| Soil microbes are the significant components of soil ecosystem,and play an important role in soil nutrients cycling and energy flow.Under the background of the increasing global nitrogen deposition,the changes of soil N may significantly change the structure of soil microbial community.We used Biolog and highthroughput sequencing method to study the effects of elevated nitrogen deposition on soil microbial community structure in poplar plantation within June and October 2015.The experimentwas conducted at Dongtai Forestry Farm in Jiangsu Province,a coastal area of eastern China.Nitrogen addition was designed at 4 levels at 0 kg·hm-2·a-1 N0,50 kg·hm-2·a-1 N1,100 kg·hm-2·a-1 N2,150 kg·hm-2·a-1N3,respectively.After 3-year nitrogen addition by NH4NO3 during May and October each year from 2012,we measured the changes of soil microbial biomass and dominant group.The results were mainly included as follows:(1)The result indicated that nitrogen addition significantly influenced SMBC and SMBN,and the maximums of SMBC and SMBN are both in N3.High level nitrogen led to the rise of SMBC and SMBN.We researched the metabolic level of soil microbial community by Biolog,and found that middle level nitrogen enhanced the intensive metabolism,and the microbes significantly influenced were those who mainly used amine or phenol.Shannon diversity indicated that nitrate nitrogen enhanced microbial metabolic level and diversity.PCA showed that carbonhydrates,amino acids and carboxylic acids were main C-source that microbe used.(2)We used highthroughput sequencing to analyze soil bacterial and fungal community structure,and the results indicated that the length of bacteria sequences were in 201-300 bpmostly,and the number of bacteria from June to October is rising before nitrogen addition,,while it decline after nitrogen addition.Fungi community diversity was influecd by growing period,and fungi community richness was influenced by growing period and nitrogen addition.The highest value of diversity and richness was in August.We used Heatmap to analyze fungi community structure,and the result indicated that the dominant population was Proteobacteria,Firmicutes,Acidobacteria in phylum.The abundance of dominant population was influenced by both growing period and nitrogen addition,and was lowest in August.The richness of Sphingomonas is influenced mostly by nitrogen addition,and it has important significance to decomposition of toxic substances and nitrogen fixation.(3)The length of fungi sequences were mostly in 201-300 bp,and nitrogen addition led to the change of fungi number in different growing period,and the lowest fungi number was both in August before and after nitrogen addition.Fungi community diversity was influecd by growing period and nitrogen addition.The highest value was in August before nitrogen addition,and become the lowest after the treatment.Fungi community richness was mainly influenced by different growing periods.The richness of June was also influenced by nitrogen addition,and was the highest of the three period before nitrogen addition,and the lowest after nitrogen addition.We used Heatmap to analyze fungi community structure,and the result indicated that the dominant population was Ascomycota and Zygomycota in phylum.The abundance of dominant population was influenced by both growing period and nitrogen addition,and was highest in August.The richness of Mortierellaceae is influenced mostly by nitrogen addition,and it has important significance to soil fertility and plant growth.(4)To analyze microbial community diversity,we found that nitrogen addition influenced the ratio of bacteria and fungi,and the value was highest before nitrogen addition in October,while the lowest after nitrogen addition.Overall,nitrogen addition and growing period change could both significantly influence microbial biomass,community diversity and dominant population in the poplar plantation in Dongtai costal area. |
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