The Relationships Among Individual Size,Stoichiometry And Rhizosphere Microbes Of Zenia Insignis And Machilus Pauhoi

Zenia insignis is a valuable deciduous broad-leaved species in southern China.Machilus pauhoi is an excellent evergreen broad-leaved species.They are both characterized by the high ecological and economic value.Taking 6-year-old Zenia insignis and 11-year-old Machilus pauhoi forests as the research objects,typical sample survey was carried out and plant individual size was classified by the diameter at breast height(DBH).The relationships among individual size,stoichiometry and rhizosphere soil microbes were analyzed..The main results are as follows:(1)Leaf N and P contents of Z.Insignis forests were higher than that of M.Pauhoi forests,while C content were in the opposite.Leaf N/P ratio of Z.Insignis forests was greater than 16,which illustrated P limit.leaf N/P ratio of M.Pauhoi forests was between 14and 16,which presented co-limitation by N and P.Leaf P content was extremely significantly correlated with DBH of Z.Insignis forests(p<0.01),with the increase of DBH showing a trend of slow decline after rise.Leaf N/P ratio was significantly negatively correlated with DBH of Z.Insignis forests(p<0.05).Leaf N and P contents were significantly positively correlated with DBH of M.Pauhoi forests(p<0.05).Leaf C/P ratio was extremely significantly correlated with DBH of Z.Insignis forests(p<0.01),with the increase of DBH showing a trend of slow rise after decline.Leaf C/N and C/P ratios were extremely significantly negatively correlated with DBH of M.Pauhoi forests(p<0.01).(2)Soil pH,water content,C,N and P contents,NH4+-N,C/N,C/P and N/P ratios in 0-10cm soil horizon of Z.Insignis and M.Pauhoi forests were all higher than those of 10-20cm soil horizon,but bulk density was in the opposite.Rhizosphere soil P content of Z.Insignis and M.Pauhoi forests were lower than mean soil P content of China flora(0.56 mg/g).Rhizosphere soil N content and N/P were extremely significantly positively correlated with DBH of M.Pauhoi forests(p<0.01).(3)Rhizosphere soil microbial total PLFAs in 0-10cm soil horizon of Z.Insignis and M.Pauhoi forests were higher than that of 10-20cm soil horizon.Rhizosphere soil bacteria,actinomycetes,total PLFAs contents and actinomycetes/bacteria ratio of Z.Insignis forests were higher than those of M.Pauhoi forests,while fungi content and fungi/bacteria ratio were in the opposite.In 10-20cm soil horizon,Rhizosphere soil Gram-positive bacteria(G+),Gram-negative bacteria(G-),bacteria,actinomycetes and fungi content were significantly correlated with DBH of Z.Insignis forests,with the increase of DBH showing a trend of rise after decline.Rhizosphere soil G+,G-and bacteria content were significantly positively correlated with DBH of M.Pauhoi forests(p<0.01).Rhizosphere soil microbial nitrogen(MBN)were significantly positively correlated with DBH of M.Pauhoi forests(p<0.05).(4)Rhizosphere soil actinomycetes/bacteria ratio was significantly negatively correlated with leaf C/N ratio of Z.Insignis forests in 0-10cm soil horizon(p<0.05),while rhizosphere soil G+/G-ratio was significantly negatively correlated with leaf C content of Z.Insignis forests in 10-20cm soil horizon(p<0.05).Rhizosphere soil actinomycetes content was significantly negatively correlated with leaf C and N contents of M.Pauhoi forests in 0-10cm soil horizon(p<0.05),while rhizosphere soil G+,G-and bacteria contents were significantly negatively correlated with leaf C and P contents of M.Pauhoi forests in 10-20cm soil horizon.Great differences of correlation between rhizosphere soil nutrients and microbes in Z.Insignis and M.Pauhoi forests were detected.In 0-10cm soil horizeon,rhizosphere soil G+ and bacteria contents were significantly positively correlated with soil C/P and N/P ratios of Z.Insignis forests,while those of M.Pauhoi forests were in the opposite.Rhizosphere soil MBN was significantly negatively correlated with leaf N content of M.Pauhoi forests(p<0.05),while it was extremely significantly positively correlated with soil N content(p<0.01).