甘肃白龙江流域水源涵养服务时空格局及其影响因素

Spatiotemporal pattern of water conservation and its influencing factors in Bailongjiang Watershed of Gansu

白龙江流域是长江上游的主要生态屏障和水源涵养区,对维系流域生态和可持续发展至关重要。以甘肃白龙江流域为例,基于参数本地化的InVEST模型对1990—2016年水源涵养时空变化及其影响因素进行分析。结果表明:流域多年平均水源涵养深度为47.50 mm,呈现先减少后回升的趋势。空间上,其高值区主要集中于迭部、文县和舟曲的中高山阴陡坡林区(平均涵养深度在该三县2500~3500 m海拔段、阴坡和半阴坡、25°以上坡段和林地高于流域的平均涵养深度);低值区主要位于宕昌和武都的中低山阳缓坡农牧区(平均涵养深度在该两县2500 m以下海拔段、阳坡和半阳坡、25°以下坡段和耕、草地低于流域的平均涵养深度)。气候背景下,人类活动驱动的土地利用/覆被格局空间差异是影响水源涵养时空变化的重要因素,退耕还林对减缓气候变暖背景下水源涵养深度的下降具有重要意义。

Bailongjiang Watershed is an important area of water conservation in the upper reaches of the Yangtze River, with great significance for maintaining the ecological balance of the watershed and promoting regional sustainable development. Taking the Bailongjiang Watershed in Gansu as an example, we used the InVEST water conservation assessment model based on parameter localization to analyze the multi-scale spatiotemporal change of water conservation in the watershed from 1990 to 2016 and its influencing factors. The results showed that the average annual water conservation depth of the watershed was 47.50 mm, with a trend of decreasing first and then rising. In terms of spatial distribution, the high value areas were mainly concentrated in the steep overcast forest area of middle-high mountain in Wenxian, Diebu and Zhouqu(the conservation depth of the three counties, 2500-3500 m altitude section, shaded and semi-shaded slopes, slope section above 25° and the forest land was higher than the average conservation depth of the watershed). The low value areas were mainly distributed in the gentle apricus farming and pastoral areas of middle-low mountain in Tanchang and Wudu(the average conservation depth in the two counties, below 2500 m elevation, sunny slope and semi-sunny slope, below 25° slope, cropland and grassland was lower than the watershed). Under the climatic background, the spatial difference of land use/cover pattern driven by human activities was an important factor affecting the spatiotemporal change of water conservation. Returning cropland to forest is of great significance in slowing down the decline of water conservation depth in the context of climate warming.