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Harvard Forest REU Symposium Abstract 2011

  • Title: Fine Woody Debris Dynamics after an Ice Storm Disturbance Event at Harvard Forest
  • Author: Jakob O Lindaas (Harvard College (Harvard University))
  • Abstract:

    The forest C cycle has major impacts on Global GHG levels and Climate Change. The exchange of C between the atmosphere and the forest has been measured at the Harvard Forest EMS for the past 22 years. Biometry measurements made in 33 plots surrounding the EMS tower help to partition the forest C cycle into three main components: Live biomass, Soil, and Detritus. Fine Woody Debris (FWD; 2 cm≤ diameter <7.5 cm), Coarse Woody Debris (CWD; 7.5 cm < diameter) and litterfall make up the Detritus C pool. A major ice storm in December of 2008 sent a pulse of FWD to the forest floor. This FWD C mass was quantified in the 33 plots during the summer of 2009. We resurveyed the FWD in a subset of the plots during the summer of 2011. Samples of different decay classes and species were taken and average densities were calculated for each species and decay class. The decomposition rate of the resurveyed FWD was calculated to be 0.09 Mg C ha-1 yr¬-1. The FWD C reservoir in 2009 was 0.39 Mg C h-1 (±0.19) and the C reservoir in 2011 was 0.20 Mg C ha-1 (±0.07) [Figure]. Because the 95% confidence intervals overlap (due to high spatial variability in FWD), we cannot claim the decrease in the FWD C mass to be statistically significant. However, the decay measured was due almost entirely to density change, making these results ecologically significant. Our density measurements show a negative C flux from the downed FWD over this time period, with a decrease of 24% yr-1 of Mg C ha-1. This can be compared to a decrease of 4.54% yr-1 of Mg C ha-1 in the CWD pool during the most recent CWD measurement period. This indicates that FWD has a higher turnover rate than CWD in temperate forests. Since FWD is an important C reservoir in temperate forests, these results suggest that disturbance events such as an ice storm may lead to rapidly increased C flux out of the FWD C pool in forested ecosystems.

  • Research Category: Forest-Atmosphere Exchange

  • Figures:
    • FWD.09vs11.good.graph.pdf