WATER REGIME OF DOUGLAS-FIR AND FOREST STANDS WITH DOUGLAS-FIR: REVIEW

Douglas-fir (DF) is thought to be a convenient substitution of declined Norway spruce (NS) in the Czech Republic. Information on water regime of DF and stand mixtures with DF is important particularly in relation to climatic oscillations posing both flood and drought risks to forests. Taking into account a lack of domestic information, the review was based also on world literature sources. Water regime of DF and forest mixtures with DF includes many topics. This study focused on water balance and its components such as precipitation of open area, throughfall, stemflow, net precipitation, interception losses, water uptake by trees, transpiration, evaporation from soil surface, forest floor and ground vegetation, hillslope runoff, surface runoff, subsurface flow, subsurface stormflow, lateral interflow, groundwater recharge, stream flow, soil water content, redistribution of soil water by tree roots etc. The most important finding is that DF is capable of using water from deeper soil layers more effectively than NS. This enables DF to transpire more water during dry periods and also to grow faster compared to NS. Mentioned hydrological impacts of tree species should be taken into account for planning future tree species compositions of forests. Given the intensive use of soil water by DF, it appears that DF can aggravate water conditions in watersheds with tense water balance (water consumption atmospheric precipitation) in dry periods.