Sun and shade leaves: clues to how salal (Gaultheria shallon) responds to overstory stand density
1991
Smith, N.J.
Salal (Gaultheria shallon Pursh) leaf biomass, leaf area index, specific leaf area, and leaf morphology, were examined in 13 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stands from 37 destructively measured 1-m2 quadrats. In response to light and stand overstory density, salal shoots produced either mainly sun leaves or mainly shade leaves. Sun leaves were associated with sunflecks in open-grown or variably stocked stands. Shade leaves were associated with diffuse light under denser stands. Sun-leaf quadrats had mean specific leaf areas less than 90 cm 2/g; shade-leaf quadrats had mean specific leaf areas greater than 90 cm2/g. Sun leaves were narrower, with average leaf widths less than 5 cm. Quadrat salal leaf biomass and leaf area index peaked at Curtis' metric relative density 5.9, which corresponded to an availability of 15% of global photosynthetically active radiation. Sun-leaf quadrats occurred below relative density 5; shade-leaf quadrats occurred above relative density 4. A mixture of sun- and shade-leaf quadrats occurred between about relative density 4 and 5, depending on the uniformity of stocking.
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