Water relations of spruce trees in low-elevation spruce stands.

The special research program "Restoration of Forest Ecosystems" investigates problems of and possible alternatives to pure spruce forests at low elevations. Project part 2 (water relations) attempts to characterise the ecophysiology, particulary water relations, of spruce trees in pure stands and in mixed forest with broadleaved trees (beech). Spruce in mixed stands face different conditions for below- and above-ground growth. This may be reflected in the trees' physiology and ultimately in their growth and stability. Main parameters measured are sapflow, stem and twig water potential, transpiration, and stem diameter variation. Tree physiology is also studied as related to bark-beetle infestation and infection with stem and twig fungi. Measurements of leaf area and stand transpiration contribute to models predicting forest growth and stability.