Plant community and soil microbial characteristics in typical grasslands of different degradation degrees

Plant community and soil microbial characteristics in undegraded, moderate and heavy degraded grasslands were studied. The important value (IM) of Stipa krylovii decreased with grassland degradation, but IM of Artemisia frigida increased. Plant diversity of undegraded and moderate grassland were higher than that of heavy degraded grassland. Total soil nitrogen concentration of heavy degraded grassland was higher than that of undegraded and moderate grasslands, but soil available phosphorus of heavy degraded grassland was the lowest. Soil carbon and nitrogen microbial biomass of undegraded grasslands were higher than degraded grassland. The effects of degradation on arbuscular mycorrhizal fungal spore density and number of bacteria, actinomyces and fungi depended on seasonal dynamics. Number of fungi in undegraded grassland was higher than heavy degraded grassland from May to August, but there was no significant difference between these two types of grassland in September. Number of bacteria in undegraded grassland was higher than heavy degraded grassland from July to September, but there was no significant difference between these two types of grassland in June. Total soil nitrogen concentration, soil available phosphorus, and number of microorganism were highest in July or August. There was significant linear correlation between number of bacteria, actinomyces or fungi and total soil nitrogen or microbial biomass nitrogen. There was significant linear correlation between Number of bacteria and actinomyces and microbial biomass carbon.