Effects Of Mixing Precious Indigenous Tree Species And Eucalyptus On Biomass,Carbon Stocks And Soil Physicochemical Preperties

Eucalyptus is a critical species introduced to China using for timber with short rotations.The management of pure Eucalyptus plantations has raised concerns regarding ecological environment problems.As a result,developing mixed plantations of precious indigenous tree species with Eucalyptus becomes the future development trend.However,there is a lack of in-depth research on the effects of mixing precious native tree species with Eucalyptus.In this study,pure Eucalyptus plantations,mixed Eucalyptus and Castanopsis hystrix plantations,and mixed Eucalyptus and Parashorea chinensis plantations were selected as the subjects to elucidate the varieties of biomass and carbon stocks of pure and mixed plantations through investigating properties of biomass and carbon stocks of pure and mixed plantations by a variety of methods such as field test and laboratory analysis.On this basis,we reveal the increasing production and carbon sequestration effects of mixing precious indigenous tree species and Eucalyptus through identifying the maincontrol factors of stand biomass and carbon storage by combining soil physical and chemical properties with microbial biomass carbon and nitrogen.The major results are as follows.(1)Mixing C.hystrix and P.cathayensis with Eucalyptus can not only significantly increase the biomass and carbon storage of Eucalyptus,but also significantly increase the ecosystem biomass and carbon storage.The biomass of Eucalyptus trees in the three stands showed a trend as EPMP(118.20 t/hm2)> ECMP(110.31 t/hm2)> EPP(102.93 t/hm2).Moreover,the biomass of the tree layers showed ECMP(121.94 t/hm2)>EPMP(120.88 t/hm2)> EPP(102.93 t/hm2)with biomass of the mixed stands significantly higher than that in EPP.The carbon stocks of Eucalyptus trees in the three stands varied from 48.09?54.90 t·C/hm2,with the highest in EPMP,followed by ECMP,and the lowest in EPP.The ecosystem carbon stocks of mixed plantations(EPMP: 227.37t·C/hm2,ECMP: 225.45 t·C/hm2)were significantly higher than EPP(197.89t·C/hm2),while there was no significant difference in carbon stocks between the two mixed plantations.(2)Mixing C.hystrix and P.cathayensis with Eucalyptus can help to improve soil physical and chemical properties,increase the surface soil water content,improve soil porosity,increase the contents of soil SOC,TP,TK,AN,AP,AK,and thus increase the contents of MBC,MBN and MBP.(3)The increases of ecosystem biomass and carbon storage in mixed plantations are closely related to the improvement of soil physical and chemical properties.