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Harvard Forest Symposium Abstract 2019

  • Title: Soil carbon stocks and fluxes in a hemlock stand infested by the hemlock woolly adelgid
  • Primary Author: Marc-Andre Giasson (Boston University)
  • Additional Authors: Adrien Finzi (Boston University)
  • Abstract:

    The introduction of the hemlock woolly adelgid (HWA) has resulted in widespread hemlock mortality. The impact of tree mortality on carbon fluxes remains poorly constrained. Exactly how much C is lost and how long it would take to recover those C stocks following succession is unknown. The HWA is now widespread at Harvard Forest and the objective of this research is to quantify the impact of hemlock mortality on components of the forest C budget. Here we present data on soil respiration.

    From April to December 2018, we continued the automated measurement of soil respiration (Rsoil) we had initiated in late 2015. As was done in the past, we deployed twelve chambers at the exact same location as previous years. Six chambers were located near the Hemlock tower in an area heavily affected by the hemlock woolly adelgid; most hemlock trees in that area are either dying or dead. Six other chambers were located downstream from the Bigelow Brook weir where hemlock trees appeared healthier.

    Each chamber made one measurement per half hour. At the time of writing, data processing is not entirely completed, but preliminary results indicate that 121,536 valid soil respiration measurements were made in 2018, for a total of 367,441 measurements since the beginning of the study.

    Similar to what was recorded in 2016–2017, in 2018 Rsoil was significantly higher at the weir (healthier) site than the tower (infested/dying) site (Fig. 1). Site-level average Rsoil in 2018 was the highest measured at the tower site (2016: 672 g C/m2/yr; 2017: 740 g C/m2/yr; 2018: 843 g C/m2/yr) and the difference was statistically significant. Average Rsoil in 2018 was similar to previous years at the weir site (2016: 1054 g C/m2/yr; 2017: 1117 g C/m2/yr; 2018: 1091 g C/m2/yr).

    Continued Rsoil measurements in future years coupled with more above- and belowground sampling of carbon stocks will help us determine temporal trends in the carbon budget of hemlock forests during and after hemlock woolly adelgid infestation.

    Figure captions:

    Fig. 1:
    Mean daily respiration at the tower (infested) and weir (healthier) sites.

  • Research Category: Soil Carbon and Nitrogen Dynamics; Invasive Plants, Pests & Pathogens; Forest-Atmosphere Exchange

  • Figures:
  • Fig1.JPG