ARCTIC VOL. 60, NO.4 (DECEMBER 2007) P. 430–438 Plant Macrofossils Associated with an Early Holocene Beaver Dam in Interior Alaska

ABSTRACT. Dynamic climate changes and expansion of new biomes characterize the late Pleistocene–early Holocene of eastern Beringia. Analysis of plant macrofossils from an early Holocene (ca. 9 300 14C yrs BP) beaver dam in central Alaska provides insight into the local environment and vegetation. The plant macrofossil assemblage comprises remains of trees and shrubs, graminoids, and forbs, including Betula sp., Carex sp., Rubus sp., Eleocharis sp., Scirpus sp., Potamogeton sp., Najas flexilis and Typha latifolia, indicative of standing water of a beaver pond. Bryophytes from the beaver dam include Warnstorfia spp. and Drepanocladus aduncus, suggesting shallow, stagnant, or slow-moving water. The presence of Najas flexilis, Typha latifolia, and modern beaver (Castor canadensis) suggest that central Alaska had a warmer climate during the early Holocene. Key words: Alaska, plant macrofossils, beaver, Holocene, Typha latifolia, paleoenvironment, post-glacial vegetation RÉSUMÉ. Changements climatiques dynamiques et expansion de nouveaux biomes caractérisent la période du Pléistocène supérieur et de l’Holocène inférieur de la Béringie de l’Est. L’analyse des macrofossiles de plantes provenant d’une digue de castor du centre de l’Alaska datant de l’Holocène inférieur (env. 9 300 14C années BP) donne des indices sur l’environnement et la végétation de la région. L’assemblage de macrofossiles de plantes est composé d’arbres et d’arbustes, de graminoïdes et d’herbe