Plant succession on dune sands in Fremont County, Idaho

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Active sand dunes in Fremont County, Idaho, move northeastward at an approximate 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. Elymus flavascens and Psoralea lanceolata dominate the pioneer stage, which lasts up to about 30 years. The second stage, dominated by Chrysothamnus nauseosus with an understory of the two pioneer species, lasts from 10 to 70 years. Purshia tridentata then replaces much of the C. nauseosus to form a third stage lasting for about 50 to 70 years. Dominant species in the fourth stage are Artemisia tridentata, P. tridentata, and in many areas Prunus virginiana var. demissa. Very little A. 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. tridentata with clumps of P. virginiana var. demissa. Vegetation on old, shallow deposits has characteristics of both that on deep sand and the Artemisia/bunchgrass type on the surrounding native soil. Fields that were plowed and abandoned in the early 1930s now support dense stands of Stipa comata. 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, and this moisture-holding difference probably accounts for the greater shrub density and vigor on sand.

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ELECTRONIC FILE - Ecology, ELECTRONIC FILE - Zoology