Tracking the influence of drought events on winter wheat using long-term gross primary production and yield in the Wei River Basin, China

The Wei River Basin (WRB) is the main winter wheat-producing area in Northwest China and plays a pivotal role in national food security and economic development. Drought is the main agro-meteorological disaster affecting winter wheat yield in this region, and the accurate assessment of the drought impacts on crop growth and yield is an important part of maintaining food security. However, commonly used assessment methods, such as correlation analysis and crop model simulation, have some limitations. In this study, based on standardized precipitation evapotranspiration index (SPEI) at multiple time scales, gross primary production (GPP) and yield data from 1990 to 2018, sensitivity analysis, Pearson correlation, and superposed epoch analysis (SEA) were used to analyze the spatiotemporal characteristics of drought in the WRB and its influence on winter wheat growth and quantitatively assess the impact of drought at different levels on winter wheat yield. The results were as follows: 1) Overall, the WRB was in a dry state with a drying trend during 1990–2018, and the droughts in spring, summer, and winter were the main driving forces of annual drought that seriously threatened the growth and yield of winter wheat, especially in spring (March–May), which is the key growth period of winter wheat. 2) The average annual GPP of winter wheat in the WRB showed a significant upward trend of 0.465 · 10a−1, and the central part of the WRB was the region where winter wheat GPP had higher sensitivity to drought. In general, winter wheat GPP during the growing season was most sensitive to SPEI-3, indicating that seasonal water deficits had the greatest impact on winter wheat growth. 3) The yield reduction of winter wheat caused by drought presented a spatial distribution that is heavy in the north and light in the south, and as the drought grade increased, the winter wheat yield decreased more significantly, even in irrigated areas. Therefore, relevant government departments still need to strengthen the risk management of agricultural droughts in the WRB and formulate reasonable policies to maintain food security.