Drought-induced productivity and economic losses in grasslands from Inner Mongolia vary across vegetation types

摘要

The frequency of extreme weather events, such as drought, is increasing under climate change in some areas. Grassland ecosystems are extremely sensitive to drought. Here we sought to determine which vegetation types are the most vulnerable drought within the Xilinguole grasslands of Inner Mongolia and to establish methods to quantitatively evaluate the effects of different drought levels on grassland productivity and economic losses. Over the past 20 years, the total annual precipitation in the Xilinguole League decreased by 24-52%, resulting in a reduction in annual pasture yield of 31-237 kg/ha and a loss of livestock grazing capacity of 3-20 head/10 ha, causing 4-26 billion yuan in direct economic losses. Across the league, 78% of drought-induced direct economic losses were concentrated in ecologically vulnerable areas, including sandy and desert grasslands and typical grasslands at the northern end and in southwestern areas. Grassland net primary productivity (NPP) was sensitive to and significantly affected by drought. As the standardised precipitation evapotranspiration index (SPEI) drought level increased, NPP loss rate increased significantly by more than 20% for each drought level. The effects of increasing drought on NPP varied within grassland types, and the effects of a given drought level were different across grassland types. Typical grasslands suffered high losses at all drought stages. Meadow grasslands adjusted relatively well to drought as the rate of grassland NPP loss changed relatively slowly with increasing drought. Desert grasslands were less affected by light-to-moderate drought than by moderate-to-severe drought. This study provides a scientific basis for improving ecosystem resilience and drought prevention and management.