Characteristics Of Soil Microbial Community And Its Influencing Mechanism During The Early Stage Of Wood Decomposition In A Subtropical Forest Ecosystem

Fallen wood decomposition is a key process driving primary productivity and nutrient cycle in forest ecosystem.Different factors such as environmental conditions,wood quality and the decomposer communities play a vital role in wood decomposition.In fact,immediately after wood fallen in the forest floor,wood is attacked by a range of decomposer guilds.In order to explore the effects of different microbial community on wood decomposition and subsequent changes of soil physical and chemical properties,we have selected two subtropical forest sites with different climatic zones,Tiantong National Forest Park and Putuo Mountain situated in Zhejiang Province,China.In each site,we have selected three sample plots,where tree species were fallen in ground and left for decomposition for 1.5 years.We also performed replacement decomposition(Tiantong mountain to Putuo Mountain or vice versa)of selected three common tree species(Cinnamomum camphora,Liquidambar formosana and Pinus massoniana)in order to explore the effect of decomposing wood on soil microbial and physic-chemical properties more accurately.We have collected soil samples from under the decomposing wood to perform required physic-chemical and microbiological analysis.To determine soil bacterial and fungal community structure,T-RFLP method was used.Results shows that in Tiantong Mountain site,1)During the decomposition process of Tiantong Mountain,the soil pH value is significantly reduced;soil organic matter and available potassium increased significantly during the decomposition of evergreen broad-leaved tree species Cinnamomum camphora and Machilus thunbergii,while the soil total nitrogen content increased significantly during the decomposition of Quercus glauca;The soil available potassium content in the deciduous broad-leaved tree species Liquidambar formosana decomposition increased significantly,the soil available phosphorus content increased significantly after the decomposition of Acer buergerianum.2)Different tree species have certain effects on soil bacterial and fungal community structure during the decomposition process,and the changes of fungal community structure are more obvious.Redundancy analysis showed that soil available phosphorus content,bark nitrogen content and phosphorus content were the main factors affecting microbial community structure changes.3)In the study of replacement tree species,there is a significant difference in the effect of the decomposition of Cinnamomum camphora on soil available potassium in different growing areas,the decomposition of Liquidambar formosana in different growing areas significantly changed the composition of soil bacterial and fungal communities,the soil fungal community structure changed significantly.Results shows that in Tiantong Mountain site,1)The soil organic matter content,carbon-nitrogen ratio,available potassium content and available phosphorus content of the evergreen broad-leaved tree species Cinnamomum camphora were significantly increased during the decomposition process;during the decomposition of deciduous broad-leaved tree species,white Quercus fabric and Acer buergerianum,the content of available potassium and available phosphorus in soil increased significantly.2)The composition of soil fungal community changed significantly during the decomposition of different tree species;significant changes in the bacterial community structure of deciduous broad-leaved tree species,Liquidambar formosana and Acer buergerianum;the components of the fungal community of the evergreen broad-leaved tree species,Cinnamomum camphora and Machilus thunbergii,,changed significantly.3)In the study of replacement tree species,there were significant differences in soil organic matter content and carbon to nitrogen ratio during the decomposition of Cinnamomum camphora in different growing areas;there were significant differences in the effects of soil extractable potassium on the decomposition of Liquidambar formosana in different growing areas.After the replacement tree species is decomposed,the composition of soil fungal community has changed significantly,the community structure has also undergone significant variation,among them,the soil fungi diversity index of the tree species Cinnamomum camphora was significantly different.We can conclude that wood decomposition can alter soil physical and chemical properties,as well as original microbial communities,especially fungal community structure depending on different tree species.Moreover,the decomposition of the same tree species in different climatic zones has different effects on soil properties.Our wood species replacement study also showed that the same species could have different effects on soil physical,chemical and microbial properties due to their own physical and chemical properties.