中国西北干旱区土地沙漠化敏感性时空格局

土地沙漠化敏感性评估是沙漠化监测的重要内容之一,也是研究如何防止和治理沙漠化的重要课题。本文以中国西北干旱区作为研究区,利用遥感技术和GIS空间分析技术为支撑,通过构建“土壤—地形—水文—气候—植被”沙漠化敏感性综合评价指标体系,并借助空间距离模型计算了沙漠化敏感性指数,进而定量评估2000年、2005年、2010年和2017年西北干旱区土地沙漠化敏感性的时空演变特征,在此基础上引入地理探测器等方法对其主要驱动因素进行了深入分析。研究结果表明：① 地形、土壤、气候、植被和水文等5个方面相互影响,彼此制约,共同构成中国西北干旱区沙漠化敏感性分布和变化的本底条件;② 西北干旱区沙漠化敏感性总体上呈现周边低、内部高的分布特征,低敏感区主要分布在阿尔泰山、天山、昆仑山、阿尔金山和祁连山等地,而高敏感区则主要分布在准噶尔盆地、塔里木盆地和内蒙古高原等大部分地区,包括塔克拉玛干沙漠、巴丹吉林沙漠和腾格里沙漠腹地。沙漠化敏感性的空间分布具有显著的区域性,高敏感区和低敏感区界限分明、分布集中;③ 从时空演变看,2000年以来沙漠化敏感性变化以稳定型占据主导,而整体上敏感性表现为缓慢降低趋势,说明潜在沙漠化区域逐年减少,区域沙漠化治理工作取得了一定成效;④ 西北干旱区的各驱动因素中,土壤及气候起直接作用,是最主要的影响因素,而植被是改变沙漠化敏感性最活跃、最基本的因素。除此之外,地形的分布和水文的变化对沙漠化敏感性起到一定的限制作用,而社会经济因素是影响区域沙漠化敏感性最为快速的因素,且经济发展对促进区域沙漠化敏感性的增长作用有逐渐加强的趋势。从整体来看,中国西北干旱区土地沙漠化得到了有效遏制,沙漠化治理工作取得了积极成效,但在全球气候变化加强和社会经济发展进入新常态的大背景下,中国沙漠化监测评估和治理工作仍然任重而道远。

Spatiotemporal changes of land desertification sensitivity in the arid region of Northwest China

The sensitivity assessment of land desertification is one of important contents of monitoring, preventing and controlling desertification. This paper took the arid region of Northwest China as the study area. Based on the RS and spatial analysis technology of GIS, we built a comprehensive index system of desertification sensitivity for evaluation on "soil-terrain-hydrology-climate-vegetation". The spatial distance model (SDM) was used to calculate the desertification sensitivity index (DSI). Then, spatiotemporal change of land desertification sensitivity in the study area covering 2000, 2005, 2010 and 2017 was quantitatively assessed. On this basis, the main driving factors were analyzed by using the geographic detector. The results showed that: (1) terrain, soil, climate, vegetation and hydrology affected each other, which were the basic conditions for the distribution and changes of sensitivity to desertification in the study area. (2) On the whole, the desertification sensitivity showed a distribution pattern of low around and high inside. The low sensitivity regions were mainly distributed in the five major mountain ranges (i.e. Altai Mountains, Tianshan Mountains, Kunlun Mountains, Altun Mountains and Qilian Mountains), and Junggar Basin, Tarim Basin and Inner Mongolian Plateau belonged to the high sensitivity regions, including the back-land of Taklamakan Desert, Badain Jaran Desert and Tengger Desert. Besides, the spatial distribution of desertification sensitivity had obvious regionality, and high and low sensitivity regions had clear boundary and concentrated distribution. (3) In terms of spatiotemporal evolution, changes of desertification sensitivity since 2000 was mainly stable type, and the overall sensitivity showed a slow decrease trend, indicating that the potential desertification regions decreased year by year and some achievements had been made in the control of regional desertification. (4) Among the driving factors affecting study area, soil and climate played a direct role, which were the most important influencing factors, and vegetation was the most active and basic factor that changed desertification sensitivity. In addition, topography and hydrology played a role in restricting the changes of desertification sensitivity, while socio-economic factors were affecting the regional desertification sensitivity, and their effects were gradually strengthened. In general, desertification has been effectively controlled in the study area, and positive results have been achieved in desertification control. However, against the backdrop of intensified global climate change and new normal of socio-economic development, the monitoring, assessment and control of desertification in China still have a long way to go.