黑河中上游地区2000—2010年土地利用变化及水土保持服务功能

基于遥感影像数据,分析了黑河中上游地区2000年到2010年土地利用变化,在此基础上,从上游、中游以及整个区域的角度综合评价了该区域的水源涵养和土壤保持生态系统服务功能物质量变化。研究结果表明:1研究区60%以上为未利用地,2000—2010年,耕地、林地和未利用地面积大量增加,草地和水域面积减少。2耕地增加以荒漠和草地转入为主;林地转入表现为草地和荒漠造林,转出主要为林地荒漠化;草地转出主要去向为造林和荒漠化,而增加主要来源于冰雪覆盖地和荒漠;未利用地增加主要来源于草地的退化。3研究区土地利用程度较低,由东南向西北递减,2000—2010年,上游土地利用程度有所降低,中游大部分地区呈上升趋势。4由于上游山区林地面积的增加,植被覆盖下土壤的水源涵养量显著增加,土壤贮水量增加了0.764×108t。5土壤保持量由1.860×108t增加到1.899×108t,主要原因为草地转化为林地。在气候变化背景下,黑河流域应控制上游地区人工林面积,减少林地蒸腾量,以增加下游可用水量;适当控制中游地区耕地面积的扩张趋势,保证湿地、草地等自然生态系统生态用水量,维持流域山地-绿洲-荒漠系统的稳定,进而持续发挥生态系统土壤保持等功能。

Changes in land use and soil and water conservation of the upper and middle reaches of Heihe river basin during 2000-2010

Based on Landsat TM/ETM image data and some other survey materials, this paper analyzed the land use change in the upper and middle reaches of Heihe river basin during 2000-2010. Subsequently, two prominent functions of ecosystem service: water conservation and soil retention were evaluated, from upstream, midstream, as well as the whole region. The findings of this study are summarized as following: (1) The main types of land use is unused land accounting for more than 60% of the total area. In recent ten years, cultivated land, forest land and unused land increased dramatically. By contrast, grassland, water area and snow cover land decreased. (2) The increase of cultivated land was chiefly derived from the conversion of desert and grassland. Desertification on forest land, afforestation on desert and grassland happened at the same time. The total area of forest land showed an ascending trend. The loss of grassland was attributed to the afforestation and desertification, whereas the increment of grassland was ascribed to the conversion from snow cover land and desert. The increase of unused land mainly came from the degradation on grassland. (3) On the whole, the degree of land use was relatively low and displayed a descending trend from the southeast to the northwest. In recent 10 years, the degree of land use dropped in upstream area and ascends in most of the middle reaches of Heihe basin. (4) Owing to the increase of forest land of the upper reaches, water conservation for soil improved significantly. Water storage in soil increased by 0.746×10⁸ t. (5) The total amount of soil retention raised from 1.860×10⁸ t to 1.899×0⁸ t as grassland conversion to forest. Under the background of climate change, some measures should be implemented in order to maintain the stability of the mountain-oasis-desert system and the sustainable of the ecosystem services like soil retention. Firstly, the area of artificial forest should be controlled in the upper reaches which can reduce transpiration and increase the amount of water available. Secondly, in the middle reaches, cultivated land area should be under control to ensure the ecological water consumption, such as grassland and wetlands.