Spatiotemporal dynamics of vegetation response to permafrost degradation in Northeast China

Permafrost in Northeast China is undergoing extensive and rapid degradation, and it is of great importance to understand the dynamics of vegetation response to permafrost degradation during different periods in this region. Based on the meteorological station data and MODIS land surface temperature data, we mapped the distribution of permafrost using the surface frost number(SFN) model to analyze the permafrost degradation processes in Northeast China from 1981 to 2020. We investigated the spatiotemporal variation characteristics of vegetation and its response to permafrost degradation during different periods from 1982 to 2020 using the normalized difference vegetation index(NDVI). We further discussed the dominant factors influencing the vegetation dynamics in the permafrost degradation processes. Results indicated that the permafrost area in Northeast China decreased significantly by 1.01×105 km2 in the past 40 a. The permafrost stability continued to weaken, with large areas of stable permafrost(SP) converted to semi-stable permafrost(SSP) and unstable permafrost(UP) after 2000. From 1982 to 2020, NDVI exhibited a significant decreasing trend in the seasonal frost(SF) region, while it exhibited an increasing trend in the permafrost region. NDVI in the UP and SSP regions changed from a significant increasing trend before 2000 to a nonsignificant decreasing trend after 2000. In 78.63% of the permafrost region, there was a negative correlation between the SFN and NDVI from 1982 to 2020. In the SP and SSP regions, the correlation between the SFN and NDVI was predominantly negative, while in the UP region, it was predominantly positive. Temperature was the dominant factor influencing the NDVI variations in the permafrost region from 1982 to 2020, and the impact of precipitation on NDVI variations increased after 2000. The findings elucidate the complex dynamics of vegetation in the permafrost region of Northeast China and provide deeper insights into the response mechanisms of vegetation in cold regions to permafrost degradation induced by climate change.