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Harvard Forest REU Symposium Abstract 2011

  • Title: Mechanisms underlining the response to soil warming: the Microbial Component
  • Author: Alanna S Yazzie (San Juan College)
  • Abstract:

    Harvard Forest is home to two long term soil warming experiments. Prospect Hill is currently in its 20th year of warming and Barre Woods is in the 9th year of warming. The first decade of warming at Prospect Hill showed an increase in soil CO₂ respiration. The initial increase in soil CO2 respiration with warming was also observed at Barre Woods, indicating that an increase in temperature will increase labile carbon respired from heated plots. Labile carbon differences between the heated and control plots at the 20 and 9 year warming plots were measured using short term carbon mineralization incubations and an infrared gas analyzer. Microbial function potential in heated and controlled plots at Prospect Hill and Barre Woods were estimated through the quantification of extracellular enzyme activity potentials for labile carbon and recalcitrant carbon using hydrolytic and oxidative enzyme assays. Hydrolytic assays performed were for enzymes β -1, 4-glucosidase (BGu) and β -D-1, 4-cellobiosidase (CBH). Oxidative assays performed for enzymes phenol oxidase and peroxidase. With nine years of warming labile carbon pools in the control and heated plots were observed to be similar. With similar reserves of labile carbon, hydrolytic enzymes are responding to temperature by breaking down more carbon in the heated than in the control plots, especially for BGlu. The data suggest that the hydrolytic enzymes, under increased soil temperature, are breaking down certain labile carbon compounds faster in heated soils. The data for Prospect Hill suggests no difference in microbial activity in relation to labile carbon turnover. Although, within the organic horizon there was a higher labile carbon pool in the control plots than in the heated plots. Comparing the two sites, further studies need to be done assess microbial function in relation to carbon turnover over time.

  • Research Category: Large Experiments and Permanent Plot Studies; Soil Carbon and Nitrogen Dynamics