PARENT SESSION
Poster Session # 10: Soil Ecology.

Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Soil aggregation: The role of arbuscular mycorrhizal fungal species.

Rillig, Matthias^*,1, Lutgen, Emily¹, Rosier, Carl¹, ¹ University of Montana, Missoula, MT

ABSTRACT- Soil structure (the arrangement of soil into aggregates and pore spaces) is an important characteristic of natural or managed ecosystems, influencing the abundance of soil-inhabiting organisms and rates of soil-borne processes. Soil biota exercise well-documented controls over soil aggregation, with a key role attributed to arbuscular mycorrhizal fungi (AMF). AMF are ubiquitous and abundant obligate biotrophs in the phylum Glomeromycota. While the general importance of AMF for soil aggregation is widely acknowledged, information concerning the role of diversity of AMF species for soil aggregation is scarce. Given the large differences in physiology and life history strategy among AMF species, we hypothesized that co-occurring AMF species will differ in their effects on soil aggregation. Here, we specifically tested for potential differences among AMF species in the production of the soil protein glomalin. There is a strong and positive curvilinear relationship between soil glomalin pools and soil aggregate water stability. In greenhouse experiments (with compartmentalized pots separating a hyphal compartment from a root-hyphae compartment) using the annual grass Bromus hordeaceus as plant host and several AMF species (from the same fungal community and the genera Glomus, Acaulospora, Gigaspora, and Scutellospora), we found significant differences in glomalin yield (expressed on a hyphal length basis). Due to the strong relationship between glomalin and aggregate stability, this result strongly points to differences in soil aggregation as a function of AMF species. Also, since glomalin yield was related to hyphal palatability across different species, an indirect effect of glomalin on soil aggregation may exist via the consequences of glomalin for differential AMF hyphal persistence in soil.

Key words: Soil aggregation, Glomalin, diversity, mycorrhiza