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Abstract

Drought analysis was done in spruce pole-stage stand within the U Dvou louček experimental catchment in the Orlické hory Mts. (Czech Republic). The model of hydrological balance of closed-canopy forest stands and soil water constant theory were chosen for doing the analysis. All model parameters were measured excepting evapotranspiration based on the balance equation. Impact of drought on the spruce stand was assessed using the point of decreased availability (temporary wilting point), the wilting point, and minimum rainfall and stream discharge data. Phenomenon of drought was demonstrated by events such as a decrease of soil moisture below point of decreased availability in cambisol and fall of soil moisture near the point of decreased availability in podzol. Reduced evapotranspiration sustained from soil water storage contributed to the spruce stand survival without visible injury over the two weeks of the drought. However, the base flow from springs decreased enormously. It appeared to be under average of 365-day-discharge during the extreme dry period. Decrease of discharge of the stream lasted from June 2nd to October 15th, i.e. 136 days. Extremely low soil moisture exhibited over two weeks from July 31st to August 11th. It was concluded that injury due to drought would appear after extreme drought events longer than two weeks. For more information see Summary at the end of the article.