Subjects: Geosciences >> Geography submitted time 2024-03-01 Cooperative journals: 《干旱区研究》
Abstract： As the most widespread ecosystem on Earth, grassland is vital for maintaining ecological security,sustainability, and human well-being. In this study, we used systemic methods of maximum synthesis, regressionanalysis, and partial correlation analysis to investigate the spatiotemporal dynamics of grassland and its responsesto temperature and precipitation on the northern slope of the Tianshan Mountains in Changji Hui AutonomousPrefecture, Xinjiang, from 2000 to 2020. The research was based on remote- sensed time series images (e.g.,MODIS NPP and EVI) and related auxiliary data. The results indicate a significant increase in grassland NPP andEVI from 2000 to 2020, with temporal fluctuations. However, after 2016, both NPP, and EVI declined year overyear. Over the past 20 years, the mean average NPP, and EVI of grassland vegetation were 0.095 kg C·m− 2 and0.186, respectively. In 2020, grassland NPP (0.099 kg C·m−2）and EVI (0.194) increased by 28.57% and 16.87%,respectively, compared to their values in 2000 (NPP: 0.077 kg C·m− 2; EVI: 0.166). The spatial heterogeneity ofgrassland vegetation NPP increased substantially and showed a trend toward expansion, while the spatialheterogeneity of grassland EVI increased annually. The range of variation observed during this research was0.038 kg C·m− 2 for NPP and 0.059 for EVI. Overall, the spatial distribution of grassland NPP and EVI wasgenerally coherent, but variations also existed. Grassland NPP and EVI showed an upward trend with altitude,with an elevated EVI along the oasis edge and the southern edge of the Gurbantunggut Desert. In this study, wesuggest that abundant water and heat induce the formation of vigorous layers of short- lived plants, resulting inhigher coverage than other grassland plants after withering. These short-lived plants begin their life cycle in earlyspring, when hydrothermal conditions (e.g., temperature, soil moisture, and root zone soil temperature) arefavorable, and they complete their germination, growth, fruiting, and withering phases from April to June. Thearea percentages of NPP (65.01%) and EVI (21.93%) showed a significant increasing trend on the northern slopeof Tianshan Mountains in the Changji Hui Autonomous Prefecture, Xinjiang, over the last 20 years. Theproportion of vegetation NPP and EVI in the 9 grassland types showed a significant positive correlation withprecipitation, which was much greater than that with temperature during the same period, confirming thatprecipitation is the major factor affecting grassland vegetation. Furthermore, the reactions of each grasslandvegetation type (e.g., NPP and EVI) to precipitation varied. While precipitation remained a key driver forgrassland, moderate warming, especially at high altitudes, was found to be suitable for the growth of grasslandvegetation. These findings provide theoretical references for evaluating grassland ecological health anddegradation, as well as the high-quality development of grassland on the northern slope of Tianshan Mountains inthe Changji Hui Autonomous Prefecture, Xinjiang.
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