Spatiotemporal dynamics of vegetation greenness and its climatic associations in Harbin based on kernel NDVI

Long-term vegetation greenness dynamics provide important evidence of ecosystem responses to climatic variability in high-latitude temperate regions. This study analyzed vegetation greenness in Harbin, Northeast China, from 2000 to 2024 using annual maximum kernel Normalized Difference Vegetation Index (kNDVI) derived from Landsat imagery. Long-term trends were assessed using Theil-Sen slope estimation and the Mann-Kendall test, with the Pettitt test used to detect temporal changes. Pixel-wise multiple linear regression with standardized climatic predictors was used to examine climatic associations. Regional median kNDVI increased from 0.56 to 0.61, with a significant change point in 2004. Significant increases and decreases accounted for 3.52% and 0.50% of the study area, respectively. Precipitation was the dominant climatic variable across 83.66% of the area, followed by temperature (13.68%), potential evapotranspiration (1.66%), and solar radiation (1.01%). Overall, Harbin showed widespread greening with spatially heterogeneous climatic associations.