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退耕还林项目引起了土地植被与土地利用景观方面的快速变化,并对生物多样性产生一定的影响。1998—2005年,我们通过野外调查方式研究该项目对陕北地区生态环境的影响,分析脆弱景观生态系统修复的成功经验与失败教训。研究结果表明,研究区域总植被盖度从1998年的29.7%上升到2005年的42.2%。但是,大面积的人工造林可能正在加剧了半干旱生态脆弱区水资源短缺风险,导致人工林地植被覆盖度和植物种类减少。退耕、禁牧对植被覆盖恢复的贡献最大,而人工造林对半干旱生态脆弱区植被修复产生了显著的负面影响。为了减少土壤侵蚀、保护植物多样性,人工造林时必须减少对自然植被的破坏。与人工造林相比,降低耕作和放牧强度是半干旱地区恢复退化植被景观系统的首要手段。在半干旱生态脆弱区,人工造林应该限制在种植乡土树种或其他一些低耗水植物种类,减少土壤水分消耗、维护土壤生态系统稳定:比如利用半干旱草原自然植物群落,水资源利用效率较高的小灌木,以及苔藓等低耗水物种进行生态修复。
The Project of Conversion of Cropland to Forest has caused rapid changes in the landscape of land use and land use and has some impacts on biodiversity. From 1998 to 2005, we investigated the impact of the project on the ecological environment in northern Shaanxi through field investigation and analyzed the successful experiences and failures of the restoration of fragile landscape ecosystems. The results show that the total vegetation cover in the study area increased from 29.7% in 1998 to 42.2% in 2005. However, large areas of afforestation may be exacerbating the risk of water scarcity in semi-arid ecologically fragile areas, leading to reduced plant coverage and plant species in plantations. Reforestation and forbidden grazing contributed the most to vegetation cover recovery, while afforestation had a significant negative impact on vegetation restoration in semi-arid ecologically fragile areas. In order to reduce soil erosion and protect plant diversity, we must reduce the damage to natural vegetation during afforestation. Reducing tillage and grazing intensity is the primary means of restoring the landscape of degraded vegetation in semi-arid areas compared with that of afforestation. In semi-arid ecologically fragile areas, afforestation should limit the number of native tree species or other low-water-consuming plant species, reduce soil water consumption, and maintain soil ecosystem stability: for example, the use of natural plant communities in semi-arid grasslands and high water use efficiency Small shrubs, and moss and other low water-consuming species for ecological restoration.