Soil variables driven by host plant and growth season affect soil microbial composition and metabolism in extremely arid desert ecosystems.

Assessment changes of soil microbial community structure and function is important in understanding the response to desert ecosystem management. In present study, variations of soil microbial community and edaphic factors associated with five desert shrubs were determined in Anxi extremely arid desert in Northwest China in growing (summer), deciduous (autumn), and snowfall (winter) seasons. For that, the microbial composition and catabolic metabolism were examined using methods of phospholipid fatty acid (PLFA) and Biolog EcoPlate, respectively. Regardless of plant species and seasonal patterns, the microbial community was mostly dominated by gram-negative bacteria (GN); and the carbohydrates, amino acids and polymers were the main carbon sources for desert microbial metabolism. Microbial biomass and metabolic levels were significantly higher in both summer and winter than those of autumn. There was no correlation between soil microbial community and carbon utilization in winter; but GN was positively correlated with metabolism of amines carbon sources in summer, while fungal community presented the strongest correlation with suites of carbon sources' metabolic levels in autumn, indicating the uncoupled relationship between microbial community and function in desert ecosystems. Desert shrubs significantly influenced the composition of soil microbial community, whereas the variation of microbial catabolic metabolism was most attributed to seasonality. Nevertheless, the effects of both plant species (21.3 %) and climate variation (84.9 %) interacted with soil properties, indicating the seasonality of soil nutrients predominately determined the changes in composition and metabolism of desert microbes. Both the comprehensive seasonal level and the intra-seasonal paired correlation analysis proved that phosphorus was the key factor in determining microbial community composition, while ammonia and nitrate nitrogen were more correlated to microbial functional metabolism. Additionally, soil moisture and organic carbon in desert environment also induced the shifts in ratio of fungi and bacterial communities. We conclude that the seasonal patterns of soil microbial community and metabolic function in extremely arid desert are predictable, and mainly influenced by specific soil factors driven by desert shrubs and climate factors. These findings will provide a basis for evaluating the management of soil resources and microbial function in desert environments.