Vegetation greenness is crucial for assessing vegetation dynamics and evaluating the effectiveness of ecological governance on the Loess Plateau. In this study, we utilized Google Earth Engine (GEE) platform and Landsat image to investigate the spatiotemporal evolution of vegetation greenness and the shift of vegetation greenness lines (VGLs) during the growing season on the Loess Plateau from 1987 to 2020. The driving factors were analyzed using a geographic detector. The results show that the average annual growth rates of NDVI and EVI in the Loess Plateau growing season from 1987 to 2020 were 0.0042/year (P < 0.01) and 0.0023/year (P < 0.01), respectively, with the growth rate after 2000 being three to four times higher. Spatially, significant increases of 78.8% in NDVI and 69.2% in EVI were observed across the entire area of the Loess Plateau. Furthermore, the average VGL based on NDVI and EVI on the Loess Plateau from 1987 to 2020 exhibited a northwestward shift at a rate of 9.79 km/year. This shift resulted in an average movement of 271.83 km over the period. The most significant shifts occurred between 2005 and 2010. Land use and precipitation emerged as the predominant driving factors influencing both the change in vegetation greenness and the shift of the VGLs. Land use and precipitation are the primary factors influencing changes in vegetation greenness and the shift of the VGLs. Land use explains 49.7% of the variation in vegetation greenness, while precipitation accounts for 43%. The combined influence of land use and precipitation explains 68% of the variation in vegetation greenness on the Loess Plateau. Prolonged growing seasons due to climate changes and the “Grain for Green” Project significantly contributed to increased vegetation greenness and northward VGL shifts. Our study offers valuable insights into the spatiotemporal dynamics of vegetation greenness and the shift of VGLs, enhancing our understanding and providing guidance for effective vegetation restoration efforts on the Loess Plateau.

中文翻译：

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黄土高原植被绿化导致植被绿度线北移


植被绿度对于评估黄土高原植被动态、评价生态治理有效性至关重要。本研究利用Google Earth Engine（GEE）平台和Landsat影像，研究了1987年至2020年黄土高原生长季植被绿度时空演化和植被绿度线（VGLs）的变化。使用地理探测器进行分析。结果表明，1987—2020年黄土高原生长季NDVI和EVI年均增长率分别为0.0042/年（P < 0.01）和0.0023/年（P < 0.01），与2000年以后的增长率相比高出三到四倍。空间上，黄土高原全区NDVI显着增加78.8%，EVI显着增加69.2%。此外，1987年至2020年黄土高原基于NDVI和EVI的平均VGL呈现出以9.79公里/年的速度向西北移动的趋势。这一转变导致在此期间平均移动 271.83 公里。最显着的变化发生在 2005 年至 2010 年间。土地利用和降水成为影响植被绿度变化和 VGL 变化的主要驱动因素。土地利用和降水是影响植被绿度变化和VGL变化的主要因素。土地利用解释了植被绿度变化的 49.7%，而降水则解释了 43%。土地利用和降水的综合影响解释了黄土高原植被绿度变化的68%。 气候变化和“退耕还林”工程导致生长季节延长，显着促进了植被绿度的增加和VGL北移。我们的研究为植被绿度的时空动态和 VGL 的变化提供了宝贵的见解，增强了我们的理解，并为黄土高原有效的植被恢复工作提供了指导。