Increasing aridity reduces soil protist diversity and weakens its link to ecosystem functioning in grassland ecosystem, northern China

Abstract

Soil protists, as critical components of soil microbial communities, play key roles in nutrient cycling and ecosystem functioning in drylands. However, the mechanisms through which increasing aridity influences their diversity and contribution to ecosystem multifunctionality remain poorly understood. To address this, we investigated soil protist richness at 14 sites along a natural aridity gradient in northern China and evaluated its relationship with ecosystem function. We found that increased aridity significantly reduced protist richness (R² = 0.296, P < 0.001), including consumer (R² = 0.413, P < 0.001), parasitic (R² = 0.302, P < 0.001), and phototrophic groups (R² = 0.188, P < 0.001) and altered soil protist community composition (PERMANOVA, P < 0.001). Protist richness (R² = 0.264, P < 0.001) and the richness of each functional group (all P < 0.001) were positively correlated with ecosystem multifunctionality, but these richness-ecosystem multifunctionality relationships were weakened by increasing aridity (all P < 0.05). Our results suggested that aridity directly reduced protist biodiversity and disrupted its contribution to ecosystem functioning. These findings highlight the importance of addressing drought-driven biodiversity loss and its cascading effects on soil ecosystem functions in dryland management strategies.

Graphical abstract

Keywords

diversity / grassland / soil protist / decouple / functional group / ecosystem multifunctionality

Highlight

	● Increased aridity significantly reduced soil protist and functional group richness.
	● Protist diversity and that of their functional groups enhanced ecosystem multifunctionality.
	● Aridity decoupled the relationship between protist biodiversity and ecosystem multifunctionality.

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