JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology. Abstract. Active sand dunes in Fremont County, Idaho, move northeastward at an approximate average rate of 3 m/year. Sand deposits, continuous in some areas for several kilometers, extend to windward from the dunes in the form of long ridges, parallel to the wind direction. Five successional vegetation stages, distinct as to dominant species, appear on the deposits as belts transverse to the direction of dune movement. Elymnuts flavascens and Psoralea lanceolata dominate the pioneer stage, which lasts up to about 30 years. The second stage, dominated by Chrysothavnnus nautseosus with an understory of the two pioneer species, lasts for 10 to 70 years. Purshia tridentata then replaces much of the C. itazysosits to form a third stage lasting for about 50 to 70 years. Dominant species in the fourth stage are Arteinisia tridentata, P.
tridlen-tta, and in many areas IPrunts virginiana var. deniissa. Very little I. tridentata is found after 700 to 900 years of stabilization, and the final and most extensive stage on deep sand is dominated by dense P. triJentata with clumps of P. virginiana var. demissa. Vegetation on old, shallow deposits has characteristics of both that on deep sand and the Arteinisia/ bunchgrass type on the surrounding native soil. Fields that were plowed and abandoned in the early 1930's now support dense stands of Stipa conata. The presence of dense shrub stands on dunes now topographically sheltered by the wind, but not on migrating dunes, indicates that establishment of a species on sand depends on relative site stability rather than on soil nutrient buildup caused by previous vegetation.Deep sand holds moisture available to plants throughout the dry part of the growing season while the native soil does not, which probably accounts for the greater shrub density and vigor on sand. This paper is based on a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Forestry at the University of Idaho, Moscow, Idaho.' Original measurements exI)ressed by the English system were converted to their metric equivalents for this caper.' Unless noted otherwise, scientific names for forbs, shrubs, and sedges follow Davis (1952); authority for grasses is Hitchcock (1950).
