Soil Organic Carbon And Nutrient Characteristics Of Larix Principis-rupprechtii Forests With Different Management Measures

Reasonable regulation of stand density and selection of mixed mode as two widely recognized forest management measures can improve soil organic carbon and soil nutrient status in forest ecosystems,and contribute to forest soil carbon cycle.In order to improve the decline of soil fertility and the decline of ecological benefits of the main afforestation species of Larix principis-rupprechtii in the Saihanba area of Hebei Province,this study has two different management measures in the Saihanba Mechanical Forest Farm:(1)Betula platypHylla-North China Larch Mixed Forest,Pinus sylvestris-Larix principis-rupprechtii forest,Larix principis-rupprechtii forest,three species of trees.(2)Harvesting intensity CK(0%),group I(20%),group ?(30%),group ?(40%)of artificial pure forest of Larix principis-rupprechtii.The analysis of variance,correlation analysis and principal component analysis(PCA)of soil bulk density,water content,porosity,organic carbon,total nitrogen,total pHospHorus,pH and conductivity were compared to compare the organic carbon between different treatments.Differences in nutrient characteristics and correlations between individual indicator factors.Comprehensive evaluation of soil organic carbon and nutrient characteristics of different treatments of forest land,in order to select the density and mixed mode of Larix principis-rupprechtii with suitable density,to improve the soil fertility of forest land and improve the stability of forest system.(1)The soil organic carbon content of the three mixed plantations ranged from 15.28 to 38.39 g·kg-1,and there was a strong correlation between soil organic carbon and other soil factors,soil organic carbon and total nitrogen.The order of total pHospHorus content and conductivity value were all Betula platypHylla-Larix principis-rupprech.>Pinus sylvestris-Larix principis-rupprechn.In different layers of soil,the content of organic carbon and total nitrogen and total pHospHorus showed that the soil surface layer content was higher than that of the soil lower layer,and it had a "concentration effect".The soil under the forest was weakly acidic,with a pH range of 5.99-6.72.The bulk density and pH were different in different mixed forests.Pinus sylvestris-Larix principis-rupprechtii>L.chinensis L.>Betula plarypHylla-Larix principis-rupprechtii.According to the results of principal component analysis,the soil comprehensive scores of the three mixed forests were ranked as:Betula platypHylla-Larix principis-rupprechtii>Larix principis-rupprechtii forest>Pinus sylvestris-Larix principis-rupprechtii.It can improve the soil condition of forest land more than the other two forest stands.(2)The content of organic carbon in different density forests of Larix principis-rupprechtii was between 8.20-23.21g·kg-1.The changes of soil organic carbon,total nitrogen and total pHospHorus in the different density groups were basically the same,and the group ?>?I group>? group>CK group.In the vertical direction of the soil,with the deepening of the soil layer,soil organic carbon,total nitrogen and total pHospHorus decreased to varying degrees,showing the "energy-concentrating effect" of nutrients in the soil layer.Among them,there is a strong correlation between soil organic carbon,total nitrogen and other soil pHysical and chemical properties,and negative correlation with bulk density and pH.The bulk density and pH in different mixed forest stands were Pinus sylvestris-Larix principis-rupprechn.>Larix principis-rupprechtii>Betula platypHylla Principal component analysis showed that the comprehensive scores of soils in different forest densities were ranked as:Group ?>Group ?>Group ?>CK group.Among the Larix principis-rupprechtii plantations in the region,Group ?(1495 plants·hm-2)is more reasonable than other forest stands.