Abstract: To quantitatively evaluate the effects of drought on vegetation productivity in the Qinling-Daba Mountains, we analyzed the temporal and spatial characteristics of gross primary productivity (GPP) and drought, identified the fluctuation of negative GPP extremes under different vegetation types, and quantified the drought vulnerability and drought risk of GPP from 2001 to 2020 with MODIS GPP products and standardized precipitation evapotranspiration index (SPEI). The results showed that the annual GPP from 2001 to 2020 had an increasing trend in 98.0% of areas in the Qinling-Daba Mountains. The GPP of all vegetation types except wetlands increased significantly. SPEI decreased in 23.8% of area in the Qinling-Daba Mountains from 2001 to 2020. The number of negative GPP extremes had no significant trend, but abnormal GPP fluctuations had intensified, especially in the cultivated land. After 2011, the proportion of concurrent negative GPP extreme and drought had decreased for all vegetation types, but the spatial and temporal range of drought in these negative GPP extremes showed an expanding trend. Compared with the pattern during 2001-2010, the proportion of area with positive drought vulnerability and drought risk increased by 104.1% and 6.7% after 2011, indicating that the area with drought-induced GPP decline had expanded. Among all the vegetation types, drought caused the largest decrease of GPP in wetlands. The results revealed that drought led to an aggravation of GPP fluctuations and increased frequency of GPP extremes in the Qinling-Daba Mountains from 2001 to 2020, which resulted in GPP decline with different magnitudes in most vegetation types.

Key words: gross primary productivity, drought, vegetation type, Qinling-Daba Mountains