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Harvard Forest Symposium Abstract 2014

  • Title: Using permanent plot data to extend spatial and temporal understanding of carbon dynamics at Harvard Forest
  • Primary Author: Audrey Barker Plotkin (Harvard Forest)
  • Additional Authors: Katherine Eisen (Amherst College); David Foster (Harvard Forest); Liza Nicoll (Harvard Forest)
  • Abstract:

    Research from the Harvard Forest provides strong evidence for Northeastern forests role as a carbon sink. More than 20 years of forest-atmosphere C flux measurements from the EMS tower (Keenan et al. 2013), and shorter, complementary flux measurements in a recent clearcut, younger deciduous forest, and primary hemlock forest (Williams et al. 2013), a 20-year synthesis of soil respiration measurements (Giasson et al. 2013), and long-term climate change experiments (Frey et al. 2013, Melillo et al. 2011) provide insights into patterns and mechanisms of carbon uptake. Remote sensing data and integrated models help to interpolate and synthesize these site-specific studies. These studies mainly date back to 1988-1990, when the Harvard Forest became an LTER site.

    The long history of permanent forest plots at Harvard Forest can be used to extend these studies across larger environmental gradients and longer periods of forest development. Permanent plot data allows estimates of aboveground live carbon stocks back 75+ years, and across many forest types. An effort to synthesize these studies is underway, and involves: compiling study-specific data into a common framework, and applying a common suite of species-specific allometries to estimate biomass from tree diameter measurements, which are the most common type of measurement associated with older studies.

    Two examples of these studies are discussed: 1) the intensive, 3 hectare Lyford Grid, in which individual tree growth, recruitment and mortality was tracked from 1969-2011, and 2) the extensive ‘PHOREST’ study, in which 60 or more 0.05 hectare plots distributed across forest and soil type, and land-use history, were sampled in 1937, 1992 and 2013. Both studies show a consistent increase in forest biomass over time. Red oak has increasingly contributed to site-level biomass since 1937, and stands with a high component of conifer species tend to have higher biomass stocks.

    The next steps in this effort are to compile a larger number of studies and to add data (where available) on other components of the carbon budget such as litterfall, dead wood pools, coarse and fine roots, soil C stocks, understory vegetation. Ultimately, this synthesis will help our understanding of how environment and stand development drive stand-level carbon uptake, and will help inform larger data-model syntheses.

  • Research Category: Large Experiments and Permanent Plot Studies