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Pinus radiata D. Don seedlots of varying genetic quality were compared in block-plot genetic-gain trials at 10 locations representing most of the site types in New Zealand. Permanent sample plots were measured annually for growth from age 6-8 yr from planting to ages 15-17 (midrotation). Seedlots from first-generation open-pollinated seed orchards and a mix of crosses that all involved the top-performing parent were, respectively, on average 4.5% and 5.3% taller and had 6% and 11% larger mean diameter, 12% and 30% more basal area, and 15% and 34% more stem volume than seedlots originating from mild mass selection in harvested stands ("climbing select"). The observed growth increases were quantified as changes in the rate of growth from that predicted by preexisting growth models in order to account for tree size and stocking differences. Seedlots from first-generation seed orchards and crosses of the top clone, respectively, grew 5.1% and 4.5% faster in height, and functions for basal area and stocking changed 13% and 26.4% faster, respectively, than the baseline growth models, which were based on climbing select. This implies that increased basal area growth must be taken into account in order to obtain accurate prediction of gain in stem volume. The incorporation of these observed increases in growth rates into stand growth models as "genetic-gain multipliers" in order to extrapolate predictions of growth of genetically improved seedlots beyond the sites, silvicultures, and seedlots represented in the genetic gain trials is discussed. For. Sci. 45(2):186-200.
New Zealand Forest Research Institute, Private Bag 3020, Rotorua, New Zealand--Phone: (+64) 7 347 5899;, Fax: (+64) 7 347 9380
Publication date: May 1, 1999
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Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.