Soil Microbial Communities,Microbial Biomass Carbon And Soil Organic Carbon Characteristics In Natural And Planted Forests Across Climatic Gradient In China

A compound-specific radiocarbon analysis method of phospholipid fatty acid?PLFA?from forest soil was found in this study.Together with soil PLFA analysis and carbon isotope analysis of soil organic carbon,microbial structure,microbial biomass carbon and soil organic carbon?SOC?characteristics were investigated in natural and planted forest soil in different climatic zones in China.A study of microbial structure,six kinds of microbial biomass carbon and SOC characteristics in 2267 m gradiant climatic-vegetational zones in Gongga mountain was chosen because the vacuum of microbial biomass carbon characteristic research in natural forest.A study of microbial structure,microbial biomass,SOC inventory,SOC and dissolved organic carbon?DOC?turnover state in natural forest soil profiles of the climatic gradient in China was designed,for the lack SOC characteristic research in continental scale natural environment,especially deep SOC characteristic.The soil microbes and SOC characteristic of five tropical forests in Hainnan were discussed under the 60 year of forest conversion for the lack of forest-to-plantation conversion influence study on SOC characteristic in China.The main results and conclusions are as follows:1.The?¹³C of PLFA was same with the?¹³C of C3 plants in 10climatic-vegetational soil samples of Gongga mountain,indicating the microbial plant carbon source comes from C3 plant;the concentration and the?¹³C and?¹⁴C variation of C16:1?9 and brC17 in three climatic-vegetational types were higher than other PLFAs,indicating the representative bacteria and actinomyces could become the potential regulator of soil organic carbon cycling in changing natural environment.2.The SOC inventory and PLFA structure in 108 natural forest soils from 27study areas in China showed that the soil organic carbon inventories were highest in cold temperate zone,alpine zone subtropical zone,less in temperate zone and lowest in tropical zone,determines mainly by the deep soil organic carbon stock;microbial total biomass did not show significant difference in six climatic zones but fungi biomass was lower in subtropical and tropical zones;microbial structure showed significant difference in different climatic zones.3.The?¹⁴C of SOC and DOC in 12 soil profiles of four climatic zones in China showed little difference in deep SOC turnover time by the SOC?¹⁴C in C horizon,and the central surface warm temperate SOC turnover faster than other climatic zone for the higher SOC?¹⁴C in A and B horizons.4.The PLFA concentration representing soil microbial biomass and structure were significantly correlated with MAT,MAP,soil density,soil pH,SOC and soil total nitrogen in 108 natural forests.Besides,microbial structure was also significantly correlated with soil total phosphate.5.The correlation analysis of environmental parameters,soil properties,microbial parameters and SOC inventories in 108 natural forests and SOC?¹⁴C in 12soil profiles showed that forest SOC inventory were significantly correlated with SOC and soil total nitrogen concentration,bacteria,fungi and gram-positive bacteria and total microbial biomass,indicating the SOC inventory was significantly correlated with soil intrinsic properties and microbial biomass;forest soil organic carbon dynamic was influenced by climate and soil intrinsic properties.The deep SOC?¹⁴C was significantly correlated with MAP and the surface soil DOC?¹⁴C was significantly correlated with MAT and the ratio of gram-positive and negative bacteria,indicating that microbes may have influence on the surface soil DOC turnover state but little influence on the total SOC turnover state.6.The SOC inventory in five tropical forests in Hainan showed that SOC inventory of planted rubber plantations did not fallen compared with natural forest but the eucalyptus plantation did and could be recovered in 20 years after the cessation of tillage.The PLFA structure showed that the microbial biomass in planted forest was obviously less than the natural forest,and the natural-eucalyptus mixed forest could only recover to half of the natural forest.The?¹⁴C pattern of SOC in planting depth of planted forest was opposite with the natural forest,indicating an obviously homogenized SOC after forest-to-plantation conversion.The SOC turnover time reflected by the?¹⁴C in natural-eucalyptus mixed forest was similar with natural forest,indicating that the SOC turnover state of eucalyptus plantation was recovering to natural state after the cessation of tillage.