| Litter decomposition is a key process of material cycle and energy flow in ecosystem,especially for maintaining the ecological function of forest ecosystem.As the main way to return carbon and nutrients in forests,litter decomposition transports organic matter and nutrients to the soil to maintain soil fertility,supply plant growth and development,and provide energy sources for soil microbes to promote soil ecological transformation.Studying the relationship between litter decomposition and soil microorganisms can deeply analyze carbon turnover and mineral nutrient cycling in forest ecosystems,which has been an important part of terrestrial ecosystem biogeochemical cycling research.In this paper,the characteristics of litter decomposition and microbial community dynamics of Picea schrenkiana forest in different snow-covered period and subsequent non-snow-covered period with different thickness were analyzed,and the litter decomposition characteristics and microbial community dynamics of spruce forests were discussed.The relationship between litter decomposition dynamics and environmental factors and microbial community under snow quilt was discussed,and the main driving factors of litter decomposition were explored.The purpose of this study is to comprehensively reveal the characteristics and driving mechanism of litter decomposition in mountain forest ecosystems in arid regions,supplement the research results driving by snow factor on forest ecological processes,promote the optimal management and rational protection of forests,and provide small-scale data for further understanding the impact of winter environmental changes on material cycle and other ecological processes under climate change.Mainly get the following results:(1)The mass loss of litter is approximately 25-28%,the decomposition coefficient K is between 0.277-0.322,and the contribution of litter decomposition in winter snow-covered period to the total decomposition is 46.0%-48.5%.The freeze-thaw period has the most obvious effect on the decomposition of litter.In addition,the litter mass loss in different snow thickness is comprehensively expressed as thick > medium > thin > no snow cover.(2)With the decomposition process,the C concentration of litter decreased,while the C was released gradually.The overall N concentration showed a trend of decreasing first and then increasing,while N was first enriched and then released.The P concentration was higher in winter and growing season,and P was first enriched slightly and then released gradually..Litter lignin was enriched in decomposition,cellulose was first released,then enriched and finally released;cellulose degradation was higher in winter than in the growing season.In addition,the decomposition period and the thickness of the snow cover have certain differences on the effects of C,N,P elements,lignin and cellulose.(3)According to OTU(operational taxonomic units)taxonomic statistics based on high-throughput sequencing results,the overall discovery of bacteria was 57 phylum,63 classes,135 orders,256 families,566 genus and 390 species;the whole consisted of fungi was 17 phylum,55 class,133 order,286 family,609 genus and 705 species.In general,the species of soil bacteria and fungi in summer(pregrowing season,middle of the growing season and late growing season)were slightly higher than those in winter(onset of the freeze-thaw period,deep freeze period and thaw period).Bacteria showed no significant difference between the snow gradients;fungi showed a moderate or thick snow gradient at the genus and species level below the thin or no snow.(4)Proteobacteria,Actinobacteria,Acidobacteria and Bacteroidetes were dominant species in soil bacteria,and the relative abundance of the three groups accounted for about 80% of the total.Mortierellomycota,Basidiomycota and Ascomycota were dominant species in soil fungi,accounting for about 70% of the total.The diversity of soil bacteria was smaller in onset of the freeze-thaw period,larger in deep freezing period and mid-growing season,and the diversity of soil fungi was the highest in mid-growing season.The effect of snow thickness on the dominant populations and diversity of bacteria and fungi is different,and there is no obvious change rules.(5)Redundancy analysis and significance level indicated that there were significant(P<0.05)or extremely significant(P<0.01)positive correlations betweendry mass and organic carbon,total phosphorus,cellulose,C:N and C:lignin of litter leaves under different snow cover gradients,and strong negative correlations with total nitrogen,lignin,C:P and lignin: cellulose of litter leaves.Strong positive correlation.Bacteria Observed species were negatively correlated with litter properties,while bacteria Shannon and Simpson index were negatively correlated with litter dry weight,C and cellulose,and positively correlated with litter lignin.Four diversity indices of fungi were negatively correlated with litter C and lignin.In addition,the structural equation model found that there was a strong positive correlation between litter decomposition and soil properties,there was a negative correlation between litter decomposition and soil microbial diversity(bacteria,fungi),and there was a negative correlation between soil properties and microbial diversity. |
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