to conserve water supply on Loess Pleatu.