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.

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Summary The life‐histories of Carlina vulgaris L., Daucus carota L., Euphrasia officinalis L., Gentianella germanica (Willd). Börner, Linum catharticum L., and Scabiosa columbaria L. in a chalk grassland in the Netherlands are described on the basis of frequent observations during a period of three and a half years. E. officinalis and a small part of the L. catharticum population were found to be annual. G. germanica and the major part of the L. catharticum population were biennial, whereas the other species took several years to reach maturity. All species except the major part of the Scabiosa columbaria population were monocarpic. Vegetation cover influenced the occurrence of short‐lived forbs, but a large variation is found in the data. In D. carota, E. officinalis and Scabiosa columbaria seed production had a marked effect on seedling density in the following year. Shoot growth in Scabiosa columbaria seedlings varied at various vegetation densities. Furthermore, a marked correlation was found between rosette size and the probability of becoming mature in the subsequent year. Within one grassland, life‐history types within the group of short‐lived species are found to vary. On the one hand, there are the small‐seeded annuals with high mortality, but rather constant density of mature plants (Euphrasia), and on the other hand there are the more conservative life histories (Carlina, Daucus and Scabiosa), with larger seeds, lower mortality rates, but higher age of first reproduction and considerable variation in the density' of individuals.

The effects of vegetation structure on population processes in five shortlived species occurring in two Dutch chalk grasslands are analyzed on the basis of some Iabaratory and field experiments. The main factors regulating population numbers appear tobe light quantity available for seedlings in dense microsites and water availability, which affects seedling survival, growth and fecundity of established plants in open micro-habitats.Two broad categories are recognized, "spenders" and "savers". These are based on seed weight, mortality of seedlings, presence of a persistent seed bank and variation in life span. We suggest that coexistence of the short-lived species is due to niche-sharing rather than niche-differentiation.

Some aspects of vegetation structure in two chalk grasslands were studied throughout the year in relation to the occurrence of some short-lived plant species per life-cycle stage. Whereas the main growth period is in May June, there is another relatively important growth period in less productive stands in August. When the species are arranged in the order of their tolerance for less to more productive micro-sites during the adult life phase the following sequence emerges considering a generally weak significance in the results. Carlina vulgaris, Euphrasia officinalis, Gentianella germanica, and Scabiosa columbaria, Linum catharticum, Anthyllis vulneraria, and Daucus carota. In some species this preference was found to shift from seedling to vegetative and reproductive phase. Each life phase usually has its special abundance with regard to vegetation density.