Influences on Upland System Structure I: Aspen Woodland

Frederic H. Wagner

in Yellowstone's Destabilized Ecosystem

Published in print June 2006 | ISBN: 9780195148213
Published online September 2007 | e-ISBN: 9780199790449 | DOI:
 Influences on Upland System Structure I: Aspen Woodland

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Aspen in western North America grows in clones, and reproduces from root shoots (ramets) that replace short-lived (100-130 year) trees. Elk browse leaves and low branches producing browse lines, peel the bark of medium-age and young trees, browse off young ramets preventing reestablishment, and convert understories to low-diversity stands of grasses and annuals. Clones outside the park in the absence of ungulates, inside park exclosures, and in early park photographs, have mixed-age ramets, no highlines, and diverse understories of shrubs and perennial forbs. Contrary to natural-regulation advocates, photographic and dencrochronological evidence shows that aspens were a significant component of the vegetation before 1872 and in early park years. There has been no tree recruitment in the northern range since the 1920s, one-third of clones in early photographs have disappeared, the area of surviving clones has declined 80%, and associated biota of browsed clones has declined, all attributed primarily to elk browsing rather than other factors proposed by natural-regulation advocates.

Keywords: clones; ramets; highlines; understory; elk

Chapter.  13394 words.  Illustrated.

Subjects: Animal Pathology and Diseases

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