Effects Of Moso Bamboo Expansion On Soil Carbon And Nitrogen Stocks In Subtropical Forests

It has raised wide consideration that subtropical moso bamboo expansion caused adjacent forests degradation.Previous studies concerning how moso bamboo expansion affects on soil carbon and nitrogen cycling have been wide conducted.To date,however,the effects of moso bamboo expansion on soil carbon and nitrogen storage are still poorly understood,especially with respect to the functions of soil microorganisms involved in the carbon and nitrogen cycles,that is most probably because the formation and storage of carbon and nitrogen usually mediated by biotic and abiotic factors,such as vegetation types,microbial communities,physic-chemical properties,etc.In the present study,field sampling and laboratory analysis combined to determine the effects of moso bamboo expansion on soil carbon and nitrogen stocks and its contrasting mechanisms.The typical transects of moso bamboo expanding to evergreen broad-leaved forest and coniferous forests were selected respectively.The soil samples of 0-10 cm,10-20 cm and 20-40 cm were taken by excavation section method to analyze the differences of soil physical-chemical properties,soil microbial functions gens involved in carbon and nitrogen cycles,soil carbon and nitrogen stocks among different forest types in the expanded transects.The results are as follows:(1)Moso bamboo expanded to evergreen broad-leaved forest significantly decreased soil water content,soil bulk density,soil organic carbon content,soil dissolve organic carbon content,and cbb L and nos Z gene copy numbers.(2)Moso bamboo expanded to evergreen broad-leaved forest significantly decreased soil carbon and nitrogen stocks.Results from the structural equation model indicate that the decreased soil carbon storage mainly and directly drive by the reduced soil water content,soil bulk density,soil organic carbon content,and soil cbb L copy numbers.On the contrast,soil water content and nos Z copy numbers mediated the decreased soil nitrogen stocks.(3)Moso bamboo expanded to coniferous forest decreased soil organic carbon content,soil total nitrogen content,soil bulk density,and nos Z copy numbers.(4)Moso bamboo expanded to coniferous forest reduced soil carbon and nitrogen stocks.Results from the structural equation model indicate that soil organic carbon mainly drives the decreased soil carbon stocks.Meanwhile,reduced soil total nitrogen content and soil bulk density is the direct factors that caused soil nitrogen stocks decreased.In conclusion,biotic and abiotic factors combined to drive the decreased soil carbon and nitrogen stocks during moso bamboo expanding to evergreen broad-leaved forest.On the contrast,abiotic factors mainly drive the reduction of soil carbon and nitrogen stocks during moso bamboo expanding to coniferous forest.Our results are helpful to deep understand the ecological effects of moso bamboo expanded to subtropical forests,and would provide a scientific basis for reasonably regulating the processes of moso bamboo expands to subtorpcial forests.