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

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added to provide proper nutrition on these volcanic ash soils. The information can aid in guiding
further fertilizer trials in forests on volcanic ash derived soil in SW Oregon and elsewhere.
642. Walstad, J.D., J.D. Brodie, B.C. McGinley and C.A. Roberts. 1986. Silvicultural value of
chemical brush control in the management of Douglas-fir. Western-Journal-of-Applied-Forestry
1(3): 69-73.
Keywords: release treatments
chemical release
growth
yield
economics
Abstract: Retrospective analyses were made of 3 Douglas fir plantations (age 12-39 yr) in
western Oregon and Washington, to determine the long-term silvicultural effects and economic
value of chemical brush control 10-25 yr earlier. Stocking and growth of Douglas fir were
significantly greater on areas that received at least one aerial application of 2,4-D or 2,4,5-T than
on untreated areas. On two sites, invading Alnus rubra virtually excluded Douglas fir in the
absence of brush control. On the third site, Ceanothus velutinus var. laevigatus reduced Douglas
fir stocking and diam. growth on untreated areas. On all three sites, projections of mature yield
and economic returns based on current stand conditions indicated substantial benefits for areas
where brush control treatments were applied.
643. Wang, T., S.N. Aitken, J.H. Woods, K. Polsson and S. Magnussen. 2004. Effects of inbreeding
on coastal Douglas fir growth and yield in operational plantations: a model-based approach.
Theoretical-and-Applied-Genetics 108(6): 1162-1171.
Keywords: genetic tree improvement
seed orchard management
planting operations
yield
Abstract: In advanced generation seed orchards, tradeoffs exist between genetic gain
obtained by selecting the best related individuals for seed orchard populations, and potential
losses due to subsequent inbreeding between these individuals. Although inbreeding depression
for growth rate is strong in most forest tree species at the individual tree level, the effect of a
small proportion of inbreds in seed lots on final stand yield may be less important. The effects of
inbreeding on wood production of mature stands cannot be assessed empirically in the short term,
thus such effects were simulated for coastal Douglas fir [Pseudotsuga menziesii var. menziesii
(Mirb.) Franco] using an individual-tree growth and yield model TASS (Tree and Stand
Simulator). The simulations were based on seed set, nursery culling rates, and 10-year-old field
test performance for trees resulting from crosses between unrelated individuals and for inbred
trees produced through mating between half-sibs, full-sibs, parents and offspring and selfpollination.
Results indicate that inclusion of a small proportion of related clones in seed orchards
will have relatively low impacts on stand yields due to low probability of related individuals
mating, lower probability of producing acceptable seedlings from related matings than from
unrelated matings, and a greater probability of competition-induced mortality for slower growing
inbred individuals than for outcrossed trees. Thus, competition reduces the losses expected due to
inbreeding depression at harvest, particularly on better sites with higher planting densities and
longer rotations. Slightly higher breeding values for related clones than unrelated clones would
offset or exceed the effects of inbreeding resulting from related matings. Concerns regarding the