Long-term grazing influences root-associated fungal communities in a common Mediterranean grass

Abstract

Background and aims: Ungulates are integral to Mediterranean ecosystems, influencing vegetation dynamics and soil microbial communities. While previous studies have documented the effects of herbivory on the soil microbiome (e.g. nitrogen-fixation groups), the impacts on root-associated fungal communities and their role in plant responses to herbivory remain poorly understood. These interactions are vital for ecosystem functioning and deserve further investigation. Methods: To explore these interactions, we used Agrostis spp. as species model, a common grass genus, highly consumed by ungulates worldwide. Roots were sampled from areas with high ungulate activity (deer density of 25–40 ind/km2) and from adjacent 14-year ungulate exclosures to assess long-term changes in root-associated fungal communities. Additionally, Agrostis plants were grown in soils from these areas under greenhouse conditions to evaluate their regrowth capacity after simulated herbivory. Results: The fungal communities of the roots differed significantly between plants grown inside and outside the ungulate exclosures. Despite these differences, the regrowth capacity after simulated herbivory was not significantly affected by the soil origin (areas with and without herbivory). Plants grown in sterilized soils with recolonized fungal communities exhibited enhanced growth compared to those in untreated soils. Conclusions: The study demonstrates that ungulate herbivory alters root-associated fungal communities in Agrostis spp., yet plant growth remains unaffected, suggesting resilient plant-fungal interactions. Our findings show that microbial diversity alone may not predict ecosystem function, emphasizing the need to consider both taxonomic and functional dimensions of soil communities in conservation strategies for Mediterranean ecosystems.