Print Report
A1642 Arenaria hookeri Rock Alliance
Type Concept Sentence: This alliance is known from northeastern Colorado on hot, dry sites such as exposed siltstone barrens and ravines on convex slopes where erosion is active and moisture penetration is minimal. Stands have a sparse, short herbaceous layer of mostly perennial, mat-forming cushion plants, particularly Arenaria hookeri, and a few grasses.
Common (Translated Scientific) Name: Hooker''s Sandwort Rock Alliance
Colloquial Name: Hooker''s Sandwort Barrens
Hierarchy Level: Alliance
Type Concept: Stands of this alliance have a sparse, short herbaceous layer of mostly perennial, mat-forming cushion plants and a few grasses. These vegetation mats are surrounded by bare ground. These perennials are very drought-tolerant. The diagnostic cushion plant is the perennial forb Arenaria hookeri. Other characteristic plants include Astragalus gilviflorus, Astragalus sericoleucus, Astragalus spatulatus, Comandra umbellata, Ipomopsis spicata, Oenothera flava, Penstemon spp., and Phlox hoodii. The characteristic graminoid is the medium-tall bunchgrass Achnatherum hymenoides. Wet springs bring an abundance of cool-season annuals. Common annuals include Vulpia octoflora and Plantago patagonica. Vegetation in this alliance has been described from the Pawnee National Grasslands in northeastern Colorado at elevations between 1300 and 1935 m. Stands are restricted to hot, dry sites such as exposed siltstone barrens and ravines on convex slopes where erosion is active and moisture penetration is minimal. Soils are shallow with little development, fine-textured and often gravelly.
Diagnostic Characteristics: Sparsely vegetated slopes on siltstone or clay with cushion plants, particularly Arenaria hookeri, dominant.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: These stands likely have less than 25% canopy cover and may be better classified in a sparsely vegetated herbaceous alliance. Little stand cover data are available to describe this alliance. More survey and sampling is needed.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Vegetation included in this alliance has a very sparse to sparse perennial forb layer of low cushion plants. Sparse perennial grasses may be present. Annual grasses and forbs are seasonally present to abundant.
Floristics: Stands have a sparse herbaceous layer less than 0.5 m tall that is vegetated mostly with perennial, mat-forming cushion plants and a few grasses. These vegetation mats are surrounded by bare ground. These perennials are very drought-tolerant. The diagnostic cushion plant is the perennial forb Arenaria hookeri. Other characteristic plants include Astragalus gilviflorus, Astragalus sericoleucus, Astragalus spatulatus, Comandra umbellata, Ipomopsis spicata, Oenothera flava, Penstemon spp., and Phlox hoodii. The characteristic graminoid is the medium-tall bunchgrass Achnatherum hymenoides (= Oryzopsis hymenoides). Wet springs bring an abundance of cool-season annuals. Common annuals include Vulpia octoflora and Plantago patagonica.
Dynamics: The harsh environmental conditions allow only drought-tolerant perennials and annual plants to survive. Most perennials are low, deep tap-rooted cushion plants.
Environmental Description: Vegetation included in this alliance occurs on barren clay and siltstone outcrops in the shortgrass steppe of northeastern Colorado at elevations between 1300 and 1935 m. Climate is semi-arid, continental with mean annual precipitation between 25 and 35 cm. Stands are restricted to hot, dry sites such as exposed siltstone barrens and ravines (Hazlett 1998). Soils are shallow with little development, fine-textured and often gravelly. Badaracco (1971) described stands on exposed Brule clays especially on convex slopes where erosion is active and moisture penetration is minimal. In Nebraska, a similar community is found in the badlands where substrates "are largely clays and marls, which absorb little storm water, and are subject to excessive erosion" (Pound and Clements 1900). Adjacent vegetation is shortgrass steppe dominated by Bouteloua gracilis and Bouteloua dactyloides, or possibly a more mesic midgrass stand dominated by Schizachyrium scoparium, Pascopyrum smithii, or Bouteloua gracilis at the foot of the slope.
Geographic Range: This alliance occurs on siltstone and clay breaks in the shortgrass steppe of northeastern Colorado and possibly the badlands of Nebraska. It likely occurs in other neighboring states where geologic substrates are similar.
Nations: US
States/Provinces: CO, NE?, WY?
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899159
Confidence Level: Low
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
| Type | Name | Database Code | Classification Code |
|---|---|---|---|
| Class | 6 Open Rock Vegetation Class | C06 | 6 |
| Subclass | 6.B Temperate & Boreal Open Rock Vegetation Subclass | S04 | 6.B |
| Formation | 6.B.1 Temperate & Boreal Cliff, Scree & Other Rock Vegetation Formation | F034 | 6.B.1 |
| Division | 6.B.1.Na Eastern North American Temperate Cliff, Scree & Rock Vegetation Division | D051 | 6.B.1.Na |
| Macrogroup | 6.B.1.Na.3 Great Plains Badlands Vegetation Macrogroup | M115 | 6.B.1.Na.3 |
| Group | 6.B.1.Na.3.a Greasewood / Few-flower Buckwheat - Broom Snakeweed Badlands Group | G566 | 6.B.1.Na.3.a |
| Alliance | A1642 Hooker''s Sandwort Rock Alliance | A1642 | 6.B.1.Na.3.a |
| Association | CEGL001951 Hooker''s Sandwort Barrens Vegetation | CEGL001951 | 6.B.1.Na.3.a |
Concept Lineage: This alliance equals old A.1642.
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: ? Clay barrens (Badaracco 1971)
? Mat formation of buttes and cliffs (Pound and Clements 1900)
? Siltstone barren (Hazlett 1998)
? Mat formation of buttes and cliffs (Pound and Clements 1900)
? Siltstone barren (Hazlett 1998)
- Badaracco, R. J. 1971. An interpretive resource analysis of Pawnee Buttes, Colorado. Unpublished dissertation, Colorado State University, Fort Collins. 341 pp.
- Faber-Langendoen, D., J. Drake, M. Hall, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, M. Russo, K. Schulz, L. Sneddon, K. Snow, and J. Teague. 2013-2019b. Screening alliances for induction into the U.S. National Vegetation Classification: Part 1 - Alliance concept review. NatureServe, Arlington, VA.
- Hazlett, D. L. 1998. Vascular plant species of the Pawnee National Grassland. General Technical Report RMRS-GTR-17. USDA Forest Service, Rocky Mountain Research Station, Fort Collins, CO. 26 pp.
- Moran, P. 1981a. Patterns of plant life at Pawnee National Grassland: A manual for the interpreter. Unpublished report prepared for the Pawnee National Grasslands, Greeley, CO. 88 pp.
- Pound, R., and F. E. Clements. 1900. The phytogeography of Nebraska, General Survey. Second edition. University of Nebraska Botanical Survey, Lincoln.