International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.6, 277-285 http://ecoevopublisher.com/index.php/ijmec 278 (Niittynen et al., 2020). These changes not only alter the seasonal distribution of water resources but also trigger a series of ecological impacts, including early greening of vegetation, increased risk of animal overwintering failure, changes in the pathogen transmission window, and a decline in the stability of permafrost. More importantly, the reduction of snow cover will lower the surface albedo and enhance ground heat absorption, accelerate regional warming, and form a positive feedback process, thereby further promoting the accelerated melting of snow cover (Jay et al., 2023; Mott et al., 2023). This coupled feedback of climate - snow cover - ecosystem makes snow cover change one of the most challenging topics in global change research (Xie et al., 2021). This study aims to construct a systematic framework to clarify the formation mechanism, physical properties and ecological process impacts of snow cover, thereby comprehensively evaluating the multiple functions of snow cover in the ecosystem. This study will sort out the formation mechanism and physical characteristics of snow cover, analyze the regulatory role of snow cover on energy, hydrological and permafrost processes, explore the impact of snow cover on plant communities, animal strategies and microhabitats, further discuss the ecological response and cross-system effects of snow cover changes, and put forward monitoring, management and policy suggestions. This research provides an important theoretical basis for understanding the stability and future trends of snow cover ecosystems under the background of climate change, and also offers scientific support for regional governance and policy-making. 2 The Formation and Physical Properties of Snow Cover 2.1 Snow cover formation mechanism The formation of snow cover is the result of the combined effects of climate, topography and atmospheric physical processes. Its core processes include water vapor transport, sublimation and nucleation, precipitation form transformation and surface accumulation. Under cold conditions, when the ascending air current cools the air below the dew point, water vapor sublimates on the surface of condensation nuclei or ice nuclei to form ice crystals, which further grow into snow crystals through polymerization, sublimation and condensation. Temperature and humidity conditions determine the types and forms of snow crystals, such as columnar, dendritic or plate-like structures, while wind speed and atmospheric turbulence affect the collision and recombination of snow particles during the falling process (Nicolaus et al., 2022). After snow reaches the ground, the existence of accumulated snow depends on the surface temperature, the nature of the underlying surface and climatic conditions. Snow accumulation under the forest is easily affected by tree canopies, showing an uneven spatial distribution. In contrast, deep snow layers are more likely to form in the open areas of high mountains. The accumulation process of snow on the ground surface is also significantly affected by wind - especially reclamation and erosion - and the phenomenon of "wind-blown snow" redistribution often occurs in topographic areas such as ridges and valley mouths (Tang et al., 2022). In polar and alpine regions, topographic effects, wind-driven deposition and microclimate change further affect snow formation, resulting in a complex spatial pattern of snow cover distribution (Figure 1)(Nicolaus et al., 2022). Therefore, snow cover is not the product of a single meteorological event, but a continuous process from the atmosphere to the surface. Its formation mechanism determines the spatio-temporal heterogeneity of snow cover distribution (Nicolaus et al., 2022; Tarca et al., 2022). 2.2 Physical properties of snow cover Snow cover is a porous, stratified and constantly evolving natural medium, and its density, thermal conductivity, particle size structure and water content change continuously over time (Royer et al., 2021). The initial density of snow cover is usually between 50 and 200 kg/m³. As it undergoes compaction, recrystallization and thawing cycles, the density gradually increases to 400-500 kg/m³ during spring thawing. The low thermal conductivity of snow makes it a natural insulating layer, significantly reducing the impact of low winter temperatures on the soil. There is also a distinct temperature gradient within the snow layer, which determines the evolution of snow crystals from "temperature ladder to snow" to "granular snow" or "ice shells", and thereby affects the strength of the snow accumulation and the melting process.
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