Response Of Soil Microbial Community To Simulated Precipitation In Stipa Breviflora Desert Steppe

Grassland ecosystem is the largest terrestrial ecosystem in China,which plays an irreplaceable role in climate regulation,material circulation and energy flow.The response of soil microbes to climate change directly determines the degree of grassland feedback to climate change.The desert steppe in Inner Mongolia is located in arid and semi-arid areas.The region is sensitive to environmental changes such as temperature and precipitation.The study on the response of Inner Mongolia desert steppe to climate change is helpful to determine the adaptation mode of desert steppe ecosystem for future climate change.In this study,a combination of field simulated precipitation test and microbial high-throughput sequencing technology was used.The study focused on the soil microbes of desert steppe in Inner Mongolia,studied the effects of soil bacterial community and soil fungus community structure and their diversity on soil physicochemical properties of desert steppe under different precipitation treatments.The completely random block design was adopted in the simulated precipitation experiment.There are four different precipitation treatment gradients,Precipitation treatment is to decrease natural precipitation by 50%,natural precipitation,increase natural precipitation by 50% and increase natural precipitation by 100%.and three repelications of each treatment,totally of 12 experimental plots.Precipitation is processed in each simulation.Samples of topsoil(0–10 cm depth)were collected from each plot,five soil cores were collected randomly using a 7 cm diameter soil drilling and mixed into a single composite sample for the plot.Then the soil samples were brought back to the laboratory for the determination of soil nutrients and microbes.The main results are as follows:(1)Different precipitation treatments changed the richness of dominant soil bacterial communities and soil bacterial diversity.The relative abundance of Actinobacteria decreased first and then increased with the increase of precipitation treatment gradient.The relative abundance of Acidobacteria increased first and then decreased with the precipitation gradient.The relative abundance of Firmicutes increased first,then decreased and then increased with the precipitation gradient.The bacterial community diversity index increased with the precipitation gradient and showed a trend of significant increase and then decrease(P<0.05).Acidobacteria Blastocatellia and Firmicutes can be used as indicator groups for changes in soil bacterial community structure.(2)Different precipitation treatments changed the richness of dominant soil fungal communities and soil fungal diversity.The relative abundance of Basidiomycota increased with the increase of precipitation gradient.With the increase of precipitation gradient,the relative abundance of Orchidophyta showed a trend of decreasing first and then increasing.The index of fungal community diversity increased with the increase of precipitation gradient(P<0.05).The genera Geminibasidiaceae,Trichosporomycetes and Blocculomycetes under Basidiomycetes could be used as indicator groups for the change of soil fungal community structure.(3)Simulated precipitation treatment,there was a significant negative correlation between precipitation and soil bacterial community structure and bacterial diversity.And soil fungal community structure and fungal diversity were significantly positively correlated(P<0.05).Among the soil physical and chemical factors,the soil total phosphorus content was the main factor that affected the Soil bacterial community structure and diversity different precipitation treatments.Soil pH value was the main factor that affected soil fungal diversity.