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growth
soil properties
tree physiology
Abstract: Application of 224 kg N/ha to young, thinned stands of Douglas fir (Pseudotsuga
menziesii) at 35 sites in W. Oregon and Washington significantly increased basal area and
volume increment over 8 years following treatment. However, response varied considerably
between sites, and relative volume increment exceeded 10% at only 19 of the 35 sites. Response
to applied N was evaluated in relation to forest floor and soil variables as well as to levels of N in
foliage. Relative responses in basal area and volume were significantly correlated with total N
concentration and the C/N ratio of the soil. However, these relationships explained only part (18-
22%) of the observed variation in response. In contrast, relative response was strongly correlated
with the level of N in the foliage of non-fertilized trees at 11 sites, accounting for 94% of the
variation between sites. It is suggested that foliar N could be used to predict growth responses to
N fertilizers in young thinned Douglas fir stands.
275. Huffman, D.W. and J.C. Tappeiner, II. 1997. Clonal expansion and seedling recruitment of
Oregon grape (Berberis nervosa) in Douglas-fir (Pseudotsuga menziesii) forests: comparisons
with salal (Gaultheria shallon). Canadian-Journal-of-Forest-Research 27(11): 1788-1793.
Keywords: thinning
stand conditions
Abstract: Seedling regeneration and morphology of Oregon grape (Berberis nervosa) and
salal (Gaultheria shallon) were studied in thinned and unthinned Douglas fir (Pseudotsuga
menziesii) stands in the central Coast Range, Oregon. Above- and below-ground growth of both
species were significantly and negatively correlated with stand density. Oregon grape appears to
have less potential for vegetative spread than does salal. It produced two to three times fewer
rhizome extensions, and rhizome extensions were only half as long as those of salal. Oregon
grape seedlings were common in areas of moss ground cover among patches of the two species.
Salal seedlings were restricted to decaying logs. Seedling densities of Oregon grape in thinned
stands were more than six times those in unthinned stands. For Oregon grape, understorey
establishment is accomplished by seedling establishment and recruitment of new genets. In
contrast, salal maintains itself in forest understories primarily through vegetative growth, since its
seedling establishment is restricted mainly to decayed wood. Continual recruitment of new aerial
stems or ramets enables Oregon grape to maintain a dense cover once it is established in the
understorey.
276. Huffman, D.W., J.C. Tappeiner, II and J.C. Zasada. 1994. Regeneration of salal (Gaultheria
shallon) in the central Coast Range forests of Oregon. Canadian-Journal-of-Botany 72(1): 39-51.
Keywords: thinning
stand conditions
Abstract: Regeneration of salal (Gaultheria shallon) by seedling establishment and
vegetative expansion was examined in Douglas fir (Pseudotsuga menziesii) stands that had been
thinned, clear felled or undisturbed in the central Coast Range of Oregon. Size and expansion rate
of individual clonal fragments were negatively correlated with overstorey stand density (p 0.039). As overstorey basal area increased from 25 to 75 msuperscript 2/ha, mean annual
growth percentage of clone rhizome systems decreased from 23.7 to 0% and mean total rhizome
length decreased from 102 to 0.89 m. Interclonal competition in dense clumps of salal apparently