Characteristics of Soil Microorganisms and Influencing Factors in Different Degradation Types of Grasslands in the Horqin Region

Taking the degraded grasslands of the Horqin region as the research object, this study combined phospholipid fatty acid (PLFA) analysis with soil factors to investigate the characteristics and regulatory factors of soil microbial communities in Healthy grassland (CK), Mildly desertified grassland (TH), Moderately desertified grassland (SH), Moderately salinized grassland(MH), and Severely salinized grassland(ZH). The results showed that both the types and contents of PLFA biomarkers varied among the five types of degraded grasslands. A total of 38 PLFA biomarkers were detected, of which 30 were ubiquitously distributed and 8 were partially distributed. The total microbial biomass in soil showed a decreasing trend in the order: CK>SH>TH>MH>ZH. The microbial community structures of TH, SH, and ZH were highly similar, while those of CK and MH showed low similarity. The total PLFA content, Gram-positive bacteria(G⁺), Gram-negative bacteria(G⁻), other bacteria, fungi, and actinomycetes in soils of the five grassland types were significantly positively correlated with TP, TN, SOC, NO₃⁻-N, and NH₄⁺-N, and significantly negatively correlated with soil pH.