Poster Session #5: Soil Ecology.
Monday, August 6, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall


Microarthropods and fungal competition: A story from Eastern Oregon’s ponderosa pine forest soils.

Grossmann, Emilie1, Moldenke, Andrew2, 1 2

ABSTRACT- Many Oribatid mites (Acari, Oribatida) and springtails (Insecta, Collembola) are considered generalist fungivores that exhibit preferences for certain types of fungi. They may help shape the soil microbial community composition through their fungal feeding habits. Using organisms from a Pinus ponderosa forest soil, we investigated two aspects of microarthropod ecology: (1) microarthropod feeding preference, and (2) microarthropod grazing's effects on fungal competition. Four microarthropod species statistically showed preference orders for the eight fungi offered in the feeding preference trials. Epicoccum nigrum was frequently the most preferred. Penicillium sp. was usually the least preferred, and Trichoderma viride was also usually low on the preference orders. Several arthropods did not show distinct preferences. There are several possible explanations for this: the preferred food was not offered, the arthropods are true generalist feeders, or the animals would not feed under laboratory culture conditions. The fungal competition studies indicate that microarthropod grazing sometimes influences fungal competition, but not always. The presence of grazers reduced E. nigrum's competitive advantage over the fungal pathogens, Leptographium wagnerii, and Armillaria ostoye, but not T. viride's. In general, the outcome of competition in my experiments depended on the relative competitive dominance of each fungus, and (indirectly) on the palatability of each fungus. Because these studies were conducted in a simplified laboratory environment, further study is needed to evaluate these interactions in the complex soil environment.

KEY WORDS: microarthropod, soil fungal community, grazing, competition