PARENT SESSION
Oral Session 15: Soil Ecology I: Mycorrhizal Communities.
Presiding: V Borowicz and X He
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room D 137.
Carbon dioxide, nitrogen and arbuscular mycorrhizal fungi influence plant and microbial communities in a simulated prairie.
Antoninka, Anita*,1, Classen, Aimee1, Wolf, Julie1, Collins Johnson, Nancy1, 1 Northern Arizona University, Flagstaff, AZ, USA
ABSTRACT- Mycorrhizae are predicted to influence community responses to anthropogenic carbon dioxide (CO2) and nitrogen (N)enrichment; however, few community-scale studies have tested this prediction. We investigated the interactive effects of arbuscular mycorrhizal (AM) fungi, CO2 and N on plant and soil communities in a two-year full factorial experiment. A prairie community was simulated in 48 mesocosms in 12 CO2-controlled greenhouse chambers. Mesocosms were planted with 14 plant species including grasses, legumes and forbs, with C3 and C4 photosynthetic pathways and varying degrees of mycotrophy (AM dependence). Treatments included ambient (aCO2) and 2 x ambient (eCO2) carbon dioxide, low (-N) and enriched (+N) nitrogen, and dead (-AM) or living (+AM) mycorrhizal fungi. The species composition of plant and soil microbial communities responded significantly to treatments. As expected, total plant biomass was greatest in +N mesocosms (P < 0.001) and root:shoot ratio was highest in eCO2 mesocosms (P < 0.05). Responses of individual plant species varied with level of mycotrophy and photosynthetic pathway. Non-mycotrophic forbs were less common in +AM and more common in +N mesocosms. Enriched N decreased the number of arbuscules (areas of carbon and nutrient exchange, P < 0.05), but did not affect total AM root colonization. Root colonization by fungi other than AM fungi was lowest in eCO2 (P < 0.05) and diversity was highest in +AM mesocosms (P < 0.05). Our findings indicate that community-scale responses to CO2 and N enrichment may be mediated by the activities of AM fungi.
Key words: carbon dioxide enrichment, community-scale, arbuscular mycorrhizal fungi, nitrogen enrichment