Application of Growth Models For Simulating Genetic Gain of Loblolly Pine
Abstract:A technique for predicting genetic gain in progeny tests using height-age models and stand simulations is presented for loblolly pine (Pinus taeda L.). Periodic remeasurements for a block-plot open-pollinated progeny test are used to examine trends in height growth, selection differential, and percent gain in height and volume. Using the Chapman-Richards model and approximate F tests, significant differences among families were detected in asymptote and rate parameters but not for the shape parameter. Separate base-age invariant height-age equations were developed for each family to account for polymorphism associated with the rate parameter. Selection differential calculated from either observed or predicted heights exhibited similar trends although estimates from the height-age equations are consistently higher than obtained with observed height after age 5. Family rankings using the height-age models are consistent with those obtained using observed heights. Also, percent gain calculated from predicted heights is within 2% of the estimates obtained with observed heights at ages greater than 3 years. Differences in survival, height, and diameter were combined to examine trends in volume production associated with families. Predicted volume for each family was simulated using a bivariate distribution of height and diameter accounting for differences in height-growth patterns among families. Family rankings for volume are also closely correlated, resulting in two or three of the same families being selected using observed and predicted data. Selection differential obtained from simulated and observed volume fluctuates in rank producing a satisfactory trend based on predicted volume after age 5. Gain based on simulated volume tends to be slightly greater than gain based on observed volume. Estimates of percent gain obtained by reinitializing the simulations with quadratic mean dbh and residual trees per acre after thinning differed more from the observed trends than the unthinned simulations. For. Sci. 35(1):211-228.
Document Type: Journal Article
Affiliations: Vice President-Breeding and Research, International Forest Seed Company, P. O. Box 290, Odenville, AL 35120
Publication date: March 1, 1989
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