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Harvard Forest REU Symposium Abstract 2010

• Title: Changes in Understory Vegetation Composition and Impacts on Carbon Sequestration in the Harvard Forest
• Author: Fiona V Jevon (Dartmouth College)
• Abstract:

  Over the last 21 years CO2 exchange has been measured at the Harvard Forest EMS tower. There has been a systematic increase in the magnitude of C-uptake, which has also been observed in biometry plots that provide ground-based measurements of C pools. Meteorological data and changes in growing season length have not significantly contributed to the observed increase in C-uptake. We examined how the understory might contribute to this trend. We quantified the biomass of all understory species (1 cm ≤ DBH < 10 cm) in the 33 biometry plots and measured in situ photosynthetic rates of the dominant species using a LI-COR LI-6400. While the overall biomass of the understory has not changed significantly (2.38 ± .51 kgC/ha in 2006 and 2.27 ± .50 kgC/ha in 2010), the species composition has. Over the last four years the understory biomass of Red Maple (Acer rubrum) has decreased 0.18 kgC/ha while the biomass of Red Oak (Quercus rubra) has increased 0.15 kgC/ha. We found that some tree species, such as Black Birch (Betula lenta), have relatively high photosynthetic rates at lower light levels but others may be light-limited in the understory. The understory only accounts for 1.82% of the total aboveground C storage in the forest and may be light-limited during the peak of the growing season. Future measurements of photosynthetic rates at the beginning and end of the growing season, when understory species are not shaded out, will help determine the influence of these trees and shrubs on overall CO2 exchange at Harvard Forest.

• Research Category: Forest-Atmosphere Exchange


• Figures:
Photosynthetic Means for All Light Levels.pdf
Red Maple and Red Oak Understory Biomass.pdf