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stand on southern Vancouver Is., British Columbia. Ammonium nitrate yielded higher growth of
diam. and vol. than urea over a 9-yr period, particularly with thinning. Ht. growth was not
affected by nitrogen source. The efficiency of nitrogen fertilizing in terms of stem vol. response
per kilogram of nitrogen applied was greatest with ammonium nitrate in thinned plots. Tree
mortality increased substantially with fertilizing for both sources, and decreased markedly with
thinning.
40. Barclay, H.J. and H. Brix. 1985a. Effects of high levels of fertilization with urea on growth of
thinned and unthinned Douglas-fir stands. Canadian-Journal-of-Forest-Research 15(4): 730-733.
Keywords: fertilization
thinning
growth
tree physiology
tree/stand health
Abstract: Diameter height and volume growth were documented for 9 yr after thinning and
fertilizing in a 24-yr-old stand on a poor site on southern Vancouver Is. The treatments involved 3
thinning treatments (0, 1/3, and 2/3 b.a. removed) and 6 fertilizer treatments (0-1344 kg/ha N)
with urea. Increments for both diameter and gross volume increased with the rate of fertilizer
application and responses were still apparent 9 yr after treatment. For unthinned plots, the 9-yr
volume growth responses were 30, 50, and 80% with fertilizer rates of 224, 448, and 896 kg/ha N,
respectively. The efficiency of fertilizer use, measured as stem volume response per unit of
nitrogen applied, decreased with rate of fertilizer application, but this result may change over a
longer response period. There was a positive interaction between fertilizing and thinning such that
high amounts of both mutually enhanced growth. Mortality increased with fertilizing, but only
noticeably in unthinned plots.
41. Barclay, H.J. and H. Brix. 1985b. Fertilization and thinning effects on a Douglas-fir ecosystem at
Shawnigan Lake: 12-year growth response. Pacific-Forestry-Centre, Canadian-Forest-Service
Information-Report BC-X-271. 34 p.
Keywords: fertilization
thinning
growth
Abstract: [See FA 45, 2316] Further results are given from the study established in 1970 in a 24yr-old
stand in British Columbia. Fertilizers (urea) and thinning both increased vol. increments
over 12 yr. Refertilization 9 yr after initial treatment has produced substantial increases in vol.
increment.
42. Barclay, H.J. and Y.A. El-Kassaby. 1988. Selection for cone production in Douglas-fir adversely
affects growth. In Proceedings: 10th North American Forest Biology Workshop, 'Physiology and
genetics of reforestation', University of British Columbia, Vancouver, British Columbia, July 10-
22, 1988. Eds. J. Worrall, J. Loo-Dinkins and D.P. Lester. pp. 149-151.
Keywords: genetic tree improvement
genetic relationships
growth
reproduction