Arbuscular mycorrhizal fungi in roots and soil respond differently to biotic and abiotic factors in the Serengeti

This study explores the relationships of AM fungal abundance and diversity
with biotic (host plant, ungulate grazing) and abiotic (soil properties,
precipitation) factors in the Serengeti National Park, Tanzania. Soil and
root samples were collected from grazed and ungrazed plots at seven sites
across steep soil fertility and precipitation gradients. AM fungal
abundance in the soil was estimated from the density of spores and the
concentration of a fatty acid biomarker. Diversity of AM fungi in roots
and soils were measured using DNA sequencing and spore identification. AM
fungal abundance in soil decreased with grazing and precipitation and
increased with soil phosphorus. The community composition of AM fungal DNA
in roots and soils differed. Root samples had more AM fungal indicator
species associated with biotic factors (host plant species and grazing)
and soil samples had more indicator species associated with particular
sample sites. These findings suggest that regional edaphic conditions
shape the site-level species pool from which plant species actively select
root-colonizing fungal assemblages modified by grazing. Combining multiple
measurements of AM fungal abundance and community composition provides the
most informed assessment of the structure of mycorrhizal fungal
communities in natural ecosystems.