PERSISTENCE BY HABITAT DOMINANCE IN THE ANNUAL IMPATIENS CAPENSIS (BALSAMINACEAE)
1983; Wiley; Volume: 71; Linguagem: Inglês
ISSN
1939-9170
Autores Tópico(s)Ecology and Vegetation Dynamics Studies
ResumoSUMMARY (1) Populations of the annual Impatiens capensis persist in relatively undisturbed, productive habitats, even in the midst of perennial herbs. Experiments were conducted to compare germination behaviour and seedling emergence and growth of Impatiens capensis with those of two perennials occurring with it, Eupatorium maculatum and Urtica dioica, and to determine whether Urtica dioica plants could become established in Impatiens capensis stands. (2) Seedling emergence in the field was earlier and occurred over a shorter period in Impatiens capensis than in the perennial species, both in shade and in full sunlight. (3) The sequence of emergence was explained by differential response to temperature. Impatiens capensis had its maximum germination at temperatures as low as 5 OC, but Eupatorium maculatum and Urtica dioica occurred only at higher temperatures. Germination of Eupatorium maculatum was greatly enhanced by temperatures cycling between 5 OC and 15 ?C. (4) Growth rates of Impatiens capensis were less suppressed by the low temperatures prevailing during seedling emergence than were those of Eupatorium maculatum and Urtica dioica. (5) Urtica dioica plants grown from seed failed to become established in Impatiens capensis stands, but previously established Urtica dioica plants, transplanted to Impatiens capensis stands, grew and sometimes set seed. (6) Transplant experiments showed that the mechanism for persistence of Impatiens capensis includes the development of a light-blocking canopy of even-aged individuals. (7) The patterns of germination and growth shown by Impatiens capensis are consistent with a stratagem of habitat dominance.
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