Growth of loblolly pine rooted cuttings compared with seedlings

Abstract

Growth and morphology of loblolly pine (Pinustaeda L.) rooted cuttings were compared with that for seedlings after several years in the field in two experiments. Experiment 1 included rooted cuttings from 1- and 5-year-old ortets and seedlings from the same five families and experiment 2 compared rooted cuttings from 4-year-old ortets with seedlings from the same 15 families. Significant age-related effects on the growth of the rooted cuttings, even with as little as 4 years difference in ortet age, were observed. Height, DBH, and number of growth cycles, but not number of branches per unit of height or per growth cycle, differed significantly between the two cutting sources. Size and condition of the rooted cuttings and seedlings at the time of planting influenced their growth for several years afterward and could be a confounding factor in comparisons among propagule types. In experiment 1 cuttings outgrew seedlings, while in experiment 2 the reverse occurred. Considering both experiments, growth in the early years seems to be related more to condition of the propagule rather than asexual or sexual origin when unconfounded with age. The family rank correlations between propagation types for the same trait were always positive but were significant for only part of the traits, while the correlations among traits for the same propagation type were generally, but not always, lower for rooted cuttings than seedlings. This effect was pronounced in the first few years after field planting and was likely the result of plant quality (variability induced by the rooting and conditioning system) rather than propagation type; nonetheless, there is cause for concern when using early field data from rooted cutting trials to rank family performance.