关键词: 火干扰, 荒漠草原, 微生物多样性, 草地灌丛化, 生态恢复

Abstract: Aims In the desert grassland ecosystem with shrub encroachment, fire disturbance significantly affects soil microbial communities and their functional processes by altering soil nutrient levels and physicochemical properties. As key drivers of material cycling and energy flow within the ecosystem, soil microbial communities are highly sensitive to environmental changes. Understanding the characteristics of changes in soil microbial community structure under different vegetation types (shrub-grass areas and grass areas) and soil layers in the context of fire disturbance in shrub-encroached grasslands is of great significance for a deeper understanding of the stability and restoration mechanisms of desert grassland ecosystems. Methods This study examined soils from fire-affected sites in the shrub-grass and grassland zones of the desert steppe in Yumin County, Xinjiang. By measuring soil physicochemical properties and enzyme activity, and analyzing fungal and bacterial community structures using ITS and 16S rRNA high-throughput sequencing technologies, the study comprehensively investigated the effects of fire disturbance on soil physicochemical characteristics, enzyme activity, and the dynamics of microbial communities. Important findings (1) Fire disturbance significantly altered the soil environment in grassland and shrub-grassland areas in the short term, as evidenced by increased soil organic carbon and electrical conductivity, as well as significantly enhanced sucrase and alkaline phosphatase activities. This suggests that fire disturbance synergistically drives increased microbial activity and the restructuring of carbon and nitrogen cycling processes by regulating soil nutrients and enzyme activities; moreover, this effect varies markedly across different vegetation types and soil layers. (2) Fire disturbance significantly reduced the microbial α-diversity indices in some treatments (e.g., surface-layer bacteria in the shrub-grass zone and deep-layer fungi in the grassland zone), while the impact on other treatments was not significant. β-diversity analysis also revealed significant differences in the soil fungal and bacterial community structures between fire-disturbed and undisturbed plots. (3) Redundancy analysis revealed that physicochemical factors such as organic carbon and pH, as well as soil nutrients, are the primary drivers of microbial community changes following fire disturbance. This study contributes to understanding the effects of fire disturbance on the soil properties and microbial communities of desert grasslands, and holds significant implications for post-fire ecological restoration and the implementation of corresponding conservation and management measures.

Key words: Fire disturbance, Desert steppe, Microbial diversity, Shrub encroachment, Ecological restoration