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

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Abstract: The impact of container-nursery management practices on the genetic
composition of seedling crops was evaluated in an experimental study in a seed orchard in British
Columbia. The study was designed to determine the cumulative effects of: (1) differences in
parental reproductive output in bulk seedlots; (2) parental variation in germination parameters
(percentage and speed); and (3) the interaction of these parameters with container-nursery
practices of thinning and culling, and their effect on the genetic representation of parents in the
resultant seedling crops. Results from the experimental study were compared with predictions of
a stochastic simulation designed to estimate the consequences of differential parental seed
contribution, and seed germination percentage and germination speed on indicators of crop
performance. The experimental study was conducted on a Douglas-fir (Pseudotsuga menziesii)
bulk seedlot that was representative of the differential seed contributions from 19 seed orchard
parents. The nursery study included a total of 42 000 seeds. Seeds were sown at three seeds per
cavity. Within the 14 000 cavities used, the identity of every seed was maintained throughout the
study. Comparisons of parents were made based on: (1) changes in their rank order from sowing
to postthinning and postculling status; and (2) relative performance from seed contribution to
seedling production. Changes were observed in both assessments. Path analysis was used to
determine the percentage contribution of each factor to seedling production. It was determined
that germination, thinning, and culling contributed 66, 20, and 14%, respectively, to seedling
production, indicating the presence of three consecutive bottlenecks in the process. Single seed or
individual family sowing in the nursery was recommended for seedling production to maintain
genetic diversity.
178. Emmingham, W.L., P. Oester, M. Bennett, F. Kukulka, K. Conrad and A. Michel. 2002.
Comparing short-term financial aspects of four management options in Oregon: implications for
uneven-aged management. Forestry-Oxford 75(4): 489-494.
Keywords: thinning
commercial thinning
economics
yield
Abstract: Private family forest owners are often more interested in comparing short-term
financial outcomes of management options, as opposed to longer time horizons and classical
economic analyses including net present value. Therefore, we compared projected 10-year value
of timber and land for four theoretical management scenarios starting with stands ripe for
thinning. The options were (1) hold for 10 years (i.e. no thinning), (2) thin for even-age, or (3)
partial cut for uneven-age and (4) clearcut now. To simulate the outcomes of these scenarios, we
marked and measured 2-ha plots in 10 stands typical of private forest ownerships across Oregon
and projected timber yields and revenues. The financial analysis included current market values
for logs, payment of taxes and typical reforestation costs and computation of net asset values
(NAV) at a 7 per cent interest rate. The hold option consistently gave the highest NAV for timber
and land after 10 years, and the thin option was within 2 per cent. For the eight western Oregon
stands, the partial-cut option averaged about 3 per cent less, and the clearcut option ranged from 8
to 17 per cent less than holding. Pine stands of eastern Oregon showed similar trends; however,
all options were within about 6 per cent of the hold option. Thus, using financial criteria typical
of those used by private forest owners, we found that there was little short-term financial loss in
choosing to thin toward even-age, partial cut toward uneven-age, or the hold approach in wellstocked
stands.