CALCULATION AND INTERPRETATION OF STEM ST ORAGE CHANGES OF A 100-YEAR-OLD SPRUCE

Increment stair step curves (Fig. 1) have been deduced from high preci sion dendrometer measurements in different stem heights of an old spru ce. These values have been used for calculations of stem volume change s and stem volume increment values (Fig. 2). Then daily stem storage c hanges were estimated and compared with soil moisture and transpiratio n data (Fig. 3 and 4). It was possible to show clear dependences betwe en soil moisture changes, stem storage changes and transpiration and t hat the tree causes time lags within the evaporation process. The tran spiration can be continued on a restricted level without water uptake from the soil(see Fig. 5). Particularly for old trees stem storage cha nges are important for investigations and models of water balances. Th ese changes can facilitate the interpretation of physiological reactio ns in drying periods.