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Jeff Carroll, Yale School of Forestry and Environmental Studies, charles.carroll@yale.edu (Presenter)

 

There is concern about the fate of conifer species under increased water stress due to climate warming within northeastern USA. We investigated anatomical and physiological characteristics of two conifers, red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea L.), along an elevation gradient in New Hampshire to determine relative water use efficiencies of these species, and the impacts of elevation on those efficiencies. Foliar and wood traits were measured at three elevations on Mt. Moosilauke (690m, 910m, and 1140m) representing the arborescent realized niche of species overlap. Isotopic analysis suggested no species-significant differences in intrinsic water use efficiency; however, a desiccation experiment indicated that red spruce responds to water stress faster than balsam fir at the lowest elevation. In addition, we determined that red spruce had a lower surface area to volume ratio at all elevations. Lastly, stomatal area index (SAI), a relative measure of stress, was measured to determine current conditions. At the lowest elevation, red spruce had a significantly higher SAI than balsam fir, without significant differences at the other elevations. Results indicate that red spruce is displaying overall higher water use efficiency than balsam fir, however, red spruce is more water stressed than balsam fir at the lowest elevation. Balsam fir appears to have a high enough efficiency to resist current water stress at all elevations despite lower water use efficiency than red spruce.