土壤侵蚀,有效耕地面积减少,粮食产量低而不稳是黄土高原区山地农田(即坡耕地)生态系统脆弱的主要表现。其根本原因是以往不合理的经营,过度垦荒,造成植被严重破坏。因此,建立一个高效而稳定的山地农田生态系统已成为刻不容缓的任务。营造山地农田防护林可改变旧有的农业生态系统而发挥多种效益的功能,它不仅能防止水土流失,减轻各种自然灾害,改善这一地区的小气候、水文、土壤和生物因素,促进农业稳定高产,同时也起到用材林、薪 Soil erosion, reduction of effective cultivated area and low and unstable grain yield are the main manifestations of the fragile ecosystem in mountainous farmland (ie, sloping farmland) in the Loess Plateau. The root cause is the unreasonable management in the past and the excessive reclamation of wasteland, causing serious damage to vegetation. Therefore, establishing an efficient and stable mountain farmland ecosystem has become an urgent task. The function of mountain farmland shelterbelts that can change the old agroecosystem and play its multiple benefits can not only prevent water and soil loss, mitigate various natural disasters, improve microclimate, hydrology, soil and biological factors in this area, and promote agricultural stability High yield, but also play a timber forest, salary