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Harvard Forest REU Symposium Abstract 2007

  • Title: Soil Warming Leads To Significant Reduction of Fine Root Biomass
  • Author: Mary G Clark (Sewanee - The University of the South)
  • Abstract:

    Climatologists predicts that by the end of the 21st century the mean global temperature will have risen 1.4° to 5.8° C due to an increase in greenhouse gases in the atmosphere. In order to investigate the effect of climate warming on carbon allocation in temperate forest ecosystems, fine root biomass was measured in a simulated warmer environment. This experimental model was created by burying underground heating cables in temperate forest plots to raise the temperature of the soil 5° C above the temperature of the adjacent control plots. Two soil warming sites at Harvard Forest, in Petersham, Massachusetts, were used in this study. One site, with eighteen 6x6 meter plots, has been heated since 1991. The other site, with two 30x30 meter plots, has been heated since 2002. During April, June, and July 2007, soil cores were collected from heated and control plots at both sites. Cores were divided in to organic and mineral layers, and fine roots (<3mm diameter) were separated from each section and classified by diameter size classes (<1 mm, 1-2 mm, 2-3 mm). The roots were then dried and weighed. Samples from the heated plots had 40 to 60 percent less fine root biomass than samples from the control plots. Soil analyses at the same sites have shown that nitrogen availability has steadily increased during the years of heating, so the heated plots have significantly more available nitrogen than the control plots. In Northeastern forests, nitrogen scarcity is usually the primary limiting factor. Increasing nitrogen availability reduces the need for trees to grow expansive root systems, and carbon that trees had once allocated to fine roots can potentially be allocated to above-ground biomass. This study suggests a strong correlation between soil warming, nitrogen availability, and fine root growth. Further studies that measure fine root biomass year-round are needed for a better understanding of root growth and carbon and nitrogen allocation.

  • Research Category: Large Experiments and Permanent Plot Studies

  • Figures:
  • Live Fine Root Biomass_Mary Clark.png