Comparative Ecophysiology Of Two High-Elevation Southern Appalachian Conifers: The Importance Of The Winter Season

ASU Author/Contributor (non-ASU co-authors, if there are any, appear on document)
Rachel Kelly Jordan (Creator)
Appalachian State University (ASU )
Web Site:
Howard Neufeld

Abstract: Southern Appalachian spruce-fir forests are glacial relicts, located as disjunct “islands in the sky” on the highest peaks in this region. Fraser fir (Abies fraseri), an endemic and valuable Christmas tree, dominates at elevations >1650 m while red spruce (Picea rubens), occurs at lower elevations (1380 – 1650 m). Winter in this forest type brings extended periods of snowfall and freezing temperatures, but is not as severe as in northern boreal regions. Southern spruce-fir forests have longer winter photoperiods, more frequent midwinter thaws, and fewer, less severe subzero temperatures. Despite milder winters in the south, this season still constitutes a substantial portion of the annual cycle for these evergreen trees, yet its importance to the ecophysiology of these trees is poorly understood, as are the potential impacts of milder winter conditions resulting from climate warming. Warming may result in more frequent occurrences of mild temperatures, shortened durations of thaws, free soil and stem (capacitance) water for uptake by trees, stimulate below- and above ground respiration, and enhance carbon uptake via photosynthesis. Our study aims to address this knowledge gap by measuring the comparative ecophysiology of both species during winter on Grandfather Mountain, NC, including pigment concentrations, photosynthesis/ respiration, fluorescence, and twig water potentials. Pigment concentrations were significantly higher in A. fraseri than in P. rubens, and concentrations declined with age in both species; no effect was found for canopy face (N or S). Photosynthetic rate was significantly higher in the one-year-old needles of P. rubens on day 4, but all other rates did not differ. Water potentials in A. fraseri were significantly more negative on two cold days, and leaf fluorescence increased significantly with air temperature. These measurements provide a physiological snapshot of these understudied trees and provide a basis to which future measurements can be compared.

Additional Information

Honors Project
Jordan, R. (2018). "Comparative Ecophysiology Of Two High-Elevation Southern Appalachian Conifers: The Importance Of The Winter Season." Unpublished Honors Thesis. Appalachian State University, Boone, NC.
Language: English
Date: 2018
Climate change, winter warming, conifer ecophysiology, high elevation

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