Structure and Functioning of China’s Dryland Ecosystems in a Changing Environment

Abstract

AbstractChina has one of the largest dryland areas worldwide, covering 6.6 million km2 and supporting approximately 580 million people. Conflicting findings showing a drier China’s drylands with increasing aridity and observed greenness indicate the complexity of environmental processes, highlighting a pressing research need to improve understanding of how active dryland processes, ecosystem structure and functioning will alter. This chapter synthesizes the changes, impacts, and their drivers in China’s dryland ecosystems. Results from analyses covering the period 2000–2015 showed that 58.69% of the vegetated area exhibited an increase in vegetation greenness, cover, and productivity, while 4.29% of those showed a decrease in all three aspects. However, 37.02% of the vegetated area showed inconsistent trends in vegetation greenness, cover, and productivity, suggesting high uncertainty in estimations of vegetation dynamics in drylands. China’s drylands are nevertheless at risk of expansion and could pass an irreversible tipping point with increasing aridity, particularly in the country’s semi-arid regions. Nitrogen enrichment and overgrazing generally reduce plant species diversity. Wind erosion, water erosion, salinization, and freeze–thaw erosion are typical processes of desertification in China’s drylands. Large-scale ecological restoration projects enhance greening and ecosystem services of China’s drylands, but also impose substantial pressure on these water-limited environments. Future research is needed to examine interactions among different drivers of environmental change (e.g., the relationships between CO2 fertilization and increased aridity). Such research could usefully include complex systems approaches to link patterns and processes across spatial and time scales, and long-term experiments on physical‐chemical‐biological process interactions.