Comparison of Selection Methods for Improving Volume Growth in Young Coastal Douglas-fir

1990

S. 219-226

1 Abb., 5 Tab., 23 Lit. Ang.

Unselbständiges Werk

200051234

Data from a Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) open-pollinated progeny test in Oregon were used for evaluating methods of selection for bole volume. Tree height and bole diameter at breast height (DBH) were measured on 12- to 13-year-old individuals from 90 families at each of three plantations, and bole-volume estimates were derived with a quadratic volume equation. Four methods were compared for both parental and progeny selection: (1) indirect selection based on height, (2) indirect selection based on DBH, (3) direct selection based on volume, and (4) selection based on an index that included all three traits. Two-stage selection was also explored, where test trees are culled on the basis of DBH in the first stage; and, height is measured only on the remaining trees, so that final selections (the second stage) are based on volume. Estimated genetic gains in volume from progeny selection wre 8% to 11% greater than those from parental selection. The relative efficiencies of the various selection methods, however, were similar for parental and progeny selection, which were achieved with the multitrait index, were only 1% better than those from selections based on volume alone. Indirect selection based on DBH produced about 90% of the gain achieved by direct selection for volume, and indirect selection based on height was about 92% to 94% as efficient as direct selection. With two-stage selection, up to two-thirds of the trees could be culled in stage 1 without significantly lower gains in bole volume than those expected if the height of all trees had been measured.