Effects Of Grazing On Artemisia Frigida Willd.Rhizosphere Soil Microbial Biomass And Community Of Bacterial And Fungal

To illustrate variations of Artemisia frigida Willd.rhizosphere soil microbial community along grazing intensity,rhizosphere soil of A.frigida?ARS?and non-rhizosphere soil?NRS?under different grazing intensities,were chosen as experimental sites in the Inner Mongolia steppe.Chloroform fumigation extraction method,the LI-7000 CO₂/H₂O system and Polymerase chain reaction denatured gradient gel electrophoresis?PCR-DGGE?were used to study the soil physical-chemical properties,microbial biomass C,microbial biomass N,basal respiration and diversity of microbial communities.The main results were shown as follows:1.Grazing increased the content of soil organic matter,total nitrogen and alkaline nitrogen,and decreased the soil pH value significantly?p<0.05?in ARS.Under light and heavy grazing,the content of ARS organic matter increased 28.66%and 19.96%,meanwhile,the content of ARS total nitrogen increased 41.75%and 29.13%,compared with the control group respectively.The ARS has a higher soil nutrient contention and lower pH value than NRS.The results of the natural grazing conditions are consistent with the plot test.2.Accompanying with the increasing of grazing intensity,soil microbial biomass C?MBC?and soil microbial biomass N?MBN?increased firstly and then reduced.These bio-indicators in rhizosphere soil of A.frigida were higher than non-rhizosphere soil of A.frigida.The group that under the light grazing and heavy grazing have a higher MBC?22.71%and 7.04%?and MBN?45.66%and25.17%?content than control group.The results of the natural grazing conditions are consistent with the plot test.3.Grazing had significant influence towards soil basal respiration in Rhizosphere of Artemisia frigida?p<0.05?.Compared with the control group,light grazing made soil basal respiration increase 17.27%,heavy grazing made it decrease 7.6%.Under light and heavy grazing,the mettabolic quotient of ARS decreased 22.71%and 7.04%compared with the control group respectively.4.The results of bacterial community PCR-DGGE showed that the number of bands in the lane decreased,the individual bands were also reduced in brightness,and the dominant population was weakened,with the grazing intensity increasing.The order of richness of bacterial community in ARS and NRS under different grazing intensity was:CK-ARS>LG-ARS=HG-ARS>CK-NRS>LG-NRS>HG-NRS.The similarity and cluster analysis showed that the effect of grazing on the bacterial community diversity of rhizosphere soil was lower than that of non-rhizosphere soil.Principal component analysis showed that grazing treatment was the main reason for the difference of bacterial community in rhizosphere and non-rhizosphere soil.The results of canonical correlation analysis showed that the relationship between soil bacterial community diversity of ARS and soil nutrient content was higher than that of NRS.5.The results of fungal community PCR-DGGE showed that the species and quantity of fungal communities in the rhizosphere soil increased first and then decreased,but the number of fungal communities in the rhizosphere soil decreased gradually,with the increasing of grazing intensity.The order of richness of fungal community in ARS and NRS under different grazing intensity was:LG-ARS>CK-ARS>CK-NRS>HG-ARS=LG-NRS>HG-NRS.The similarity and cluster analysis showed that the effect of grazing on the fungal community diversity of rhizosphere soil was lower than that of non-rhizosphere soil.Principal component analysis showed that grazing treatment was the main reason for the difference of fungal community in rhizosphere and non-rhizosphere soil.The results of canonical correlation analysis showed that the relationship between soil fungal community diversity of ARS and soil nutrient content was higher than that of NRS.In summary,the nutrient content of rhizosphere soil decreased and the pH value decreased after grazing treatment.Soil microbial biomass C and N and basal respiration increased firstly and then reduced.Light grazing and heavy grazing made the bacterial community diversity decreased.Fungal community diversity of ARS increased firstly and then reduced.The root system of Artemisia frigida provides a good rhizosphere environment for microbes,and the enrichment of microorganisms in turn promotes the growth of Artemisia frigida and increases its resistance to grazing.