Spatial patterns of tree height variations in a series of Douglas-fir progeny trials: implications for genetic testing

Spatial variation patterns of tree heights at ages from 6 to 12 years in a series of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) progeny trials that were conducted on 66 test sites over southern coastal British Columbia were examined with conventional statistics and geostatistical techniques. It was found that there were large variations in tree height over the years within and among the 66 test sites. The estimated proportions of the within-site variance explained by family, row, column, patchiness, and within-plot were on average 11, 7, 5, 12, and 47%, respectively, plus 7% due to unknown factors, and the applied blocking removed about 5% of the within-site variance. Significant gradients in row and column directions were observed in more than 44 test sites, and the estimated slopes ranged in average from 0.33 to 1.52 cm/plot. Patch sizes varied greatly over the test sites and ranged in average from 5.21 to 6.47 (plots), indicating that the average patch size for these trials was 18 m across. Temporal variations were large for family variance but not for those variance proportions explained by row, column, patchiness, and within-plot. More gradients and larger patch sizes were found with older trees. Implications of these results are discussed for forest genetic testing.