RILLIG, MATTHIAS C.1, MICHAEL F. ALLEN2 & CHRISTOPHER B. FIELD.1
1Carnegie Institution of Washington, Department of Plant Biology, Stanford CA 94305, USA. 2 Biology Department, San Diego State University, San Diego CA 92182, USA.
After exposure to elevated atmospheric CO2 in the field for six years, we measured arbuscular mycorrhizal and non-mycorrhizal fungal root colonization for 10 plant species from two different annual grassland communities (sandstone and serpentine). We found changes in the ratio of AM fungal to non-mycorrhizal fungal root colonization. Additionally, we documented shifts in the ratio of root colonization by fine endophyte AM fungi to coarse AM fungal hyphae. Root colonization by arbuscules increased for several plant species in both communities. We also compared extraradical hyphal length responses to the treatment and found differential responses in the two communities. Furthermore, a series of growth chamber and open-top chamber pot experiments was carried out to elucidate changes in AM functioning in elevated CO2. We found significant mycorrhiza X CO2 interactions, which provided evidence to support the notion that AM fungi provide an additional benefit to plants grown in elevated CO2.