Relating historical vegetation cover to aridity index patterns in the greater desert region of northern China: Implications to planned and existing restoration projects

Abstract. Desert regions of northern China have always been the most severely affected by climate change, especially in terms of their ecological integrity and social sustainable development. Assessments of dryness in both space and time are central to the development of adaptation strategies to climate change. Earlier studies have identified long-term patterns of dryness in northern China, but these studies have usually been of limited value to land-management planning as they ignore local-to-regional-scale climate features. To identify potential cause-and-effect relationship between aridity and vegetation cover, changes in aridity index (AI) and vegetation cover were tracked with the assistance of a chronological series of surfaces based on the mapping of AI and normalized difference vegetation index (NDVI) and convergent cross mapping. By tracking regional-scale variation in precipitation, air temperature, AI from 1961–2013 (53 years), and vegetation cover dynamics from 1982–2013 (32 years), we show that precipitation increased in approximately 70 % of the greater desert region, including in the Ulanbuh, Tengger, Badain Jaran, Qaidam, Kumtag, Gurbantunggut, and Taklimakan Deserts. This increase was statistically strongest for the Gurbantunggut (p < 0.01) and Taklimakan Deserts (p < 0.1). Unsurprisingly, air temperature rose in nearly all deserts (p < 0.01) at approximately 2.5 times greater than the global rate. Changes in AI was analogous to that of precipitation (low AI, denoting hyperarid conditions), except for the Tengger Desert. Increasing AI (i.e., wetting) was statistically strongest for the Gurbantunggut (p < 0.01), Qaidam (p < 0.05), and Taklimakan Deserts (p < 0.05). Vegetation growth largely improved in oases of the western desert region and Mu Us Desert over the 1982–2013 period (p < 0.1). For the most part, aridity had a moderate control on NDVI (p < 0.05), with no indication of vegetation feedback. The wetting trend observed in the western desert region (increasing AI) improved ecological conditions of the region by increasing NDVI, particularly in the region’s oases. In contrast, continued drying in the eastern desert regions (decreasing AI) had caused NDVI to decrease. Future planning of new restoration projects should ideally take into account drying/wetting trends currently being observed in northern China.