THE ECOLOGY OF SHORT‐LIVED FORBS IN CHALK GRASSLANDS: DISPERSAL OF SEEDS

Abstract

SUMMARY Wind dispersal of some characteristic short‐lived species in Dutch chalk grasslands was studied. Field observations were in agreement with a model and indicated a rather limited dispersal of seeds (0.3 to 3.5 m). Species with inherently short inflorescences have more extensive and less concentrated dispersal in open vegetation than in dense turf despite the fact that they are slightly taller in dense turf. In dense turf the slight increase in plant height does not sufficiently compensate for the reduced wind velocity in that habitat. In contrast, in species which have inherently longer inflorescences, dispersal is usually more extensive and less concentrated in dense turf. Apparently, in this case additional height more than counterbalances the reduced wind velocity in such turf. In all cases dispersal seems to be more affected by the interaction of stem height and wind profile at each site, and by the terminal vertical movement of seeds, than by other factors. Heterogeneity in the seed bank in the soil is partly explained by limited dispersal of seeds but may also be due to variation in seed production and to the pattern of distribution of fruiting individuals.