Effects Of Plant Diversity On Soil Labile Carbon And Nitrogen Contents In A Subtropical Forest

In recent years,with the rapid loss of biodiversity,the relationship between biodiversity and forest ecosystem functions has become a research hotspot in ecology.As an important ecosystem function,even minor changes in soil organic carbon stock can have an important impact on the global carbon budget.Compared to soil organic carbon stock,soil labile organic carbon(C)and nitrogen(N)are the most active components of soil organic matter,and they can respond rapidly to different forest management practices.However,the effect of plant diversity on forest soil labile organic C and N content is still poorly understood so far.Based on this,this thesis relies on the Biodiversity-Ecosystem Functioning Experiment China(BEF-China)platform established in 2009 to select plots planted with one to eight tree species and distinguish different functional groups(evergreen and deciduous)to conduct experiments.Soil samples were collected and soil organic C,soil labile organic C,N content and other indicators,as well as tree biomass were measured to explore the impact of plant diversity on soil labile organic C and N content.The main results are as follows:(1)The results of the effect of plant diversity on soil labile organic C content showed that the content of soil labile organic C increased significantly with the increase of plant diversity.After distinguishing different functional groups,When a single tree species is planted,the soil labile organic C content of evergreen tree species(Schima superba,Cyclobalanopsis myrsinifolia)and the deciduous tree species(Rhus chinensis,Choerospondias axillaris,Quercus serrate)are significantly higher than that of other tree species among treatments.when tree species are planted in pairs,the soil labile organic C content of deciduous-evergreen combination(Quercus fagri-Cyclobalanopsis glauca)and evergreen-evergreen combination(Cyclobalanopsis myrsinifoliaCastanopsis eyrei)are significantly higher than that of other combinations among treatments.when the four tree species are mixed planted,the soil labile organic C content of deciduous-evergreen combination(Quercus fagri-Cyclobalanopsis glaucaSchima superba-Rhus chinensis)and the deciduous-deciduous combination(Castanea henryi-Nyssa sinensis-Liquidambar formosana-Sapindus mukorossi)are significantly higher than that of deciduous-evergreen combination(Cyclobalanopsis myrsinifoliaCastanopsis eyrei-Koelreuteria bipinnata-Quercus fagri).(2)The results of the effect of plant diversity on soil labile organic N content showed that the content of soil labile organic N increased significantly with the increase of plant diversity,After distinguishing different functional groups,When a single tree species is planted,the soil labile organic N content of deciduous tree species(Nyssa sinensis,Sapium sebiferum,Castanea henryi)and the evergreen tree species(Schima superba)are significantly higher than that of deciduous tree species(Quercus fagri,Liquidambar formosana)when tree species are planted in pairs,the soil labile organic N content of deciduous-evergreen combination(Quercus fagri-Cyclobalanopsis glauca)and evergreen-evergreen combination(Cyclobalanopsis myrsinifolia-Castanopsis eyrei)are significantly higher than that of deciduous-deciduous combinations(Choerospondias axillaris-Sapium sebiferum,Liquidambar formosana-Sapindus mukorossi).when the four tree species are mixed planted,the soil labile organic N content of deciduous-evergreen combination(Cyclobalanopsis myrsinifoliaCastanopsis eyrei-Koelreuteria bipinnata-Quercus fagri)is significantly higher than that of other combinations among treatments.(3)The results of the effect of plant diversity on soil organic C stock showed that both soil organic C stock and tree biomass increased significantly with the increase of plant diversity.After distinguishing different functional groups,When a single tree species is planted,the soil organic C stock of deciduous tree species(Choerospondias axillaris,Rhus chinensis)and the evergreen tree species(Schima superba,Cyclobalanopsis myrsinifolia)are significantly higher than that of other tree species except(Quercus serrata,Koelreuteria bipinnata,Lithocarpus glaber)tree species.when the tree species are planted in pairs,the soil organic C stock of deciduous-evergreen combination(Koelreuteria bipinnata-Lithocarpus glaber)is significantly higher than that of other combinations among treatments.when the four tree species are mixed planted,the soil organic C stock of deciduous-evergreen combination(Cyclobalanopsis myrsinifolia-Castanopsis eyrei-Koelreuteria bipinnata-Quercus fagri)is significantly higher than that of other combinations among treatments.In summary,the results show that plant diversity increases soil labile organic C and N content,soil organic C stock,and tree biomass significantly after 10 years of treatment.Our results highlight the importance of plant diversity,and suggest that planting stands with more diverse tree species in the future,thereby increasing forest soil carbon sinks and mitigating climate warming.