Zróżnicowanie banków nasion w naturalnie i antropogenicznie przekształconych zbiorowiskach leśnych [Diversity of soil seed banks in natural and man-modified forest communities

Abstract

The objective of the study was to reveal diversity in species composition and size of soil seed banks derived from forest communities undergoing different intensity of human impact as well as to show the seed bank strategy as an adaptation of species to many kinds of disturbances occurring in natural deciduous forests. On the basis of the study of soil seed bank in natural, stabilised deciduous forest communities in Białowieża National Park and taking into account data from literature it was found that: (1) Densities of seed banks of fertile, undisturbed deciduous forest vary from three to eight thousand seeds per one m<sup>2</sup>. The majority of these seeds (60–80%)come from the herb layer. Persistance of such banks do not exceed a few years. Species which arę dominant in seed bank of such forest are characterized by mean light requirements. The impulses which break their secondary dormancy arę slight disturbances in the herb layer. (2) Species structure of seed bank derived from such forest does not reflect floristic composition of the herb layer because this layer is dominated by species whose survival strategy is connected with vegetative propagation. (3) In seed banks of even very stable forest communities there are species which are absent from the herb layer of the forest. The species need light gaps in trees canopy for establishment. They are very light demanding and persistent in soil. Percentage of these species in soil seed banks grows with the intensity of human impact on forest communities. These species dominate also in seed banks of relatively natural forests but small and surrounded by meadows and fields. Seedlings of these species occur spontanously during the first phase of regeneration of forest gaps. After the canopy close-up, the species disappear from cover vegetation but their numerous and very persistant seeds wait in soil seed bank for the next disturbance.