泾河流域不同时期土壤侵蚀状况及分区的植被建设研究

从20世纪80年代到2003年，泾河流域侵蚀呈更强的发展态势。其中，极强和剧烈侵蚀比重分别增加了1.30%和1.97%。按照侵蚀模数所属侵蚀等级，把2000年流域土地利用类型进行分类，得出以中、低覆盖度草地和丘陵耕地为主的土地利用结构是流域水土流失产生的主要原因。植被建设与恢复是缓解区域水土流失的重要途径。根据泾河流域内和流域周边25个气象站点的林地生态需水量与当地生长季降水量的匹配程度，通过插值方法，将流域分为适宜或较适宜造林区（乔灌林区）、欠适宜造林区（耐旱灌木林与高覆盖度草地区）和非适宜造林区（中覆盖度草地区）3类，结果显示，这3类区由东北向西南呈倾斜的条带状分布，分别占流域总面积的53.69%，22.16%和24.15%。为研究气候变化对植被分区的影响，分别评价了1961-1980年和1981-2004年两个时段流域林地生长季降雨量变化及对应的林地区域分异状况，结果显示：生长季降雨量整体表现为减少趋势，最大减幅在50 mm左右，总体减幅高于全年平均降水量的减幅，减幅区涉及范围较广；在局部地区降雨有所增加，最大增幅为20 mm左右，增幅区位于下游的泾阳县、淳化县以及上游的定边县，受此影响，非适宜造林区和欠适宜造林区呈现向南推进态势，适宜或较适宜造林区面积减少了11.44%。本文的研究结果可为当地植被建设提供参考。

Research on Soil Erosion and Regional Differentiation of Forestland in the Jinghe Watershed

Located in the Loess Plateau,the Jinghe Watershed is an arid and semiarid area,where land use structure is dominated by grasslands with moderate or low vegetation coverage,and hilly farmland is an important factor resulting in severe water loss and soil erosion in the drainage basin.Therefore,the emphases of its ecological construction are to convert land for farming to forests or grassplots and improve vegetation coverage of the grasslands.According to the match degree of ecological water requirement of the local forestlands and local precipitation in growing season,in this paper,the Jinghe Watershed was divided into three kinds of areas: suitable or relatively suitable forestlands,relatively unsuitable forestlands,and unsuitable forestlands.The research results show that the three kinds of areas are distributed as sloped belts from northeast to southwest,and proportions of their areas were 53.69%,22.16% and 24.15% of the total respectively.The climate change effects on regional differentiation of vegetation were analyzed.Precipitation in growth season of forestlands during the periods of 1961-1980 and 1981-2004 was compared and evaluated,and the corresponding change of regional differentiation of vegetation in the watershed was researched.It was found that precipitation in growth season of forestlands was in a decrease trend in most area of the Jinghe Watershed,and the most decrease was about 50 mm.Owing to the impact of precipitation change,the unsuitable and relatively unsuitable forestlands were expanded southeastward,and the area of suitable or relatively suitable forestland was reduced by 11.4%.The study results can be referred for regenerating local vegetation.