Spatiotemporal distribution patterns of soil ciliate communities in the middle reaches of the Yarlung Zangbo River

Abstract

Introduction: Soil ciliates, as protozoa, play a crucial role in biogeochemical cycling and the soil food web, yet they are highly sensitive to environmental fluctuations in soil conditions. The diversity and biogeographic characteristics of soil ciliates in the Tibetan Plateau remain poorly understood. As part of a regional survey focused on soil ciliate diversity, we investigated the composition and spatiotemporal variations of soil ciliate communities along the Yarlung Zangbo River, a representative soil habitat in the Tibetan Plateau.Methods: A total of 290 soil samples were collected from four habitat types of grassland, shrubland, forestland and wetland in the middle reaches of the Yarlung Zangbo River during the wet and dry seasons, and 138 species of ciliates were identified.Results: Soil ciliate diversity exhibited greater variation across habitat types than seasons. Moreover, soil ciliate diversity was higher during the wet season compared to the dry season, with the wetland habitat showing the highest diversity and the grassland habitat displaying the lowest. We observed spatiotemporal heterogeneity in the composition of soil ciliate communities across different seasons and habitat types. Notably, Litostomatea, Karyorelictea, and Prostomatea predominated in ciliate communities during the wet season and in grassland habitat. Phyllopharyngers dominated during dry seasons and in forested regions, while Spirotrichea species were prevalent in wetland and forested areas. The co-occurrence network analysis showed that soil ciliate community was more complex in wet season than in dry season, and the stability of soil ciliate community in wet season was higher than that in dry season. The stability of soil ciliate community in wetland was higher than that in forestland, shrubland and grassland, and the anti-interference ability was stronger. Soil temperature (ST), Total nitrogen (TN), Soil organic matter (SOM) and Soil water content (SWC) are important factors affecting the structure of soil ciliate community. By influencing the metabolic rate and nutrient acquisition of soil ciliates, the distribution pattern of soil ciliate community diversity in the middle reaches of Yarlung Zangbo River is shaped.Discussion: In summary, this study revealed the distribution pattern of soil ciliate community diversity in the Yarlung Zangbo River Basin, and the key factors affecting the spatial and temporal differences and stability of the community, enhancing our understanding of how ciliates adapt to environmental conditions in soil habitats across the Tibetan Plateau.