Effects Of Land Use Patterns On Soil Organic Carbon Stability And Microbial Community Diversity In Yellow Sea Forest Park

Due to the increasing greenhouse gas emissions such as carbon dioxide in the atmosphere,which have a profound impact on global climate change,people have been actively seeking low cost and sustainable carbon sequestration methods.Soil is the largest carbon pool in biosphere,which has the greatest carbon sequestration potential to mitigate the impact of climate change.Land use change may lead to carbon dioxide emissions or sequestration,and then affect the atmospheric carbon pool,which is a key factor affecting the global soil organic carbon balance.At the same time,understanding how soil quality changes after land use change is essential to better understand the potential of soil production and its sensitivity to land use change.Soil disturbance and plant species change caused by land use change will also affect the composition and abundance of soil microbial community.Therefore,it is of great significance to study the effects of different land use patterns on soil physical and chemical properties,organic carbon components,microbial communities and organic carbon mineralization for improving carbon retention in soil and slowing down climate change.In this study,five main land use patterns(ginkgo plantation(Ginkgo biloba L.),wheat field(Triticum aestivum L.),metasequoia plantation(Metasequoia glyptostroboides Hu et Cheng),ginkgo and wheat agroforestry system and ginkgo and metasequoia agroforestry system)in Yellow Sea Forest Park were investigated.The differences of soil physical and chemical properties,soil enzyme activity,the components and chemical composition of organic carbon,and bacterial and fungal communities in 0-20 cm and 20-40 cm soil layers of different land use patterns were studied.The organic carbon mineralization in 0-20 cm and 20-40 cm soil layers of different land use patterns was studied through indoor culture.The results can provide theoretical basis for the rational use and sustainable management of land.The main conclusions are as follows:(1)In terms of physical and chemical properties,in the 0-20 cm soil layer,compared with wheat fields,other systems had higher total nitrogen,soil organic carbon content,and microbial carbon content.Ginkgo and wheat system had the highest total nitrogen,soil organic carbon content,microbial carbon,and easily oxidizable organic carbon,as well as the nitrogen and organic carbon stock.Ginkgo and wheat system had the lowest aromatic carbon and the highest alkoxy carbon.The soil urease activity in other systems was higher than in the wheat field.The soil alkaline phosphatase,invertase,and catalase activities were highest in the ginkgo and wheat system.In the 20-40 cm soil layer,compared with wheat fields,other systems had higher total nitrogen content.Only ginkgo and wheat system had the higher soil organic carbon conten than the wheat field.The easily oxidized organic carbon content was the highest in metasequoia system.The contents of nitrogen,phosphorus and organic carbon decreased with the deepening of soil layer(except dissolved organic carbon).With the exception of cellulase and catalase,the activities of other enzymes decreased with the increase of soil depth.Afforestation and agroforestry practices have significantly improved the physical and chemical properties of the soil.(2)In terms of fungal community,the richness indices(ACE and CHAO1)of the wheat field was the highest,the diversity index(Shannon)of the ginkgo and wheat system was higher than other systems,and the Alpha indices of the 0-20 cm soil layer was significantly higher than the 20-40 cm soil layer.The Alpha indices were significantly positively correlated with total nitrogen and nitrate nitrogen content.Ascomycota and Basidiomycota are the dominant fungal phyla of all land use patterns,and the Faecalis and Ascomycetes are the main dominant fungal class.The relative abundance of Ascomycota in the ginkgo and wheat system was significantly higher than in other systems.Total nitrogen,nitrate nitrogen,and available phosphorus significantly affected the composition of fungal communities.(3)In terms of bacterial community,the metasequoia system had the highest Alpha indices in the 0-20 cm and 20-40 cm soil layers,followed by the ginkgo and wheat system.The effect of different land use patterns on the bacterial community composition of 0-20 cm soil layer was greater than that of 20-40 cm soil layer.The dominant phyla of all land use patterns were Proteobacteria,Acidobacteria,Chloroflexi,Actinobacteria,and Nitrospirae.Acidobacteria,Actinobacteria,Alphaproteobacteria,Betaproteobacteria,Deltaproteobacteria,Anaerolineae and Nitrospira were the dominant bacteria class.Total nitrogen,total phosphorus,organic carbon,and easily oxidizable carbon were the most critical factors explaining the differences in bacterial communities.(4)In terms of organic carbon mineralization,the cumulative mineralization of the 0-20 cm and 20-40 cm soil layers was between 99.08-118.80 mg CO2-C kg-1 dry soil and 60.79-78.08 mg CO2-C kg-1 dry soil,respectively.The accumulated mineralization of metasequoia system was the highest,and that of ginkgo and wheat system was the lowest.The ratio of respiratory metabolic entropy and potential mineralizable carbon to total organic carbon content in the wheat field system was significantly higher than in other systems.The ratio of potentially mineralizable carbon to total organic carbon content in the ginkgo and wheat systems was the lowest,indicating the strongest carbon sequestration capacity.The cumulative release of CO2 was significantly positively correlated with organic carbon and easily oxidizable carbon.Stepwise regression analysis showed that Shannon index was the main factor to explain the differences of organic carbon mineralization.