IntensIve sIlvIculture - Forest Science Labs - Research Network ...

population size and composition of organisms between mature forests and both low management
and high management clearcuts demonstrated the impacts forest management practices may have
on the soil ecosystem.
142. Dosskey, M.G., L. Boersma and R.G. Linderman. 1993. Effect of phosphorus fertilization on
water stress in Douglas fir seedlings during soil drying. Plant-and-Soil 150(1): 33-39.
Keywords: fertilization
tree/stand protection
growth
tree physiology
photosynthesis
Abstract: A growth chamber experiment was conducted to determine if P fertilizing to
enhance the P nutrition of otherwise N and P deficient Douglas fir (Pseudotsuga menziesii)
seedlings reduces water stress in the seedlings during drought periods. Seedlings were grown in
pasteurized mineral soil under well watered conditions and fertilized periodically with a small
amount of nutrient solution containing P at three levels: 0, 20, or 50 mg/litre. By age 6 months,
leaf nutrient analysis indicated that N and P were deficient in control (0 mg P/litre) seedlings. The
highest level of P fertilizer, which doubled leaf P concentration, did not affect plant biomass,
suggesting that N deficiency was limiting growth. When these seedlings were subjected to
drought, there was no effect of P fertilizing on leaf water potential or osmotic potential.
Furthermore, P fertilized seedlings had lower stomatal conductance and net photosynthesis rate.
These results indicate that enhanced P nutrition, in the presence of N deficiency, does not reduce
water stress in Douglas fir seedlings during drought periods.
143. Drever, C.R. and K.P. Lertzman. 2003. Effects of a wide gradient of retained tree structure on
understory light in coastal Douglas-fir forests. Canadian-Journal-of-Forest-Research 33(1): 137-
146.
Keywords: thinning
stand conditions
Abstract: We characterize understorey light of seven stands that varied along a gradient of
tree retention. Using hemispherical canopy photographs and digital image, we estimated gap light
or solar radiation reaching the understorey through the canopy. Using nonlinear regressions, we
related gap light to several structural attributes in the examined silvicultural treatments. The
silvicultural treatments affected both the median and range of gap light in the understorey. As
overstorey removal increased from uncut second growth to green-tree retention, the median value
of light increased from 8 to 68% full sun, while the range of light increased from 3-22% to 26-
88% full sun. We found strong, significant, and negative nonlinear relationships between gap
light at a particular microsite (0.04 ha) in the understorey and the height, diameter at breast
height, density, and volume of surrounding retained trees (ra2=0.77-0.94). These relationships
can aid planning of treatments that retain forest structure, such as variable retention, by allowing
predictions of understorey light from commonly used field data. These predictions allow forest
managers to understand some of the ecological consequences and tradeoffs associated with
retaining structure during harvesting.
144. Drew, A.P. 1983. Optimizing growth and development of 2-0 Douglas-fir seedlings by altering
light intensity. Canadian-Journal-of-Forest-Research 13(3): 425-428.
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