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    Author(s): Joseph B. Davis
    Date: 2009
    Source: Highlands Biological Station 8-22 p.
    Publication Series: Miscellaneous Publication
    PDF: View PDF  (9.77 MB)


    Eastern hemlock (Tsuga canadensis (L.) Carr.) is declining throughout the eastern United States as a result of infestation of the hemlock woolly adelgid (HWA). As a principal species in riparian cove habitats in the southern Appalachians, its loss will have impact on the hydrologic budget in these systems. To estimate the impact on the hydrologic budget, we quantified transpiration over five years for T. canadensis, and over two years for co-occurring species Acer rubrum, Betula lenta, and Rhododendron maximum. Further, to understand the impacts of climate on transpiration, we compared transpiration to photosynthetically active radiation (PAR) and to vapor pressure deficit (VPD). Given the loss of T. canadensis from the ecosystem, we modeled implications on transpiration from two resulting succession scenarios, one in which R. maximum dominates, and one in which A. rubrum and B. lenta dominate. Transpiration was shown to decline since 2004 for T. canadensis, and no such decline was observed for the other species from 2006. The decline in transpiration was not shown to be a result of a changing climate conditions from the same study period. Using data from other studies, we modeled the succession of R. maximum following the loss of T. canadensis leaf area from the canopy. Also, we modeled the succession of A. rubrum and B. lenta resulting from a shift in sapwood area from T. canadensis to these species. Under both post-mortality scenarios, the transpiration component of the hydrologic budget increased. Although actual post-mortality scenarios are difficult to predict, the loss of T. canadensis will result in changes in the function of this ecosystem.

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    Davis, Joseph B. 2008. Quantifying the decline in transpiration of Tsuga Canadensis and predicting water budget implications of succession in southern Appalachian forests. Highlands Biological Station. 8-22 p.

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