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.
Subjects: Geosciences >> Geography submitted time 2022-04-14 Cooperative journals: 《干旱区地理》
Abstract：基于MOD17A3HGF NPP（Net primary productivity）与气温、降水量等数据，采用趋势分析与偏相关分析，在多个尺度（全疆、北疆与南疆、各地州市与11种草地类型）探讨了20002018年新疆天然草地NPP时空动态及其对气候变化的响应。结果表明：近20 a新疆草地NPP呈波动递增， 多年均值为0.103 kg Cm-2，由准噶尔西部山地、伊犁河谷、天山、阿尔泰山向准噶尔盆地、塔里木盆地逐渐降低；北疆草地多年平均NPP（0.149 kg Cm-2）高于南疆（0.055 kg Cm-2 ），北疆、南疆草地 NPP均表现为增加趋势；各地、州、市草地NPP总体为增加，但年际变化分异明显；11种天然草地类型（除高寒荒漠类）NPP表现为递增趋势，但不同草地类型存在差异。2000年后，新疆气候暖湿化有利于草地植被生长，但降水年际变化增强导致草地NPP年际波动剧烈。研究结果为新疆天然草地碳收支评估提供基础数据，能够促进天然草地健康评价以及可持续利用。
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc. submitted time 2022-01-26 Cooperative journals: 《干旱区研究》
Abstract：草地是重要的陆地生态系统类型，草地生态系统健康评价是干旱区草地健康研究的重要组成部分。新疆位于中亚干旱区，典型的山盆地形结构孕育的天然草地具有鲜明的垂直地带性，又因水热组合差异形成了丰富多样的草地类型，这使得新疆草地生态系统健康评价成为一项系统的复杂工作，急需构建适用于新疆的草地生态系统健康评价体系。本研究以新疆草地生态系统为研究对象，构建新疆草地生态系统健康评价总体框架，从数据来源与评价方法阐述了新疆草地生态系统健康评价体系。基于草地样方、生物气象与多源遥感数据建立草地生态系统基础数据库，针对草地健康评价方法，明确评价目标，确定评价区域与参照系统，进而筛选评价指标，最后通过选择评价方法开展草地健康评价，采用四分法将评价结果划分为健康、亚健康、警戒与崩溃。采用该体系在新疆和田地区民丰县开展草地生态系统健康评价，结果显示围栏内的温性荒漠类草地处于健康状态，围栏外的温性荒漠类草地为亚健康状态。通过构建新疆草地生态系统健康评价体系，能够为基层草原部门开展草地生态健康评价提供参考，促进草地可持续发展。
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