The Study On Utilization Of Carbon Sources By Soil Bacteria In Different Plant Functional Groups In Songnen Grassland

In the grassland ecosystem,the plants that on the ground have a close relationship with soil bacterial community that under the ground.The soil bacterial community function could be changed by the composition of plant community and its structural changes.Analysis of soil bacterial community function in different vegetation types by Biolog fingerprinting that could explore the relationship between plant community and soil bacterial community in grassland.It is important to maintain the stability and development of grassland ecosystem that in defining functional diversity of soil bacteria further to the sensitive degree of external conditions changes.In this research,we used the Biolog-ECO technology to study and compare the difference of soil bacteria carbon source utilization that in different plant functional groups before and after grazing in songnen steppe.The results showed that:(1)The analysis in the comparative of plant community composition showed that there were significant differences in plant composition and community structure that in different plant functional groups(Leymus chinensis,grass,Legume and forb).The height,coverage,density and aboveground biomass of the communities were different.There were significant differences between the 4 communities in the functional groups of L.chinensis(P<0.05);The height,density and aboveground biomass were the largest in the plant community of L.chinensis,and the biggest coverage just below brushed Calamagrostis epigeios.The density was lowest in Potentilla chinensis;The height,coverage,aboveground biomass were lowest in Artemisia mongolica.There were significant differences in community height,coverage and aboveground biomass among the functional groups of grass(P<0.05);The height and aboveground biomass were largest in Hemarthria sibirica,but the density and coverage were largest in Setaria viridis.There were significant differences between the 4 communities in the functional groups of legume(P<0.05).The coverage,density and aboveground biomass of L.chinensis were the largest;But the highest height of Lespedeza bicolor.There were significant differences in coverage,density and aboveground biomass among the functional group of forb(P<0.05).The density and aboveground biomass were largest in Kalimeris interifolia,and the height and coverage were largest in Kochia scoparia.Compared with the former plant communities,the characteristics of plant community changed obviously,but the richness of community decreased slightly.(2)The analysis of utilization of carbon sources by soil bacteria in different plant communities showed that the utilization of carbon source by soil bacteria in plant communities increased with the extension of culture time,and the variation curves of AWCD value of soil bacteria to carbon source utilization were different.In the same functional group,the composition of the plant communities that had been changed and the degree of utilization of carbon source were different,but there was no obvious regular change.The change of plant community structure which caused the difference in the carbon source utilization of soil bacteria and the change of the richness and evenness of soil bacterial community.For the utilization of different carbon sources,the species and quantity of carbon sources were different in different plant communities,and the types and numbers of soil bacteria were more extensive.All the plant communities had the best use of two kinds of carbon sources such as Carbohydrate and amino acids.In the same plant functional groups,the 5 soil physical and chemical indexes of different plant communities were different;RDA analysis showed that the organic matter content had the largest influence in the carbon source utilization of soil bacteria.(3)The analysis of the effect in 5 kinds of plant functional groups on soil bacterial diversity showed that there were significant differences in the utilization of carbon sources by soil bacterial in the 5 kinds of plant functional groups.The highest utilization rate of carbon sources by soil bacteria was in L.chinensis and weeds,but the lowest in legume.The factors that affected the functional diversity of soil bacterial community were studied by RDA analysis,and it showed that total N and organic matter had the largest influence in the utilization of carbon source of soil bacteria.On the use of carbon source,Carbohydrate and amino acids were better used and the amine were lower used in 5 plant functional groups.The utilization of carbon source that in types and numbers in the soil bacteria of the L.chinensis and weeds,forb were significantly higher than that of the other 3 kinds of functional groups.