Communities of arbuscular mycorrhizal fungi associated with perennial grasses of different forage quality exposed to defoliation

Abstract

Vegetation management practices, such as defoliation may alter the composition of plant communities and/orthe fungi-forming arbuscular mycorrhiza (AMF). We determined the species identity, density, frequency anddiversity of AMF spores from soil under the canopies of three native perennial grass species in rangelands ofArgentina: 1) Poa ligularis and Nassella tenuis (preferred by livestock) and 2) Amelichloa ambigua (not preferred).For each species, plants either remained undefoliated or were defoliated twice to a 5 cm stubble height duringthe growing season. Most active meristems remained on the plants after defoliations. AMF communities weresampled prior to (i.e., 48 soil samples) and following (i.e., 72 soil samples) each defoliation event. Spores weregrouped in 15 morphospecies. Density, richness and diversity of AMF spores were not influenced by defoliation,and species richness and diversity of AMF were similar among species. Total spore density was greatest for P.ligularis at the sampling prior to defoliation, but this difference did not persist following the defoliation events.The most abundant AMF families were: Acaulosporaceae, Diversisporaceae and Glomeraceae. These resultsdemonstrate that responses of the studied variables were insensitive to the defoliation treatments, and werelargely unaffected by the studied grass species.