Nutrient Limitation in Three Birch Populations and the Possible Function of Alternative Respiration as a Growth Regulating Mechanism

1993

28 S.

33 Lit. Ang.

Bandaufführung

37973

The effects of different summer temperatures and nutrient conditions on growth were investigated in seedlings of three mountain birch populations (Betula pubescens Ehrh.) by growing the plants at two different elevations. At the lowland site growth was about doubled by adding nitrogen and phosphorus as compared with control plants without these two elements. The increase was highest in the fast-growing lowland ecotypes. The subarctic population tended to keep a high nitrogen concentration in its tissue by reducing its growth when being deprived of nutrients. This was interpreted as adaptation to low temperatures and a short growing season. Dark respiration rates were increased in leaf and stem tissue by low temperature treatment, while they were decreased in roots. There was relatively less cyanide-sensitive respiration in leaves of subalpine mountain birch than in the two southern populations at low nutrient level. This suppression of leaf growth is a useful adaptation in cold climate with slow decomposition rates in soil.