Summary:

The Uroczysko Warta is one of most important concentrations of floodplain forest in Poland. Building of the Jeziorsko reservoir contributed to change of the Warta River regime (limitation of surface overflows, their frequencies), what in consequence negatively influencing on floodplain forest areas. Flood plain forests are the richest and highly picturesque forest ecosystems. Unfortunately, river regulation and flood control contribute to their degradation. In Poland only 0.2% of total area is covered by flood plain forests. The Uroczysko Warta forest district constitutes one of the most important clusters of these sites. The construction of the Jeziorsko reservoir in the middle course of the Warta River has contributed to changes in the river regime (reduced flooding areas and decreased flooding frequency). It seems that the use of simple land improvement systems, i.e. gates, river bars and culverts with flap check valves, may result in the recreation of advantageous hydrological conditions. In such a case storage volume of oxbow lakes would be increased and ground water would be maintained at a higher level over longer periods of time. Planned building of numerous dams on water-courses and devices to dam up water on reservoirs are cheapest methods of enlarging of water supplies in catchments. Build of these technical devices no doubt will contribute also to protection very valuable marshland biotopes, fulfilling mostly functions protective and recreational. In paper a influences of climatic factors and levels of surface water in oxbow and ground water on deadwood quantity are presented.