Effects Of Canopy Damage On Community Structure Of Soil CO₂ Fixation Bacteria In Nanling Forest

Soil CO2 fixation bacteria are an important component of soil carbon cycling,and their changes directly affect the soil carbon fixation efficiency.In this paper,soil samples were collected from canopy damaged plots caused by simulated ice disaster and typhoon.The soil DNA was extracted and the cbbL gene fragment of soil CO2 fixation bacteria was sequenced by Miseq sequencing.It aims to understand the effects of canopy damage on the diversity and community structure of soil CO2 fixation bacteria and their changes in the process of ecological restoration.The results are as follows:(1)The canopy openness and litter inputs had a significant effect on the soil CO2 fixation bacteria community structure.After a year of canopy damage,richness of the soil CO2 fixation bacteria was decreased and its diversity indexws were increased.After 2 years of damage,the richness and diversity indexes of in damaged samples were lower than the control.It suggests that canopy damage reduces the population quantity of soil CO2 fixation bacteria and increases their diversity in the short term.With the restoration of damaged forests,their diversity indexes were decreased significantly.After 4-5 years of canopy damage,the canopy opening,litter inputs,and the richness,diversity indexes and community structure of soil CO2 fixation bacteria in damaged samples are similar to those in the control.It indicates that the damaged forest can be restored through 4-5 years.(2)In the early stage of canopy damage,the effect on richness and diversity indexes of soil CO2 fixation bacteria in TD samples were greater than in TR or UD samples.However,with the restoration of damaged forests,the richness and diversity indexes of soil CO2 fixation bacteria in TD samples were closer to those in the control than in TR and UD samples.It indicates that the double treatments of canopy damage and litter inputs were easier to restorate than the single treatment in damaged forest ecosystems.(3)In 2013,the population quantity and diversity indexes of soil CO2 fixation bacteria were lower than those in other years.Pearson correlation analyses showed that they were directly related to rainfall.The excessiverainfall reduced the richness and diversity of soil CO2 fixation bacteria,and had a significant effect on communties structure.The richness of Nitrosospira was decreased,while those of Saccharomonospora and Ideonella were significantly increased.It indicates that rainfall had a great influence on the richness,diversity and community structure of s soil CO2 fixation bacteria.(4)The correlation analyses showed that there were positive correlations or negative correlations among canopy openness,litter inputs,the richness,diversity and communities composition of soil CO2 fixation bacteriaand soil pH,Organic carbon,total nitrogen,total phosphorus,available phosphorus and nitrate.It indicates that the community structure of soil CO2 fixation bacteria was affected by the surrounding factors in the forest ecosystem,and the ecological factors such as forest,litter,soil and microbes were closely related.(5)Forests soil CO2 fixation bacteria communities were classified into 5 phylums,namely,Actinobacteria,Proteobacteria,Cyanobacteria,Chloroflexi and Firmicutes.Actinobacteria and Proteobacteria were dominant phylums and their richnesses were 98.54% of the total soil CO2 fixation bacteria.These bacteria were classified into 59 genus.In the genus level,soil CO2 fixation bacteria communities included: Nitrosospira,Streptomyces,Saccharomonospora,Mycobacterium,Nocardia,Bradyrhizobium were more than 5% of the total;the communities proportions of Ideonella,Stappia,Paraburkholderia,UN--s-Alcaligenaceae,UN--s-Bradyrhizobiaceae,Burkholderia,Methyloferula,Rubrivivax,Thermomonospora,UN--s-Pseudonocardiaceae,Xanthobacter,Hydrocarboniphaga,Chroococcidiopsis,Caballeronia were between 1%-5%.