Spatial variations and driving factors of soil microbial traits in healthy and unhealthy Populus euphratica along riparian gradients

Abstract

Water availability and soil microbes critically influence plant survival and health in extreme desert ecosystems. Here, we investigated the dynamic changes in soil microbial traits associated with healthy and unhealthy Populus euphratica trees at varying distances from the river, while also examined the assembly mechanisms and ecological relationships between biotic and abiotic drivers. The results revealed nonlinear responses of microbial traits—including diversity, composition, functions, and network structure—to river proximity, exerting stronger effects than tree health status. Dominant and key taxa, as well as functions, differed between healthy and unhealthy trees. Mycorrhizal fungi were enriched in healthy stands, peaking at 4 km, while saprotrophic and parasitic fungi were more abundant in unhealthy stands, peaking at 6 km. Both healthy and unhealthy trees exhibited enrichment in primary bacterial functional categories—metabolism, environmental information processing, and cellular processes; however, differed in tertiary functional composition. Fungal networks were less complex than bacterial networks, though both were dominated by positive interactions. Community assembly for both fungal and bacterial communities was primarily driven by stochastic dispersal limitation. Soil available phosphorus, pH, grass cover, and litter cover were identified as critical ecological factors, regulating fungal and bacterial traits via distinct pathways. Biotic and abiotic interactions accounted for 42%‒72% of fungal and 68%‒84% of bacterial traits variation. β-diversity exhibited strong and contrasting effects on fungal and bacterial functional traits. Network intensity significantly positively influenced specific bacterial functional traits. These findings provide a theoretical foundation for understanding microbial adaptation mechanisms and ecological restoration in arid riparian forests.

Graphical abstract

Keywords

soil microbes / diversity / functions / networks / ecological drivers

Highlight

	● River proximity exerted greater direct influence on microbial traits than the health status of Populus euphra tica .
	● Dominant and key taxa, as well as functions, differed between healthy and unhealthy trees.
	● Fungal networks were less complex than bacterial networks, though both were dominated by positive interactions and exhibited distance-dependent variations.
	● Stochastic dispersal limitation primarily dictated microbial community assembly.
	● Biotic and abiotic interactions accounted for 42%‒72% of fungal and 68%‒84% of bacterial traits variation.

References

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