The features of growth and anatomical structure of stag-headed and healthy trees in larch stand growing in permafrost

In previous decades on the background of ex-treme weather events increasing high percentage of dead and stag-headed trees in northern forests has been registered. The researchers suggest that the reason for the desiccation is in drought, which can lead to the reduction of the efficiency of the process of water carrying out in tree trunks. In the study the distinctions in dynamics of radial growth along the trunk in larch trees of Larix gmelinii (Rupr.) Rupr., growing in permafrost conditions of the north-facing slope (Central Siberia, 64°19´23˝ N, 100°13´28˝ E ) were revealed. The purpose of the research was to receive additional arguments in favor of the assumption that water stress could be the reason of top shrinkage in larch trees in perma-frost. Thirteen healthy and twelve stag-headed model trees were chosen for the study. From each tree sampled disks at several stem heights: close to root collar, at 1/4, 1/2, 3/4 of stem height and at 20-30 cm beneath apex were cut. Stag-headed trees differed from intact according to xylotomy charac-teristics: strong violation of lane tracheids of the last rings, the lack of division into early and late wood of year rings, smaller average values of the width of year rings (WYR), the thickness of cellular walls and lumens. Distinct lagging in growth in height was revealed and on the diameter of stag-headed trees senior than 30-40 years. The conclusion was drawn that rather high temperature of air (causing high transpiration) might provoke water stress in trees revealed in trees' top drying.