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Harvard Forest Symposium Abstract 2010

  • Title: The autotrophic contribution to soil respiration in Northeastern Deciduous Forests: A case study from a tree girdling experiment in Black Rock Forest
  • Primary Author: Jennifer Levy-Varon (Columbia University in the City of New York)
  • Additional Authors: Kevin Griffin (Columbia University in the City of New York); William Schuster (Black Rock Forest Consortium)
  • Abstract:

    Growing evidence for a large autotrophic contribution to total soil respiration has motivated the broader ecological community to work towards a better understanding of respiratory partitioning and associated environmental influences on a global scale. The goal of this study was to evaluate the contribution of Quercus spp. (Oak) and its associate mychorrizal fungi, to total soil respiration, and to better understand partitioning of autotrophic and heterotrophic respiration at Black Rock Forest. Trees on twelve plots (75m x75m) in a randomized block design grouped by slope position (upper, middle, and lower) were girdled according to four treatments: girdling all the oaks on the plot (OG), girdling half of the oak trees on a plot (O50), girdling all non-oaks on a plot (NO), and a control (C). In addition to the 12 established plots, one circular plot (50m diameter) was created where all trees were girdled (ALL). Soil respiration was measured from May through October. A conservative estimate of the total autotrophic contribution is 51% as revealed from a fully girdled plot. Rapid declines in CO2 flux from both the ALL and OG plots observed within the first two weeks following the treatment, 37% and 33% respectively, support a fast turnover between recently fixed carbon and its release back to the atmosphere. Responses from the NO and O50 treatments were similar to the C. A non-proportional decline in respiration rates along the biomass gradient, complicated the assessment of the contribution of Quercus to the overall rate of soil respiration and indicate that belowground carbon flux is not linearly related to above ground disturbance. Our findings suggest that as disturbance alters aboveground forest composition, there may be a threshold beyond which the mycorrhizal network and belowground community function shift dramatically. In our system, this threshold falls between 35-74% of live aboveground biomass.

  • Research Category: Large Experiments and Permanent Plot Studies

  • Figures:
  • Experimental Design.jpg
    Repiration Response.jpg