Print Report

CEGL000196 Pinus ponderosa / Purshia tridentata / Achnatherum hymenoides Woodland

Type Concept Sentence: No Data Available


Common (Translated Scientific) Name: Ponderosa Pine / Antelope Bitterbrush / Indian Ricegrass Woodland

Colloquial Name: No Data Available

Hierarchy Level:  Association

Type Concept: Pinus ponderosa dominates the tree layer of this open woodland. Scattered individuals of Juniperus occidentalis and occasional patches of dense Pinus ponderosa saplings can occur. The poorly developed understory is dominated by Purshia tridentata (4% cover). Trace amounts of Chrysothamnus viscidiflorus and Artemisia tridentata are present. The herbaceous layer is very sparse and dominated by perennial bunchgrasses that total about 5%. Grasses can include Achnatherum hymenoides, Poa secunda, Festuca idahoensis, Elymus elymoides, and Stipa sp. Perennial forbs contribute less than 1% cover.

Diagnostic Characteristics: No Data Available

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: In Washington, this association is considered part of the ~Pinus ponderosa / Purshia tridentata Central Rocky Mountain Woodland (CEGL005648)$$.

Similar NVC Types: No Data Available
note: No Data Available

Physiognomy and Structure: No Data Available

Floristics: Little quantitative information is available for this association. It is an open woodland dominated by the evergreen needle-leaved tree Pinus ponderosa, with very scattered individuals of another conifer, Juniperus occidentalis. Occasional patches of dense ponderosa saplings do occur. The understory is poorly developed, with a sparse shrub layer composed predominantly of the broad-leaved deciduous Purshia tridentata (4% cover). The microphyllous, evergreen shrubs Chrysothamnus viscidiflorus and Artemisia tridentata are present in trace amounts. The herbaceous layer is very sparse and dominated by perennial bunchgrasses which total about 5% cover. Grasses commonly present include Achnatherum hymenoides (= Oryzopsis hymenoides), Poa secunda, Festuca idahoensis, Elymus elymoides, and Stipa spp. Perennial forbs contribute less than 1% cover. Small annual forbs, lichens and bryophytes are not represented, possibly because of wind erosion of the sandy soil.

Dynamics:  No Data Available

Environmental Description:  This association is found within a Pleistocene lake basin (Christmas Lake Basin) formed by block faulting of underlying Pliocene basalt flows. Lacustrine, alluvial and eolian deposits are found throughout the basin and are the parent materials of the soils. The climate of this region can be characterized as cool desert. Average annual precipitation is 23 cm, 28% of which falls during December and January, with another smaller peak during May and June. However, both yearly and monthly amounts are very erratic. Summers are cool, and winters cold. This association occurs on partially stabilized, deep sandy soils. These soils are underlain by a caliche layer typically up to 10 cm thick, through which plant roots rarely penetrate. Ponderosa pine is able to effectively utilize whatever precipitation infiltrates the porous sands. Elevations range from 1340 to 1410 m.

Geographic Range: This association appears to be of very limited distribution.

Nations: US

States/Provinces:  CA, OR




Confidence Level: Low - Poorly Documented

Confidence Level Comments: No Data Available

Grank: G1

Greasons: No Data Available


Concept Lineage: No Data Available

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available

Synonomy: No Data Available

Concept Author(s): M.S. Reid

Author of Description: M.S. Reid and M. Schindel

Acknowledgements: No Data Available

Version Date: 12-15-93

  • Berry, D. W. 1963. An ecological study of a disjunct Ponderosa pine forest in the northern Great Basin in Oregon. Ph.D. dissertation, Oregon State University, Corvallis. 291 pp.
  • Bourgeron, P. S., and L. D. Engelking, editors. 1994. A preliminary vegetation classification of the western United States. Unpublished report. The Nature Conservancy, Western Heritage Task Force, Boulder, CO. 175 pp. plus appendix.
  • Clausnitzer, R. R., and B. A. Zamora. 1987. Forest habitat types of the Colville Indian Reservation. Unpublished report prepared for the Department of Forest and Range Management, Washington State University, Pullman. 110 pp.
  • Kagan, J. S., J. A. Christy, M. P. Murray, and J. A. Titus. 2004. Classification of native vegetation of Oregon. January 2004. Oregon Natural Heritage Information Center, Portland. 52 pp.
  • Moir, W. H., C. Maser, and J. F. Franklin. 1973b. Bagby Research Natural Area. Supplement #2 to: J. F. Franklin, C. T. Dyrness, and C. Maser. 1972. Federal Research Natural Areas in Oregon and Washington: A guidebook for scientists and educators. USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Portland, OR.
  • Moir, W. H., J. F. Franklin, and C. Maser. 1973a. Lost Forest Research Natural Area. Supplement #3 to: Federal Research Natural Areas in Oregon and Washington: A guide book for scientists and educators by J. F. Franklin, F. C. Hall, C. T. Dyrness and C. Maser. USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Portland, OR.
  • Western Ecology Working Group of NatureServe. No date. International Ecological Classification Standard: International Vegetation Classification. Terrestrial Vegetation. NatureServe, Boulder, CO.