Effects Of Nomadic And Settled Grazing On Vegetation And Soil Characteristics Of Autumn Pasture In Seriphidium Transiliense Desert

The Seriphidium transiliense desert degraded in the northern slope of Tianshan Mountain was taken as the research object.The effects of nomadic and settled grazing on vegetation community characteristics,community species diversity,soil chemical properties,soil fungi and bacterial community structure in S.transiliense desert grassland were studied,though field investigation,laboratory analysis and high-throughput sequencing techniques.Meanwhile,correlation between community characteristics,soil chemistry and microbiota were analyzed.This study aims to provide theory basis for ecosystem stability and rational grazing of S.transiliense desert grassland.The main results were as follows:(1)The survey results of plant community characteristics showed that annual herbs were dominant in plant life forms of nomadic(N)and settled(S)grazing,and the number of plant species showed N>S;important values of S.transiliense in N and S were similar,and important value of Salsola collina and Chenopodium album were S>N.The height,coverage and density of plant communities in N were significantly higher than that in S(P<0.05),and above-ground biomass was N>S,but difference was not significant between them(P>0.05).The Margalef richness index,Shannon-Wiener diversity index and Pielou evenness index of plant community were N>S.(2)The results of soil chemical properties showed that pH was S>N,while contents of SOC,AP and AK were significantly higher than those in S(P<0.05).The contents of TN,TP,TK and AN were N>S,but differences were not significant between them(P>0.05).(3)A total of 7124 OTUs were produced in soil fungi communities.The diversity and abundance in nomadic grazing were highest.10 phylum,25 class,86 order,175 family and 337 genus were found in nomadic and settled grazing.There were significant differences in relative abundance of Zygomycota,Ascomycota,and unidentified at phylum level(P<0.05),no significant differences between class and family level(P>0.05).There were significant differences in Pleosporales and Agaricales at order level(P<0.05),and in Mycocentrospora at genus level(P<0.05).A total of 11130 OTUs were produced in soil bacterial communities.The diversity and abundance in settled grazing were highest.32 phylum,90 class,135 order,170 family and 193 genus were identified.There were no significant differences in relative abundance at phylum and family level(P>0.05).While,there were significant differences in Chloracidobacteria,MB-A2-108 and Thaumarchaeota at class level(P<0.05),in Actinomycetales,RB41 and 0319-7L14 at the order level(P<0.05),and in Streptomyces at genus level(P<0.05).(4)Correlation showed that plant communities characteristics in nomadic and settled grazing were significantly positively correlated with SOC(P<0.05).The relative abundance of soil fungi communities was positively correlated with pH,TN and AN(P<0.05),and negatively correlated with TP in nomadic gazing(P>0.05).The relative abundance of soil bacteria was positively correlated with SOC,TN and TK(P<0.05),and negatively correlated with AK in nomadic gazing(P<0.05).Fungi communities were significantly positively correlated with TP and AP in settled grazing(P<0.05).Relative abundance of bacteria was positively correlated with pH,AN,SOC,AK,TN and TP(P<0.05).In summary,nomadic and settled grazing affect vegetation community and soil characteristics of S.transiliense desert grassland.Compared with nomadic grazing,settled grazing reduced diversity and abundance of plant communities and soil fungi communities,deteriorated soil chemical properties,decreased relative abundance of soil bacterial communities.Those were more sensitive to environmental changes.For S.transiliense desert,light nomadic grazing is a more reasonable way of grazing.