Exploring the contribution of vegetation and climate factors to changes in terrestrial evapotranspiration in China

Evapotranspiration (ET) is a key component of the global water cycle, integral to the interactions among water, carbon, and energy exchanges between the terrestrial biosphere and the atmosphere. With global warming anticipated to intensify the water cycle, understanding the spatiotemporal characteristics and driving factors of terrestrial ET in China is increasingly critical. This study categorizes China (Total) into arid and semi-arid (ASA) and humid and semi-humid (HSH) sub-regions based on the aridity index (AI) and utilizes the GLEAM (Global Land Evaporation Amsterdam Model) v3.8a dataset to analyze variations in transpiration (T), ET, and the T/ET from 1982 to 2022. Findings reveal distinct interannual variation trends. The average annual T, ET, and T/ET in the Total area show changes of 0.93 mm/a, 1.40 mm/a, and 0.0001/a, respectively. The ASA region exhibited higher growth rates for T (1.18 mm/a), ET (1.61 mm/a), and T/ET (0.001/a), whereas the HSH region showed lower rates for T (0.81 mm/a) and ET (1.31 mm/a), with a slight decline in T/ET (-0.0004/a). The LMG (Lindeman-Merenda-Gold) analysis highlights the varying contributions of controlling factors to T, ET, and T/ET across different regions. In the Total area and the HSH region, vapor pressure deficit (VPD) is the primary driver of T, while the normalized difference vegetation index (NDVI) dominates in the ASA region. For ET, temperature (TEM) is the leading contributor in the Total area and the HSH region, whereas precipitation (PRE) plays the dominant role in the ASA region. Regarding T/ET, PRE is the most influential factor in the Total area and the HSH region, while NDVI emerges as the key contributor in the ASA region.