Arbuscular mycorrhizal fungi in a mountain grassland II: Seasonal variation of colonization studied, along with its relation to grazing and metabolic host type

The relationships among seasons, host metabolic type, grazing and arbuscular mycorrhizal colonization were analyzed in a high South American native grassland. This study investigated seasonal changes and grazing effects on the symbiotic endo- mycorrhizal interaction in 5 Poaceae (C3 metabolic pathway: Briza subaristata Lam., Deyeuxia hieronymi (Hack.) Turpe and Poa stuckertii (Hack.) Parodi; with C4 metabolic pathway: Eragrostis lugens Nees and Sor- ghastrum pellitum (Hack.) Parodi; and a Rosaceae (Alchemilla pinnata Ruiz & Pav.)). All hosts were dominant species in the mountain grassland in cen- tral Argentina. It was found that the seasons mark- edly influenced endomycorrhizal colonization, whereas grazing did not affect this interaction. C4 grasses presented the highest root colonization. Hosts Briza subaristata (C3 metabolic pathway) and Sorghastrum pellitum (C4 metabolic pathway) showed Arum- and Paris-type colonization and intermediate forms.