Response of gross primary productivity of vegetation to persistent drought-induced water deficit in the Yellow River Basin

Using data on the gross primary productivity (GPP) of vegetation and high-precision stratified soil moisture content, the spatiotemporal distribution and change characteristics of GPP during the growing season in the Yellow River Basin from 2001 to 2020 were analyzed. The correlation between soil moisture at different depths in the basin was quantified, and the response of GPP of different vegetation types to continuous soil moisture deficit events during the growing season was investigated. The results indicate that GPP in the Yellow River Basin exhibits a spatial distribution characterized by higher in the east and south, and lower in the west and north. During the growing season, the cumulative GPP is highest in cropland, followed by woodland and grassland. There is an overall increasing trend of GPP in the basin in the study period, with cropland showing the highest relative growth rate, followed by grassland and woodland. There are significant spatial and temporal differences in soil moisture across the basin. The influence of surface soil moisture fluctuation on deep soil water content diminishes with increasing depth, and the correlation between surface and deep soil moisture contents in woodland and cropland is much higher than that in grassland. The sensitive depth range of GPP to soil moisture is 0 to 40 cm in grassland and cropland in the Yellow River Basin, while it extends to 0 to 100 cm in woodland. Within the depth sensitive zones, as the duration of continuous soil moisture deficit increases, GPP of grassland and cropland undergoes a process of brief stability, followed by an accelerated decline, and then a decelerated decline. In contrast, GPP of woodland shows a brief decline, followed by a process of prolonged stability, and then an accelerated decline. © 2024 Editorial Board of Water Resources Protection. All rights reserved.