Height–Diameter Relationships for Jack Pine Seedlots of Different Genetic Improvement Levels

Abstract

Differences in height-diameter (H-DBH) relationship were investigated using the Chapman-Richards function among jack pine seedlots planted in a realized genetic gain test in New Brunswick. Three seedlots representing the bulk mixed cone collection from the 1979 J.D. Irving’s first-generation seedling seed orchard (JDISSO) before rogueing (UNR), after the first time genetic rogueing (1STR) and after the second time genetic rogueing (2NDR), respectively, were planted in the test. Unimproved commercial seedlots (UC) were also included for comparison. Results indicate that an overall H-DBH relationship for all the seedlots was not appropriate. Seedlot pairwise comparisons in H-DBH relationships showed that, whereas most seedlot pairs were significantly different from each other, there was no significant difference between the UNR and UC and between the 1STR and 2NDR. Two models were developed with one targeting the UNR and UC (UNIMPROVED) and the other targeting the 1STR and 2NDR (IMPROVED). The difference between the UNIMPROVED and IMPROVED models was caused only by asymptote of the Chapman-Richards function. Applying the UNIMPROVED or IMPROVED model to predict height of the 1STR and 2NDR or the UNR and UC would result in an under-estimated or an over-estimated bias by 2 to 3% in height. In light of this study, seedlot differences in H-DBH relationships should be integrated into growth and yield models by a multiplier for height depending on genetic improvement levels.

Tree improvement effects on tree size distributions forPicea glaucaandPicea marianain New Brunswick, Canada

“…In radiata pine improvement programs with selection primarily for dbh, Carson et al (1999) found that an adjustment for dbh growth but not height would be adequate, while in other programs with selection primarily for height, a modifier for height growth but not dbh will be needed to account for tree improvement effects (Johnson, 2002;Weng et al, 2008a). For both white spruce and black spruce in this study, height growth was the primary selection target.…”

“…Experiences with radiata pine (Carson et al, 1999), Douglas fir (Johnson, 2002) and jack pine (Weng et al, 2008a) suggest that growth modifiers will be adequate to adjust tree improvement effects on growth and yield. The high association and similarity in size (statistically not significant) between the realized gain and D Scale in this study suggest that the growth modifier method is applicable to adjust the scale value.…”

“…menziesii] (Johnson, 2002) and jack pine (Pinus banksiana Lamb.) (Weng et al, 2008a). Results of these studies generally suggest that it will be adequate to incorporate tree improvement effects into growth and yield modeling frameworks using growth modifiers or multipliers.…”

“…The approach is becoming more popular as more data are collected from realized genetic gain tests of large plots, where improved seedlots (or genotypes) are compared with unimproved seedlots with minimal environmental variation. Realized genetic gain tests of large plots seem to be ideal for this purpose as they are established to meet the requirements for both growth and yield prediction and genetic evaluation (Foster, 1992;Weng et al, 2008a). Published examples using realized gain tests of large plots to compare growth functions between commercially improved and unimproved seedlots can be found in radiata pine (Pinus radiata D. Don) (Carson & Hayes, 1998;Carson et al, 1999), Douglas fir [Pseudotsuga menziesii (Mirb.)…”

Effects of phenotypic selection on height-diameter ratio of Norway spruce and Scots pine in Sweden

“…Similar results have been found in block-plot trials of jack pine (Pinus banksiana Lamb.) (Weng et al 2008) and loblolly pine (Sabatia and Burkhart 2013; Egbäck et al 2015). Nevertheless, the extent to which stem slenderness changes with the level of genetic improvement in Norway spruce and Scots pine is still unclear and needs further investigation.…”