Note:  This research report is available from the Pedology Laboratory for the xerox charges.

     Sagebrush Communities and Soils at Birch Creek Valley in East-Central Idaho

Donald L. Hauxwell, Minoru Hironaka, Maynard A. Fosberg, and Anita L. Falen
November 1977


Introduction

The objectives of this study were 1) to characterize the soils associated with five different species or subspecies of sagebrush in an area where the soils have developed from glacial outwash from limestone, and 2) to determine if the soils associated with each sagebrush type differ consistently from those associated with the other sagebrush types. The soils supporting the following sage species and subspecies were studied:

1. Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis Beetle)
2. black sagebrush (Artemisia nova Nelson)
3. low sagebrush (Artemisia arbuscula Nutt.)
4. treetip sagebrush (Artemisia tripartita Rybd.)
5. mountain big sagebrush (Artemisia tridentata subsp. vaseyana Rybd. Beetle)

These sagebrush types are designated by the letters W, N, A, T, and V respectively.

The Birch Creek Valley occupies parts of Butte, Clark, and Lemhi Counties in east central Idaho. The valley is oriented in a northwest-southeasterly direction, is approximately 65 km long, and ranges from 6-15 km wide. The valley floor drops from an elevation of about 2200-m at Gilmore Summit on the northwest end to open out on the upper Snake River Plains at an elevation of 1600 m. Birch Creek, which drains the valley, never reaches the Snake River, but disappears into the Snake River Plains just beyond the mouth of the valley in what is known as the Birch Creek Sinks.

The Beaverhead Mountains bordering the valley on the northeast and the Lemhi Mountains on the southwest are both composed principally of limestone, although in places there is considerable quartzite in the Lemhi Range. Soils on the floor of the valley have formed in glacial outwash from the limestone. The outwash has been deposited in large coalescing fans.

The five sagebrush types tend to be arranged in an elevational sequence across the valley (Figure 1). Artemisia tridentata vaseyana occupies the highest position on the upper ends of the fans and the footslopes of the mountains.  In order of descending elevation below that are Artemisia tripartita, Artemisia arbuscula, Artemisia nova, and Artemisia tridentata wyomingensis.  Artemisia nova does not appear to occur on the west side of the valley at its upper end.