Studies on upper timberline: morphology and anatomy of Norway spruce (Picea abies) and stone pine (Pinus cembra) needles from various habitat conditions

Abstract

The importance of the anatomy of the needles of coniferous trees in determining alpine timberline was studied in the Austrian Alps. Samples of 1- and 2-year-old needles of Picea abies (L.) Karst. and Pinus cembra L. were made from wind-exposed and wind-protected timberline (2140 m above sea level (a.s.l.)), and from the kampfzone (2040 m a.s.l.), forestline (1940 m a.s.l.), and valley bottom (1000 m a.s.l.). The samples were measured for number of needles per centimetre twig, twig length, needle length, cuticle thickness, thickness of epidermis and hypodermis, and depth of stomatal crater. There is a decrease in cuticle thickness with increasing altitude and with increasing wind exposure at timberline, and this is correlated with increased transpiration. The role of inadequate cuticle formation in desiccation damage and mortality of the needles is a significant factor in the control of upper timberline.