Demography of Short-Lived Forbs in Chalk Grassland in Relation to Vegetation Structure

Abstract

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.

Alternate plant life history strategies and coexistence in randomly varying environments

“…Studies of chalk grassland forbs in the Netherlands (reviewed by During et al, 1985) have been summarized by arranging the species along a gradient from 'savers' to 'spenders,' which is very similar to the low-risk vs. high-risk comparison in Table 1 (although they were done independently). 'Savers' are characterized (relative to 'spenders') by a longer lifespan; fewer, larger seeds; reproduction spread over several years; a persistent seed bank; and less reaction to spatial and temporal variations (During et al, 1985).…”

“…comm.]. Competition with the matrixforming perennials, and the annual mowing of the community, may kee~ the forbs at densities too low for competition withir~ t~e guild to have any importance (During et al, 1985; H. During, pers. comm.…”

Effects of a dense moss layer on germination and establishment of vascular plants in newly created calcareous grasslands

“…As most seedlings germinated in autumn and spring, moist conditions seem to be necessary to trigger germination (Czarnecka, 2004;During et al, 1985;Fenner and Thompson, 2005).…”

Fifty years vegetation development of a xerothermic calcareous grassland in Central Europe after heavy disturbance

“…It was not influenced by summer precipitation. The range of values of standing crop in the different years (170-840 g d.w. m À2 ) comprised the whole range of mean values found by other authors, namely 100-200 g d.w. m À2 measured in open grasslands by During et al (1985), 200-300 g d.w. m À2 measured by Gluch (1973), Hartmann andOertli (1984), Dierschke and Engels (1991), Braschler et al (2004) and up to 500 g d.w. m À2 or even more (During et al, 1985, in dense grassland). The high variability of our values is probably caused by the small size of the samples.…”