The Study On Change Characteristics Of Rhizosphere Soil Microbial Community With Continuous Planting Of Cunninghamia Lanceolata

Chinese fir(Cunninghamia lanceolata(Lamb.)Hook),which was planted at south of China is the very important coniferous timber species.With the demand going up,the area of plantation has been enlarging for many years.The producer found that all the increment and amount of growing stock of the Chinese fir decreased with the species undergoing a long-term monoculture.In the end,the consecutive monoculture problem has appeared.So the production and operation of the Chinese fir is affected.Therefore,the consecutive monoculture problem has become a very hot and focus issue for lots of biological,ecological,forestry researchers.In this study,we chose Youxi National Forest Farm,Fujian Province,China as the experiment site.The rhizospheric soil microorganisms of the Chinese fir were our research object.Three samples were first Chinese fir rotation plantation(FCP),second rotation plantation(SCP)and third rotation plantation(TCP).Three techniques Bio log,PLFA,T-RFLP and the soil properties used to analyze the root rim soil microbial structure and catabolic activity.This study revealed how the root rim soil microbes of the Chinese fir respond the consecutive monoculture process from a new microbe prospective.In addition,this study not only provided the theoretical foundation for the problem but also gave some advices of scientific operation and management for the other timber forest.The specific research results are as follows:(1)Correlation analysis of microbial community diversity and soil properties show that,all the soil chemical property indices significantly correlated with the diversity indexes except soil pH.There was extremely significant correlation between diversity index and TOC and AN.In contrast,the C/N ratio showed a significant negative correlation with diversity index,suggesting that soil C and N contents play an important role on soil microbial diversity.(2)The Biolog analysis of different planting time soil microbes show that,The AWCD valuesincreased with the incubation time in all soil samples.The utilization rate of FCP soil was much higher than SCP and TCP soils,indicated that The soil microbial catabolic activity decreased with the increasing planting rotations(FCP>SCP>TCP).For the carbon substrates,there was a significant difference between these samples,however the basic rule of the utilization on these carbon substrates was basically same,whatever the amino acids,carbohydrates,polymers,phenolic acids,the rule was:FCP>SCP>TCP.In addition,carbohydrates and carboxylic acids were the dominating carbon substrates,follow by the amino acids,phenolic acids,polymers and the amines was the least.As for the functional diversity index,including Simpson index,Shannon index,Evenness index,the rule was FCP>SCP>TCP,so it showed that,the functional diversity decreased with the consecutive monoculture time goes on.(4)Used the T-RFLP technique to analyze the soil microbes of Chinese fir and we identified 12 phyla:including Proteobacteria;Actinobacteria;Planctomycetes;Firmicutes;Cyanophyta;Spirochaete;Bacteroidetes;Thermomicrobia;Tenericutes;Fusobacteria;Clostridi um;Fiber,others.Percentage was more than 10%of FCP bacteria including 3 phyla:Firmicutes(34.97%);Actinobacteria(12.57%);Prot ebacteria(10.93%).Percentage was more than 10%of SCP bacteria including 3 phyla:Firmicutes(28.77%);Proteobacteria(14.16%);Acti nobacteria(10.96%).Percentage was more than 10%of TCP bacteria including:Firmicutes(20.47%);Proteobacteria(20.18%),Actinobacter ia(17.51%).Used the Alu I T-RFs to analyze different rotation plantation soil microbes diversity index(Shannon-Weiner Index;Simpson Index;Evenness Index)of Chinese fir show that,Shannon-Weiner Index(5.79±0.16)and Simpson Index(0.97±0.01)of TCP was higher than FCP(5.47±0.03;0.96±0.01)and SCP(5.58±0.26;0.96±0.01)As for the relative abundance of specific bacteria in Chinese fir soil with different monoculture,we classified the bacteria as five group by their functions including Carbon cycling;Sulfur cycling;Cellulose degradation;Probiotics and Pathogens.The results showed that,the relative amount(percentage)variation trend of Flavobacteriacolumnare for the Carbon cycling was FCP(0.28)>SCP(0.16)>TCP(0);the relative amount(percentage)variation trend of Methylophilus LW3 was FCP(1.30)>SCP(1.10)>TCP(0.74).As for the Cellulose degradation,the relative amount(percentage)variation trend of Capnocytophagaochracea was FCP(0.30)<SCP(0.40)<TCP(0.58).As for the Sulfur cycling,the relative amount(percentage)variation trend of Sulfobacillus-Sulfobacillusdisulfidooxdans was FCP(1.91)<TCP(2.09)<SCP(2.15).As for the Probiotics,the relative amount(%)variation trend of Bacilluspasteurii was:FCP(0.83)>SCP(0)≥TCP(0).As for the Pathogens,the relative amount(percentage)variation trend of Corynebacteriumgenitalium was FCP(5.13)<SCP(5.57)<TCP(7.46).Overall,the soil probiotics of Chinese fir decreased with consecutive monoculture increasing;while the pathogens increased with time going by.