黄土高原森林草原区退耕还林还草土壤保持效应评估

黄土高原地处生态过渡带和环境脆弱区,区内大范围的土壤侵蚀严重影响了当地的生态环境。以黄土高原森林草原区为研究对象,应用修正通用土壤流失方程,根据2000、2005、2010年气象数据及土地利用等数据,从不同坡度、植被覆盖度、土地利用类型评估了黄土高原森林草原区退耕还林还草工程的土壤保持效应。结果表明,(1)随着退耕还林还草工程的实施,林地和草地面积明显增加,分别增加2 219.41 km~2、2 205.27 km~2,研究区植被覆盖度逐渐改善。(2)2000—2010年土壤保持量增加2.41亿t,单位面积土壤保持量由3 033.15 t·km~(-2)·a~(-1)增加至5 114.86 t·km~(-2)·a~(-1),土壤保持效应显著提升。(3)研究区土壤保持效应与植被覆盖度呈正相关关系,在不同土地利用类型中,林地、草地和耕地具有较高的土壤保持效应,单位面积土壤保持量分别为5 405.57、3 598.41、3 078.81 t·km~(-2)·a~(-1)。退耕还林还草工程的实施提升了区域的土壤保持效应,但是,区内东北部由于矿产资源开采导致的植被破坏、地表塌陷以及土壤侵蚀问题亟待解决。

Evaluation on soil conservation effect of returning cropland to forest and grassland in forest-steppe zone of loess plateau

As an ecological transition zone and fragile eco-environmental region, Loess Plateau has suffered severe and large-scale soil erosion, and which has in turn greatly affected regional environment. In our study, on the basis of 2000, 2005 and 2010 meteorological data, soil conservation benefits under different slope gradients, vegetation coverage and land-use types were separately assessed with the method of Revised Universal Soil Loss Equation (RUSLE) at the forest-steppe zone of Loess Plateau. By analyzing, the main conclusions (results) were as follows: (1) Since the implementation of Grain for Green Project in 1999, the total vegetation coverage of the study area has gradually increased, and the area of woodland and grassland have also significantly increased, with increment of 2 219.41 km² and 2 205.27 km²respectively. (2) From 2000 to 2010, soil conservation quantity increased by 241 million ton, and soil conservation quantity per unit area increased from 3 033.15 t·km^-2·a^-1 to 5 114.86 t·km^-2·a^-1, indicating a remarkable improvement of regional soil conservation benefits. (3) Soil conservation benefits were positively correlated to vegetation coverage. In different land use types, woodland, grassland and cultivated land had much higher soil conservation benefits than others, whose soil conservation quantity per unit area of 5 405.57, 3 598.41 t·km^-2·a^-1 and 3 078.81 t·km^-2·a^-1 respectively. Soil conservation benefits of the study area have notably improved in the help of Grain for Green Project, however there is a series of serious problems of vegetation deterioration, surface subsidence and soil erosion caused by exploitation of mineral resources in northeastern part of this area. More measures should be taken to harmonize the exploitation activities with ecological restoration.