This work aimed to explore the evolutionary characteristics of soil bacterial community composition and diversity in cold temperate larch forests under snow cover, and investigate its influencing factors and the response mechanism of snow ecology.

The Illumina Miseq high-throughput sequencing technology and redundancy analysis method were used to analyze the changes and influencing factors of soil bacterial community structure and diversity under snow removal (NS), natural snowfall (CK), double snowfall (DS), and extreme snowfall (ES) treatments.

The study found that different thickness of snow cover changed the soil micro-environment of larch forests, soil temperature (Tem) was increased significantly with the increase of snow cover thickness, but OC was decreased significantly, and Tem, pH, OC, TN, AP showed significant differences in the soil of each snow cover treatment. The comparative analysis of bacterial communities showed that a total of 30 bacterial phyla were detected in the four groups of snow-covered environments. The dominant bacterial phyla were Verrucomicrobia and Proteobacteria in the soil of the snow-removed group and other three snow-covered groups, respectively, and the dominant bacterial genera were Candidatus Udaeobacter. In addition, the flora of Planctomycetota, Oxalobacteraceae_Norank and Arenimonas showed significant or extremely significant differences in each snow cover treatment. In terms of community diversity, although different thicknesses of snow cover affected the structure and population distribution of soil bacteria, they did not significantly change the Alpha diversity of bacterial community within the group. However, snow cover significantly changed the Beta diversity of bacterial communities at the OTU level while considering the species differences and abundances among different groups. The correlation analysis of environmental factors showed that pH, OC and TN were environmental factors with low multicollinearity which affect bacterial community structure in the snow cover environment. Among them, pH was significantly correlated with bacterial community at the genus level, which showed an extremely significant correlation at the OTU level. OC showed a significant correlation at the OTU level. Community function prediction and inter-group difference analysis showed that bacteria mainly performed ecological functions such as nitrate and nitrite reduction, nitrogen fixation, methane and aromaticity degradation, cellulose hydrolysis and photochemical energy, and there were significant differences in urea decomposition and iron redox among the groups.

Snow cover affects the composition and diversity of soil bacterial communities in cold temperate larch forests to different degrees, and this effect has important scientific significance for the function of the cold temperate forest ecosystem and its regulation on global climate change in which microorganisms are participated.

This study aimed to explore the changes in the composition, diversity and function of bacterial communities during the decomposition process of different dominant fallen log species in the woodland of the Daxing'an Mountains and investigate the differentiated responses of distribution patterns of major bacterial communities driven by nutrients.

The content of water, pH, TC, TN, cellulose, hemicellulose and lignin in the fallen logs of Betula platyphylla, Pinus sylvestris and Larix gmelini were determined. Illumina MiSeq high-throughput sequencing technology was used to analyze the bacterial composition, relative abundance and ecological functional groups. The relationship between the bacterial community composition of different fallen log species and the nutrient of fallen logs was investigated by redundancy analysis.

In descending order, the bacterial species in the decomposition process of the three fallen logs species were Betula platyphylla, Larix gmelini, and Pinus sylvestris. Among them, the number of unique bacteria in Betula platyphylla was significantly higher than that in Larix gmelini and Pinus sylvestris. The community composition and distribution study showed that Proteobacteria was the absolute dominant phylum in the three fallen log species, and its relative abundance within the group showed significant differences among these fallen log species. Lysinimonas, Sphingomonas and Luteibacter were the dominant genus, and their relative abundance within the group had no significant difference among different fallen log species. The difference analysis of community diversity showed that the difference in fallen log species significantly changed the Alpha diversity within the bacterial communities of Pinus sylvestris and Larix gmelini as well as Pinus sylvestris and Betula platyphylla, which also significantly changed the Beta diversity between groups at the phylum and genus levels. Redundancy analysis showed significant differences in the pH, TC, TN, C/N, hemicellulose and lignin contents among the three fallen log species. Among them, pH, TC, TN, C/N, cellulose and lignin were the key factors affecting the composition and distribution of bacteria at the phylum level, and pH, TN, C/N and cellulose were the key factors at the genus level. The results of bacterial function prediction showed that carbohydrate metabolism and amino acid metabolism were the main functional pathways in the bacteria without fallen log species specificity.

The composition of bacterial communities in different dominant fallen log species showed significant differences in the decomposition process. However, the main bacterial function did not show fallen log species specificity.