Spatial patterns and ecological drivers of soil nematode β-diversity in natural grasslands vary among vegetation types and trophic position

1. Understanding biogeographic patterns of community assemblages is a core
objective in ecology, but for soil communities these patterns are poorly
understood. To understand the spatial patterns and underlying mechanisms
of β-diversity in soil communities, we investigated the β-diversity of
soil nematode communities along a 3200 km transect across semi-arid and
arid grasslands. 2. Spatial turnover and nested-resultant are the two
fundamental components of β-diversity, which have been attributed to
various processes of community assembly. We calculated the spatial
turnover and nested-resultant components of soil nematode β-diversity
based on the β-partitioning framework. Distance matrices for the
dissimilarity of soil nematode communities were computed using the
“Sørensen” method. We fitted negative exponential models to compare the
distance decay patterns in nematode community similarity with geographic
distance and plant community distance in three vegetation types (desert,
desert steppe, and typical steppe) and along the whole transect. Variation
partitioning was used to distinguish the contribution of geographic
distance and environmental variables to β-diversity and the partitioned
components. 3. Geographic distance and environmental filtering jointly
drove the β-diversity patterns of nematode community, but environmental
filtering explained more of the variation in β-diversity in the desert and
typical steppe, whereas geographic distance was important in the desert
steppe. Nematode community assembly was explained more by the spatial
turnover component than by the nested-resultant component. For nematode
feeding groups, the β-diversity in different vegetation types increased
with geographic distance and plant community distance, but the
nested-resultant component in the desert ecosystem decreased with
geographic distance and plant community distance. 4. Our findings show
that spatial variation in soil nematode communities is regulated by
environmental processes at the vegetation type scale, while spatial
processes mainly work on the regional scale, and emphasize that the
spatial patterns and drivers of nematode β-diversity differ among trophic
levels. Our study provides insight into the ecological processes that
maintain soil biodiversity and biogeographic patterns of soil community
assemblage at large spatial scales. 28-Jan-2021