Heracleum mantegazzianum Sommier & Levier. Can. J. Plant Sci. 86: 569-589. Heracleum mantegazzianum (giant hogweed) is an invasive alien plant of management concern in southern Canada where it has escaped from horticulture and established and spread in natural, ruderal, and agricultural ecosystems. It poses a threat to natural ecosystems and human health, and is also a weed in agricultural and urban areas. It is a member of the Carrot family (Apiaceae) and is closely related to the native species Heracleum maximum Bartram (cow-parsnip). It is a monocarpic perennial, which generally flowers in its 3rd or 4th year. Large size, leaf shape, dark reddish pigments in patches on stems and petioles, and fruit characteristics readily distinguish H. mantegazzianum from other plants in Canada. It is increasingly common in riparian areas, floodplains, and forest edges in or near urban areas in southwestern British Columbia and southern Ontario. Based on herbarium specimens, H. mantegazzianum was first recorded in Ontario in 1949, British Columbia in 1964, Nova Scotia in 1980, Quebec in 1990, and New Brunswick in 2000. The development of dense stands of H. mantegazzianum can also reduce the richness of native plants. Contact with H. mantegazzianum can cause phytophotodermatitis, a serious skin inflammation caused by UV photo-activation of furanocoumarins present in the sap. Control methods include herbicide application, mechanical cutting, and animal grazing, but strategies to address seed dispersal and re-establishment from dormant seed must also be adopted. Widespread establishment in southern Canada suggests that eradication is unlikely. However, range expansion and rapid population growth can be prevented through strategic management including public education. Heracleum mantegazzianum (berce du Caucase) est une espèce exotique envahissante qui préoccupe les producteurs du sud du Canada, car la plante s'est échappée des jardins pour coloniser les écosystèmes naturels, rudéraux et agricoles. En plus d'être une adventice dans les régions agricoles et urbaines, l'espèce s'avère une menace pour les écosystèmes naturels et la santé humaine. Membre de la famille de la carotte (Apiacées), la berce du Caucase est étroitement apparentée à l'espèce indigène Heracleum maximum Bartram (berce laineuse). Cette vivace monocarpienne fleurit habituellement la troisième ou la quatrième année. Il est facile de la distinguer des autres plantes à cause de sa grande taille, de la forme de ses feuilles, des taches rouge foncé sur la tige et les pétioles et des fruits très caractéristiques. On la trouve de plus en plus dans les habitats riverains, les plaines inondables et la lisière des forêts, ou à proximité des zones urbaines dans le sud-ouest de la ColombieBritannique et le sud de l'Ontario. D'après les spécimens conservés dans les herbiers, H. mantegazzianum a été identifiée pour la première fois en 1949 en Ontario, en 1964 en Colombie-Britannique, en 1980 en Nouvelle-Écosse, en 1990 au Québec et en 2000 au Nouveau-Brunswick. Le développem...

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We present the results of sclerochronologically calibrated growth and stable isotope analyses of the freshwater bivalve Margaritifera falcata collected from an agricultural, suburban setting near Vancouver, BC. The oxygen isotope range of shell aragonite can be explained by the temperature range during the growing season, assuming the water d 18 O composition remained constant. However, shell growth is strongly influenced by local summer precipitation and potentially runoff of nutrient-rich stormwater. About 44% of the variability of annual shell growth can be explained by amounts of local summer (June-September) rainfall. Local winter precipitation and El Niñ o-Southern Oscillation (ENSO) strength during the preceding year exert a weak, but significant control on shell growth. In combination, summer and winter precipitation can explain up to 50% of the variability in annual shell growth. Spectral analyses substantiate the effect of precipitation on shell growth and demonstrate that shell growth and ENSO are coupled by precipitation. Common spectral density was found at periods of 6.5-9 years, particularly between 1985 and 2004. Higher frequency oscillation corresponding to periods of 3-5 years occurred during the early 1970s, early to mid 1980s, and later 1990s. These results suggest that skeletal records of bivalve mollusks provide suitable archives of ENSO-coupled precipitation in areas where other climate proxies such as tree-rings and speleothems may not be available.

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