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

373. McClain, K.M. and D.P. Lavender. 1988. Tissue water relations and survival of conditioned
conifer seedlings during drought stress. In Proceedings: 10th North American Forest Biology
Workshop, 'Physiology and genetics of reforestation', University of British Columbia, Vancouver,
British Columbia, July 10-22, 1988. Eds. J. Worrall, J. Loo-Dinkins and D.P. Lester. pp. 177-185.
Keywords: nursery operations
tree/stand protection
tree physiology
tree/stand health
165
Abstract: Jack pine (Pinus banksiana) and Douglas fir (Pseudotsuga menziesii) 23-weekold
seedlings were subjected to an 8-week drought stress period on two soil types (sandy clay
loam and loamy sand) in protected cold frames in a nursery in Oregon in July-August 1984.
Before transplanting, treatments consisting of daily or weekly irrigations, combined with 0 or 100
p.p.m. KCl, were applied to the seedlings for 6 weeks. The results showed that weekly irrigated
(stress conditioned) seedlings maintained higher water potentials than daily irrigated (non-stress
conditioned) seedlings. Decreases in water potential were more rapid for seedlings grown on sand
than for seedlings grown on loam. By the end of the assessment period, relative water contents of
Douglas fir on sand and loam were 88.3% and 91.5%, respectively, and 72.7% and 81.8%,
respectively, for jack pine. Turgor pressures were maintained at higher levels in Douglas fir than
in jack pine on both soil types. On sand, mortality in both species was dependent on conditioning
treatment, indicating that stress conditioning enhanced seedling drought resistance during a
period of rapidly increasing soil water deficit. KCl treatment was not implicated in response to
drought, but increased mortality of jack pine on sandy clay loam.
374. McCreary, D.D., D.P. Lavender and R.K. Hermann. 1990. Predicted global warming and
Douglas-fir chilling requirements. Annales-des-Sciences-Forestieres 47(4): 325-330.
Keywords: genetic tree improvement
nursery operations
tree phenology
growth
Abstract: Containerized Douglas fir (Pseudotsuga menziesii) seedlings from warm coastal
and cool mountainous Oregon seed sources, grown under natural conditions, were chilled at
constant temperatures of 5, 7 or 9 degrees C for 9, 11, 13 or 15 weeks beginning in mid-October.
After a growth period of 9 weeks following chilling, degree of budbreak and dry weight of new
shoot growth were measured. The longest and coldest chilling treatment produced the greatest
growth response for all seed sources. Results are discussed with reference to predicted global
warming, in particular the potential difficulty of reducing Douglas fir chilling requirements
through tree breeding programmes.
375. McDonald, P.M. and G.O. Fiddler. 1993. Feasibility of alternatives to herbicides in young conifer
plantations in California. Canadian-Journal-of-Forest-Research 23(10): 2015-2022.
Keywords: genetic tree improvement
site preparation
prescribed fire
release treatments
manual release
chemical release