Physiological and morphological responses of pine and willow saplings to post-fire salvage logging
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Date
2015
Authors
Millions, Elizabeth L.
Journal Title
Journal ISSN
Volume Title
Publisher
Lethbridge, Alta. : University of Lethbridge, Dept. of Geography
Abstract
With global warming, forest fires may be increasing in frequency, and subsequently post-fire salvage logging may become more common. The ecophysiological impacts of this practice on tree saplings remain poorly understood. In this study, I examined the physiological and morphological impacts of increased light intensity, due to post-fire salvage logging, on the conifer Pinus contorta (pine) and deciduous broadleaf Salix lucida (willow) tree and shrub species in the Crowsnest Pass region of southern Alberta. Photosynthetic gas-exchange and plant morphological measurements were taken throughout the summer of 2013 on approximately ten year-old saplings of both species. Neither species exhibited photoinhibition, but different strategies were observed to acclimate to increased light availability. Willow saplings were able to slightly elevate their light-saturated rate of net photosynthesis (Amax) when exposed to higher
photosynthetic photon flux density (PPFD), thus increasing their growth rate. Willow
also exhibited increased leaf inclination angles and leaf mass per unit area (LMA), to
decrease light interception in the salvage-logged plot. By contrast, pine, which exhibited
lower Amax and transpiration (E), but higher water-use efficiency (WUE = Amax/E) than
willow, increased the rate at which electrons were moved through and away from the
photosynthetic apparatus in order to avoid photoinhibition. Acclimation indices were
higher in willow saplings, consistent with the hypothesis that species with short-lived
foliage exhibit greater acclimation. LMA was higher in pine saplings growing in the
logged plot, but whole-plant and branch-level morphological acclimation was limited and
more consistent with a response to decreased competition in the logged plot, which had
much lower stand density.
Description
Keywords
plant physiology , plant stress ecology , photosynthesis , salvage logging , stable isotope ecology , stress acclimation , subalpine , Rocky Mountains , Alberta , forestry , ecophysiology , pine , willow