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Harvard Forest Symposium Abstract 2018

  • 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 2017, we continued the automated measurement of soil respiration (Rsoil) we had initiated in late 2015. Shortly after snowmelt, we deployed six chambers near the Hemlock tower in an area heavily affected by the hemlock woolly adelgid. Six more chambers were located downstream from the Bigelow Brook weir where hemlock trees appeared to be healthy. Because the soil respiration collars were left in place over the winter, we could deploy the chambers at the exact same location as previous years, which allowed interannual comparisons.

    The autochambers have run mostly continuously, with the exception of loss of power during some storms or other electrical and equipment problems. Each chambers made one measurement per half hour. 126,872 valid soil respiration measurements were made in 2017, for a total of 245,905 measurements since the beginning of the study.

    During both years, Rsoil was significantly higher at the weir (healthy) site than the tower (infested) site (Fig. 1). Rsoil was slightly lower in 2016 than in 2017, potentially because of the severe drought conditions that affected Harvard Forest in 2016 (Fig. 2). Rsoil also varied between chambers (Fig. 3).

    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 (healthy) sites.

    Fig. 2:
    Mean annual soil respiration.

    Fig. 3:
    Total annual soil respiration for each collar in 2016 and 2017.

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

  • Figures:
  • Fig1.JPG