Growth responses of sessile oak to climate and hydrological regime in the Zbytka Nature Reserve, Czech Republic

Complex of Nature reservation Zbytka is the rest of various fen vegetation in the northeast part of the Czech Republic. It represents an important spring area which provides high quality potable water for more than 150 000 inhabitants. Waterworks utilization was started in the 1960s and the change of land-use practices has had a strong effect on the ecosystem. Oak chronology has been showing different tree growth trends since the start of the waterworks utilization. Also the occurrences of negative pointer years differ markedly before and after initiation of pumping underground water. Dendroclimatological analyses primarily revealed a close relationship between the temperature and tree growth — positive influence of spring and summer temperature. The period 1983–1992 of maximum artesian water pumping is expressed as higher tree-ring increments, but linear model analyses showed that the growth reaction of oak is not due to simple causality between temperature and under-ground water level. The radial increments reacted positively to the combination of high temperature during the vegetation season and low or, the contrary, high depth of underground water level. No direct relationship was detected between tree growth and fluctuation of underground water level; despite of the results dendrochronological data may be useful in historical ground water modelling studies. Results are also crucial for conflict of interests between nature preservation and potable water supply.