| Soil physical,chemical and biological properties,soil organic carbon and soil microbial structure can be altered by the quantity and quality of plant litter and root exudates of different tree species.Under the background of global climate change,to study the soil carbon dynamics under plantations of different tree species is of great importance to understanding the mechanisms of how tree plantations will respond to climate change.Among the numerous studies in this area but few studies to compare the plantations with species treatments which start from seedling and under the same soil and climate conditions.Using 13 major silvicultural species in China we established an experiment with the same climate,soil and management history conditions in mid-subtropical China in 2012.This research focused on soil carbon under pure plantations of five tree species,including three broad-leaved species(Michelia macclurei,Schima superba,Castanopsis carlesii)and two conifer species(Pinus massoniana,Cunninghamia lanceolata).Each treatment had four replicates.Five years after establishment we measured soil organic carbon components,soil property,soil microbial community and soil enzyme activity at the 0-10 cm depth to examine tree species effect on soil organic carbon dynamices.The major results are as follows:(1)Tree species significantly influenced the soil active organic carbon.The contents of soil dissolved organic carbon(DOC),ease oxidize carbon(EOC)and H2SO4-labile carbon pool(LP ?-C,LP?-C)were higher in broad-leaved tree species than coniferous tree species with the lowest in C.lanceolata species.There were significant correlations between the labile soil organic carbon among the five tree species.There was no significant difference in soil organic carbon(SOC)and H2SO4-recalcitrant carbon pool(RP-C)between the different tree species treatments(P>0.05).This due to the common garden experiment,the tree age of the tree species is too small(5 years),and the amount of litter input to the soil is limited.It has not accumulated enough to affect or change t soil organic carbon(SOC)and H2SO4-recalcitrant carbon pool(RP-C)contents.(2)The ratios of soil active organic carbon to total soil organic carbon for DOC/SOC,MBC/SOC,EOC/SOC and LP-C/SOC were 0.16%?0.56%,0.34%?3%,14.48%?23.25%and 45.07%?52.73%respectively.There was a trend that the ratios of DOC/SOC,EOC/SOC and LP-C/SOC were higher in the broad-leaved species.The ratio of EOC/SOC and LP-C/SOC were not significantly higher in broad-leaved species than the conifer species treatments.These results indicate that broad-leaved species were more beneficial to the accumulation of soil active organic carbon compared to conifer species.The ratio of H2SO4-recalcitrant carbon pool to total soil organic carbon was lower in broad-leaved tree species than in conifer species,but did not reach a significant level.(3)Soil microbial community structure and soil enzyme activity were significantly different between the tree species treatments.The content of Gram-positive bacteria(GP),Actinomycete(ACT),total PLFA biomass and Bacteria were significantly higher in C.carlesii plots than in C.lanceolata plots,there was no significant difference in GP,ACT and total PLFA biomass Bacteria between the broad-leaved species but for conifer species P.massoniana was significantly higher than C.lanceolata.This may be due to higher coverage of understory shrubs and forest floor with denser root biomass in P.massoniana plots.The activity of Cellobiohydrolase(CBH)was significantly higher in broad-leaved species than in conifer species.Acid phosphatase(AP),?-glucosidase(?G)and?-N-acetylglucosaminidase(NAG)activity were the difference law were not obvious in in broad-leaved species and conifer species.Peroxidase(PEO)was higher in conifer species than in broad-leaved tree species with the highest value in C.lanceolata plots.H2SO4-labile carbon pool ?(LP?-C)was important factor affecting soil microbial community structure and enzyme activity.At the same time,microbial biomass carbon(MBC),nitrate nitrogen and soil water content(SWC)were also important factors affecting soil enzyme activity.This indicates that tree species alters the content of soil active organic carbon and soil properties and consequently affect the soil microbial community and soil enzyme activity. |
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