黄土丘陵区山桃灌木林地土壤水分过耗与调控恢复

在黄土丘陵区的荒山荒坡采用工程整地措施 ,进行灌草合理布局与立体配置。研究结果表明 :山桃灌木林生长到第 4年 ,根系的分布深度达 3 2 0～ 3 60cm ,0～ 5 0 0cm土壤含水量比造林前降低了2 1～ 3 3个百分点 ,土壤干层厚度为 1 5 0cm ;生长到第 8年 ,根系的分布深度达 480cm以上 ,土壤干层由第4年 1 5 0cm扩大到 3 0 0cm ,含水量最低为 4 2 % ,最高为 8 4% ;生长的第 1 2年土壤干层明显 ,尤其是 5 0～40 0cm土壤含水量最低为 5 0 % ,最高为 8 6% ,土壤干层厚度达 3 5 0cm ;生长的第 1 6年土壤干层的分布深度在 5 0～ 3 5 0cm ,土壤含水量最低为 4 3 % ,最高为 6 6% ,土壤干层厚度达 3 0 0cm。但通过水平阶、水平沟和鱼鳞坑整地调控 ,0～ 1 0 0cm土壤含水量分别比荒山提高 0 7～ 6 3个百分点 ;1 0 0～ 3 0 0cm提高 0 6～ 4 6个百分点 ;3 0 0～ 5 0 0cm提高 1 4～ 4 6个百分点 ,这充分表明采用合理的整地措施造林 ,土壤水分调控效果显著。

EXCESSIVE DEPLETION OF SOIL WATER AND REGULATION AND RESTORATION OF SOIL WATER REGIME IN LOESS HILLY REGION UNDER PRUNUS DA VIDIANA VEGETATION

Engineering measures, and reasonable and stereoscopic collocation of shrub-grass vegetation were performed over on large tracts of barren hills and slopes. The results showed that in the forth growth year, the root system of Prunus davidiana reached 320~360 cm deep, soil water content in the soil layer 0~500 cm deep decreased by 2.1%~3.3% compared to that before reforestation and the thickness of dry soil layer was 150 cm. And in the eighth growing year, the roots distributed as deep as 480 cm, the dry-layer reached 300 cm in thickness, the lowest and highest soil water content was 4.2% and 8.4% respectively. And in the twelfth year, the dry soil layer became very distinct, reaching 350 cm in thickness, and, especially in the 50~400 cm soil layer, the lowest and highest soil water content was 5.0% and 8.6%, respectively. While in the sixteenth year, the dry soil layer distributed in the depth of 50~350 cm, and its thickness was 300 cm, with the lowest and highest soil water content reaching 4.3% and 6.6%, respectively. But by building leveled terrace fields, contour ditches and fishscale pits, soil water content increased by 0.7%~6.3% in the depth of 0~100 cm, 0.6%~4.6% in 100~300 cm and 1.4%~4.6% in 300~500 cm compared to that in the barren hill, respectively. It showed that applying reasonable combined measures plus afforestation could regulate soil moisture region with significant effect.