在黄土高原,植被重建是减少水土流失改善区域生态环境的有效措施,因而植被重建对水分循环的影响成为黄土高原地区生态环境问题研究的核心。论文利用流域对比分析法,以位于甘肃省西峰市南小河沟流域的一条森林小流域和一条荒坡草地小流域为对象,通过对1956～2000年水文要素的监测和分析,得出:44年内森林植被累积减少地表径流37％;前15-20年内植被减流作用随树龄的增长而增加,后24～30年植被的减流作用几乎保持不变;月径流量的减少主要集中在6-9月份;森林小流域相对于对比小流域,44年内土壤含水量累积减少约222mm,平均每年减少5mm;而蒸散量相对荒坡草地流域累积增加了620mm,平均每年多蒸散14mm。

Soil erosion results in soil degradation, pollutes water resource, blocks riverways and ditches, and imperils eco-environmental construction in Northwest China, especially in the gully region of the Loess Plateau.Re-vegetation is an effective method to reduce soil and water loss and improve eco-environment in the Loess Plateau.Therefore,the impacts of re-vegetation on water cycle have been one of the key issues in eco-environmental study in the loess region.Using a paired watershed approach,the impacts of re -vegetation on water cycle was studied in a watershed on the Loess Plateau during the period of 1956 to 2000.Deciduous trees,including locust (locusta L.),apricot (praecox L.)and elm (ulmus L.),were planted on a watershed with treated area exceeding 80% ,while a natural grassland watershed remained unchanged.The cumulative runoff yield in the treated watershed was reduced by 37% as a result of afforestation in 44 years.During the first 15-20 years,annual runoff reduction increased with the increase of the age of the trees planted and it didn't change much during the next 24-30 years. Reduction in monthly runoff occurred mainly from June to September.Compared with the natural grassland watershed,cumulative reduction of volumetric water content was about 222mm as a result of afforestation at a rate of 5mm per year.The cumulative evapotranspiration in treated watershed comparatively increased by 620mm at a rate of 14mm per year,which will cause soil desiccation.