Microbial Dispersal, Including Bison Dung Vectored Dispersal, Increases Soil Microbial Diversity in a Grassland Ecosystem

Abstract

Microbial communities display biogeographical patterns that are driven by local environmental conditions and dispersal limitation, but the relative importance of underlying dispersal mechanisms and their consequences on community structure are not well described. High dispersal rates can cause soil microbial communities to become more homogenous across space and therefore it is important to identify factors that promote dispersal. This study experimentally manipulated microbial dispersal within different land management treatments at a native tallgrass prairie site, by changing the relative openness of soil to dispersal and by simulating vector dispersal via bison dung addition. We deployed experimental soil bags with mesh open or closed to dispersal, and placed bison dung over a subset of these bags, to areas with three different land managements: active bison grazing and annual fire, annual fire but no bison grazing, and no bison grazing with infrequent fire. We expected microbial dispersal to be highest in grazed and burned environments, and that the addition of dung would consistently increase overall microbial richness and lead to homogenization of communities over time. Results show that dispersal rates, as the accumulation of taxa over the course of the 3-month experiment, increase taxonomic richness similarly in all land management treatments. Additionally, bison dung seems to be serving as a dispersal and homogenization vector, based on the consistently higher taxon richness and increased community similarity across contrasting grazing and fire treatments when dung is added. This finding also points to microbial dispersal as an important function that herbivores perform in grassland ecosystems, and in turn, as a function that was lost at a continental scale following bison extermination across the Great Plains of North America in the nineteenth century. This study is the first to detect that dispersal and vector dispersal by grazing mammals promote grassland soil microbial diversity and affect microbial community composition.

Barley farmland harbors a highly homogeneous soil bacterial community compared to wild ecosystems in the Qinghai-Xizang Plateau

“…These findings support a classic deterministic process of selection via abiotic features in determining microbial community assemblage. However, variation of microbial communities can also be affected by stochastic processes such as dispersal ( Hawkins and Zeglin, 2022 ), evolutionary diversification ( Shapiro et al, 2012 ), and ecological drift ( Jones et al, 2023 ). Given the irreplaceable fundamental functions of microorganisms in biosphere, understanding both patterns and processes of microbial biogeography is not only helpful for us to investigate forces generating biodiversity, but also crucial for monitoring ecological responses to environmental changes caused by human activities.…”

Bison (Bison bison) dung Decays Slowly but Can Still be Used to Track Short- and Long-Term Habitat Usage

“…Grazers also play an important but understudied role in affecting habitat availability and nutrient cycling. Dung represents an important food source, microclimate, and habitat for many invertebrates and microbes (Hanski and Camberfort 1995; Hawkins and Zeglin 2022). Grazers are generally thought to increase the rate of nutrient decomposition by consuming large quantities of forage, and then excreting it in a more labile form than plant litter (McNaughton, Banyikwa, and McNaughton 1997).…”

Data_Sheet_2.PDF

“…These findings support a classic deterministic process of selection via abiotic features in determining microbial community assemblage. However, variation of microbial communities can also be affected by stochastic processes such as dispersal (Hawkins and Zeglin, 2022), evolutionary diversification (Shapiro et al, 2012), and ecological drift (Jones et al, 2023). Given the irreplaceable fundamental functions of microorganisms in biosphere, understanding both patterns and processes of microbial biogeography is not only helpful for us to investigate forces generating biodiversity, but also crucial for monitoring ecological responses to environmental changes caused by human activities.…”