TEMPERATURE EFFECTS ON SEEDLING EMERGENCE FROM BOREAL WETLAND SOILS - IMPLICATIONS FOR CLIMATE CHANGE

Temperature treatments simulated global warming effects on seedling emergence of wetland species from soil seed banks of the Peace-Athabasca Delta, Alberta. Canada. Introduced weedy species. such as Tanacetum vulgare L., bad up to a 10-fold greater emergence at high temperature (30-degrees-C for 18 h with light. 15-degrees-C for 6 h in the dark) than at low temperature (20/10-degrees-C). Seedling emergence of native weedy species, such as Calamagrostis canadensis (Michx.) Beauv., was 1.5-3 times greater at low temperature. Other native weedy species. such as Rubus idaeus L., emerged only from samples at low temperature. Emergence of native non-weedy species was greatest at high temperature, even though mature plants of species such as Ranunculus hyperboreus Rottb. and Carex eburnea Boott are normally found in cool and moist habitats. Of those species expected to persist in warm and dry habitats. only introduced weedy species showed consistent and significantly greater seedling emergence at high temperature. It is hypothesized, therefore. that the abundance of introduced weedy species would increase in disturbed or sparsely vegetated zones around water bodies as these zones become dry and warm with climate change.