LAI‐based reduction in growth of semiarid grasslands and its responses to climate change on China's Loess Plateau

Abstract

Understanding the response of vegetation growth to climate change can provide key information for predicting future ecosystem dynamics. Over the past 6 years, the semiarid regions of the Loess Plateau in China have experienced a transition from wet to dry years, but little is known about the response of grass growth to this change. Thus, this study aimed to analyze and evaluate the effect of climate change on grass growth. Using observed climate data and leaf area index (LAI) data obtained with hemispherical photography from 2016 to 2021, we investigated changes in trends of five climatic factors, including precipitation (P), temperature (T), relative humidity (RH), wind speed (WS), and solar radiation (Rs), and their impact on the growth of alfalfa (Medicago sativa) and Stipa bungeana plantations in the semiarid area of the Loess Plateau. The results showed a tendency to become colder in spring and drier in summer and autumn. In response, LAI tended to decrease in alfalfa and S. bungeana plots with interannual variation rates of 0.21 year−1 and 0.12 year−1, respectively. Additionally, linear regression methods showed that P had the greatest effect on LAI of two grasslands during the growing season (R2 > 0.84, p < 0.01), followed by RH and T (0.30 < R2 < 0.50, p < 0.01), a negative effect of WS (R2 = 0.36, p < 0.01), and no significant effect of Rs on LAI were found. Conversely, the path analysis indicated that Rs and P were the largest decision coefficients affecting the monthly LAI of alfalfa and S. bungeana, respectively, due to the different time‐to‐peak LAI and root growth depth of these two grass species. This study can provide theoretical support for ecological restoration and system management of semiarid grasslands.