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Harvard Forest Symposium Abstract 2009

  • Title: Sequestration of atmospheric carbon dioxide in regenerating New England forests: quantifying pools and constraining fluxes
  • Primary Author: Allison Dunn (Worcester State University)
  • Abstract:

    We initiated a field-based study to measure sequestration of atmospheric carbon dioxide in different-aged forest stands at Harvard Forest. We established long-term biometric plots suitable for measuring changes in carbon storage through time in three forest stands: an early-20th-century conifer plantation, a naturally regenerating former conifer plantation, and a conifer plantation clearcut in 2008. The first year of this project focused on deploying the infrastructure to determine the initial carbon stocks in these forest stands. Data collected in the summer 2009 field season will measure carbon fluxes into and out of these stands, providing a baseline for future investigations.

    The experimental design consists of eighteen plots across three separate study areas. The control site is the unharvested portion of plantation 25-H in the Prospect Hill Tract, which was planted in 1925 with red pine (Pinus resinosa). Two harvested sites were also chosen: the portion of plantation 25-H harvested in summer 2008, and a similar former red pine plantation to the west that was harvested in 1990. Six 10-m radius circular plots were established at random locations in each of the study areas. All trees ≥ 5 cm diameter breast height (DBH; 1.3 m) were identified, measured, and tagged, totaling nearly 800 trees across the 18 plots. Coarse and fine woody debris ≥ 2.5 cm diameter was surveyed using the line-intercept method (Van Wagner 1968) along randomly oriented 10 m transects.

    The initial surveys from summer 2008 will be followed up with repeat surveys and new measurements during summer 2009. Changes in DBH from 2008-2009 will be converted to changes in aboveground carbon storage using species-specific allometric equations. Recruitment and mortality will be determined during these surveys and results incorporated into the appropriate carbon pools (live or dead biomass). Carbon loss due to woody debris respiration will be calculated using the Liu et al. (2006) respiration model calibrated at Harvard Forest. The DBH and species of woody shrubs 1-5 cm DBH will also be measured to assess the size of the carbon pool and changes to this pool through time. Growth of biomass in this pool is an important first step towards re-establishing carbon sequestration in sites following harvest, as small trees in this pool represent future recruits towards larger tree size classes that sequester significant amounts of carbon. Traps to capture leaf litter will be built and deployed before autumn senescence in order to quantify carbon fluxes through these short-lived pools.

    The work has both short- and long-term goals. The 2008 surveys and 2009 resurveys allow study of how forest carbon fluxes are affected by both silvicultural practices and normal ecosystem processes on relatively short timescales. These sites also provide the foundation for longer-term investigations into atmosphere-biosphere interactions across a range of stand age and forest management practices. The sites will be revisited in subsequent years to investigate changes in carbon sequestration patterns across the successional trajectory of the three forest types. The knowledge generated by this work, on yearly to decadal timescales, will provide insight into how different forest stands remove CO2 from the atmosphere and how New England forests may better be managed to mitigate climate change.

    Liu WH, DM Bryant, LR Hutyra, SR Saleska et al. 2006. Woody debris contribution to the carbon budget of selectively logged and maturing mid-latitude forests. Oecologia, doi:10.1007/s00442-006-0356-9.

    Van Wagner CE. 1968. The line intersect method in forest fuel sampling. Forestry Science 17, 20-26.

  • Research Category: Forest-Atmosphere Exchange