| Vegatation restoration can significantly improve soil physicochemical properties,improve soil fertility and increase soil carbon storage to improve ecological efficiency.Thus,it is very important to clarify the changing pattern of ecological restoration process on soil organic carbon and its stability of different vegetation types.In order to explore the microbial mechanism of soil organic carbon sequestration in different vegetation restoration.We studied the soil microorganisms,metabolic pathways and functional genes involved in carbon cyclying via metagenomics sequencing.The soil organic carbon chemical structure and its stability were determined by CP/MAS 13 C NMR.What's more,the relationships between soil organic carbon and microbial community as well as functional genes under different revegetation types were analyzed.The results demonstrated that:(1)Compared with coniferous forests(Larix gmelinii plantation,Pinus koraiensis plantation)and conifer-broadleaf forest,broadleaved forests(Juglans mandshurica forest,Quercus mongolica forest)could increase the contents of soil total carbon,total nitrogen,available nitrogen,dissolved organic carbon and microbial carbon.(2)The dominant soil organic carbon of different vegetation types was O-alcoxyl C(45.36%-48.12%),followed by alkyl C(17.14%–21.84%),aromatic C(17.34%–20.69%)and carbonyl C(13.61%–15.82%).Broadleaved forests(Juglans mandshurica forest,Quercus mongolica forest)had higher aromatic C,aromaticity,aromatic C/ O-alcoxyl and lower aliphatic/aromatic and aliphaticity.The alkyl C content and alkyl C / O-alcoxyl of coniferous forests(Larix gmelinii plantation,Pinus koraiensis plantation)were significantly higher than those of broadleaved forests and conifer-broadleaf forest.The relative abundances of functional genes degradation of alkyl C in coniferous forest were higher than in broadleaved forests and conifer-broadleaf forest,and the potential for degradation was greater.It could be seen that the organic carbon in broadleaved forests was relatively more stable.(3)The carbon utilization capacity by soil microbial communities was following the order Juglans mandshurica > Quercus mongolica > conifer-broadleaf forest > Larix gmelinii > Pinus koraiensis.Juglans mandshurica hold the highest Shannon index,Simpson index and Mclntosh index,which was 0.957,3.22 and 8.01,respectively.The soil microbial community function existed significant differences under different vegetation types.Soil microbial community function in coniferous forests(Larix gmelinii plantation,Pinus koraiensis plantation)was obviously separated from broadleaved forests and conifer-broadleaf forest along the PCA1,and principal different carbon sources included esters and carbohydrate.(4)There were significant differences in microbial diversity index and microbial community composition among different vegetation types.Soil bacterial ACE index and Chao1 index of conifer-broadleaf forest were the highest,which was 3637.79 and 3568.24,respectively.While Shannon index and Simpson index in Juglans mandshurica were the highest,which was 9.71 and 0.9950 respectively.The dominant bacteria phyla in this area were Proteobacteria(39.98%-45.11%)and Acidobacteria(15.18%-27.32%),and the dominant bacterial class was ?-Proteobacteria.The taxonomic groups enriched in Juglans mandshurica were Verrucomicrobia,Actinobacteria and Nitrospirae.Bacteroidetes was enriched in the soil of Pinus koraiensis plantation.Broadleaved forests(Juglans mandshurica,Quercus mongolica),conifer-broadleaf forest and coniferous forests(Larix gmelinii,Pinus koraiensis)hold different bacterial communities.The nodes in the soil bacterial network of broadleaved forests were more tight connectivity,and broadleaved forest could better enhance the connections and interactions among soil bacterial communities.Soil p H,total carbon,microbial biomass carbon,dissolved organic carbon and available phosphorus were the main control factors affecting the soil bacterial communities in this area.(5)Significant differences of soil fungal diversity indexes were observed under different vegetation types.Soil fungal Shannon index,ACE index,Chao1 index and Simpson index were the highest in Juglans mandshurica forest,which was 8.18,879.57,879.08 and 0.99,respectively.The dominant fungal phyla in this area were Basidiomycetes(21.31%-66.08%),Ascomycetes(24.82%-51.88%),Zygomycetes(2.21%-6.37%)and Rozellomycota(0.42%-2.09%).Significant differences of soil fungal community structure of different vegetation types were observed,especially between coniferous forests and broadleaved forests.Among them,the soil fungal communities of Larix gmelinii plantation,Pinus koraiensis plantation and coniferbroadleaf forest were similar,which was a cluster;soil fungal communities of Quercus mongolica forest and Juglans mandshurica forest were similar,which was another cluster.The nodes in the soil fungal network of broadleaved forests were more tight connectivity,and broadleaved forest could better enhance the connections and interactions among soil fungal communities.(6)Significant differences of carbon cycle pathway were observed between coniferous forests and broadleaved forests.The phylogenetic distance of soil microorganisms in different revegetation types increased from broadleaved forest to coniferous forest.The soil microbial phylogenetic distance of Larix gmelinii plantation,Pinus koraiensis plantation was similar,and Quercus mongolica forest and Juglans mandshurica forest had similar soil microbial phylogeny distance.Soil environmental factors had significant influences on the relevant pathways of soil microbial carbon cycle.Soil total nitrogen,soil organic carbon and microbial biomass carbon were the main factors that determined the soil carbon cycling pathway.Soil environment factors had significant impacts on carbon fixation and carbon metabolic pathway.Soil total nitrogen and soil organic carbon were the main factors determining carbon sequestration pathway,while soil organic carbon was the main factor determining carbon degradation pathway.(7)The carbon cycle in the soil is co-acted by highly diverse microbial groups.Proteobacteria,Acidobacteria and Actinobacteria were the main microbial groups in soil carbon reactions and carbon cycles.The joints between soil microorganisms and organic carbon of broadleaved forests had higher degree of connectivity,and broadleaved forest could improve the relationships and interactions between soil microbial communities and carbon.The enhanced relationship between the molecular structure of soil organic carbon and soil bacteria and fungi might affect the transformation and storage of carbon in the soil.Changes in the soil microbial network were important biological factors affecting the molecular structure of soil organic carbon.In summary,different vegetation types change the functional genes of microorganisms involved in the carbon cycle by changing the composition of soil microbial communities,which affected soil organic carbon sequestration and its stability.Vegetation restoration with Quercus mongolica forest and Juglans mandshurica in the eastern mountainous region of Liaoning Province could better improve soil nutrient conditions,increase soil organic carbon storage and stability.Our results analyze the microbial mechanism of soil organic carbon sequestration in broadleaved forest,coniferous and broadleaved forest,and coniferous forest at the genetic level,providing new insights into the interactions between carbon response in soil and microorganism... |
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