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Harvard Forest Symposium Abstract 2015

  • Title: The effect of season exceeds that of soil warming treatment in driving microbial degradation potential of key biopolymers
  • Primary Author: Grace Pold (University of Massachusetts - Amherst )
  • Additional Authors: Andrew Billings (University of Massachusetts - Amherst ); Jeffrey Blanchard (University of Massachusetts - Amherst ); Kristen DeAngelis (University of Massachusetts Amherst); Jerry Melillo (Marine Biological Laboratory); William Rodriguez (University of Massachusetts - Amherst )
  • Abstract:

    The more than two decades of warming at the Prospect Hill soil warming experiment has shown us that soils will store less carbon in a warmer world. We previously reported a fundamental change in the bacterial community in the organic soil at this site, and elevated gaseous carbon loss concentrated in spring and fall. Extracellular enzyme activity shows strong seasonality in forest soils, but warming-induced changes in the availability of litter components and the microbial community may affect these temporal trends. Furthermore, increased nitrogen mineralization under warming indicates that the microbial community may be carbon-limited, and accessing N-rich carbon sources such as protein and chitin to meet these needs. We sampled soils from the organic and mineral horizons of the six heated and six disturbance control plots at Prospect Hill to determine how warming treatment has affected potential enzyme activity over the course of the growing season (six time-points April to October; 144 samples). We assayed the potential activity of phosphatase, leucine aminopeptidase, N-acetylglucosaminidase, cellobiohydrolase, beta-glucosidase, phenol oxidase, peroxidase, and beta-xylosidase using artificial substrates. Warming treatment tended to decrease extracellular enzyme activity when standardized per gram of dry weight soil, but it increased the activity of some enzymes when standardized per unit total organic nitrogen. This data will be used to inform a model of how warming has affected soil carbon cycling, which is being developed using sequence data.

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