长江流域植被的时空演变及驱动力分析

Spatio-Temporal Evolution and Driving Force Analysis of the Vegetation in the Yangtze River Basin

The Yangtze River Basin is a crucial part of China’s ecological system, and its vegetation cover status is of far-reaching significance for regional ecological balance and the coordinated development of human-land relationships. This study is based on the MODIS-NDVI image data of the Yangtze River Basin from 2000 to 2023. By integrating socio-economic and natural environment data, methods such as Sen + Mann-Kendall analysis, correlation coefficient calculation, and residual trend analysis were used to deeply explore the spatial-temporal evolution characteristics and driving mechanisms of the vegetation coverage in the Yangtze River Basin. The Sen + Mann-Kendall analysis was employed to study the dynamic changes of vegetation coverage, the correlation between NDVI and rainfall and temperature was calculated, and the residual trend analysis was utilized to distinguish the impacts of climate change and human activities on vegetation growth. The results show that from 2000 to 2023, the vegetation coverage in the Yangtze River Basin generally showed an increasing trend. The growth rate was relatively fast from 2000 to 2011, with the annual average NDVI increasing from 0.68 to 0.73, and it slowed down from 2012 to 2023. In terms of spatial distribution, the areas with improved vegetation were concentrated in the western and southern parts of the basin, while the degraded areas were concentrated in the eastern, central, and northern parts. In terms of area proportion, the area of rapidly increasing vegetation coverage accounted for 59.47%, approximately 1,002,576 km²; the area of rapidly decreasing vegetation coverage accounted for 1.28%, approximately 21,608 km². The area of improved vegetation (about 1,455,000 km²) was much larger than that of degraded vegetation (about 44,000 km²). The correlation analysis between NDVI in the growing season and climate factors shows that NDVI is positively correlated with precipitation in 78.29% of the areas and positively correlated with temperature in 80.80% of the areas. Regarding the driving factors, 91.26% of the areas are driven by climate factors. Among them, 67.83% of the areas are jointly driven by temperature and precipitation, concentrated in the central and eastern parts of the basin; 10.46% of the areas are mainly driven by precipitation, concentrated in the eastern part of the Hanshui River Basin, the Jialing River Basin, and the upper part of the Jinsha River Basin. In terms of human activities, 58.6% of the areas are jointly driven by human activities and climate, and among them, the areas where the contribution rate of human activities exceeds 40% account for 32.5%; human activities damage vegetation in 12.27% of the areas, mainly concentrated in urban-intensive areas. This study clearly presents the spatial-temporal evolution law and driving mechanism of the vegetation coverage in the Yangtze River Basin, providing a scientific basis for ecological restoration, rational resource utilization, and sustainable development in the basin.

长江流域作为我国生态体系的关键部分，分析其植被覆盖状况对区域生态平衡与人地关系协调发展意义深远。本研究基于2000-2023 年长江流域MODIS-NDVI影像数据，结合社会经济与自然环境数据，通过Sen+Mann-Kendall方法分析植被覆盖度动态变化，并计算NDVI与降雨、温度的相关性，借助残差趋势分析区分气候变化和人类活动对植被生长的影响。结果显示：（1）2000-2023 年长江流域植被覆盖度总体呈增长态势，2000-2011 年增长速率较快，年平均NDVI从0.68 提升至0.73，2012-2023 年增长趋缓。（2）空间分布上，植被改善区域集中在流域西部和南部，退化区域集中于东部、中部及北部。从面积占比来看，植被覆盖度快速增加区域占比59.47%，面积约1002,576 km²；快速下降区域占比1.28%，面积约21,608 km²，改善区域面积（约1455,000 km²）远超退化区域（约44,000 km²）。（3）生长季NDVI与气候因子相关性分析表明，78.29%的区域NDVI与降水呈正相关，80.80%的区域NDVI与气温呈正相关。（4）驱动因素方面，91.26%的区域受气候因素驱动，其中67.83%的区域受气温和降水共同驱动，集中在流域中、东部；10.46%的区域以降水驱动为主，集中在汉水流域东部、嘉陵江流域和金沙江流域上游部分地区。人类活动方面，58.6%的区域受人类活动与气候共同驱动，其中人类活动贡献率超40%的区域占32.5%；12.27%的区域人类活动破坏植被，主要集中在城市化密集区。本研究清晰呈现了长江流域植被覆盖度时空演变规律及其驱动机制，为流域生态修复、资源合理利用和可持续发展提供了科学依据。