1 The dynamics of populations of Filipendula ulmaria during succession in an abandoned meadows in the centre of the Bialowieza Primeval Forest was studied over the period 1974-90. The growth and disintegration of individual genets was followed throughout succession. 2 In patches originally dominated by grasses and macroforbs, the number of genets increased rapidly to reach five to seven times the original number within about 8 years. A second increase in numbers was seen between 12 and 14 years, due to disintegration of the genets. In a patch dominated by sedges, the population grew slowly and the resulting small genets seldom disintegrated. 3 Expansion is followed by disintegration once critical size is attained. Change in size of genets and the ratio between generative and vegetative offspring resulted in the overall spatial structure changing from uniform to more clumped over the 17-year study period. 4 The number of ramets in a genet is correlated with the size and age of the genet. The growth and survivorship of new genets and genet fragments are limited by the gradually increasing necromass cover, and by the willow canopy. 5 Overall vegetation dynamics is strongly related to F. ulmaria populations in that: (a) the increase of abundance of F. ulmaria coincided with the start of succession; (b) the maximum abundance coincided with a transient stage in the succession from macroforbs to willow; (c) the decrease in abundance of F. ulmaria began when the meadow became dominated by willow. 6 The advancing senescence of Filipendula ulmaria genets, manifested in the necrosis of their senile parts, gives rise to free space within the genet area which is subsequently colonized by other species. The number of colonizers increases with the age and size of the genet, with continued species turnover taking place above 10 years of age. Senescence and disintegration of genets thus influence succession in abandoned meadows.
