Temperature Effects on the Growth of Mountain Birch (Betula pubescens Ehrh.) , Elm (Ulmus glabra Huds.) and Maple (Acer platanoides L.) Seedlings in Continuous Light.

1991

44 S.

7 Abb., 11 Tab., 46 Lit. Ang.

Unselbständiges Werk

200037921

As a case study to investigate the growth/relationships and climatic adaptions in ecotypes of mountain birch (Betula pubescens Ehrh.), simple growth experiments were carried out on mountain birch seedlings of three different populations in South and Central Norway from different altitudes and latitudes. The seedlings were grown in continuous light at different constant temperatures. For comparison two other tree species were included, one with a continental distribution (Acer platanoides L.) and one with an oceanic distribution (Ulmus glabra Huds.). Large differences were found in survival strategy among species and ecotypes. The maple and elm populations and the two southern birch populations all reacted to high temperatures by rapid leaf expansion as a possible compensation for increased respiration loss, and the maple and birch also by increasing their stem elongation rates and thereby competing more efficiently for available light. In the northern subalpine birch population, however, the seedlings developed leaves with high net assimilation rates instead of increasing their leaf area and stem elongation rates. In this population abiotic climatic factors rather than competition therefore seem to be the most important adaptive force.