Thompson Clover RNA, located near Wenatchee in Chelan County, Washington, was established to protect one of several small areas of Thompson's clover (Trifolium thompsonii) known to exist on Federal land. Thompson's clover is a Federally threatened species that only occurs in the Swakane Canyon area, and it generally occurs on well-drained, grassy hillsides just below the edge of the ponderosa pine (Pinus ponderosa) woodland. The topography of the 81 ha tract is steep and south facing, and elevations range from 593 to 1,102 m. Forbs and halfshrubs comprise the dominant vegetation in Thompson Clover RNA, and stiff sagebrush (Artemisia rigida)/Sandberg bluegrass (Poa secunda) is the dominant community. Prominent perennial forbs and halfshrubs include arrowleaf balsamroot (Bahia sagittata), parsnipflower buckwheat (Eriogonum heracleoides), Thompson's clover, western yarrow (Achillea millefolium var. occidentalis), and low pussytoes (Antennaria dimorpha). Bluebunch wheatgrass (Pseudoroegneria spicata) is the major grass species. The natural area occupies the Ponderosa Pine Zone, and, except for ravines, ponderosa pine is found as individuals or small clumps (2-3 trees) throughout the RNA. Areas along the ravines have more continuous tree cover than open grassy slopes, although the highest density of ponderosa pine is found at the upper end of the tract. The entire RNA was burned in the Dinkelman Ridge Fire in 1988. After the fire, there was evidence of a significant expansion of the Thompson's clover population into dead Douglas fir (Pseudostuga meziesii) stands on the north side of the canyon (across from the RNA). While completeing his Master's research, George Shearer discovered that the greatest density of Thompson's clover was found in the shrub-steppe communities, but plants found in Douglas fir/pinegrass (Calamagrostis rubescens) were larger and had more flower heads. The population inside the RNA is also believed to be doing well. Thompson's clover is an ideal subject for studies on factors that affect species distribution, and some research on the topic has been done in the past.

Township/Range/Section:

Part of sec 15, T24N, R20E.

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Threatened or Endangered Species:

The RNA was established to preserve on of several small tracts of Trifolium thompsonii (Thompson's clover), an endangered plant species. The bald eagle (Haliaeetus leucocephalus alascanus), endangered in the continental US, uses the RNA.

Exotic Species Present:

Bromus tectorum (cheatgrass brome), an exotic plant, occurs on the RNA. Ovis canadensis californiana (California bighorn sheep) were introduced in the area and use a portion of the RNA. Sturnus vulgaris (starling), an exotic, is assumed to be present. Alectoris graeca (chukar partridge), an introduced bird, has been observed on the RNA.

Plant Communities:

The RNA was established to preserve several tracts of Thompson's clover (Trifolium thompsonii), an endangered species. Plant association type most closely matches Stiff sagebrush/Sandberg's bluegrass.

Aquatic Features Present:

None.

Soils:

Soils are all Haploxerolls in either the Typic or Lithic subgroup. All are mixed, mesic and most are coarse-loamy. For more detailed information, see the Guidebook.

Other Physical Features:

Past Disturbance History:

Other Comments:

Access by road