Dynamics of the climate-permafrost-vegetation coupling system at its southernmost zone in Eurasia under climate warming.

Climate warming is suspected of causing notable degradation of permafrost at the regional and global levels, resulting in carbon release and substantially high carbon storage, which in turn, accelerates climate warming. However, analysis of Siberia's carbon dioxide and methane fluxes reveals that permafrost dynamics are more stable than previously estimated. We systematically reviewed previous studies on the climate-permafrost-vegetation coupling system in southern Siberia and the Russian Far East, the Greater Khingan and Smaller Khingan Mountains in northeast China and northern Mongolia, which is the southernmost distribution of the Eurasian zonal permafrost and is characterized by the largest ecosystem-protected permafrost area in the world. Climate warming in recent decades has strongly affected the species composition of vegetation in this permafrost region. It has also contributed to the expansion or contraction of vegetation patches on a local scale. The increasing number of days of shallow frozen soil thawing per year leads to the deepening of the active layer, resulting in the degradation of permafrost. Permafrost degradation has both direct and indirect impacts on plant species composition and community structure. Permafrost melting changes local water conditions, which directly affects vegetation and indirectly affects the composition and growth of plant species through the impact of soil moisture change on soil nutrients. The interception and redistribution of snow by vegetation complicate the distribution of solar radiation and surface water received by the ground, which also indirectly affects the permafrost environment. However, there is still a large knowledge gap about the interactions among climate, permafrost, and vegetation, particularly at the regional level, which requires additional study.