PARENT SESSION
Contributed Oral Session 107: Soil Biota and Communities
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 524 B, Level 5, Palais des congrès de Montréal
Microbial Community Responses to Soil Warming.
Frey, Serita*,1, Smith, Heather1, Drijber, Rhae2, Melillo, Jerry 3, 1 University of New Hampshire, Durham, NH, USA2 University of Nebraska-Lincoln, Lincoln, NE, USA3 The Ecosystems Center, Woods Hole, MA, USA
ABSTRACT- We evaluated the response of the soil microbial community to long-term soil warming. We collected soil cores from the control, disturbance control, and heated plots at the Harvard Forest soil warming experiment where soils in the heated plots have been elevated 5°C above ambient since 1991. Each core was divided into O-horizon material and the top 10 cm of mineral soil. Microbial biomass, measured by substrate induced respiration or as extractable lipid P, was 26-44% and 26-28% lower in heated compared to control plots for the organic and mineral horizons, respectively. Lower biomass in the mineral soil of heated plots was concomitant with significantly less labile C and a trend, though not significant, toward lower total and particulate organic matter C contents. We observed a significant effect of warming on the overall respiratory response (normalized for differences between treatments in microbial biomass) following addition to soil of 25 organic substrates, with the heated soils exhibiting a lower relative utilization compared to the control for the majority of the added substrates. However, six substrates were utilized to a relatively greater degree in the heated plots. Microbial community composition was determined by fatty acid methyl ester (FAME) analysis, where specific FAMEs are used as biomarkers for fungal and bacterial cell components. Samples collected from the mineral horizon of the heated plots had significantly lower concentrations of the fungal biomarker, the arbuscular mycorrhizal fungal biomarker, and several bacterial biomarkers. Additionally, a shift from gram negative to gram positive bacteria was observed for both organic and mineral horizons in the heated plots. In summary, microbial community structure and function has been significantly altered by long-term soil warming.
Key words: soil warming, microbial community composition, microbial biomass, soil carbon