LONG-TERM POPULATION-DYNAMICS OF 2 CARER CURVULA SPECIES IN THE CENTRAL ALPS ON NATIVE AND ALIEN SOILS

The demography of two closely related alpine sedges, Carex curvula sub sp. curvula and Carex curvula subsp. rosae (= C. curvula and C. rosae) has been investigated on their typical sites in the Central Alps. Bot h species proliferate vegetatively and develop dense tussocks but they show different dominance behaviours in their respective grasslands. I t was hypothesized that this may be caused by different growth abiliti es. The main aim of the study was to compare the vegetative growth of the species under field conditions, under competition-free conditions and under changed soil conditions. An attempt was also made to clarify whether vegetative growth is density dependent. Permanent plots were established in the respective grasslands of the two species and the ra met density was counted over 3 years. Groups of 10 and of 30 ramets of each species were grown in pots with typical and with alien substrate and their growth was observed for 5 years at the field site. The gras sland populations of both species were very stable and the overall ram et growth rate (lambda) was close to 1.0. Within the pots, both specie s reached a high ramet number. Only the group of 30 ramets of C. curvu la on alien soil could not recover from the transplantation shock. Wit hin the pots, C. rosae showed a greater ramet turnover and a higher in crease in ramets than C. curvula. On their native substrate, both spec ies had a significantly higher ramet increase than on the alien substr ate. Ramet growth was found to be density dependent for both species, the increases recorded for the groups of 10 being significantly greate r than for the groups of 30. Although C. curvula produced fewer ramets than C. rosae, the aboveground dry weight of the former was significa ntly higher. This may be decisive for its greater competitive success in closed grasslands.