An Approximate Formula for Selection Intensity
Silvae Genetica: 1986 35:249-249
This paper deals with the results from a half-sib progeny trial of lodgepole pine (Pinus contorta ssp. latifolia Engelm.) in Sweden at 64.degree. N. The progenies originate from 69 open-pollinated plus trees selected from 13 areas in British Columbia and the Yukon. The trial was planted on previous agricultural land. At age 10 years, condition and height growth differed significantly between areas of origin and between half-sib families. Northern material was healthier and more vigorous and height growth did not vary clinally with latitude. Stepwise regression analysis with height growth showed that altitude of origin gave a maximum at 650 m and, above 800 m, there was a clear decrease in height growth with increasing altitude of origin. Frequency of extra whorls differed between half-sib families only and was positively correlated with height growth and negatively correlated with forking. Genetic gain by selecting the top 15 parent trees based on 10-year-old progeny trials was estimated to be 10% for volume.
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