© 2007 Heron Publishing—Victoria, Canada
Leaf-level acclimation to gap creation in mature Acer saccharum trees
T. A. Jones (1, 2) and S. C. Thomas (1)
1. Faculty of Forestry, University of Toronto, 33 Willcocks Street, Toronto ON, M5S 3B3, Canada / 2. Corresponding author (trevor.jones@utoronto.ca) / Received November 30, 2005; accepted April 9, 2006; published online November 1, 2006
Summary
Leaf-level morphological and physiological responses of mature, winter-deciduous, shade-tolerant Acer saccharum Marsh. trees to gap formation caused by selection harvest were studied experimentally over a 2-year period. We found no evidence
for either physiological stress or positive acclimation following gap creation during the 1–2-week post-harvest period. Rather,
lower-canopy leaves showed gradual increases in area-based maximum photosynthetic rates (Amax-area), stomatal conductance (gs), and leaf nitrogen concentration (Narea) over the entire 2-year study. These acclimation responses were directly related to changes in leaf mass per unit area (LMA)
in the subsequent two leaf flushes. No change in Amax-area, gs, Narea, or photosynthetic nitrogen-use efficiency was observed that could not be accounted for by changes in LMA. The gradual acclimation
responses in the lower canopy may account, in whole or in part, for the ~2-year lag in post-harvest growth response observed
in Acer saccharum.
Keywords:
canopy trees, gap creation, gas exchange, leaf morphology, light acclimation, nitrogen content, photosynthetic nitrogen use
efficiency, selection management, shade leaves, sun leaves.
