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

Abstract: A review is given of studies leading to the establishment of nitrogen deficiency
as a factor reducing growth and the development of N fertilization programmes. Data from
several long-term fertilizer trials in Washington and Oregon support the conclusion that N
deficiency is frequently a controlling factor in the growth of Douglas fir and that additions of N
can result in long-term growth increases. The economics of fertilization and the continued
availability of nitrogen fertilizers are discussed.
216. Gessel, S.P., R.E. Miller and D.W. Cole. 1990. Relative importance of water and nutrients on the
growth of coast Douglas fir in the Pacific Northwest. Forest-Ecology-and-Management 30(1-4):
327-340.
Keywords: fertilization
growth
soil properties
Abstract: The Douglas-fir region in northwestern North America is characterized by
abundant moisture supply during winter, extended dry periods during the growing season and
significant differences in water availability. Many soils have low fertility and indigenous tree
species respond to nitrogen fertilization, especially Douglas fir (Pseudotsuga menziesii).
Although irrigation of commercial forests in this region is currently impractical, questions arising
about the relative importance of water and nutrients were examined using long-term growth data
from three studies. At Pack Forest (Washington), fertilization without irrigation doubled growth
rates, and no positive growth responses were measured from irrigation. Short-term (5 yr)
irrigation with sewage effluent containing many nutrients resulted in a six-fold increase in
biomass production for poplar and three-fold for Douglas fir as compared to irrigation with equal
volumes of river water. Volume growth in 12- to 65-yr-old stands in southwestern Oregon was
increased by fertilization at about 70% of the locations; annual gain averaged 2.73 msuperscript
3/ha for 5-12 yr. Response was not related to annual precipitation, which ranged from 81 to 279
cm, nor other moisture-related variables. Absolute and relative volume response showed highest
correlation with soil carbon : nitrogen ratio. Compared with nutrition, moisture does not seem to
be a major limiting factor for growth in the Douglas fir region of the Pacific Northwest.
217. Gessel, S.P., E.C. Steinbrenner and R.E. Miller. 1981. Response of Northwest forests to elements
other than nitrogen. In Proceedings: Forest Fertilization Conference, University of Washington,
Seattle, Washington, USA. Eds. S.P. Gessel, R.M. Kenady and W.A. Atkinson. pp. 140-149.
Keywords: fertilization
growth
economics
Abstract: This paper reviews the development of forest tree nutrition research in the
Northwest. Field observations, foliar analysis, and greenhouse cultures using both solution and
forest soil as media established deficiency symptoms and levels for major and minor elements.
Field experimentation with the entire range of essential elements has failed to demonstrate
widespread deficiencies of elements other than nitrogen. Certain test areas have shown somewhat
better response to combinations of elements; but because of the limitations of experimental
design and field variation, the response does not generally have a high statistical significance. In
some cases of apparent response, application of fertilizer materials other than nitrogen does not
appear to be economic. There is sufficient evidence of response to other elements to suggest that
much work needs to be done. Increased utilization of forest materials, shorter rotation, and greater
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