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

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plots was 18% less in 1988 and 15% less in 1989 than root growth in ungrazed plots. It is
concluded that repeated cattle grazing of orchardgrass reduced transpirational surface area and
root growth sufficiently to increase soil water availability to tree seedlings. Thus, prescribed
cattle grazing on conifer plantations can enhance seedling physiological status by acting as a
regulator of above- and belowground competition.
301. Kastner, W.W., Jr., S.M. Dutton and D.M. Roche. 2001. Effects of Swiss needle cast on three
Douglas- fir seed sources on a low-elevation site in the northern Oregon Coast Range: results
after five growing seasons. Western-Journal-of-Applied-Forestry 16(1): 31-34.
Keywords: genetic tree improvement
tree/stand protection
growth
tree/stand health
Abstract: Douglas-fir (Pseudotsuga menziesii var. menziesii) seedlings grown from three
seed sources were evaluated for 5 years for their relative tolerance to Swiss needle cast (caused
by the ascomycete Phaeoxryptopus gaeumannii), on a high-disease-hazard site located
approximately 3 miles northeast of Tillamook, Oregon, USA. The seed sources were: (1) seed
collected from trees showing an apparent degree of tolerance to Swiss needle cast in natural
stands in the coastal fog belt, (2) open-pollinated seed orchard seed collected from random singlepair
crosses of parent trees in natural stands outside of the coastal fog belt, but west of the Oregon
Coast Range summit, whose progeny demonstrated an apparent degree of disease tolerance in
coastal Douglas-fir progeny test sites, and (3) standard reforestation seed purchased from a
commercial vendor. There were no significant differences among seed sources in basal diameter
and total height for all five growing seasons. Needle retention varied among seed sources over the
5-year period, but current-year needle retention did not vary significantly after the fifth growing
season, and retention of 1- and 2-year-old needles was relatively low for all seed sources. The
intense disease pressure on this site may have overwhelmed expression of disease tolerance
among seed sources. We do not recommend planting Douglas-fir on such high-hazard sites.
302. Kaya, Z. 1992. The effects of test environments on estimation of genetic parameters for seedling
traits in 2-year-old Douglas-fir. Scandinavian-Journal-of-Forest-Research 7(3): 287-296.
Keywords: genetic tree improvement
nursery operations
genetic relationships
growth
tree phenology
Abstract: The effects of test environments (dry versus wet) on the estimation of genetic
parameters in seedling traits were studied in 160 open-pollinated families of Douglas fir
(Pseudotsuga menziesii) from southwestern Oregon. Seedlings from four populations were grown
in two test nursery environments between which a water potential difference of -9 bars was
created over two growing seasons, by withholding water for 4 and 8 wk, respectively. Estimated
genetic variances in most growth and phenology traits were considerably higher for seedlings
grown in the wet environment than for those in the dry. Estimated genetic correlations between
the same traits measured in different test environments indicated that most seedling traits studied
for two growing seasons were genetically stable in both environments, suggesting that genotype
environment interaction in these traits are weak. However, it is emphasized that the effect of test
environment on estimation of genetic parameters in seedling traits, especially in adaptive seedling