Winter Water Relations of Tree-Line Plant Species on MT. Washington, New Hampshire

Abstract

The extent and causes of winter desiccation were studied in three tree-line species on Mt. Washington, New Hampshire. We did not find excessively low relative water contents in intact foliage of balsam fir (Abies balsamea [L.] Mill.) or black spruce (Picea mariana [Mill.] BSP.) during the winter. Relative water contents were lowest following damage by ice abrasion and in intact stems of paper birch (Betula papyrifera Marsh.). Winter transpiration in conifer foliage is very low perhaps due to several dormancy-related mechanisms. Transpiration is further reduced by high wind speeds which maintain thermal equilibrium between leaf and air. Thus winter desiccation is not universal at tree line and is probably related to factors other than the high-wind regime.