A development cycle of the forest with fir (Abies alba Mill.) and beech (Fagus sylvatica L.) in its species composition in the Świętokrzyski National Park

The objectives of this study are to determine the progress of the development cycle of the forest taking into account untypical development periods caused by fir decline and recovery, and to compare the per cent participation of individual phases and periods of forest development in the Święta Katarzyna and Święty Krzyż Forest Ranges of the Świętokrzyski National Park. The development stages, phases, and periods was determined in P6 fields of the SINUS System of Information on Natural Environment. Tree age distribution, stand structure, volume increment tendency (an increasing or decreasing one), and also the radial increment of fir and beech, and the age of the stand upper story or upper layer were taken as criteria. Fir until about 1960 was characterized by more or less even growth while during 1960-1985 a strong increment collapse occurred, followed by its recovery since 1986. On the other hand, beech during the whole analysed period (1890-1994) did not exhibit any significant decrease in its radial increment. After taking into account the progress of diameter increment of fir and beech the hypothetical series of successive changes of stand phases, mainly caused by decline and then recovery of fir, were developed. Seven new development phases taking place during the periods of decline, recovery and transformation, and not occurring in typical KORPEĽ's (1982) development cycle, are described. New phases were found in 140 P6 fields out of 206 analysed fields. It was proved on the basis of the fraction equality chi-squared test that there was no reason to reject a null hypothesis according to which the per cent participation of phases during the recovery period in the Święta Katarzyna Forest Range is the same as in the Święty Krzyż Forest Range (2 = 2.756; df = 3; p = 0.4308). The absence of significant difference between these two forest ranges indicates, among others, an extensive and strong process of fir decline in the analysed part of the Świętokrzyski National Park (in the Łysogóry Mountain Range). In order to improve the description of the development phases of the forest during the periods of decline, recovery and transformation these studies should be continued, especially on permanent research plots.