Effects of various driving factors on potential evapotranspiration trends over the main grain-production area of China while accounting for vegetation dynamics

Potential evapotranspiration (PET) is an important consideration in the study of agricultural water management and climate change. Although a number of studies have already explored the effects of climate factors on changes in PET, the quantitative effects of various driving factors needs to be further studied, as most studies have not accounted for vegetation dynamics by characterizing changes in leaf area and stomatal resistance. Here, we used the Shuttleworth–Wallace (S-W) model based on climate, vegetation, and energy factors to quantitatively analyze the effects of various driving factors at multiple spatial scales over the main grain-producing area of China (MGPAC) from 1982 to 2016. The S-W model had a satisfactory performance because S-W based Standardized Precipitation Evapotranspiration Index (SPEI) had a higher determination coefficient (0.33 VS. 0.26) than Penman-Monteith based SPEI for soil moisture standardized anomaly over MGPAC. MGPAC had a mean annual PET of 926.20 mm and showed a marked increase of 3.844 mm yr−1 during the study period. Evergreen broadleaf forest and grassland had the highest and lowest annual average PET values (1535.65 mm and 633.67 mm), respectively. Although climate factors could directly explain 79.42% of the PET increase over the MGPAC, vegetation dynamics were also identified to be a non-negligible factor explaining the increase in PET (directly explaining 18.91% of the PET trend). Specifically, vegetation dynamics contributed to explaining 67.30% and 48.91% of the PET trend in the Huang-Huai-Hai and Loess Plateau regions. These findings are closely related to changes in the temperature and leaf area index (LAI), which notably increased by 0.04 °C yr−1 (P < 0.01) and 0.0038 m2 m−2 yr−1 (P < 0.01), respectively. Regarding single drivers, variation in temperature and LAI significantly increased the PET by 3.582 mm yr−1 (P < 0.01) and 1.127 mm yr−1 (P < 0.01) across the MGPAC, respectively. This study can provide a new insight to improve agricultural production and management in China.