基于T-RFLP方法的连栽杉木根际土壤细菌群落变化研究

Analysis of terminal restriction fragment length polymorphisms in soil bacterial communities in Chinese fir plantations that have undergone continuous cultivation

运用末端限制性片段长度多态性技术(T RFLP),研究福建省尤溪国有林场的多代连栽杉木根际土壤细菌群落变化特征。结果表明:杉木多代连栽后根际微生态失衡,表现为碳循环菌和氮循环菌等有益菌数量减少,病原菌数量增加。在不同代数杉木土壤中,4种内切酶消化后产生的末端限制性片段(T RFs)数量具有显著差异,第一代杉木(first Chinese fir rotation plantation,FCP)最高,第二代杉木(second Chinese fir rotation plantation,SCP)次之,第三代杉木(third Chinese fir rotation plantation,TCP)最少。土壤理化性质结果表明连栽导致土壤养分逐代降低,除土壤碳氮比与细菌群落多样性呈显著负相关外,土壤养分含量指标与细菌群落多样性呈显著正相关。T RFLP实验共鉴定出细菌门类12门,其中厚壁菌门、蓝藻门、放线菌门和变形菌门是主要优势菌群。随栽植代数的增加,变形菌门细菌比例递增,而厚壁菌门细菌比例递减。土壤细菌群落多样性指数,表现为随栽植代数增长而减少,呈现FCP>SCP>TCP趋势,与T RFs片段数量变化趋势基本一致,表明多代连栽降低了杉木根际土壤细菌群落多样性。依据功能性不同,可将鉴定出的细菌划分为5类:碳循环功能菌、硫循环功能菌、氮循环功能菌、纤维降解菌及病原菌。连栽导致碳循环菌和氮循环菌相对含量降低,硫循环菌和纤维降解菌相对含量提高,病原菌相对含量随栽植代数增加而上升。

To analyse variations in soil bacterial communities in Chinese fir plantations that have undergone continuous cultivation,terminal restriction fragment length polymorphism(T RFLP)technique was used to assess the soil microbial community structure,diversity,and function in Youxi National Forest Farm.The results showed that continuous cultivation resulted in an imbalance in the soil microbial communities in the Chinese fir plantations.The pathogenic bacteria increased,whereas the carbon cycling and nitrogen cycling bacteria gradually decreased to a significant extent.The number of terminal restriction fragments(T RFs)was significantly different among three rotations of continuous cultivation in the Chinese fir plantations.The T RFs were the highest in first Chinese fir rotation plantation(FCP),followed by second Chinese fir rotation plantation(SCP)and third Chinese fir rotation plantation(TCP).The soil chemical properties were significantly and positively correlated with bacterial community diversity,except C/N and pH.A total of 12 bacterial families were identified,and Firmicutes,Cyanophyta,Actinomyces,and Proteobacteria were the four main types of bacteria in all the samples.The proportion of Proteobacteria increased with the increase in cultivation rotations,whereas the proportion of Firmicutes decreased with the increase in cultivation rotations.The soil bacterial community diversity indexes showed a trend of FCP>SCP>TCP,which was consistent with the number of T RFs and indicated that the long term pure plantation pattern exacerbated the microecological imbalance in the rhizospheric soils of the Chinese fir and markedly decreased the soil microbial community diversity.On the basis of function,we classified the bacteria into five categories:carbon cycling bacterium,sulphur cycling bacterium,nitrogen cycling bacterium,fibrinolytic bacterium,and pathogenic bacterium.Overall,the relative numbers of carbon cycling and nitrogen cycling bacteria gradually decreased in the Chinese fir plantations.Conversely,the relative numbers of sulphur cycling,fibrinolytic,and pathogenic bacteria increased in the Chinese fir plantations.