Light-growth response relationships in Pacific silver fir (Abies amabilis) and subalpine fir (Abies lasiocarpd)

Abstract

Pacific silver fir and subalpine fir, both typically inhabiting high-elevation forests in northwestern North America, were considered shade-tolerant species, the former more tolerant than the latter. To determine their relative shade tolerance, established advance regeneration was sampled along a light gradient ranging from open areas to inside a forest stand, and analysis of irradiance, growth, and leaf measures was obtained. Relationships between the percentage of above-canopy light (in the photosynthetically active wavelengths) associated with each study tree and its 1991 height increment, 1991 lateral increment, caliper at the base of the 1991 leader, and specific leaf area were examined for individual sites, and sites were grouped according to soil moisture. There were strong, consistent, and similar relationships between irradiance, growth performance, and specific leaf area for both species. As irradiance decreased, growth performance decreased and specific leaf area increased. In spite of ecological differences between the study sites for each species, it was concluded that on fresh sites, Pacific silver fir and subalpine fir are very tolerant of shade. Both are equally well adapted to survive under high shade and snowpack by allocating more resources to caliper and lateral growth than to height growth and by increasing specific leaf area. Key words: shade tolerance, advance regeneration, irradiance, growth performance, specific leaf area, Pacific silver fir, subalpine fir.

Juvenile growth and crown morphological plasticity of eastern white pines (Pinus strobus L.) planted along a natural light gradient: Results after six years

“…This seems to suggest that our six-year-old planted saplings were not heavily suppressed by the light gradient found in the understory. Similar effects of a light gradient on growth in situ have been reported for more shade-tolerant conifers (Klinka et al 1992, Parent and Messier 1995, Chen et al 1996. However, shade-tolerant conifers tended to reach maximum growth at lower light levels of approximately 25% PPFD and to have a much reduced height growth at low light levels.…”

Growth limitations of planted conifers regenerating under Montane Alternative Silviculture Systems (MASS): Seven-year results

“…These results are consistent with other studies from several coastal sites in British Columbia that found the maximum growth potential for amabilis fir and western hemlock occurs when canopy light transmittance is greater than 75% Klinka 1992, Klinka et al 1992) a level that occurred in less than half of the SW microsites (Beese et al 2004). Gaps in the dispersed SW were variable in size, most being under one tree height in diameter (approximately 0.1 ha), a gap size below which growth declines have been reported in both western hemlock and amabilis fir (Gray andSpies 1996, Coates 2000).…”

Use of a spatially explicit individual-tree model (SORTIE/BC) to explore the implications of patchiness in structurally complex forests

“…Understory light availability is a good proxy for predicting juvenile tree growth in complex structured northern latitude forests (e.g., Klinka et al, 1992;Chen, 1997;Wright et al, 1998;Coates and Burton, 1999;Drever and Lertzman, 2001;Claveau et al, 2002). SORTIE/BC can predict light levels after any type of partial cutting, and it can be easily parameterized for different forest ecosystems (Canham et al, 1994(Canham et al, , 1999Beaudet et al, 2002).…”