The physiological basis for the establishment of bare-root larch seedlings

Abstract

Data on physiological attributes and early forest performance of bare-rooted Japanese and hybrid larch in Britain are summarised. Physiological attributes included root growth potential (RGP), root membrane function, bud dormancy, shoot and root frost hardiness, resistance to desiccation, rough-handling and cold-storage, and sensitivity to insecticide. The survival pattern of freshly planted stock followed that of RGP, which was bimodal with peaks in October and March, whereas the survival pattern of cold-stored stock was more closely related to root membrane function at planting. Seasonal trends in bud dormancy and stress resistance are described. The optimum time for handling, as opposed to planting, larch was in December–February when shoots were hardy to about −30°C, roots were hardy to around −13°C, and root electrolyte leakage (REL) had fallen to about 10%. The optimum cold storage time varied from year to year but seemed to be generally best from mid-November to late December. Undercutting and wrenching improved survival. RGP was of major importance in determining establishment with fine root membrane function, root fibrosity and root:shoot ratio of secondary importance. Since the larches’ unique pattern of RGP seems related to their deciduous habit, it is probable that RGP will be an important determinant of survival in other species of larch.