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

202
stands in plots where only C. velutinus was eliminated. In the absence of shrubs and forbs, soil
water potential at 100 cm was near field capacity throughout the season. Predawn stem water
potential during late summer was significantly lower on control plots than on the treatment plots
for all 5-yr-old stands and for two of the 10-yr-old stands. By 1986, tree stems were 2-6 cm larger
in basal diam. and 1-2 m taller in the absence of competitors. The increase in stem size was
greater in the stand treated at 5 yr old than in that treated at 10 yr old. The correlation between
growth and water stress suggests that interspecific competition for soil water during summer
drought is a limiting factor in stemwood production.
462. Peterson, C.E. 1984. Fertilization of Douglas-fir plantations in the Pacific Northwest RFNRP
Cooperative. In Proceedings IUFRO Symposium on Site and Productivity of Fast Growing
Plantations Volume 2, South African Forest Research Institute, Pretoria, South Africa. Eds. D.C.
Grey, A.P.G. Schonau and C.J. Schutz. pp. 637-645.
Keywords: planting operations
fertilization
thinning
precommercial thinning
growth
Abstract: Since 1975, the RFNRP cooperative has established 26 installations in young
widely spaced plantations of Douglas-fir for testing response to 224 kg-N/ha. These plantations
ranged in breast-height age from 3 to 23 years, and although response to fertilization was
favorable in all Douglas-fir plantations, those which were spaced to 1000 trees/ha responded
significantly better than plantations of 725 trees/ha, in both absolute and relative 2-year basal area
increment (msuperscript 2 ha-1 year-1). Response also appears to be greater when fertilizer was
applied 2 years after precommercial thinning, as opposed to fertilizing and thinning at the same
time. The relationship of growth response with stocking level is discussed, as well as the timing
of fertilization relative to spacing, in young Douglas-fir plantations.
463. Peterson, C.E. and J.W. Hazard. 1990. Regional variation in growth response of coastal Douglasfir
to nitrogen fertilizer in the Pacific Northwest. Forest-Science 36(3): 625-640.
Keywords: fertilization
thinning
growth
Abstract: Hypothesis-testing for differences in growth responses among physiographic
strata, thinning levels, and fertilizer dosage levels resulted in a set of empirical models for
predicting the volume increment response of even-aged coastal Douglas fir (Pseudotsuga
menziesii) in W. Washington and Oregon to N fertilizer treatment. Absolute and percentage
responses are estimated for both thinned and unthinned stands as a function of dosage levels and
physiographic provinces. Although not 'highly' significant, the physiographic factor was retained
in the models for purposes of refinement.
464. Peterson, C.E., P.J. Ryan and S.P. Gessel. 1984. Response of northwest Douglas-fir stands to
urea: correlations with forest soil properties. Soil-Science-Society-of-America-Journal 48(1):
162-169.
Keywords: fertilization
thinning