Evolutionary Trajectories of Vegetation Productivity and Their Driving Factors in the Central Yunnan Urban Agglomeration

As a key region in China's Western Development Strategy and a leading exemplar of ecological civilization construction, the Central Yunnan Urban Agglomeration (CYUA) is pivotal for regional sustainable development. Investigating the evolutionary trajectories of vegetation ecosystem productivity in CYUA is essential for improving regional ecological quality and landscape character, as well as supporting the development of a livable plateau urban agglomeration. Based on MOD13A3 Version VI normalized difference vegetation index (NDVI) data, this study analyzed the spatiotemporal evolution of vegetation ecosystem productivity trajectories and their natural and socio-economic drivers in CYUA from 2000 to 2022 using a multi-model trajectory diagnosis framework and a spatial random forest model. The results indicate that: (1) During 2000-2022, vegetation ecosystem productivity trajectories in CYUA comprised 71.55% positive, 6.67% negative, and 21.78% non-significant trends. Linear trajectories dominated positive trends, whereas negative trajectories were most frequently characterized by abrupt declines. Overall, vegetation productivity exhibited an upward tendency, with large areas showing sustained and stable improvement, while abrupt shifts between positive and negative occurred frequently across the region. (2) Positive trajectories were mainly distributed in the northern and southwestern regions, whereas negative trajectories clustered in east-central and south-central areas. At elevations of 1 000-3 000 m, negative trajectories predominated at lower elevations, while the proportion of positive trajectories increased with elevation. (3) Human activities exerted stronger impacts than natural factors on vegetation productivity. Nighttime light intensity and population density were key anthropogenic drivers, whereas mean annual temperature, potential evapotranspiration, and total soil nitrogen were the dominant natural drivers. Land-use conversions from forestland, cropland, and grassland to construction land tended to induce significant negative abrupt shifts in vegetation productivity. Interactive effects among temperature, precipitation, and potential evapotranspiration critically shaped productivity patterns. These findings provide a scientific basis and decision support for urban planning, ecological restoration, and environmental protection engineering in CYUA.