黄土丘陵沟壑区主要水保林类型及草地水保效益的研究

A STUDY ON BENEFITS OF SOIL AND WATER CONSERVATION BY MAIN WOODLAND AND GRASSLAND TYPES IN LOESS HILLY REGION

本文分析了黄土丘陵沟壑区主要水保林类型及草地水保效益动态的观测资料,结果表明:柠条成林、刺槐成林、沙棘林保水保土效益好,柠条幼林及沙棘与油松、杨树混交幼林保土效益低于荒坡;林地的侵蚀量与林地的覆盖度呈二次多项式关系,并呈负相关,且覆盖度60％～70％为有效盖度;在林冠郁闭度相近情况下,林地活地被物层盖度越大,林地土壤侵蚀量越小;降雨强度特别是暴雨对林地的径流和冲刷影响极大,而且水土流失主要由暴雨造成,其流失量为总量的20％～97％;人工牧草地水保效益均高于农地,以沙打旺草地最好。

The effects of water conservation and sediment reduction of nine woodland types and five grassland types in loess hilly region were analysed in the paper.The results of the experiment showed that the benefits of soil and water conservation in the plantations of Caragana microphylla and Robinia pseudoacacia were the best of all plantations. Compared with the natural rangland, they reduced runoff and soil loss by more than 90% and 97%, respectively. In the meantime, the young growth of C.microphylla and mixed plantations Hippophae rhamnoides with Pinus tabulaeformis or Populus benefited the water conservation, but did not benefit the sediment re- duction, they reduced only runoff by 40%, but increased soil loss. The relationship between the erosion modulus of woodland and its cover degree was an equation in quadratric multinomial and 60～70% of cover degree was regarded as effective cover degree for soil and water conservation. Under the same canopy density the erosion modulus reduced with ground cover increase.Rain intensity, especially storm,affected strongly runoff and erosion in woodland,and the water loss and soil erosoin were caused dominantly by storm. The conservation benefits in artificial grassland were better than that in farmland. Among them Astragalus adsurgens grassland was the best