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

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Abstract: This study investigated bark growth and decay development after thinning
damage at two western Oregon sites, and estimated value loss with a tree growth model. All scars
that remained open in western hemlock (Tsuga heterophylla) and Sitka spruce (Picea sitchensis)
had advanced decay 13 years after initial wounding. Scars less than 4 inches wide closed in 8
years. Douglas-fir (Pseudotsuga menziesii) was more resistant to decay; no rot was observed in
scars less than 21 years old. Advanced decay and pitch rings, however, were observed in 29-yearold
scars, both open and closed. Because of these defects, future value loss increased with time
after wounding and with higher stand damage levels. Fifty years after thinning, about 2% of the
total future log value, or $189/ac. (1997$), could be lost in Douglas-fir stands with 20% stand
damage and a 2-inch diameter deduction. This loss could be reduced to $58/ac. if stand damage
were minimized to 5% with more careful techniques. The increase in thinning costs ($61/ac. for
tractor thinning; $79/ac. for cut-to-length; $124/ac. for skyline; with a 5% increase in production
time) that is incurred while trying to minimize stand damage could be justified if it reduced future
value losses to crop trees.
241. Hansen, E.M., J.K. Stone, B.R. Capitano, P. Rosso, W. Sutton, L. Winton, A. Kanaskie and M.G.
McWilliams. 2000. Incidence and impact of Swiss needle cast in forest plantations of Douglas-fir
in coastal Oregon. Plant-Disease 84(7): 773-778.
Keywords: tree/stand protection
growth
tree/stand health
Abstract: An epidemic of Swiss needle cast, caused by the ascomycete Phaeocryptopus
gaeumannii, is causing defoliation and growth reductions in Douglas-fir forest plantations along
the Oregon Coast. The area of symptomatic plantations has been monitored annually since 1996
by aerial survey; in spring 1999, 119,500 ha were affected. Pathogen and symptom development
have also been monitored on nine permanent plots in stands of differing disease severity.
Infection levels and symptom severity are greatest in low elevation plantations close to the coast.
In areas of severe disease, trees retain only current year needles. Defoliation is proportional to the
number of stomata occluded by pseudothecia of the fungus, with needles being shed when about
50% of stomata are occupied, regardless of needle age. Fungus sporulation and premature needle
abscission are greatest on the upper branches of trees. Annual application of fungicides increases
needle retention significantly. Tree height and diameter growth and total tree volume are reduced
by disease, and tree volume is significantly correlated with needle retention on our plot trees. The
epidemic continues to be most severe in Douglas-fir plantations established on sites where Sitka
spruce and western hemlock or red alder predominated in earlier times.
242. Harper, P.A. and A.S. Harestad. 1986. Vole damage to coniferous trees on Texada Island.
Forestry-Chronicle 62(5): 429-432.
Keywords: thinning
precommercial thinning
tree/stand protection
tree/stand health
growth
Abstract: Microtus townsendii injured trees by removal of bark and cambium from stems,
branches and roots of Douglas fir, western hemlock and, rarely, Pinus monticola on Texada
Island, British Columbia. Damage occurred more frequently in precommercially thinned stands