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increased growth following density reduction. The diameter growth response of 271 Douglas-fir
(Pseudotsuga menziesii), ponderosa pine (Pinus ponderosa) and sugar pine (Pinus lambertiana)
trees in Oregon, USA, ranging in age from 158 to 650 years was examined 20 to 50 years after
density reduction. Density reduction involved either light thinning with removal of less vigorous
trees, or shelterwood treatments in which overstorey trees were not removed. Ratios of basal area
growth after treatment to basal area growth before treatment, and several other measures of
growth, all indicated that the old trees sometimes benefited and were not harmed by density
reduction. Growth increased by 10% or more for 68% of the trees in treated stands, and nearly
30% of trees increased growth by over 50%. This growth response persisted for at least 20 years.
During this 20-year period, only three trees in treated stands (1.5%) exhibited a rapid decrease in
growth, whereas growth decreased in 64% of trees in untreated stands. The length of time before
a growth response to density reduction occurred varied from 5 to 25 years, with the greatest
growth response often occurring 20 to 25 years after treatment. These results have important
implications both for the basic biology of aging in woody plants as well as for silvicultural
practices in forests with old-growth trees.
334. Lavender, D.P. and S.G. Stafford. 1985. Douglas-fir seedlings: some factors affecting chilling
requirement, bud activity, and new foliage production. Canadian-Journal-of-Forest-Research
15(2): 309-312.
Keywords: nursery operations
tree/stand health
tree physiology
tree phenology
Abstract: Potted 2-yr-old seedlings were exposed to a range of natural and artificial
environments at the Forest Research Laboratory, Oregon State University during the autumn and
winter before a 9-wk period in an environment designed to permit active shoot growth. Seedling
response demonstrated (i) that exposure to a period of short (9 h), mild (20 degrees C) days
prepared seedlings for the beneficial effects of subsequent chilling (4.4 degrees C) temperatures
and (ii) that the physiology of dormancy of Douglas-fir seedlings may be adversely affected by
environments that differ markedly from those prevailing in the Pacific Northwest during the
autumn.
335. Lavender, D.P. and R.B. Walker. 1981. Nitrogen and related elements in nutrition of forest trees.
In Proceedings: Forest Fertilization Conference, University of Washington, Seattle, Washington,
USA. Eds. S.P. Gessel, R.M. Kenady and W.A. Atkinson. pp. 15-22.
Keywords: fertilization
tree physiology
soil properties
mycorrhizal response
Abstract: This paper discusses the principal inorganic ions used by forest trees and their
respective roles in tree physiology, their common range of concentration in coniferous foliage,
and the general symptoms associated with their deficiency. The factors governing effective
concentrations of each ion at an active metabolic site are redistribution or internal nutrient
cycling, nutrient uptake, and soil status (temperature, moisture, and concentration of each
nutrient). Also described are endogenous patterns of nutrient storage and translocation, and the
possible effects of fertilizers upon them and upon the mechanisms of ion uptake, especially the