Climate drivers the spatial distribution of soil nematode communities across geographical gradients on the eastern Qinghai-Tibetan Plateau

Abstract

Soil nematodes are critical bioindicators of ecosystem responses to environmental change, yet their spatial patterns across geographic gradients in alpine grasslands of the Qinghai-Tibetan Plateau (QTP) are not well characterized. We examined the taxonomic composition, diversity, trophic structure, and ecological traits of soil nematodes along longitudinal, latitudinal, and altitudinal gradients on the eastern QTP. From 2019 to 2021, 90 sampling sites were investigated across these gradients. Taxonomic composition varied markedly, and total nematode abundance and all trophic groups showed unimodal longitudinal patterns, decreased with latitude and increased with altitude. Taxonomic richness and Shannon index also exhibited unimodal longitudinal patterns and significant latitudinal decreases, but no clear altitudinal trend. Trophic structure also varied, with bacterivore relative abundance increased longitudinally and latitudinally, whereas predator-omnivore decreased longitudinally. With increasing altitude, the relative abundances of bacterivores and fungivores decreased, while herbivores increased and dominated at 3500 m. Ecological indices displayed contrasting spatial patterns, with cp2 peaking at 101°E and cp3-5 showing opposite longitudinal trends, and their latitudinal patterns converging near 30°N. Mean annual precipitation, temperature, and aboveground biomass were the primary drivers of nematode distributions. These results reveal complex geographical patterns of soil nematode communities in eastern QTP alpine grasslands and indicate 101°E, 30°N and 3500 m as key ecological transition zones. This highlights the joint influence of longitude, latitude, and altitude on nematode community assembly. Environmental tolerance thresholds may further shape these spatial patterns, influencing climate responses and ecosystem functions such as carbon cycling and nutrient mineralization.

Graphical abstract

Keywords

soil nematode / diversity / trophic structure / ecological functions / geographic pattern / Qinghai-Tibetan Plateau

Highlight

	● Abundance varies unimodally with longitude and declines with latitude, whereas diversity decreases latitudinally.
	● Relative abundance decreased for He and Pr but increased for Ba with longitude.
	● Relative abundances decreased for Ba and Fu but increased for He with altitude.
	● cp2 and cp3-5 relative abundances vary oppositely along longitude and latitude.
	● He dominates east of 101°E and above 3500 m, Ba elsewhere.

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