Growth and Water Balance Parameters of a Natural Spruce–Larch Forest in Tatra National Park, Slovakia

Abstract

The transpiration and stem circumference changes of spruce (Picea abies [L.] Karst.) and larch (Larix decidua Mill.) trees were investigated during the vegetative period of 2009 in the Smrekovec research plot, which is located in Tatra National Park in Slovakia. The plot is situated in a primeval 125-year-old mixed forest (80 % spruce trees and 20 % larch trees) at an altitude of 1,250 m. Meteorological parameters and soil water potentials were also measured during the same period within the investigated plot. Whole-tree transpiration was continuously measured based on the stem-tissue heat balance method in five larch and five spruce tree samples. Stem circumference changes were continuously measured using automatic dendrometers. We also investigated the seasonal and diurnal changes in transpiration. Air temperatures from 6 to 10 °C appeared to control the initiation of cambial bole growth in both species at the beginning of June. The stem circumference increment experienced accelerated growth through the end of June, at which point 80 % of the annual growth in diameter had occurred. Diameter increment ceased to grow in early October. The transpiration rates and stem circumference changes of both species were significantly correlated with micrometeorological factors. On sunny days, we found a linear relationship between transpiration and stem circumference changes (R2 = 0.60 for spruce trees and R2 = 0.56 for larch trees). After the leaves were fully developed, transpiration in larch exceeded that in spruce and lasted as long as the needles were retained on larch trees. We suggest that the phenological state of the larch tree needles is important for regulating the timing of physiological processes, such as transpiration and growth, and that the differences in transpiration rates between these species support the formation of mixed (larch–spruce) multistory stands in an area that was disturbed by a heavy windstorm in 2004.