2000-2019年新疆植被覆盖度时空格局及重心变化分析

    Spatial-temporal pattern and gravity center change of fractional vegetation cover in Xinjiang, China from 2000 to 2019

    • 摘要: 植被对生态环境稳定有着极其重要的意义,研究植被覆盖变化及驱动机制,可为区域生态保护工作提供参考。该研究利用2000-2019年MODIS/EVI数据,基于像元二分法获取植被覆盖度(Fractional Vegetation Cover,FVC),运用线性回归分析揭示了FVC变化规律,进一步利用重心模型分析了植被、气温和降水的空间变化过程。结果表明:1)2000-2019年新疆平均FVC值为0.255,空间分布差异明显,以极低覆盖度为主,极高覆盖度区域主要分布在西北部、北部以及南疆的绿洲地区。2)新疆FVC呈上升趋势,变化平稳。东疆波动较大,2015年FVC高于平均值近20%,其他地区FVC在平均值5%上下波动;全疆植被减少趋势区域占总面积的53.04%,极显著恶化区域占总面积的4.73%。3)从重心迁移分析,气温是新疆FVC空间变化的主要驱动因素,在经度方向上呈正相关(相关系数为0.734);伊犁河谷地区植被重心和降水重心在经度方向上呈负相关(相关系数为?0.492)。新疆植被覆盖度低且分布不均匀,具有显著性变化(P<0.05)的像元主要分布在人类活动区域,好转区域面积大于恶化区域,生态恢复工作效果明显,在恶化区域应当继续加强植被保护工作。

       

      Abstract: Abstract: Vegetation has become the main producer to serve as an integral part of natural ecosystem, as well as perform various vital ecological functions. Vegetation coverage has some direct effects on the structure, functions, and health of an ecosystem. The vegetation coverage can also be one of the key ecological parameters that can reflect the level and quality of an ecosystem, particularly on Xinjiang, China, characterized by shortage of water resources and fragile ecological environment in the arid hinterland of Eurasia. New challenge has posed on the ecological system in Xinjiang, as "the Belt and Road" initiative is being promoted. Furthermore, the area and quality of vegetation coverage is degrading, as adverse effects increased from the climate change and human activities in the last 20 years, leading to severe negative impacts on the ecological environment and social economy. Therefore, it is necessary to carry out the long-term sequence monitoring on the vegetation coverage at the regional scale, in order to promote the eco-friendly development model, and further to ensure the sustainable development of the "Silk Road of Green Development". In this study, MODIS/EVI data was employed to obtain the Fractional Vegetation Coverage (FVC) based on pixel dichotomy, thereby to explore the change in vegetation coverage and its driving mechanisms. The variation of FVC was revealed using the percentage of deviation from normal and linear regression analysis. The driving mechanism of FVC change was also analyzed by the gravity center model and correlation analysis. The results showed that: 1) The average vegetation coverage was 0.255 in Xinjiang from 2000 to 2019, where the area with an very low coverage accounting for 63.53%. The vegetation coverage was higher in Yili River Valley, where the area with an extremely high coverage accounting for 77.9%, whereas that in southern Xinjiang only accounted for 6.94%. 2) The FVC was on the rise in Xinjiang as a whole, with a stable variation. The percentage of abnormal change was within the normal range. However, the fluctuation of FVC was relatively large in eastern Xinjiang. In 2015, the FVC value was nearly 20% higher than the average level, with other regions fluctuating in the range of ±5%. The reduction area of vegetation coverage was larger than that of the increasing area, where 53.04% of the area tended to decrease. At the level of significance less than 0.05, the area with increasing trend was large. 3) In the driving mechanisms for the variation of vegetation coverage, the spatial position of vegetation centers, temperature and precipitation were calculated to analyze the change and relationship between the gravity centers of various elements from the spatial level. The vegetation center of gravity fluctuated to high longitude and high latitude. In terms of longitude change, temperature was the main driving factor of vegetation spatial change in Xinjiang, indicating a positive correlation between the center of vegetation and temperature. There was a negative correlation between the vegetation center and precipitation center in Yili River Valley, with R value of -0.492. However, there was no significant relationship between the vegetation center and the center of temperature and precipitation in eastern Xinjiang. The significant change of vegetation coverage was less than 0.05 under the level of low vegetation coverage and uneven distribution. The increased area was greater than the reduced area, indicating an obvious effect of ecological restoration. A recommendation can be to strengthen the vegetation protection, especially in the area of reduced vegetation coverage. The evaluation of vegetation change and its driving mechanisms in different regions of Xinjiang can provide a scientific basis to protect the fragile ecological environment.

       

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