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A0556 Picea engelmannii Rock Alliance
Type Concept Sentence: These wooded scree communities are characterized by Picea engelmannii as the dominant mature tree species and occur on steep slopes of any exposure in the southern Rocky Mountains of southern Colorado and northern New Mexico.
Common (Translated Scientific) Name: Engelmann Spruce Rock Alliance
Colloquial Name: Engelmann Spruce Wooded Scree
Hierarchy Level: Alliance
Type Concept: These wooded screes are characterized by Picea engelmannii as the dominant mature tree species. The trees are typically widely spaced and rarely reach over 20% cover. A few other trees can occur, usually as seedlings and saplings, including Abies lasiocarpa, Pinus flexilis, or Populus tremuloides. The shrub layer, also very sparse, can include Jamesia americana, Juniperus communis, Ribes montigenum, and Ribes wolfii. The herbaceous component is nearly unnoticeable, as plants typically are found only in crevices in the talus where small amounts of soil may have accumulated. Species can include Carex rossii, Festuca brachyphylla, Koeleria macrantha, Saxifraga bronchialis, Sedum lanceolatum, and Senecio atratus. These wooded scree communities occur on steep slopes of any exposure in the southern Rocky Mountains of southern Colorado and northern New Mexico. Differences in rock size and rates of movement cause heterogeneity in the development of vegetation. Elevations are upper montane to subalpine, ranging from about 3000 to 3600 m. Winter snowfall comprises the major portion of annual precipitation in this region. Melting snow can be held within the rocky matrix of these scree slopes, providing greater moisture-holding capacity than at first appearance. Slopes of these screes are typically greater than 50%. Greater than 80% of the substrate is composed of coarse rock fragments, with mineral soils confined to pockets.
Diagnostic Characteristics: Needle-leaved evergreen sparsely vegetated scree slopes of the southern Rocky Mountains where Picea engelmannii is the dominant species but typically not exceeding 20% cover.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: Scree and talus slopes with sparse vegetation have been poorly sampled and classified in the West. Undoubtedly there are coniferous tree-dominated communities in mountainous areas throughout the West occurring on talus, such as in this alliance. Also, several other wooded scree associations (e.g., dominated by Abies lasiocarpa, Abies concolor, Pinus aristata, Pinus ponderosa, and Pseudotsuga menziesii, and others) have been mentioned in the literature (Pfister et al. 1977, DeVelice et al. 1986, Fitzhugh et al. 1987), and are currently placed into their respective woodland alliances. Without more quantitative data for these scree communities, it is difficult to judge their proper classification and placement in the hierarchy. Wooded screes should be reviewed, and most probably belong in the Sparse Vegetation Class in the USNVC.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: The primary feature of this alliance is its occurrence on semi-stabilized talus slopes. These are very open woodlands dominated by needle-leaved evergreen trees up to 30 m in height and of only sparse cover (5-20%). There is a very sparse layer of short shrubs, primarily of scale-leaved evergreen species, although some cold-deciduous species may be present. There are very few forbs or graminoids present in most stands, typically found in crevices in the rocks where small amounts of soil may have accumulated. Total cover is characteristically less than 10%, although some stands may be somewhat higher.
Floristics: These wooded screes are characterized by Picea engelmannii as the dominant mature tree species. The trees are typically widely spaced and rarely reach over 20% cover. A few other trees can occur, usually as seedlings and saplings, including Abies lasiocarpa, Pinus flexilis, or Populus tremuloides. The shrub layer, also very sparse, can include Jamesia americana, Juniperus communis, Ribes montigenum, and Ribes wolfii. The herbaceous component is nearly unnoticeable, as plants typically are found only in crevices in the talus where small amounts of soil may have accumulated. Species can include Carex rossii, Festuca brachyphylla, Koeleria macrantha, Saxifraga bronchialis, Sedum lanceolatum, and Senecio atratus.
Dynamics: Vegetation on scree slopes reaches a quasi-equilibrium with the shifting substrate. Differences in rock size and rates of movement cause heterogeneity in the development of vegetation (Pfister et al. 1977), and there is a corresponding variability in species composition from one slope to another. The instability of the substrate leads to lack of soil development and slow regeneration of trees. Why some screes are dominated by Picea engelmannii and others by Abies lasiocarpa (or other conifers) is not documented in the literature.
Environmental Description: These wooded scree communities occur on steep slopes of any exposure in the southern Rocky Mountains of southern Colorado and northern New Mexico. Elevations are upper montane to subalpine, ranging from about 3000 to 3600 m. Winter snowfall comprises the major portion of annual precipitation in this region, although summer monsoon rain events contribute as well. Maximum snowfall accumulations range from 5 m in northern New Mexico to over 13 m in the San Juan Mountains. Melting snow can be held within the rocky matrix of these scree slopes, providing greater moisture-holding capacity than at first appearance. Slopes of these screes are typically greater than 50% (24°). Greater than 80% of the substrate is composed of coarse rock fragments, with mineral soils confined to pockets (DeVelice et al. 1986). Differences in rock size and rates of movement cause heterogeneity in the development of vegetation (Pfister et al. 1977).
Geographic Range: This woodland alliance is presently known only from the mountains of southern Colorado and northern New Mexico. It is probable that it occurs elsewhere in the Rocky Mountain cordillera.
Nations: US
States/Provinces: CO, NM
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899000
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.Nb Western North American Temperate Cliff, Scree & Rock Vegetation Division | D052 | 6.B.1.Nb |
| Macrogroup | 6.B.1.Nb.1 Douglas-fir - Ponderosa Pine / Moss Western North American Cliff, Scree & Rock Vegetation Macrogroup | M887 | 6.B.1.Nb.1 |
| Group | 6.B.1.Nb.1.b Nonvascular Rocky Mountain Cliff, Scree & Rock Vegetation Group | G565 | 6.B.1.Nb.1.b |
| Alliance | A0556 Engelmann Spruce Rock Alliance | A0556 | 6.B.1.Nb.1.b |
| Association | CEGL000893 Engelmann Spruce / Yellow-spot Saxifrage Scree Sparse Vegetation | CEGL000893 | 6.B.1.Nb.1.b |
Concept Lineage: equivalent to A.556
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: ? Picea engelmannii Series (DeVelice et al. 1986) [Scree Forests and Habitat Types]
- DeVelice, R. L., J. A. Ludwig, W. H. Moir, and F. Ronco, Jr. 1986. A classification of forest habitat types of northern New Mexico and southern Colorado. General Technical Report RM-131. USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO. 59 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.
- Fitzhugh, E. L., W. H. Moir, J. A. Ludwig, and F. Ronco, Jr. 1987. Forest habitat types in the Apache, Gila, and part of the Cibola national forests. General Technical Report RM-145. USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO. 116 pp.
- Pfister, R. D., B. L. Kovalchik, S. F. Arno, and R. C. Presby. 1977. Forest habitat types of Montana. General Technical Report INT-34. USDA Forest Service, Intermountain Forest and Range Experiment Station, Ogden, UT. 174 pp.