Changes and drivers of vegetation productivity in China’s drylands under climate change

Abstract

Increasing aridity can sharply reduce vegetation productivity in drylands, but elevated CO _2 and warming can enhance vegetation growth. However, the extent to which these positive effects counteract the negative effects of heightened aridity on vegetation productivity remains uncertain. Here, we used space-for-time substitution to assess the responses of 15 ecosystem variables to aridity in China’s drylands and predicted vegetation productivity under future aridity, temperature, precipitation, nitrogen deposition, and CO _2 . The results showed that vegetation productivity decreased abruptly as aridity (1-precipitation/potential evapotranspiration) increased to the threshold of 0.7, which corresponds to the vegetation decline stage in the dryland ecosystem’s response to increasing aridity. Future projections suggest that 12.8% of China’s drylands will cross aridity thresholds (0.7, 0.8, and 0.95) by 2100, in which vegetation productivity will significantly increase by 40.0%. Elevated CO _2 will stimulate vegetation growth, but continuously rising temperature and CO _2 by 2100 will have adverse effects, particularly in regions with limited nitrogen and water. This study suggests that effective adaptation and mitigation actions should be developed for regions crossing aridity thresholds, to ensure that drylands maintain the capacity to provide essential ecosystem services required to support the increasing population.

Keywords

• gross primary productivity
• increasing aridity
• non-linear response
• driving factors
• drylands