Effects of permafrost stability changes on vegetation dynamics in the middle part of the Greater Khingan Mountains

Abstract

Permafrost in the middle section of the Greater Khingan Mountains is highly sensitive to climate change; however, the specific mechanisms by which its degradation affects vegetation dynamics remain unclear. This study utilized vegetation and climate data, along with 30-meter high-resolution frozen soil distribution data from 2003 to 2021, to investigate the impact of changes in frozen soil stability on vegetation dynamics and phenology. Analysis of satellite observations reveals significant changes in the spatiotemporal distribution of permafrost in the area, with the stability of permafrost in low-altitude regions being particularly affected. The area of stable and extremely stable permafrost has significantly decreased, while the area of transitional or unstable permafrost has increased annually, indicating a negative correlation between climate warming and frozen soil stability. The study also identified an overall greening trend in the region, with the proportions of increased normalized vegetation index (Gr-NDVI), advanced start of the growing season (SOS), and delayed end of the growing season (EOS) being 93.84%, 75.12%, and 68.83%, respectively. Ridge regression and partial correlation analyses indicated that frozen soil status, precipitation, and evapotranspiration are the primary factors influencing vegetation dynamics, accounting for 32.90%, 30.45%, and 27.15%, respectively. High-altitude areas are mainly influenced by permafrost stability and precipitation, while mid- and low-altitude areas are predominantly affected by evapotranspiration and precipitation. Vegetation dynamics exhibited spatial heterogeneity; some low-altitude areas maintained high growth vitality despite a shortened growing season, whereas Gr-NDVI decreased in other regions. These research findings underscore the critical role of changes in permafrost stability in shaping vegetation dynamics, which has significant implications for the carbon budget and ecological stability in the context of future climate warming.

Keywords

• permafrost degradation
• climate factors
• vegetation dynamics
• central Greater Khingan Mountains