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CEGL001800 Achnatherum lemmonii / Racomitrium canescens Grassland
Type Concept Sentence: No Data Available
Common (Translated Scientific) Name: Lemmon''s Needlegrass / Silver Moss Grassland
Colloquial Name: Lemmon''s Needlegrass / Silver Moss Grassland
Hierarchy Level: Association
Type Concept: This type is currently only known from the southern end of the Willamette Valley in Oregon. The bunchgrass Achnatherum lemmonii and the moss Racomitrium canescens dominate this sparse, bunchgrass association found on hilltop balds along valley margins. Cover values are not available, but frequency in 0.01-m2 plots show Achnatherum from 15-56% and Racomitrium from (74-100%). Other native bunchgrasses include Festuca idahoensis and Koeleria macrantha. Quercus garryana trees are usually found on the margins of this type, but most areas are two shallow soiled to support much tree or shrub growth. Toxicodendron diversilobum is found under the isolated trees, and on the margins of these grasslands. Native forbs from this grass bald include Trifolium microcephalum, Viola douglasii, Lotus micranthus, Allium amplectens, and Eriogonum nudum. Exotic grasses which invaded the sites include Aira caryophyllea, Bromus hordeaceus, Bromus diandrus ssp. rigidus, Cynosurus echinatus, Holcus lanatus, and Arrhenatherum elatius.
Diagnostic Characteristics: No Data Available
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: No Data Available
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: No Data Available
Floristics: This unusual association is composed of an herbaceous layer over a dense mat of nonvascular species. The herbaceous layer is dominated by the short perennial bunchgrass Achnatherum lemmonii (= Stipa lemmonii), which has cover of 50%. Other perennial grasses may occasionally occur, including Festuca rubra, Koeleria macrantha, and Danthonia californica. There is a dense layer of nonvascular species, strongly dominated by the moss Racomitrium canescens. Cover of this layer is not available but is likely to be at least 50%, and possibly much higher. A diverse component of perennial forb species is present, the most abundant being Lotus micranthus, with lesser amounts of Viola douglasii, Eriogonum nudum, and Allium amplectens. The broad-leaved deciduous shrub Toxicodendron diversilobum, or the broad-leaved deciduous tree Quercus garryana occur infrequently, growing in pockets of soil. Cover of the Quercus may be as high as 5%, giving the appearance of a savanna. This association is extremely sensitive to disturbance by grazing, and the only two known stands are codominated (with Achnatherum lemmonii) by introduced grasses such as Aira caryophyllea, Bromus hordeaceus (= Bromus mollis), Bromus diandrus ssp. rigidus (= Bromus rigidus), Cynosurus echinatus, and Vulpia myuros (= Festuca megalura). Exotic forbs are also common, including Hypochaeris radicata, Lathyrus sphaericus, and Rumex acetosella.
Dynamics: No Data Available
Environmental Description: This association is found on the margins of the Willamette Valley, one of the warmest and driest regions of Oregon west of the Cascades. The climatic characteristics are due to the rainshadow effect of the Coast Ranges to the west, which results in annual precipitation of less than 100 cm (as compared to well over 200 cm on the coast). Summers in this valley are hot and dry, with potential evapotranspiration far exceeding the moisture recharged during the wet, mild winters.
This association typically occurs on the driest sites of open balds, largely on the southern slopes of basalt "buttes," in the southern portion of the valley. The elevation of one of the two known stands is 330 meters. There is little, if any, soil development, and the underlying shallow bedrock results in very poor drainage and extremely wet conditions in the early spring. These sites become extremely dry during the summer and fall months.
This association typically occurs on the driest sites of open balds, largely on the southern slopes of basalt "buttes," in the southern portion of the valley. The elevation of one of the two known stands is 330 meters. There is little, if any, soil development, and the underlying shallow bedrock results in very poor drainage and extremely wet conditions in the early spring. These sites become extremely dry during the summer and fall months.
Geographic Range: This type is currently only known from the southern end of the Willamette Valley. Small, badly disturbed remnants have been located at the north end of the Willamette Valley, and in southwestern Oregon.
Nations: US
States/Provinces: OR
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.685627
Confidence Level: Moderate
Confidence Level Comments: No Data Available
Grank: G1
Greasons: No Data Available
| Type | Name | Database Code | Classification Code |
|---|---|---|---|
| Class | 2 Shrub & Herb Vegetation Class | C02 | 2 |
| Subclass | 2.B Temperate & Boreal Grassland & Shrubland Subclass | S18 | 2.B |
| Formation | 2.B.2 Temperate Grassland & Shrubland Formation | F012 | 2.B.2 |
| Division | 2.B.2.Nf Western North American Grassland & Shrubland Division | D022 | 2.B.2.Nf |
| Macrogroup | 2.B.2.Nf.4 Southern Vancouverian Lowland Grassland & Shrubland Macrogroup | M050 | 2.B.2.Nf.4 |
| Group | 2.B.2.Nf.4.a Manzanita species / Roemer''s Fescue - California Oatgrass Shrubland & Grassland Group | G488 | 2.B.2.Nf.4.a |
| Alliance | A3739 Red Fescue - Pacific Reedgrass Exposed Coastal Headland Grassland Alliance | A3739 | 2.B.2.Nf.4.a |
| Association | CEGL001800 Lemmon''s Needlegrass / Silver Moss Grassland | CEGL001800 | 2.B.2.Nf.4.a |
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: ? Achnatherum lemmonii Association (Chappell 2006a)
- 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.
- Chappell, C. B. 2006a. Plant associations of balds and bluffs of western Washington. Natural Heritage Report 2006-02. Washington Natural Heritage Program, Washington Department of Natural Resources, Olympia. [http://www.dnr.wa.gov/nhp/refdesk/communities/pdf/balds_veg.pdf]
- 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.
- Kagan, J. S., and S. C. Seyer. 1982. Native grassland search in Willamette Valley, Oregon. Unpublished report to The Nature Conservancy, Portland, OR.
- Macdonald, C. 1992. Fire effects on a Stipa lemmonii - Rhacomitrium canescens grassland community. Unpublished report prepared for The Nature Conservancy, Portland, OR. 6 pp.
- Macdonald, C. A. 1989. Plant colonization of gopher mounds in adjacent pasture and prairie communities. Unpublished thesis, Oregon State University, Corvallis. 67 pp.
- ORNHP [Oregon Natural Heritage Program]. No date. Unpublished data files. Oregon Natural Heritage Program, The Nature Conservancy, Portland, OR.
- Western Ecology Working Group of NatureServe. No date. International Ecological Classification Standard: International Vegetation Classification. Terrestrial Vegetation. NatureServe, Boulder, CO.