GOG community descriptions May 2013

Vegetation Community Descriptions forGolden Gate Canyon State Park, Colorado

CEMML – Warner College of Natural ResourcesColorado State University, Fort Collins

June 2013

The vegetation communities documented at Golden Gate Canyon State Park (GGC) were compiled from previous mapping (Colorado Parks Department 2003) and community survey work (Kittel and Spears 1996, Malone 2009) to support the development of a new vegetation map in 2013 using 2012 imagery. The Natureserve Ecological System is not part of the U.S. National Vegetation Classification System (USNVC) hierarchy, but here has been nested within the hierarchy below the USNCV Group level. This document provides a framework for planning mapping and monitoring projects and management activities. The sources of the community type names and descriptions are listed below:

The Macrogroup, Group and Association descriptions are from the NatureServe Explorer website (USNVC.org) Accessed on various dates in April of 2013.

Natureserve Ecological System descriptions are from the Colorado Natural Heritage Program. 2005. Ecological System Descriptions and Viability Guidelines for Colorado. Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado. Published online

Alliance descriptions are from the NatureServe MSAccess Database NVC Version 1, November 2011.

Galatowitsch Classification descriptions are from Galatowitsch (1988).

The list and descriptions include those types that have been mapped at GGC. Plant association descriptions are provided for those communities that have been mapped at the association level or where alliances were mapped and there is only a single association within the alliance. The vast majority of the park has been mapped to the alliance level using the NVC Version 1 descriptions. The newer NVC Version 2 alliance descriptions are currently in development and review, so the older names and descriptions are included here. After the new NVC is fully developed, the older alliances will need to be translated to the NVC 2.

SECTION I – U.S. NATIONAL VEGETATION CLASSIFICATION SYSTEM (USNVC). .1

1 Macrogroup: Central Rocky Mountain Dry Lower Montane & Foothill Forest..............................................11.1 Group: Pseudotsuga menziesii - Pinus ponderosa Central Rocky Mountain Forest Group........................1

1.1.1 Ecological System: Southern Rocky Mountain Ponderosa Pine Woodland (CES306.648).................11.1.1.1 Alliance: Pinus ponderosa Woodland Alliance (A.530).................................................................1

2 Macrogroup: Rocky Mountain Subalpine & High Montane Conifer Forest...................................................12.1 Group: Pinus contorta Rocky Mountain Forest & Woodland Group..........................................................1

2.1.1 Ecological System: Inter-Mountain Basins Aspen-Mixed Conifer Forest Woodland (CES304.776)....1Description not currently available.....................................................................................................................1

2.1.1.1 Alliance: Pinus contorta - Populus tremuloides Forest Alliance (A.424)........................................12.1.2 Ecological System: Rocky Mountain Lodgepole Pine Forest (CES306.960).........................................1Overview: 1

2.1.2.1 Alliance: Pinus Contorta Forest Alliance (A.118)...........................................................................12.2 Group: Picea engelmannii - Abies lasiocarpa - Pinus contorta Dry-Mesic Forest & Woodland Group.......1

2.2.1 Ecological System: Rocky Mountain Subalpine Dry-Mesic Spruce-fir Forest and Woodland (CES.306.828)......................................................................................................................................................1

2.2.1.1 Alliance: Picea engelmannii Forest Alliance (A.164)......................................................................12.3 Group: Populus tremuloides Rocky Mountain Forest & Woodland Group................................................1

2.3.1 Ecological System: Rocky Mountain Aspen Forest and Woodland (CES306.813)..............................12.3.1.1 Alliance: Populus tremuloides Forest Alliance (A.274)..................................................................1

2.4 Group: Pinus flexilis - Pinus aristata Rocky Mountain Subalpine-Montane Woodland Group...................12.4.1 Ecological System: Rocky Mountain Subalpine-Montane Limber-Bristlecone Pine Woodland (CES306.819).......................................................................................................................................................1

2.4.1.1 Alliance: Pinus flexilis Woodland Alliance (A.540).........................................................................1

3 Macrogroup: Rocky Mountain & Great Basin Riparian Forest......................................................................13.1 Group: Picea engelmannii - Picea pungens - Populus angustifolia Riparian Forest....................................1

3.1.1 Ecological System: Rocky Mountain Lower Montane Riparian Woodland and Shrubland (CES306.821).......................................................................................................................................................1

3.1.1.1 Alliance: Populus angustifolia Temporarily Flooded Woodland (A.641).......................................13.1.1.1.1 Association: Populus angustifolia / Alnus incana Woodland (CEGL002642)...........................1

3.1.2 Ecological System: Rocky Mountain Subalpine-Montane Riparian Woodland (CES306.833)............1Overview: 1

3.1.2.1 Alliance: Populus tremuloides Temporarily Flooded Forest Alliance (A.300)................................13.1.2.1.1 Association: Populus tremuloides / Salix drummondiana Forest (CEGL002902).....................14.2.1.1.1 Association: Danthonia parryi Herbaceous Vegetation (CEGL001795)...................................1

4.2.1.2 Alliance: Festuca arizonica Herbaceous Alliance (A.1245)............................................................1

5 Macrogroup: Southern Rocky Mountain Lower Montane Forest.................................................................15.1 Group: Abies concolor - Pseudotsuga menziesii Southern Rocky Mountain Dry Forest Group..................1

5.1.1 Ecological System: Inter-Mountain Basins Aspen-Mixed Conifer Forest and Woodland (CES304.776).......................................................................................................................................................1Description not currently available.....................................................................................................................1

5.1.1.1 Alliance: Pinus ponderosa - Populus tremuloides Forest Alliance (A.399)....................................15.2 Group: Pinus ponderosa Southern Rocky Mountain Forest & Woodland Group........................................1

5.2.1 Ecological System: Southern Rocky Mountain Ponderosa Pine Woodland (CES306.648).................15.2.1.1 Alliance: Pinus ponderosa Forest Alliance (A.124)........................................................................1

6 Macrogroup: Western North American Montane & Subalpine Wet Shrubland & Wet Meadow...................16.1 Group: Carex species – Calamagrostis species Montane Wet Meadow Group..........................................1

6.1.1 Ecological System: Rocky Mountain Alpine Montane Wet Meadow (CES306.812)...........................16.1.1.1 Alliance: Carex (rostrata, utriculata) Seasonally Flooded Herbaceous Vegetation (A.1403)..........16.1.1.2 Alliance: Juncus balticus Seasonally Flooded Herbaceous Alliance (A.1374)................................1

6.2 Group: Salix species Riparian and Seep Shrubland....................................................................................16.2.1 Ecological System: Rocky Mountain Subalpine-Montane Riparian Shrubland (CES306.832)............1

6.2.1.1 Alliance: Dasiphora fruticosa ssp. Temporarily Flooded Shrubland Alliance (A.958)....................16.2.1.2 Alliance: Salix bebbiana Temporarily Flooded Shrubland (A.981).................................................1

6.2.1.2.1 Association: Salix bebbiana Shrubland Association (CEGL001173).........................................16.2.1.3 Alliance: Salix drummondiana Temporarily Flooded Shrubland (A.973).......................................1

6.2.1.3.1 Association: Salix drummondiana / Mesic Forbs Shrubland (CEGL001192)............................16.2.1.4 Alliance: Salix monticola Temporarily Flooded Shrubland Alliance (A.981)...................................1

6.2.1.4.1 Association: Salix monticola / Calamagrostis canadensis Shrubland (CEGL001222)...............16.2.1.4.2 Association: Salix monticola / Carex aquatilis Shrubland (CEGL002656)................................16.2.1.4.3 Association: Salix monticola / Mesic Graminoids Shrubland (CEGL002659)...........................1

6.2.1.5 Alliance: Salix planifolia Seasonally Flooded Shrubland Alliance (A.1008)....................................16.2.1.5.1 Association: Salix planifolia / Carex utriculata Shrubland (CEGL005937)................................1

SECTION II – GALATOWITSCH CLASSIFICATION................................................................1

1 Galatowitsch Classification......................................................................................................................... 11.1 Mixed Mountain Shrublands (6.6)..............................................................................................................11.2 Aspen Forests (6.8).....................................................................................................................................11.3 Deciduous Riparian Forest (6.10)................................................................................................................1

1.3.1 Narrowleaf Cottonwood Riparian Forests (6.10.2).............................................................................11.4 Wet Meadows (6.13)..................................................................................................................................11.5 Ponderosa Pine Woodlands (7.7)................................................................................................................11.6 Montane Forests (8.1)................................................................................................................................1

1.6.1 Lodgepole Pine Forests (8.1.1)...........................................................................................................11.6.2 Mixed Montane Forests (8.1.3)..........................................................................................................11.6.3 Montane Woodlands (8.2).................................................................................................................1

1.7 Riparian and Wetland Forests (8.7)............................................................................................................11.7.1 Wetland Forests (8.7.2)......................................................................................................................1

1.7.1.1 Aspen Wetland Forests (8.7.2.1)....................................................................................................11.8 Willow Carrs (8.8).......................................................................................................................................1

1.8.1 Upper Montane Willow Carrs (8.8.1).................................................................................................11.8.2 Lower Montane Willow Carrs (8.8.2).................................................................................................1

1.9 Montane Grasslands (8.4)...........................................................................................................................11.9.1 Lower Montane Grasslands (8.4.2)....................................................................................................1

References.......................................................................................................................................................... 1

SECTION I – U.S. National Vegetation Classification System (USNVC)

1 Macrogroup: Central Rocky Mountain Dry Lower Montane & Foothill Forest1.1 Group: Pseudotsuga menziesii - Pinus ponderosa Central Rocky Mountain Forest

Group

1.1.1 Ecological System: Southern Rocky Mountain Ponderosa Pine Woodland (CES306.648)

Overview:This widespread ecological system is most common throughout the cordillera of the Rocky Mountains, but is also found in the Colorado Plateau region, west into scattered locations in the Great Basin, and north into southern British Columbia. These matrix-forming woodlands occur at the lower treeline/ecotone between grassland or shrubland and more mesic coniferous forests typically in warm, dry, exposed sites.

Characteristic Species:Pinus ponderosa is the predominant conifer; Pseudotsuga menziesii, Pinus edulis, and Juniperus spp. may be present in the tree canopy. The understory is usually shrubby, with Artemisia nova, Artemisia tridentata, Arctostaphylos patula, Arctostaphylos uva-ursi, Cercocarpus montanus, Cercocarpus ledifolius, Purshia stansburiana, Purshia tridentata, Quercus gambelii, Symphoricarpos oreophilus, Prunus virginiana, Amelanchier alnifolia, and Rosa spp. being common species. Pseudoroegneria spicata and species of Hesperostipa, Achnatherum, Festuca, Muhlenbergia, and Bouteloua are some of the common grasses.

Grace's warbler, Pygmy nuthatch, and flammulated owl are indicators of a healthy ponderosa pine woodland.

Environment: This ecological system occurs at the lower treeline/ecotone between grassland or shrubland and more mesic coniferous forests typically in warm, dry, exposed sites at elevations ranging from 6,500-9,200 ft (1,980-2,800 m). It can occur on all slopes and aspects, however, it commonly occurs on moderately steep to very steep slopes or ridgetops. This ecological system generally occurs on igneous, metamorphic, and sedimentary material derived soils, including basalt, basaltic, andesitic flows, intrusive granitoids and porphyrites, and tuffs (Youngblood and Mauk 1985). Characteristic soil features include good aeration and drainage, coarse textures, circumneutral to slightly acid pH, an abundance of mineral material, and periods of drought during the growing season. Surface textures are highly variable in this ecological system ranging from sand to loam and silt loam. Exposed rock and bare soil consistently occur to some degree in all the associations. Annual precipitation is 8-24 in (25-60 cm), mostly through winter storms and some monsoonal summer rains. Typically a seasonal drought period occurs throughout this system as well.

Dynamics:Pinus ponderosa is a drought-resistant, shade-intolerant conifer which usually occurs at lower treeline in

Vegetation Communities of Golden Gate Canyon State Park Page 1

the major ranges of the western United States. Historically, ground fires and drought were influential in maintaining open-canopy conditions in these woodlands. With settlement and subsequent fire suppression, occurrences have become denser. Presently, many occurrences contain understories of more shade-tolerant species, such as Pseudotsuga menziesii and/or Abies spp., as well as younger cohorts of Pinus ponderosa. These altered occurrence structures have affected fuel loads and alter fire regimes. Presettlement fire regimes were primarily frequent (5-15 year return intervals), low-intensity ground fires triggered by lightning strikes or deliberately set fires by Native Americans. With fire suppression and increased fuel loads, fire regimes are now less frequent and often become intense crown fires, which can kill mature Pinus ponderosa (Reid et al. 1999).

Variation:This system intergrades with Rocky Mountain Ponderosa Pine Savanna. The two are distinguished by the high frequency, surface-fire regime, less steep or rocky environmental setting, and more open grassy understory structure of the savanna system.

1.1.1.1 Alliance: Pinus ponderosa Woodland Alliance (A.530)

This alliance is one of the most widespread wooded alliances in the western United States; there are currently over 50 plant associations in this alliance. The alliance is found throughout the western half of the U.S. and southwestern Canada, as well as the Trans-Pecos of Texas and the western portions of the Great Plains, such as in western Oklahoma and the Dakotas. Sites are dry/dry-mesic to xeric, and soils are generally well-drained and coarse-textured. Pinus ponderosa often dominates these woodlands, but codominant species may include Pseudotsuga menziesii, other Pinus species, and species of Juniperus, Abies, or Picea. The understory ranges from dense shrub or graminoid layers to barren rock. The associated plant species vary with changes in geography and environmental conditions. Associated trees include species of Pinus, Quercus, Juniperus, Abies, Pseudotsuga, Populus, and Picea. Shrubs can include species of Arctostaphylos, Artemisia, Cercocarpus, Ceanothus, Symphoricarpos, Physocarpus, Rosa, Purshia, and others. Important graminoids include species of Carex, Elymus, Poa, Festuca, Muhlenbergia, Piptochaetium, and many others.

2 Macrogroup: Rocky Mountain Subalpine & High Montane Conifer Forest2.1 Group: Pinus contorta Rocky Mountain Forest & Woodland Group

2.1.1 Ecological System: Inter-Mountain Basins Aspen-Mixed Conifer Forest Woodland (CES304.776)

Description not currently available.

2.1.1.1 Alliance: Pinus contorta - Populus tremuloides Forest Alliance (A.424)

This mixed evergreen-deciduous forest alliance has been described on mountain slopes and plateaus in Utah. Sites occur on gentle to steep slopes on all aspects. Soils are derived from alluvium and colluvium. Seral forests included in this alliance are characterized by an open to moderately closed, mixed evergreen-deciduous tree canopy that is codominated by Populus tremuloides and Pinus contorta. Several other species of conifers may be scattered within the stands, including Pseudotsuga menziesii, Abies lasiocarpa, Picea engelmannii, Picea pungens, and Pinus flexilis. Younger stands typically have dense Populus tremuloides with Pinus contorta mixed in. As stands age, Populus tremuloides cover is slowly reduced until Pinus contorta becomes dominant. The understory is moderately dense to sparse and becomes sparser as Pinus contorta becomes more dominant. The short-shrub layer is often


dominated by juniperus communis or Symphoricarpos oreophilus. Other shrubs may include Arctostaphylos uva-ursi, Artemisia tridentata, Mahonia repens, Paxistima myrsinites, Rosa woodsii, Shepherdia canadensis, and Symphoricarpos albus. Scattered tall shrubs Amelanchier alnifolia and Prunus virginiana may be present. The relatively sparse herbaceous layer is a mixture of graminoids and forbs and is often dominated by Calamagrostis rubescens, Carex geyeri, Lathyrus lanszwertii, or Thalictrum fendleri. Other common graminoids include Bromus carinatus, Carex rossii, Elymus glaucus, Elymus trachycaulus, and Achnatherum occidentale (= Stipa occidentalis). Forbs, such as Achillea millefolium, Arnica cordifolia, Balsamorhiza spp., Fragaria vesca, Geranium spp., Lupinus argenteus, Osmorhiza berteroi (= Osmorhiza chilensis), and Potentilla spp., may be present. The exotic species Poa pratensis and Taraxacum officinale are common in livestock-impacted stands. Diagnostic of this forest alliance is the codominance of Pinus contorta and Populus tremuloides in the tree canopy.

2.1.2 Ecological System: Rocky Mountain Lodgepole Pine Forest (CES306.960)Overview:

This matrix forming system is widespread in upper montane to subalpine elevations of the Rocky Mountains, Intermountain region, and north into the Canadian Rockies. These are subalpine forests where the dominance of Pinus contorta is related to fire history and topo-edaphic conditions. Most forests in this ecological system are early to mid-successional forests which developed following fires. Following stand-replacing fires, Pinus contorta will rapidly colonize and develop into dense, even-aged stands. This system consists of extensive stands of pure lodgepole pine or, to a lesser extent, stands in association with other conifer species.

Characteristic Species:These forests are dominated by Pinus contorta with shrub, grass, or barren understories. Sometimes there are intermingled mixed conifer/Populus tremuloides stands with the latter occurring with inclusions of deeper, typically fine-textured soils. The shrub stratum may be conspicuous to absent; common species include Arctostaphylos uva-ursi, Ceanothus velutinus, Linnaea borealis, Mahonia repens, Purshia tridentata, Spiraea betulifolia, Spiraea douglasii, Shepherdia canadensis, Vaccinium caespitosum, Vaccinium scoparium, Vaccinium myrtillus, Symphoricarpos albus, and Ribes spp. Shrub and herbaceous layers are often poorly developed in lodgepole pine forests, and plant species diversity is low. This low understory diversity is probably related to the single age class and dense canopy of many stands.

Environment:Soils supporting these forests are typically well-drained, gravelly, have coarse textures, are acidic, and rarely formed from calcareous parent materials. In Colorado, lodgepole pine forests generally occur between 8,000-10,000 feet on gentle to steep slopes on all aspects.

Dynamics: Pinus contorta is an aggressively colonizing, shade-intolerant conifer which usually occurs in lower subalpine forests in the major ranges of the western United States. Establishment is episodic and linked to stand-replacing disturbances, primarily fire. The frequency of natural fires in Rocky Mountain lodgepole pine stands ranges from a few years to 200 or more years (Davis et al. 1980). Low to moderate serverity surface fires are likely to have a return interval on the order of a few decades, while stand-replacing fires are generally less frequent (Crane 1982).

Variation:


The incidence of serotinous cones varies within and between varieties of Pinus contorta, being most prevalent in Rocky Mountain populations. Closed, serotinous cones appear to be strongly favored by fire, and allow rapid colonization of fire-cleared substrates (Burns and Honkala 1990). Hoffman and Alexander (1980, 1983) report that in stands where Pinus contorta exhibits a multiaged population structure, with regeneration occurring, there is typically a higher proportion of trees bearing nonserotinous cones.

Some Pinus contorta forests will persist on sites that are too extreme for other conifers to establish. These include excessively well-drained pumice deposits, glacial till and alluvium on valley floors where there is cold air accumulation, warm and droughty shallow soils over fractured quartzite bedrock, and shallow moisture-deficient soils with a significant component of volcanic ash.

2.1.2.1 Alliance: Pinus Contorta Forest Alliance (A.118)

This alliance is found in the upper montane and subalpine zone of most major mountain ranges of the western U.S., as well as forested dunes of the Oregon and northern California coast. Pinus contorta occupies the broadest array of habitats of any coniferous species in the western United States. Forests included in this alliance are characterized by a closed to moderately open tree canopy that is dominated by the conifer Pinus contorta. Stands may be even-aged or multi-aged depending on geographic location, edaphic characteristics, and how the stands were established following wildfire. Shrub and herbaceous layers may be present or absent depending on tree canopy. Other tree species, such as Abies grandis, Abies lasiocarpa, Picea engelmannii, Tsuga heterophylla, Tsuga mertensiana, or Pseudotsuga menziesii, may be present to abundant as seedlings and saplings. Associated shrub and herbaceous species vary across the range of this alliance. In the coastal dunes stands important species include Gaultheria shallon, Vaccinium ovatum, Rhododendron macrophyllum, and Morella californica (= Myrica californica). Herbaceous cover is very sparse. Common subalpine and montane shrub species include Arctostaphylos uva-ursi, Arctostaphylos patula, Arctostaphylos nevadensis, Ceanothus velutinus, Linnaea borealis, Mahonia repens, Purshia tridentata, Spiraea betulifolia, Spiraea douglasii, Shepherdia canadensis, Vaccinium caespitosum, Vaccinium scoparium, Vaccinium membranaceum, Symphoricarpos albus, and Ribes spp. The cover of the herbaceous stratum can be dominated by either graminoids or perennial forbs and tends to vary inversely with shrub cover. Important graminoids include Carex pensylvanica, Carex geyeri, Carex rossii, Calamagrostis rubescens, Danthonia californica, Elymus glaucus, or Achnatherum occidentale (= Stipa occidentalis). Important forbs are Arnica cordifolia, Chimaphila umbellata, Orthilia secunda, Osmorhiza berteroi (= Osmorhiza chilensis), Pedicularis racemosa, Xerophyllum tenax, and Thalictrum spp. Diagnostic of this upland forest alliance is the dominance of Pinus contorta in the tree canopy without significant regeneration of Abies lasiocarpa or similar shade-tolerant species.

2.2 Group: Picea engelmannii - Abies lasiocarpa - Pinus contorta Dry-Mesic Forest & Woodland Group

2.2.1 Ecological System: Rocky Mountain Subalpine Dry-Mesic Spruce-fir Forest and Woodland (CES.306.828)

Overview:Spruce-fir dry-mesic forest and spruce-fir moist-mesic forest ecological systems form the primary matrix systems of the montane and subalpine zones of the Southern Rocky Mountains ecoregion. These systems comprise a substantial part of the subalpine forests of the Cascades and Rocky Mountains from southern British Columbia east into Alberta, south into New Mexico and the Intermountain region.


Despite their wide distribution, the tree canopy characteristics are remarkably similar rangewide, with Picea engelmannii and Abies lasiocarpa dominating either mixed or alone. Disturbances include occasional blow-down, insect outbreaks and stand-replacing fire.

Characteristic species: Picea engelmannii and Abies lasiocarpa dominate the canopy, either mixed or alone. Pinus contorta is common in many occurrences and patches of pure Pinus contorta are not uncommon, as well as mixed conifer/Populus tremuloides stands. Xeric species may include Juniperus communis, Linnaea borealis, Mahonia repens, or Vaccinium scoparium. Mesic understory shrubs include Rhododendron albiflorum, Amelanchier alnifolia, Rubus parviflorus, Ledum glandulosum, Phyllodoce empetriformis, and Salix spp. Herbaceous species include Actaea rubra, Maianthemum stellatum, Cornus canadensis, Erigeron eximius, Saxifraga bronchialis, Luzula glabrata var. hitchcockii, or Calamagrostis canadensis.

Pine martens (Martes americana) are primarily a spruce-fir obligate species that require a healthy and sizeable occurrence of mature forest and are an indicator of a healthy and viable occurrence of the spruce-fir system.

Environment:These are the matrix forests of the subalpine zone, with elevations ranging from 5,000-11,000 ft (1,525 to 3,355 m). Sites within this system are cold year-round, and precipitation is redominantly in the form of snow, which may persist until late summer. Snowpacks are deep and late-lying, and summers are cool. Frost is possible almost all summer and may be common in restricted topographic basins and benches. In some areas, such as Wyoming, Picea engelmannii dominated forests are on limestone or dolomite, while nearby codominated spruce-fir forests are on granitic or volcanic rocks.

Moist-mesic occurrences are typically found in locations with cold-air drainage or ponding, or where snowpacks linger late into the summer, such as north-facing slopes and high-elevation ravines. They can extend down in elevation below the subalpine zone in places where cold-air ponding occurs; northerly and easterly aspects predominate. These forests are found on gentle to very steep mountain slopes, high-elevation ridgetops and upper slopes, plateaulike surfaces, basins, alluvial terraces, well-drained benches, and inactive stream terraces.

Dynamics:Picea engelmannii can be very long-lived, reaching 500 years of age. Fire is an important disturbance factor, but fire regimes have a long return interval and so are often stand-replacing. Picea engelmannii can rapidly recolonize and dominate burned sites, or can succeed other species such as Pinus contorta or Populus tremuloides. Due to great longevity, Pseudotsuga menziesii may persist in occurrences of this system for long periods without regeneration. Old-growth characteristics in Picea engelmannii forests will include treefall and windthrow gaps in the canopy, with large downed logs, rotting woody material, tree seedling establishment on logs or on mineral soils unearthed in root balls, and snags.

Fire, spruce-beetle outbreaks, avalanches, and windthrow all play an important role in shaping the dynamics of spruce-fir forests. Fires in the subalpine forest are typically stand replacing, resulting in the extensive exposure of mineral soil and initiating the development of new forests. Stand replacing fires are estimated to occur at intervals of about 300 years for dry-mesic areas, and longer (350-400 years) for more mesic sites (Romme and Knight 1981). Fire return intervals, intensity, and extent will of course depend on a variety of local environmental factors. Fire is much less important in krummholz communities (Crane 1982). Depending on site conditions, spruce and fir may share the post-fire site with


shade-intolerant species such as lodgepole pine, limber pine, and quaking aspen. Many stands in the subalpine zone of the Colorado Front range are of post-fire origin from about the mid 1700’s (Veblen 1986).

Spruce beetle (Dendroctonus rufipennis) outbreaks may be as significant as fire in the development of spruce-fir forests. In addition to fires and beetle kill, wind disturbance in spruce-fir forests has been well documented (Schaupp et al. 1999). Blowdowns involving multiple treefalls add to the mosaic of spruce-fir stands.

Under a natural disturbance regime, subalpine forests were probably characterized by a mosaic of stands in various stages of recovery from disturbance, with old-growth just one part of the larger forest mosaic (Peet 1981). This mosaic was constantly changing and highly variable from place to place, so the extent of presettlement old-growth forest is uncertain. The current subalpine landscape is perhaps more homogeneous (in terms of stand age) than in the presettlement era, mainly due to the synchronizing effect of very extensive, regional disturbance (e.g., fires in the mid 1700s, beetle outbreak in the mid to late 1800’s (Peet 1981)).

Variation: Individual community types may be matrix or large patch in character, though most typically occur as a mosaic of large patches across the landscape. Spruce-fir dominated stands occur on all but the most xeric sites above 10,000 ft (3,100 m), and in cool, sheltered valleys at elevations as low as 8,200 ft (2,500 m). The relative dominance of the two canopy tree species and the understory composition vary substantially over a gradient from excessively moist to xeric sites (Peet 1981). The mesic spruce-fir type occurs on cool, sheltered, but well-drained sites above 8,850 ft (2,700 m) and is one of the most widespread forest types in the subalpine zone. Open slopes above 9,850 ft (3,000 m) are typically characterized by Peet’s (1981) xeric spruce-fir type, with varying amounts of lodgepole and limber pine. Towards lower elevations, the spruce-fir types give way, often along abrupt fire-induced boundaries, to lodgepole pine or aspen-dominated forests.

Spruce-fir forest also exhibit changes with latitude including treeline elevation, species composition, and dominance. Abies lasiocarpa decreases in importance relative to Picea engelmannii with increasing distance from the region of Montana and Idaho where maritime air masses influence the climate. Fir increases in importance with increasing latitude, and shares dominance with spruce at tree line over the northern half of the Southern Rocky Mountains ecoregion. Treeline occurs at over 12,450 ft (3800 m) at the southern end of the Southern Rocky Mountain ecoregion, whereas it does not exceed 11,150 ft (3400 m) at the northern end (Peet 1978). Possible explanations for this geographic variation include a genetic differentiation in Abies at the southern end of the ecoregion and variation in moisture or exposure conditions experienced by these high-elevation forests. That the degree of dominance by Abies could, in part, reflect the degree of drought stress or exposure of the site is suggested by the absence of Abies in the forests of Pikes Peak, a xeric mountain (Peet 1978).

2.2.1.1 Alliance: Picea engelmannii Forest Alliance (A.164)

This forest alliance occurs in the upper montane or subalpine zone from the Oregon Cascades and Rocky Mountains, south into Arizona and New Mexico. Overall, this alliance is found in similar elevational ranges as Abies lasiocarpa, but occurs on sites either too cold or too dry for Abies lasiocarpa dominance. Sites include gentle to very steep mountain slopes, ridgetops, plateaus, basins, alluvial terraces and benches. All aspects are represented, but northerly and easterly aspects predominate, and southerly aspects are found only at higher elevations. Soils are variable, but often gravelly or rocky, relatively


shallow with thick duff layers and sometimes high moss or lichen cover. Forests included in this alliance are dominated by Picea engelmannii. In early to mid-successional stands, other conifers can be dominant or codominant, but Picea engelmannii (or Picea engelmannii X glauca hybrids in western Montana) are the most abundant seedlings and saplings. Associates vary geographically. Common associated conifers can include Pseudotsuga menziesii, Larix occidentalis, Pinus contorta, Abies lasiocarpa, Pinus albicaulis, and Pinus flexilis. Pinus aristata, Pinus strobiformis, Picea pungens, and Abies concolor are common in southern stands. The shrub layer is often absent, but when present is often dominated by species of Vaccinium. Other common shrub species may include Acer glabrum, Cornus canadensis, Holodiscus dumosus, Juniperus communis, Linnaea borealis, Lonicera utahensis, Physocarpus malvaceus, Ribes spp., Shepherdia canadensis, Spiraea betulifolia, or Symphoricarpos albus. The herbaceous layer is often dominated by perennial forbs. Graminoids are generally sparse. Diagnostic characteristics of these forests are that the average tree canopy is greater than 60% cover with Picea engelmannii often codominant in the tree canopy as well as being the predominant conifer in the tree-regeneration layer alliance.

2.3 Group: Populus tremuloides Rocky Mountain Forest & Woodland Group

2.3.1 Ecological System: Rocky Mountain Aspen Forest and Woodland (CES306.813)Overview:This widespread ecological system occurs throughout much of the western U.S. and north into Canada, although it is more common in the montane and subalpine zones of the southern and central Rocky Mountains. In Colorado this system is quite common on the west slope, with smaller stands represented on the east slope. These are upland forests and woodlands dominated by Populus tremuloides without a significant conifer component (<25% relative tree cover). They usually occur as a mosaic of many plant associations and may be surrounded by a diverse array of other systems, including grasslands, wetlands, coniferous forests, etc.

Characteristic Species:Occurrences have a somewhat closed canopy of trees of 15-65 ft (5-20 m) tall, dominated by Populus tremuloides. Conifers that may be present but never codominant include Abies concolor, Abies lasiocarpa, Picea engelmannii, Picea pungens, Pinus ponderosa, and Pseudotsuga menziesii. Conifer species may contribute up to 15% of the tree canopy before the occurrence is reclassified as a mixed conifer occurrence. Common shrubs include Acer glabrum, Amelanchier alnifolia, Artemisia tridentata, Juniperus communis, Prunus virginiana, Rosa woodsii, Shepherdia canadensis, Symphoricarpos oreophilus, and the dwarf-shrubs Mahonia repens and Vaccinium spp. The herbaceous layers may be lush and diverse. Common graminoids may include Bromus carinatus, Calamagrostis rubescens, Carex siccata (= Carex foenea), Carex geyeri, Carex rossii, Elymus glaucus, Elymus trachycaulus, Festuca thurberi, and Hesperostipa comata. Associated forbs may include Achillea millefolium, Eucephalus engelmannii (= Aster engelmannii), Delphinium spp., Geranium viscosissimum, Heracleum sphondylium, Ligusticum filicinum, Lupinus argenteus, Osmorhiza berteroi (= Osmorhiza chilensis), Pteridium aquilinum, Rudbeckia occidentalis, Thalictrum fendleri, Valeriana occidentalis, Wyethia amplexicaulis, and many others. Exotic grasses such as the perennials Poa pratensis and Bromus inermis and the annual Bromus tectorum are often common in occurrences disturbed by grazing.

Environment:Elevations generally range from 5,000-10,000 feet (1,525 to 3,050 m), but may be lower in some regions. Topography is variable, sites range from level to steep slopes. Occurrences at high elevations are restricted by cold temperatures and are found on warmer southern aspects. At lower elevations


occurrences are restricted by lack of moisture and are found on cooler north aspects and mesic microsites. The soils are typically deep and well developed with rock often absent, and texture ranges from sandy loam to clay loams. Parent materials are variable and may include sedimentary, metamorphic or igneous rocks, but this type appears to grow best on limestone, basalt, and calcareous or neutral shales (Mueggler 1988).

Distribution of this ecological system is primarily limited by adequate soil moisture required to meet its high evapotranspiration demand, and secondarily is limited by the length of the growing season or low temperatures. Climate is temperate with a relatively long growing season, typically cold winters and deep snow. Mean annual precipitation is greater than 15 in (38 cm) and typically greater than 20 in (50 cm), except in semi-arid environments where occurrences are restricted to mesic microsites such as seeps or large snow drifts.

Dynamics:Occurrences in this ecological system often originate, and are likely maintained, by stand-replacing disturbances such as crown fire, disease and windthrow, or clearcutting by man or beaver. The stems of these thin-barked, clonal trees are easily killed by ground fires, but they can quickly and vigorously resprout in densities of up to 30,000 stems per hectare (Knight 1994). The stems are relatively short-lived (100-150 years), and the occurrence will succeed to longer-lived conifer forest if undisturbed. Occurrences are favored by fire in the conifer zone (Mueggler 1988). With dequate disturbance a clone may live many centuries. Although Populus tremuloides produces abundant seeds, seedling survival is rare because the long moist conditions required to establish them are rare in these habitats. Superficial soil drying will kill seedlings (Knight 1994).

Variation:Because of the open growth form of Populus tremuloides, enough light can penetrate for lush understory development. Depending on available soil moisture and other factors like disturbance, the understory structure may be complex with multiple shrub and herbaceous layers, or simple with just an herbaceous layer. The herbaceous layer may be dense or sparse, dominated by graminoids or forbs.

2.3.1.1 Alliance: Populus tremuloides Forest Alliance (A.274)

This alliance is widespread in the western United States, the northern Great Plains, and extends into the western Great Lakes area. Stands are found on a variety of landscape positions but are consistently in mesic habitats. In the Midwest, average precipitation is usually enough to support associations in this alliance across broad areas of the landscape where other conditions favor it. In the Great Plains and western U.S., forests in this alliance are typically restricted to areas with above-average available moisture (lower slopes, near watercourses, basins) or where moisture stress is lessened (shaded canyons, cooler higher elevation sites, north-facing slopes). Stands in this alliance often occur between grasslands and other forest types. The soils are usually deep, well-developed, and loamy. Stands in this alliance often originate following disturbance. The dominant species of the canopy is Populus tremuloides. In the midwestern United States, Quercus macrocarpa and Betula papyrifera are common associates and can even be codominant in some stands. The shrub layer can be made up of several shrubs common to the Great Plains, including Corylus cornuta, Corylus americana, Prunus virginiana, Symphoricarpos occidentalis, Amelanchier alnifolia, and Rubus spp. In wetter stands Cornus spp. and Salix spp. may also be present. The herbaceous layer may contain Aralia nudicaulis, Carex pensylvanica, Maianthemum canadense, Maianthemum stellatum, Viola spp., and Thalictrum dioicum. In the western United States common associates include Acer glabrum, Amelanchier alnifolia, Symphoricarpos oreophilus, Bromus carinatus, Calamagrostis rubescens, Thalictrum fendleri, Carex siccata (= Carex


foenea), Carex geyeri, Carex rossii, and Hesperostipa comata (= Stipa comata). In the Dakotas and Wyoming, these stands may remain successionally stable for many dozens of years, while in the more mesic, eastern portion of the range, Populus tremuloides forests succeed to other community types much more quickly. Populus tremuloides (the species) reaches Texas, Virginia, and West Virginia, but it is unclear whether Populus tremuloides communities occur in any of these states. Stands of Populus tremuloides in the Trans-Pecos of western Texas occur in ravines and on open talus slopes above 2134 m (7000 feet) elevation; they may best be treated as Populus tremuloides communities, or merely as other communities with a component of aspen. Texas stands of Populus tremuloides are of limited extent and variable in structure.

2.4 Group: Pinus flexilis - Pinus aristata Rocky Mountain Subalpine-Montane Woodland Group

2.4.1 Ecological System: Rocky Mountain Subalpine-Montane Limber-Bristlecone Pine Woodland (CES306.819)

Overview:This large patch ecological system occurs throughout the Rocky Mountains on dry, rocky ridges and slopes. Although it can be found near upper treeline above the matrix spruce-fir forest, it also occurs at lower elevations. These are typically woodlands of xeric, high elevation sites, but may also extend down to the lower montane in the central and northern Rocky Mountains, particularly along the Front Range north into Canada. Limber and bristlecone pine do not necessarily occur together, but the two species occupy a similar ecological niche. Where the two are co-occuring, limber pine is often confined to the lower portion of its potential habitat. Pinus aristata is more-or-less endemic to the Southern Rocky Mountian ecoregion, reaching its northernmost station in Gilpin County, Colorado. Pinus flexilis is more widely distributed and also occurs in mixed conifer systems. It largely replaces bristlecone pine north of I-70.

Characteristic species: The open tree canopy is often patchy and is strongly dominated by Pinus flexilis or Pinus aristata with the latter restricted to southern Colorado and northern New Mexico. Other trees such as Juniperus spp., Pinus contorta, Pinus ponderosa, or Pseudotsuga menziesii are occasionally present. Arctostaphylos uva-ursi, Cercocarpus ledifolius, Juniperus communis, Mahonia repens, Purshia tridentata, Ribes montigenum, or Vaccinium spp. may form an open shrub layer in some stands. The herbaceous layer, if present, is generally sparse and composed of xeric graminoids, such as Calamagrostis purpurascens, Festuca arizonica, Festuca idahoensis, Festuca thurberi, Pseudoroegneria spicata, or alpine plants such as Trifolium dasyphyllum.

Environment:Sites are harsh, exposed to desiccating winds with rocky substrates and a short growing season that limit plant growth. Higher elevation occurrences are found well into the subalpine - alpine transition on wind-blasted, mostly south to west-facing slopes and exposed ridges. Pinus aristata forests are typically found on steep, south-facing slopes from 8,850 to 12,140 ft (2,700-3,700 m). Pinus flexilis woodlands occupy similar habitats, but may occur at lower elevations than P. aristata. Calcareous substrates are important for P. flexilis-dominated communities in the northern Rocky Mountains and possibly elsewhere.

Dynamics:Both bristlecone and limber pine are slow-growing, long-lived species in which individuals may live for


1000 or more years. Fire is an important source of disturbance that facilitates stand regeneration in this system. Older woodlands are often broadly even-aged stands where seedlings are nearly absent, while areas that have recently burned may have abundant seedlings. Bristlecone is somewhat more tolerant of fire than is limber pine; however, both species appear to depend on fire for regeneration. Regeneration of limber pine on burned areas is largely due to the germination of seeds cached by Clark’s nutcrackers.

Variation: This system is distinguished from lower montane and foothill limber pine stands in Wyoming and Montana. The foothill system is found at the lower treeline, below the zone of continuous Pinus ponderosa or Pseudotsuga menziesii woodlands and forest, and extends out into the eastern portions of these states in the foothill zones of mountain ranges, along rock outcrops, breaks along rivers, and on sheltered sites where soil moisture is slightly higher than surrounding grasslands.

2.4.1.1 Alliance: Pinus flexilis Woodland Alliance (A.540)

Woodlands included in this alliance occur intermittently from timberline to lower montane and foothill zones throughout much of the Rocky Mountains, on escarpments and other geographic breaks in the northwestern Great Plains and basins and plains in Wyoming, and in mountains in the Great Basin and southern California. Elevations range from 850-3500 m. Sites are typically xeric on exposed, wind-swept rocky slopes and ridges from subalpine to foothills and prairie breaks. Some stands are on eroded substrates and resemble 'badlands' while others may occur on lava flows. These open woodlands occur on all aspects, but are most common on dry south- and west-facing slopes. Soils are typically shallow, skeletal and coarse-textured, such as gravelly, sandy loams or loams, but may include alkaline clays. Exposed bedrock is common and many stands have over 50% bare soil. The vegetation is characterized by an open canopy typically 3-10 m tall, but individuals may reach 15 m. Stands are solely dominated or codominated by the evergreen needle-leaved tree Pinus flexilis. Other trees species that may be present to codominant vary by geography and elevation zones throughout the woodland's range and include Pinus albicaulis, Picea engelmannii, or Pseudotsuga menziesii in the subalpine; Pinus contorta, Pinus ponderosa, or Pseudotsuga menziesii in the montane zone; and Juniperus osteosperma or Juniperus scopulorum in the lower montane transition zone from woodlands to grasslands or shrublands. In California, other associates may include Abies concolor, Pinus albicaulis, Pinus balfouriana, Pinus contorta, Pinus jeffreyi, and Pinus longaeva. The understory vegetation is typically sparse because sites are dry and have a large cover of rock. A sparse shrub layer may be present that includes tall shrubs such as Artemisia tridentata, Cercocarpus ledifolius, Jamesia americana, Rhus trilobata, Shepherdia canadensis, and Symphoricarpos oreophilus. Arctostaphylos uva-ursi, Artemisia arbuscula, Artemisia nova, Juniperus communis, Mahonia repens, Purshia tridentata, and Yucca glauca are the most frequent low shrubs. The herbaceous layer often dominates the understory and is composed primarily of graminoids such as Bouteloua gracilis, Calamagrostis purpurascens, Carex rossii, Festuca idahoensis, Festuca campestris, Leucopoa kingii (= Festuca kingii), Koeleria macrantha, Achnatherum hymenoides (= Oryzopsis hymenoides), and Pseudoroegneria spicata. Scattered forbs may include species of Achillea, Antennaria, Arenaria, Arnica, Astragalus, Erigeron, Eriogonum, Hymenopappus, Hymenoxys, Liatris, Sedum, Solidago, and Thermopsis.

3 Macrogroup: Rocky Mountain & Great Basin Riparian Forest3.1 Group: Picea engelmannii - Picea pungens - Populus angustifolia Riparian Forest

3.1.1 Ecological System: Rocky Mountain Lower Montane Riparian Woodland and


Shrubland (CES306.821)Overview: The Rocky Mountain Lower Montane Riparian Woodland and Shrubland system is found throughout the Rocky Mountain region within a broad elevation range from approximately 2950 to 9100 ft (900 to 2800 m). In Colorado this system is primarily found in the western half of the state at elevations above 5100 ft (1550 m), where it occurs within the flood zone of rivers, on islands, sand or cobble bars, and immediate streambanks. This system often occurs as a mosaic of multiple communities that are tree-dominated with a diverse shrub component.

Characteristic Species:Dominant trees may include Acer negundo, Populus angustifolia, Populus x acuminata, Populus balsamifera, Populus deltoides, Populus fremontii, Pseudotsuga menziesii, Picea pungens, Salix amygdaloides, or Juniperus scopulorum. Dominant shrubs include Acer glabrum, Alnus incana, Betula occidentalis, Cornus sericea, Crataegus rivularis, Forestiera pubescens, Prunus virginiana, Rhus trilobata, Salix monticola, Salix drummondiana, Salix exigua, Salix irrorata, Salix lucida, Shepherdia argentea, or Symphoricarpos spp. The exotic trees Elaeagnus angustifolia, Tamarix spp., and Salix fragilis are common in some stands. The upland vegetation surrounding this riparian system ranges from grasslands to forests.

Environment: This ecological system is found within the flood zone of rivers, on islands, sand or cobble bars, and immediate streambanks. It can form large, wide occurrences on mid-channel islands in larger rivers or narrow bands on small, rocky canyon tributaries and well-drained benches. It is also typically found in backwater channels and other perennially wet but less scoured sites, such as floodplains swales and irrigation ditches. It may also occur in upland areas of mesic swales and hillslopes below seeps and springs. The climate in the range of this system is continental with typically cold winters and hot summers. Surface water is generally high for variable periods. Soils are typically alluvial deposits of sand, clays, silts and cobbles that are highly stratified with depth due to flood scour and deposition. Highly stratified profiles consist of alternating layers of clay loam and organic material with coarser sand or thin layers of sandy loam over very coarse alluvium. Soils are fine-textured with organic material over coarser alluvium. Some soils are more developed due to a slightly more stable environment and greater input of organic matter.

Dynamics: This system is dependent on a natural hydrologic regime, especially annual to episodic flooding. These woodlands and shrublands grow within a continually changing alluvial environment due to the ebb and flow of the river, and riparian vegetation is constantly being “re-set” by flooding disturbance.

Variation:This ecological system contains early-, mid- and late-seral riparian plant associations. It also contains non-obligate riparian species. Cottonwood communities are early-, mid- or late-seral, depending on the age class of the trees and the associated species of the occurrence (Kittel et al. 1999). Mature cottonwood occurrences do not regenerate in place, but by "moving" up and down a river reach. Over time a healthy riparian area supports all stages of cottonwood communities (Kittel et al. 1999).


3.1.1.1 Alliance: Populus angustifolia Temporarily Flooded Woodland (A.641)

This riparian alliance occurs in lower to mid-montane floodplains and streams throughout much of the western U.S., north into Alberta, Canada. Sites include narrow benches along narrow stream channels and on large floodplains along broad, meandering rivers. Stands are usually found between 0.5-2 m above the stream channel. The alluvial soils are highly permeable with large amounts of coarse fragments in the subsurface horizons. Vegetation within this alliance is characterized by a typically open-tree canopy and is dominated by Populus angustifolia with 20-70% cover. Other trees can include Acer negundo, Juniperus scopulorum, Picea pungens, Pinus ponderosa, and Picea engelmannii in the Rocky Mountains and Populus balsamifera or Populus deltoids in the northern areas. The shrub layer can be very dense and diverse with 10-80% cover of Cornus sericea, Alnus incana, Amelanchier utahensis, Rosa woodsii, Acer glabrum, Quercus gambelii, Salix spp., Crataegus rivularis or Lonicera involucrate. Juniperus deppeana, Brickellia californica, and Alnus oblongifolia have been reported from stands in New Mexico and Arizona, as has significant cover of woody vines such as Vitis arizonica, Parthenocissus quinquefolia (= Parthenocissus inserta), Clematis ligusticifolia, and Humulus lupulus var. lupuloides (= Humulus americanus). Symphoricarpos occidentalis and Salix exigua have been reported with significant cover in stands from Alberta. The forb layer is moderately dense to absent and includes species such as Maianthemum stellatum, Heracleum maximum (= Heracleum lanatum), Achillea millefolium, and Osmorhiza depauperata. Graminoid cover is insignificant in New Mexico and Arizona. Diagnostic of this alliance is the dominance of Populus angustifolia in the tree canopy in woodlands that are briefly flooded during the growing season.

3.1.1.1.1 Association: Populus angustifolia / Alnus incana Woodland (CEGL002642)

This plant association is found in narrow bands on the floodplains and benches of montane streams (1900-2700 m elevation) in Colorado and New Mexico, primarily in the southern Rocky Mountains. Stands occur on banks and benches along narrow streams with active floodplains in broad valleys and narrow canyons. These narrow streams may be higher gradient, fast-moving or low gradient, highly sinuous stream reaches. Substrates are typically deep sand or shaly sandy loam but may be stratified with finer-textured alluvial layers. The vegetation is characterized by a open to nearly closed deciduous tree canopy of Populus angustifolia with a dense layer of Alnus incana lining the streambank. Populus angustifolia is always present, although sometimes only as a sapling. A variety of riparian and upland tree species may also be present. Alnus incana is the most abundant shrub within the stand with a minimum of 10% cover. Other shrubs may include Salix bebbiana, Salix monticola, Salix drummondiana, Salix ligulifolia (= Salix eriocephala var. ligulifolia), Salix lucida ssp. caudata, Salix exigua, Rosa woodsii, Rubus idaeus, Acer glabrum, and Betula occidentalis. If present, Cornus sericea does not codominate. Herbaceous growth is generally a sparse mixture of mesic and wetland graminoids and forbs.

3.1.2 Ecological System: Rocky Mountain Subalpine-Montane Riparian Woodland (CES306.833)

Overview:This linear riparian woodland system is comprised of seasonally flooded forests and woodlands found at montane to subalpine elevations in the Rocky Mountain cordillera, from southern New Mexico north into Montana, and west into the Intermountain region and the Colorado Plateau. This system contains the conifer and aspen woodlands that line first- and second-order montane streams. Although many of the association names have been simplified to include a single overstory species, Colorado occurrences of the Abies lasiocarpa or Picea engelmannii series typically contain both species.

Characteristic Species:


Dominant tree species include Abies lasiocarpa, Picea engelmannii, Pseudotsuga menziesii, Picea pungens, Populus tremuloides, and Juniperus scopulorum. Other trees that may be present include Alnus incana, Abies concolor, Pinus contorta, Populus angustifolia, Acer negundo, and Juniperus osteosperma.

Environment:These are communities tolerant of periodic flooding and high water tables. Snowmelt moisture in this system may create shallow water tables or seeps for a portion of the growing season. Stands in Colorado typically occur at elevations between 6,000-10,830 feet (1,800-3,300 m) and are confined to specific riparian environments occurring on floodplains or terraces of rivers and streams, in V-shaped, narrow valleys and canyons (where there is cold-air drainage). Less frequently, occurrences are found in moderate-wide valley bottoms on large floodplains along broad, meandering rivers, and on pond or lake margins.

Dynamics:Many first- and second-order streams run through subalpine spruce-fir or aspen forests providing habitats for obligate riparian shrubs, forbs, and grasses, forming riparian Abies lasiocarpa-Picea engelmannii or Populus tremuloides plant associations. Although Abies lasiocarpa and Picea engelmannii are not obligate riparian species, the two species strongly influence many subalpine riparian ecosystems. The fire frequency of Abies lasiocarpa and Picea engelmannii in moist areas is lower than on the dry upland sites, but the trees in riparian areas do burn. Following a crown fire, both Abies lasiocarpa and Picea engelmannii colonize the burned area. Picea engelmannii establishment is greater for the first several decades, but as the ground becomes shaded, Abies lasiocarpa seedlings increase in abundance.

Variation:This system is distinguished from the adjacent upland forest and woodland communities by the presence of obligate riparian species. Community composition may be determined by a combination of floodplain width and steepness, streamflow volume and flooding patterns, and adjacent upland vegetation.

3.1.2.1 Alliance: Populus tremuloides Temporarily Flooded Forest Alliance (A.300)

This alliance contains a number of communities found from the Great Lakes to the western and southwestern United States, with an outlier in the Central Appalachians. Most stands of this alliance are found in riparian zones. Some may be near lakes where the ground is flooded or saturated for a short time in the spring. The moderate to closed tree canopy is dominated by Populus tremuloides, sometimes with Populus balsamifera codominant. More open stands have a prominent shrub layer containing species such as Alnus incana, Cornus sericea, and Salix spp. The sole reference cited for Populus tremuloides Canyon Formation Forest (CEGL000576) does not mention Populus tremuloides.

3.1.2.1.1 Association: Populus tremuloides / Salix drummondiana Forest (CEGL002902)

This forest association is currently only known from Great Sand Dunes National Park and Preserve in Colorado, and the following description is based on occurrences there. Additional information will be added as it becomes available. This association occurs in streambeds and drainage channels at 2710 to 3150 m elevation. Terrain is flat to gently sloping and southwest-facing. This palustrine type ranges from seasonally flooded to permanently flooded with moderately drained sandy loam soils. Litter and duff dominate the ground cover with a significant portion of wood and rock. This forested association is dominated by Populus tremuloides in the canopy and subcanopy layers with cover ranging from 30-50%. The tall-shrub layer is dominated by Salix drummondiana with 10-20% cover. Other shrub species that may be present include Acer glabrum, Lonicera involucrata, Rosa woodsii, Ribes spp., Rubus idaeus, and


Sambucus racemosa. The herbaceous layer is sparse and generally includes both graminoids, such as Calamagrostis canadensis and Carex spp., and forbs, such as Actaea rubra, Artemisia franserioides, Fragaria virginiana, Geranium richardsonii, Heracleum maximum, Oreochrysum parryi, and Thalictrum fendleri.

4 Macrogroup: Rocky Mountain-Vancouverian Subalpine & High Montane Mesic Grass & Forb Meadow

4.1 Group: Festuca arizonica - Festuca thurberi - Muhlenbergia montana Grassland Group

4.2 Extra Tite (for Bromopsis inermis Alliance)4.2.1 Ecological System: Southern Rocky Mountain Montane-Subalpine Grassland

(CES306.824)Overview: This ecological system typically occurs between 2200-3000 m (in the Colorado Rockies) on flat to rolling plains and parks or on lower sideslopes that are dry. These large patch grasslands are intermixed with matrix stands of spruce-fir, lodgepole, ponderosa pine, and aspen forests. In limited circumstances (e.g., South Park in Colorado) they form the "matrix" of high-elevation plateaus. Although the largest occurrences are primarily within Colorado, examples are scattered throughout the region from Wyoming to New Mexico.

Characteristic Species: These large patch grasslands are intermixed with forests of spruce-fir, lodgepole, ponderosa pine, mixed conifers, and aspen. Within the subalpine zone, forbs tend to be more prominent at higher elevations, and shrubs at lower elevations (Turner and Paulsen 1976). Associations are variable depending on site factors such as slope, aspect, precipitation, etc., but generally lower elevation montane grasslands are more xeric and dominated by Muhlenbergia spp., Pseudoroegneria spicata, Festuca arizonica, and Festuca idahoensis, while upper montane or subalpine grasslands are more mesic and may be dominated by Festuca thurberi or Danthonia intermedia. Danthonia parryii is found across most of the elevational range of this system. Montane grasslands in the Colorado Front Range are often dominated by Leucopoa kingii or Muhlenbergia montana (Peet 1981). In the San Juan Mountains of southwestern Colorado, these grasslands are dominated by Festuca thurberi and other large bunch grasses (Jamieson et al. 1996). Grasses of the foothills and piedmont, such as Bouteloua gracilis, Bouteloua curtipendula, Hesperostipa comata, Koeleria macrantha, Pascopyrum smithii, Poa secunda, and Schizachyrium scoparium may be included in lower elevation occurrences. Higher, more mesic locations may support additional graminoid species including Agrostis spp., Carex spp., Festuca brachyphylla, Juncus drummondii, Phleum alpinum, Poa spp., or Trisetum spicatum. Woody species are generally sparse or absent, but occasional individuals from the surrounding forest communities may occur. Scattered dwarf shrubs may be found in some occurrences; species vary with elevation and location. Forbs are more common at higher elevations.

Environment: These are typically grasslands of forest openings and park-like expanses in the montane and subalpine coniferous forests. Although smaller montane grasslands are scattered throughout the Southern Rocky Mountains ecoregion, the largest occurrence by far (over a million acres) is on the valley floor of South Park in central Colorado. This ecological system typically occurs between 2,200 and 3,000 m (7,200 and 10,000 feet) on gentle to steep slopes, parks, or on lower sideslopes that are dry, but it may extend up


to 3,350 m (11,000 ft) on warm aspects.

The general climate in the range of this ecological system is typically montane to subalpine, characterized by cold winters and relatively cool summers, although temperatures are more moderate at lower elevations. Precipitation patterns differ between the east and west sides of the Continental Divide. In general, these grasslands experience long winters, deep snow, and short growing seasons. Average annual precipitation ranges between 20 to 40 inches, and the majority of this falls as snow (Turner and Paulsen 1976). Snowcover in some areas can last from October to May, and serves to insulate the plants beneath from periodic subzero temperatures. Other areas are kept free from snow by wind. Rapid spring snowmelt usually saturates the soil, and, when temperatures rise plant growth is rapid. Precipitation during the growing season is highly variable, but provides less moisture than snowmelt. Growing seasons are short, typically from June through August at intermediate locations, although frost can occur at almost any time.

The geology of the Southern Rocky Mountains is extremely complex. Not surprisingly, soils are also highly variable, depending on the parent materials from which they were derived and the conditions under which they developed. Podzolic soils have developed on most high mountain areas as a result of cool to cold temperatures, relatively abundant moisture, and the dominant coniferous forest vegetation. In the intermingled parks and open treeless slopes or ridges, grassland soils have developed. Soil texture is important in explaining the existence of montanesubalpine grasslands (Peet 2000). These grasslands often occupy the fine-textured alluvial of colluvial soils of valley bottoms, in contrast to the coarse, rocky material of adjacent forested slopes (Peet 2000). Soils are often similar to prairie soils, with a dark brown A-horizon that is rich in organic matter, well drained, and slightly acidic (Turner and Paulsen 1976). Other factors that may explain the absence of trees in this system are soil moisture (too much or too little), competition from established herbaceous species, cold air drainage and frost pockets, high snow accumulation, beaver activity, slow recovery from fire, and snow slides (Daubenmire 1943, Knight 1994, Peet 2000). Where grasslands occur intermixed with forested areas, the less pronounced environmental differences mean that trees are more likely to invade (Turner and Paulsen 1976).

Dynamics:A variety of factors, including fire, wind, cold-air drainage, climatic variation, soil properties, competition, and grazing have been proposed as mechanisms that maintain open grasslands and parks in forest surroundings. Observations and repeat photography studies in sites throughout the southern Rocky Mountains indicate that trees do invade open areas, but that the mechanisms responsible for this trend may differ from site to site. Anderson and Baker (2005) discounted fire suppression as the cause of tree invasions in Wyoming’s Medicine Bow Mountains, concluding that edaphic conditions were the most likely factor limiting tree establishment. In the San Juan Mountains of southeastern Colorado, Zier and Baker (2006) also found that the probability of tree invasion varied with forest type. Climatic variation, fire exclusion, and grazing appear to interact with edaphic factors to facilitate or hinder tree invasion in these grasslands (Zier and Baker 2006). In the Gunnison Basin, Schauer et al. (1998) identified seedling mortality as the primary factor preventing invasions of Engelmann spruce, but did not determine if this was due to competition from established grassland plants, or to edaphic conditions. The work of Coop and Givnish (2007) in the Jemez Mountains of northern New Mexico suggests that both changing disturbance regimes and climatic factors are linked to tree establishment in some montane grasslands. Pocket gophers (Thomomys spp.) are a widespread source of disturbance in montane-subalpine grasslands. The activities of these burrowing mammals result in increased aeration, mixing of soil, and infiltration of water, and are an important component of normal soil formation and erosion (Ellison 1946). In addition, Cantor and Whitham (1989) found that below-ground herbivory of


pocket gophers restricted establishement of aspen to rocky areas in Arizona mountain meadows. The interaction of multiple factors indicates that management for the maintenance of these montane and subalpine grasslands may be complex.Grazing by domestic livestock may act to override or mask whatever natural mechanism is responsible for maintaining an occurrence. Montane-subalpine grasslands were first grazed by domestic livestock beginning in the late 1800’s (Turner and Paulsen 1976). After lower-elevation, more accessible rangelands were overstocked in the 1870’s and 1880’s, use of montane and subalpine grasslands increased dramatically. By the turn of the century nearly all grazable land was being utilized, and much was already overgrazed (Turner and Paulsen 1976). As National Forests were established following the Organic Administration Act of 1897, regulation of grazing on these high elevation grasslands was instituted. Use levels peaked near the end of the first World War, and current use levels are substantially lower than the highest previous level (Turner and Paulsen 1976).

Floristic composition in these grasslands is influenced by both environmental factors and grazing history. Grazing is generally believed to lead to the replacement of palatable species with less palatable ones more able to withstand grazing pressure (Smith 1967, Paulsen 1975, Brown 1994, but see Stohlgren et al. 1999). In general, palatable grasses are replaced by nonpalatable forbs or shrubs under cattle grazing (Smith 1967), while palatable forbs are characteristically absent from grasslands with a long history of sheep use (Turner and Paulsen 1976). Annual species are uncommon except on heavily disturbed areas.

Variation:Montane and subalpine grasslands are generally interspersed in forest communities as park-like openings that vary in size from a few to several thousand acres. A few exceptional occurrences are much larger, and should be considered separately from the majority of occurrences.

4.2.1.1 Alliance: Danthonia parryi Herbaceous Alliance (A.1316)

These grasslands are found in small but re-occurring montane parks in the Pinus ponderosa forests of the northern Front Range of Colorado and in Wyoming. Elevations range from 2260-3350 m (7400-11,000 feet). Sites are moderately sloping (10-20%), with southern and western aspects. Soils are shallow to moderately deep (>60 cm) usually with less than 20% coarse fragments. Soil texture is sandy loam and pH 6.4-6.6. Parent material is alluvium and colluvium derived from gneiss and schist. These dry grasslands form a mosaic with the Pinus ponderosa forest. They have a moderately dense (60-70% cover) herbaceous layer that is dominated by the perennial bunchgrass Danthonia parryi. Other frequent graminoids are Carex inops ssp. heliophila, Muhlenbergia montana, Festuca arizonica, Koeleria macrantha, Poa secunda, and Poa fendleriana. Forbs are diverse but contribute little cover (usually less than 10%) and include Antennaria rosea, Eriogonum umbellatum, Gaillardia aristata, Gentiana spp., Mertensia lanceolata, Penstemon spp., and Potentilla hippiana. The dwarf-shrub Artemisia frigida is often scattered through these stands. At higher elevations these grasslands occur in an ecotone with Pinus contorta forests, and at lower elevations mountain shrub and other dry grassland communities are common neighbors.

4.2.1.1.1 Association: Danthonia parryi Herbaceous Vegetation (CEGL001795)

This plant association most commonly occurs in forest openings, in montane meadows or parks in the Colorado Rocky Mountains and in adjacent parts of Wyoming. Stands occur from 2260-3350 m (7400-11,000 feet) elevation. Sites are moderately sloping (10-20%), with south and western aspects. Soils are shallow to moderately deep (>60 cm), usually with less than 20% coarse fragments. Soil texture is sandy to silt loam. The soils are moister than those of adjacent grasslands dominated by Festuca arizonica. The


most common adjacent vegetation is Pinus ponderosa forest. At higher elevations there is an ecotone with Pinus contorta forests, and at lower elevations mountain shrub and other dry grassland communities are common. The vegetation is characterized by a moderately dense (60-70% cover) herbaceous layer that is typically dominated by the perennial bunchgrass Danthonia parryi. Other common species include Carex inops ssp. heliophila, Elymus trachycaulus, Festuca arizonica, Festuca idahoensis, Koeleria macrantha, Muhlenbergia montana, Poa fendleriana, Poa pratensis, and Poa secunda. Muhlenbergia montana may be more abundant on drier sites or those impacted by livestock grazing. Forbs are diverse but contribute little cover (usually less than 10%) and include Achillea millefolium var. occidentalis (= Achillea lanulosa), Antennaria rosea, Besseya plantaginea, Eriogonum umbellatum, Heterotheca villosa, Gaillardia aristata, Gentiana spp., Geum macrophyllum, Mertensia lanceolata, Penstemon spp., Potentilla hippiana and Potentilla pulcherrima. The dwarf-shrub Artemisia frigida is often scattered through these stands.

4.2.1.2 Alliance: Festuca arizonica Herbaceous Alliance (A.1245)

This alliance includes grasslands dominated by Festuca arizonica. In western Texas, these grasslands occur at high elevations (1430-2500 m [4700-8200 feet]) in the Davis Mountains, Guadalupe Mountains, and Chisos Mountains in protected areas and on open slopes. Associated species include Blepharoneuron tricholepis, Allium cernuum, Salvia arizonica, Achillea millefolium, Muhlenbergia minutissima, Muhlenbergia filiculmis, Muhlenbergia montana, Commelina dianthifolia, Bouteloua gracilis, Artemisia carruthii, Elymus elymoides, Castilleja spp., and Silene sp.

5 Macrogroup: Southern Rocky Mountain Lower Montane Forest5.1 Group: Abies concolor - Pseudotsuga menziesii Southern Rocky Mountain Dry

Forest Group

5.1.1 Ecological System: Inter-Mountain Basins Aspen-Mixed Conifer Forest and Woodland (CES304.776)

Description not currently available.

5.1.1.1 Alliance: Pinus ponderosa - Populus tremuloides Forest Alliance (A.399)

This successionally intermediate alliance occurs in the Black Hills and western and northwestern United States. This description is strongly based on the portion of this alliance that occurs in the Black Hills. This is a mixed evergreen - deciduous forest composed of short to moderately tall trees. Sites can be on gentle to steep slopes and have any aspect. The canopy is variable, ranging from moderately open to closed. Younger stands typically have dense Populus tremuloides with Pinus ponderosa mixed in. As the stands age, Populus tremuloides is slowly reduced and Pinus ponderosa becomes dominant. Betula papyrifera and Picea glauca may be minor components of the canopy. The shrub layer contains species such as Arctostaphylos uva-ursi, Juniperus communis, Prunus americana, Prunus pensylvanica, Prunus virginiana, Rubus idaeus, Sorbus scopulina and Vaccinium scoparium. Aralia nudicaulis, Castilleja sulphurea, Clematis columbiana, Geranium richardsonii, Oryzopsis asperifolia, Pteridium aquilinum, and Sedum stenopetalum are found in the herbaceous stratum. Stands of this alliance typically develop after a crown fire or other disturbance has removed the Pinus ponderosa overstory.

5.2 Group: Pinus ponderosa Southern Rocky Mountain Forest & Woodland Group

5.2.1 Ecological System: Southern Rocky Mountain Ponderosa Pine Woodland (CES306.648)


Overview:This widespread ecological system is most common throughout the cordillera of the Rocky Mountains, but is also found in the Colorado Plateau region, west into scattered locations in the Great Basin, and north into southern British Columbia. These matrix-forming woodlands occur at the lower treeline/ecotone between grassland or shrubland and more mesic coniferous forests typically in warm, dry, exposed sites.

Characteristic Species:Pinus ponderosa is the predominant conifer; Pseudotsuga menziesii, Pinus edulis, and Juniperus spp. may be present in the tree canopy. The understory is usually shrubby, with Artemisia nova, Artemisia tridentata, Arctostaphylos patula, Arctostaphylos uva-ursi, Cercocarpus montanus, Cercocarpus ledifolius, Purshia stansburiana, Purshia tridentata, Quercus gambelii, Symphoricarpos oreophilus, Prunus virginiana, Amelanchier alnifolia, and Rosa spp. being common species. Pseudoroegneria spicata and species of Hesperostipa, Achnatherum, Festuca, Muhlenbergia, and Bouteloua are some of the common grasses.

Grace's warbler, Pygmy nuthatch, and flammulated owl are indicators of a healthy ponderosa pine woodland.

Environment: This ecological system occurs at the lower treeline/ecotone between grassland or shrubland and more mesic coniferous forests typically in warm, dry, exposed sites at elevations ranging from 6,500-9,200 ft (1,980-2,800 m). It can occur on all slopes and aspects, however, it commonly occurs on moderately steep to very steep slopes or ridgetops. This ecological system generally occurs on igneous, metamorphic, and sedimentary material derived soils, including basalt, basaltic, andesitic flows, intrusive granitoids and porphyrites, and tuffs (Youngblood and Mauk 1985). Characteristic soil features include good aeration and drainage, coarse textures, circumneutral to slightly acid pH, an abundance of mineral material, and periods of drought during the growing season. Surface textures are highly variable in this ecological system ranging from sand to loam and silt loam. Exposed rock and bare soil consistently occur to some degree in all the associations. Annual precipitation is 8-24 in (25-60 cm), mostly through winter storms and some monsoonal summer rains. Typically a seasonal drought period occurs throughout this system as well.

Dynamics:Pinus ponderosa is a drought-resistant, shade-intolerant conifer which usually occurs at lower treeline in the major ranges of the western United States. Historically, ground fires and drought were influential in maintaining open-canopy conditions in these woodlands. With settlement and subsequent fire suppression, occurrences have become denser. Presently, many occurrences contain understories of more shade-tolerant species, such as Pseudotsuga menziesii and/or Abies spp., as well as younger cohorts of Pinus ponderosa. These altered occurrence structures have affected fuel loads and alter fire regimes. Presettlement fire regimes were primarily frequent (5-15 year return intervals), low-intensity ground fires triggered by lightning strikes or deliberately set fires by Native Americans. With fire suppression and increased fuel loads, fire regimes are now less frequent and often become intense crown fires, which can kill mature Pinus ponderosa (Reid et al. 1999).

Variation:This system intergrades with Rocky Mountain Ponderosa Pine Savanna. The two are distinguished by the high frequency, surface-fire regime, less steep or rocky environmental setting, and more open grassy


understory structure of the savanna system.

5.2.1.1 Alliance: Pinus ponderosa Forest Alliance (A.124)

Forests dominated by Pinus ponderosa occur in mountainous regions of the western United States, from the Cascades and Black Hills, throughout the Rocky Mountains, southeast to the mountains of Arizona, New Mexico, and western Texas. This alliance may range into southern British Columbia, and although Pinus ponderosa is found in Mexico, it is uncertain whether this alliance ranges into that country. This alliance can be found on slopes of a variety of aspects and pitches, but is most often on gentle to moderate, northeast- to northwest-facing slopes. It can be on slopes of other aspects where the soil is heavier and retains more moisture or if other conditions make the site relatively mesic. Periodic ground fires are important in maintaining Pinus ponderosa forests. In the prolonged absence of fires, some stands will succeed to other communities. Throughout its range, Pinus ponderosa is found at elevations from sea level to 3050 m (10,000 feet). Within the central Rocky Mountains, Pinus ponderosa grows at elevations between 1800-2600 m (6000-8500 feet). In the Black Hills and northeastern Wyoming, it can be found from 1080-2100 m (3600-7000 feet). In the southeastern United States, these forests are restricted to the high elevations (over 1800 m [6000 feet]) of the Guadalupe, Davis, and Chisos mountains in western Texas, where associations are dominated by Pinus ponderosa var. scopulorum. Associated species vary with elevation and geography, but consistently include Quercus gambelii, Pinus strobiformis, Juniperus deppeana, Quercus grisea, Quercus muehlenbergii, Pinus arizonica var. stormiae, Cupressus arizonica, Juniperus flaccida, Festuca arizonica, Schizachyrium scoparium var. scoparium (= Schizachyrium scoparium ssp. neomexicanum), Panicum bulbosum, and Piptochaetium pringlei (= Stipa pringlei).

6 Macrogroup: Western North American Montane & Subalpine Wet Shrubland & Wet Meadow

6.1 Group: Carex species – Calamagrostis species Montane Wet Meadow Group

6.1.1 Ecological System: Rocky Mountain Alpine Montane Wet Meadow (CES306.812)

Overview: The Rocky Mountain Alpine-Montane Wet Meadow system includes high-elevation herbaceous dominated communities found throughout the Rocky Mountain and Intermountain regions. These communities occur as large meadows in montane or subalpine valleys, as narrow strips bordering ponds, lakes, and streams, and along toe slope seeps. They are typically found on flat areas or gentle slopes, but may also occur on sub-irrigated sites with slopes up to 10%. In alpine regions, sites typically are small depressions located below late-melting snow patches or on snowbeds. Often alpine dwarf-shrublands, especially those dominated by Salix, are immediately adjacent to the wet meadows. Wet meadow ecological systems provide important water filtration, flow attenuation, and animal habitat.

Characteristic Species:This system often occurs as a mosaic of several plant associations, often dominated by graminoids, such as Calamagrostis stricta, Carex illota, Carex microptera, Carex nigricans, Carex scopulorum, Carex utriculata, Carex vernacula, Deschampsia caespitosa, Eleocharis quinqueflora, and Juncus drummondii. Common forb species include Caltha leptosepala, Cardamine cordifolia, Phippsia algida, Rorippa alpina, Senecio triangularis, Trifolium parryi, and Trollius laxus. Within the elevational gradient coverd by this system, some communites are typically confined to the alpine, hile others are usually found only at montane elevations.


Environment:Occurrences range in elevation from montane to alpine (in Colorado from 7,000 to 11,800 ft; 2,100-3,600 m), and are found on wetter sites with very low-velocity surface and subsurface flows. Wet meadows are tightly associated with snowmelt and typically not subjected to high disturbance events such as flooding. Moisture for these communities comes from groundwater, stream discharge, overland flow, overbank flow, and on-site precipitation. Salinity and alkalinity are generally low due to the frequent flushing of moisture through the meadow.

Soils typically possess a high proportion of organic matter, but this may vary considerably depending on the frequency and magnitude of alluvial deposition (Kittel et. al. 1999). Organic composition of the soil may include a thin layer near the soil surface or accumulations of highly sapric material of up to 4 ft (120 cm) thick. Soils may exhibit gleying and/or mottling throughout the profile.

Dynamics:Associations in this ecological system are adapted to soils that may be flooded or saturated throughout the growing season. They may also occur on areas with soils that are only saturated early in the growing season, or intermittently. Typically these associations are tolerant of moderate-intensity ground fires and late-season livestock grazing (Kovalchik 1987). Most appear to be relatively stable types, although in some areas these may be impacted by intensive livestock grazing.

Variation: Depending on the slope, topography, hydrology, soils and substrate, intermittent, ephemeral, or permanent pools may be present. These areas may support species more representative of purely aquatic environments. Standing water may be present during some or all of the growing season, with water tables typically remaining at or near the soil surface. Fluctuations of the water table throughout the growing season are not uncommon, however. On drier sites supporting the less mesic types, the late-season water table may be 3 ft (1m) or more below the surface.

6.1.1.1 Alliance: Carex (rostrata, utriculata) Seasonally Flooded Herbaceous Vegetation (A.1403)

This alliance is found in the upper midwestern United States and most western states as well as several Canadian provinces. Stands usually occur on wet mineral soil, muck, or shallow peat (<0.5 m). Standing water (generally stagnant) is present in the spring and after heavy rains, but the water table is generally below the surface for most of the growing season. This permits the breakdown of dead organic matter and the release of nutrients. Where stands are found along stream courses or lake margins, water levels may be more constant relative to stands in depressions or basins. This vegetation is dominated by tall wider-leaved sedges, with a mixture of forbs. Typical dominants include Carex rostrata or Carex utriculata (= Carex rostrata var. utriculata), as well as Carex vesicaria. Further study is needed to clarify the floristic characteristics of this alliance.

6.1.1.2 Alliance: Juncus balticus Seasonally Flooded Herbaceous Alliance (A.1374)

This alliance often occupies seasonally flooded swales and wet, low- to mid-elevation sites. Habitats are often alkaline meadows and may have long-term grazing disturbance. It is a wide-ranging alliance, occurring from the plains to montane regions to boreal regions, and has much variability. Elevations range from sea level in California to 3500 m in Colorado. Montane plant associations can occur on alluvial terraces, floodplains, overflow channels, seeps, meadows, and near springs. Sites are typically gently sloping (1-3%) on all aspects. An association was documented in northern California coastal salt marshes. Soils are mineral with dark surface horizons containing large amounts of well-decomposed


organic matter. Soils are Mollisols or rarely Entisols. Soil texture ranges from silt to sandy loam. Water tables are often at or near the soil surface in early summer but may drop below 50 cm by late August. Soil reaction ranges from neutral to mildly alkaline (pH 7.0-8.0). The graminoid layer is dense with up to 98% cover and dominated by Juncus balticus, a creeping, often sod-forming, rhizomatous perennial. Other graminoid cover is minor but can include Carex pellita (= Carex lanuginosa), Carex aquatilis, Carex canescens, Leymus cinereus, Deschampsia caespitosa, Hordeum jubatum, or Sporobolus airoides. Forb cover is typically minor and may include Achillea millefolium, Iris missouriensis, or Geum macrophyllum. The plant associations from California are composed of various forbs and the graminoids Bromus spp., Distichlis spicata, Carex lyngbyei, Carex obnupta, Hordeum brachyantherum, Leymus triticoides, Lolium perenne ssp. multiflorum, and Schoenoplectus robustus (= Scirpus robustus). Occasionally, a few tree or shrub seedlings are present, including Populus angustifolia, Dasiphora fruticosa ssp. floribunda (= Pentaphylloides floribunda), and Salix exigua. Salix exigua shrublands, Distichlis spicata marshes, or Carex spp. meadows may occur in adjacent riparian areas. Abies lasiocarpa - Picea engelmannii, Pseudotsuga menziesii, and Populus tremuloides forests, Pinus edulis - Juniperus spp. woodlands, and Ericameria nauseosa (= Chrysothamnus nauseosus), Sarcobatus vermiculatus, and Artemisia tridentata shrublands may occur on adjacent hillslopes. In low-disturbance areas, Juncus balticus plant associations appear to be a stable, climax community. However, in some areas, this association is considered to be grazing-induced. Juncus balticus is considered an increaser due to its low forage value and high tolerance to grazing. It usually increases in abundance on sites formerly dominated by Deschampsia caespitosa or Calamagrostis canadensis. Nearly pure stands of Juncus balticus indicate that the site may have been heavily grazed in the past. Juncus balticus is listed as a facultative wetland species.

6.2 Group: Salix species Riparian and Seep Shrubland

6.2.1 Ecological System: Rocky Mountain Subalpine-Montane Riparian Shrubland (CES306.832)

Overview: This system is found throughout the Rocky Mountain cordillera from New Mexico north into Montana, and also occurs in mountainous areas of the Intermountain region and Colorado Plateau. These montane to subalpine riparian shrublands may occur as narrow bands of shrubs lining streambanks and alluvial terraces, or as extensive willow carrs in broad, hummocky floodplains and subalpine valleys.

Characteristic Species: The dominant shrubs reflect the large elevational gradient and include Alnus incana, Betula nana, B. occidentalis, Cornus sericea, Salix bebbiana, S. boothii, S. brachycarpa, S. drummondiana, S. eriocephala, S. geyeriana, S. liguifolia, S. monticola, S. planifolia, and S. wolfii. Generally the upland vegetation surrounding these riparian systems are either conifer or aspen forests.

Environment: This system is more commonly found at higher elevations, but occurs anywhere from 5,600 to 11,800 ft (1,700-3,595 m). Occurrences can also be found around seeps, fens, and isolated springs on hillslopes away from valley bottoms. This system often occurs as a mosaic of multiple communities that are shrub- and herb-dominated and includes above-treeline, willow-dominated, snowmelt-fed basins that feed into streams.

Dynamics:Many of the plant associations included in this system are associated with beaver activity, which can be


important for maintaining the health of the riparian ecosystem. Beaver dams abate channel down cutting, bank erosion, and downstream movement of sediment. Beaver dams raise the water table across the floodplain and provide year-round saturated soils. Plant establishment and sediment build-up behind beaver dams raises the channel bed and creates a wetland environment.

Variation:At lower elevations in the range of this system, occurrences are more likely to be non-willow shrublands dominated by Alnus incana, Betula occidentalis, or Cornus sericia. At the highest elevations communities dominated by short-statured species such as Betula nana, Salix brachycarpa, S. planifolia, and S. wolfii are most common.

6.2.1.1 Alliance: Dasiphora fruticosa ssp. Temporarily Flooded Shrubland Alliance (A.958)

This shrubland alliance is highly variable, occupying various landforms in the foothills, montane, and subalpine regions in the Rocky Mountain region. Sites include glacial depressions, terraces along meandering streams, slopes near springs and seeps, steep scree slopes, or broad mountain meadows. Typically, stands occur on broad, gently sloping valley bottoms and floodplains or along the drier edges of isolated wetlands and fens. Surface water is present for brief periods during the growing season, but the water table usually lies well below the soil surface. The soils are typically sandy loams over sand and gravel layers. Peat accumulation is common in stands located on fens. Soil texture can be fine-textured with occasional mottling and gleying. This alliance is dominated by Dasiphora fruticosa ssp. floribunda (= Pentaphylloides floribunda). Associates include Artemisia cana and Deschampsia caespitosa and Trifolium longipes on wetter sites. Other graminoids present in the wetter sites may include Poa secunda, Festuca rubra, Carex aquatilis, Carex buxbaumii, Carex microptera, Carex pachystachya, Juncus balticus, and Muhlenbergia filiformis. The drier sites typically are composed of a dense graminoid layer that includes Festuca idahoensis, Festuca campestris, Schizachyrium scoparium, and Andropogon gerardii. Diagnostic of this alliance is the dominance of Dasiphora fruticosa ssp. floribunda in a shrub layer with over 25% cover.

6.2.1.2 Alliance: Salix bebbiana Temporarily Flooded Shrubland (A.981)

This alliance occurs along rivers and streams in the western Great Plains and Rocky Mountains. This alliance is a briefly flooded, scrub-shrub wetland on slightly to moderately alkaline soils, usually near low-gradient streams. The water table is well below the soil surface for over half the growing season. However, there are periods of several days to a few weeks when water is at the surface. These communities are typically dominated by a dense growth of shrubs 0.5-3 m tall. Multiple-stemmed trees and/or shrubs 0.5-5 m tall have 30-100% cover; single-stemmed trees have less than 30% cover. The most abundant species in the shrub layer are Salix bebbiana, Salix scouleriana, and Salix lucida ssp. caudata (= Salix fendleriana). Other species found in this stratum include Betula occidentalis, Cornus sericea, Salix exigua, Salix fluviatilis, and Prunus virginiana. The herbaceous layer often contains Scirpus spp., Carex spp., Triglochin palustris, Calamagrostis canadensis, and Equisetum spp. along the wetter margins of the alliance. In the drier areas Gentianella amarella ssp. acuta (= Gentiana strictiflora), Prunella vulgaris, Pyrola asarifolia, Ranunculus macounii, Sanicula marilandica, Viola canadensis, Vicia americana, and Zizia aptera (= Zizia cordata) are frequently present.

6.2.1.2.1 Association: Salix bebbiana Shrubland Association (CEGL001173)

This riparian willow shrubland is found in the montane regions and western plains of the United States, and also along the eastern Front Range of the Rocky Mountains in Alberta. This community is a briefly flooded scrub-shrub wetland on slightly to moderately alkaline soils, usually near low-gradient streams.


This shrubland is typically dominated by a dense growth of shrubs 0.5-3 m tall. The most abundant species in the shrub layer are Salix bebbiana, Salix scouleriana, and Salix lucida ssp. caudata (= Salix fendleriana). Other species found in this stratum include Betula occidentalis, Cornus sericea ssp. sericea, Salix exigua, Salix melanopsis (= Salix fluviatilis), Salix lutea, Salix prolixa (= Salix rigida ssp. mackenzieana), Amelanchier alnifolia, and Prunus virginiana. A shorter shrub layer is sometimes present, with Symphoricarpos occidentalis, Ribes inerme, Lonicera involucrata, and Rosa acicularis. The herbaceous layer can be very abundant and predominantly graminoids; common species include Schoenoplectus spp. and/or Scirpus spp., Carex spp., Triglochin palustris, Calamagrostis canadensis, Bromus carinatus, Poa palustris, and Equisetum spp. along the wetter margins of the community. Forbs can be abundant and variable in composition, ranging from mesic-site forbs to ones adapted to drier conditions. Species include Heracleum maximum, Cicuta maculata, Geranium richardsonii, Geum macrophyllum, Gentianella amarella ssp. acuta (= Gentiana strictiflora), Prunella vulgaris, Pyrola asarifolia, Zizia aptera (= Zizia cordata), Sanicula marilandica, Viola canadensis, Vicia americana, and Ranunculus macounii.

6.2.1.3 Alliance: Salix drummondiana Temporarily Flooded Shrubland (A.973)

Communities within this alliance occur on alluvial terraces adjacent to mountain rivers and streams. They range in elevation from 2135-3300 m, on slopes that range from 5-30%. These shrublands occur as small, isolated patches in forest and shrubland openings along channels in narrow valley bottoms along steep, narrow stream margins. They are often associated with beaver activity and can occasionally occur along low-gradient streams. Soils are usually poorly developed and contain high percentages of gravel and cobbles. Water table depths range from surface level to greater than 1 m. Open, corridor-like canopies characterize this major riparian alliance with a dense graminoid layer in the understory. They are cold-deciduous, temporarily flooded shrublands that are dominated by Salix drummondiana. Alnus incana and Salix geyeriana are often present in the shrub layer. The graminoid layer is dominated by Calamagrostis canadensis with cover of 50-75%. Carex aquatilis and Carex utriculata can be present is lesser amounts (0-30% cover). Forb cover is relatively low. It is characterized by Geum macrophyllum, Equisetum arvense, and Canadanthus modestus (= Aster modestus). Populus tremuloides woodlands and Abies lasiocarpa - Picea engelmannii forests occur on adjacent hillsides.

6.2.1.3.1 Association: Salix drummondiana / Mesic Forbs Shrubland (CEGL001192)

This riparian shrubland most commonly occurs on relatively steep streams and rarely forms more than a narrow, 1.5- to 7.5-m (5-25 feet) wide band along streambanks. It is known from the mountains of Colorado, Utah, Wyoming and Montana, from 960-3450 m (3150-11,300 feet). It occurs in narrow, V-shaped valleys as a dense, narrow band along high-gradient (1-41%) streams and as large willow shrublands in broad valleys, 50-305 m (150-1000 feet) wide, along low-gradient (1-3%), moderately sinuous streams. Stands also occur along broad, highly sinuous streams and broad, actively down-cutting channels. This association can also occur near seeps. Soils range from deep sandy loams and sandy clay loams with no coarse fragments to shallow silty clay loams and sandy clay loams over coarse, angular cobbles. The closed to partially open canopy of Salix drummondiana and a thick carpet of many forb species, with no single species dominant nor consistently present, characterize this plant association.

6.2.1.4 Alliance: Salix monticola Temporarily Flooded Shrubland Alliance (A.981)

This is a montane riparian shrubland alliance that occurs in the mountains along stream reaches in moderately wide to narrow valleys (20-120 m) with broad, swift-moving streams and active, flat (3-8%) floodplains. Elevations range between 2310 and 3350 m. Large stands occur between meanders and at


the edges of beaver ponds. The ground surface is usually undulating, from past flooding or beaver activity. These shrublands occur right at stream's edge, and up to 15 m from the channel, usually >0.5 m above the channel elevation. Soils are predominantly heavy silty clays with occasional to abundant mottling evident. Some stands occur on coarse, well-drained alluvium. The tall-shrub layer is characterized by a tall, nearly closed canopy of Salix monticola (8-70%), typically with Salix geyeriana (40-50%) or Salix drummondiana (10%). Other shrubs present include Salix lucida ssp. lasiandra (= Salix lasiandra), Betula glandulosa, Salix planifolia, and Salix wolfii. The short-shrub layer is dominated by Cornus sericea and Lonicera involucrata. The forb layer is dense (up to 50%) and consists of Angelica ampla, Geum macrophyllum, Solidago canadensis, Senecio bigelovii, and Galium boreale. Calamagrostis canadensis comprises a dense graminoid layer of 40-50% cover. Carex utriculata and Carex aquatilis also contribute to the graminoid understory in several associations.

6.2.1.4.1 Association: Salix monticola / Calamagrostis canadensis Shrubland (CEGL001222)

This plant association occurs along broad floodplains and narrow streams in the montane to upper montane elevations of Colorado. The elevational range is 2530-2865 m (8300-9400 feet). Stands have a shrub layer 1.5-2 m (4-5 feet) tall with a typically closed canopy of willows and a lush undergrowth of grasses. The dense shrub layer is dominated by Salix monticola. Other shrubs that may be present include Salix drummondiana, Salix wolfii, Salix geyeriana, and Salix boothii. Calamagrostis canadensis dominates a sparse to dense graminoid layer. Other graminoids that may be present include Carex aquatilis, Carex utriculata, Carex microptera, Deschampsia caespitosa, and Glyceria grandis. Canopy cover for forb species is usually very sparse (<1%). Forb species may include Cardamine cordifolia, Geranium richardsonii, Mertensia ciliata, Oxypolis fendleri, Geum macrophyllum, Solidago canadensis, Senecio bigelovii, and Galium boreale.

6.2.1.4.2 Association: Salix monticola / Carex aquatilis Shrubland (CEGL002656)

This plant association is a tall (1.5-2.5 m [5-8 feet]), deciduous shrubland with a fairly open willow canopy and a thick carpet of grasses and sedges. It occurs in the southern Rocky Mountains on coarse-textured streambanks and floodplains of narrow, sinuous streams in narrow valleys, often forming a continuous canopy across the entire valley floor at elevations of 2100-2980 m (7000-9760 feet). Salix monticola, with 27-88% cover, has the highest abundance, though other willow species may have a higher combined canopy cover. Other shrubs (with percent cover) include Salix bebbiana (7-17%), Salix drummondiana (1-40%), Cornus sericea (70%), and Lonicera involucrata. The undergrowth is dominated by patches of Carex aquatilis (10-50%), though Carex utriculata and Calamagrostis canadensis are often present. Dominance of Carex aquatilis (numerically or in constancy) distinguishes this plant association from Salix monticola / Carex utriculata Shrubland (CEGL002657) and Salix monticola / Calamagrostis canadensis Shrubland (CEGL001222).

6.2.1.4.3 Association: Salix monticola / Mesic Graminoids Shrubland (CEGL002659)

This association is known only from Colorado and Wyoming but may occur in the mountains of New Mexico and Utah. It dominates broad, swift mountain streams with active floodplains at 2000-3350 m (6600-11,000 feet) elevation. Stands usually occur 0.5 m (2 feet) above the bankfull channel up to 15 m (50 feet) away from the stream edge in both narrow and wide valleys (20-120 m [65-400 feet] wide). The soils are fine-textured loams, and the ground surface is usually undulating due to past flooding or beaver activity. Salix monticola is either the dominant or most abundant species in a variable canopy (15-80% total cover). Other shrubs present at higher elevations include Salix planifolia (10-40% cover), Salix geyeriana (2-20% cover), and Salix brachycarpa. Species present at lower elevations include Salix


irrorata, Salix lucida ssp. caudata (= Salix lasiandra ssp. caudata), Alnus incana, and Dasiphora fruticosa ssp. floribunda (= Pentaphylloides floribunda). The herbaceous undergrowth is diverse, with a variety of graminoid and forb species. This association is distinguished from Salix monticola / Mesic Forbs Shrubland (CEGL002658) by having a higher cover of graminoid species. Stands with predominantly non-native graminoid species in the undergrowth are considered grazing-induced.

6.2.1.5 Alliance: Salix planifolia Seasonally Flooded Shrubland Alliance (A.1008)

Communities within the Salix planifolia Seasonally Flooded Shrubland Alliance (A.1008) are common and abundant in the upper montane and subalpine zones (above 1525 m) throughout the western United States. They occur in wide, wet valleys on snowmelt-fed swales. They also occur in narrow valleys with sinuous streams and wet floodplains associated with beaver ponds. Snowmelt is the primary source of moisture during the growing season. Soils have an organic peat top layer over mineral silty clays, heavy silty clay loams, silty loams, sandy loams, or loamy sands. Mottling is often evident. The water table at several stands is usually near the surface throughout the growing season and may be perched by a clay horizon. Still other stands occur on deep, dark clay loams with high organic content or a fibric or hemic layer on top. Soil pH levels are acidic, ranging from 4.8-7.8. Salix planifolia dominates the shrub layer with at least 70% cover. Other willows can include Salix monticola, Salix wolfii, Salix boothii, Salix geyeriana, and Salix drummondiana. The undergrowth is dominated by graminoids and can include Carex aquatilis, Carex utriculata, Calamagrostis canadensis, and Deschampsia caespitosa. Forb cover is typically less than 20% of the total undergrowth cover and may include Caltha leptosepala, Cardamine cordifolia, and Pedicularis groenlandica. Adjacent riparian and wetland vegetation includes Carex aquatilis, Carex utriculata, or Calamagrostis canadensis wet meadows. Salix brachycarpa shrublands occur on higher ground. At higher elevations, Abies lasiocarpa - Picea engelmannii or Pinus contorta forests occur on adjacent hillsides.

6.2.1.5.1 Association: Salix planifolia / Carex utriculata Shrubland (CEGL005937)

This association is a low-statured willow shrubland known from high mountain valleys on saturated, usually organic soils from central Utah and western Colorado north to southwestern Montana. Elevation ranges from 1750 to 2690 m (5740-8830 feet) in Montana and Wyoming and from 2710 to 3350 m (8900-11,000 feet) in Colorado and Utah. The shrub canopy is dominated by Salix planifolia with 30-98% cover. Other willows can be present to codominant and include Salix geyeriana, Salix wolfii, Salix monticola, Salix boothii, and Salix commutata. The herbaceous undergrowth is usually dense with graminoids, often low in species diversity. Carex utriculata (erroneously reported as Carex rostrata in several references) is the most abundant and characteristic sedge in the understory with 10-80% cover. Other graminoids that may be present include Carex aquatilis, Calamagrostis canadensis, Juncus balticus, Juncus ensifolius, Equisetum arvense, Luzula parviflora, Phleum alpinum, and Poa pratensis. Forbs are generally much less abundant than graminoids and include a wide variety of species, none being characteristic of the plant association but indicative of high montane to subalpine wetland habitats. Typical forbs include Arnica mollis, Caltha leptosepala var. leptosepala, Conioselinum scopulorum, Epilobium spp., and Mertensia ciliata.


SECTION II – Galatowitsch Classification

1 Galatowitsch Classification1.1Mixed Mountain Shrublands (6.6)Occupies sites drier than montane forests and more mesic than sagebrush shrublands and pinyon-juniper woodlands. Mixed mountain shrublands occur from 6500 to 9000 feet on loamy soils. These communities typically have a diverse overstory including Cercocarpus montanus, Amelanchier utahensis, Quercus gambelii, Prunus virginiana, Symphoricarpos oreophilus, and occasionally Artemisia tridentata. Mesic montane shrublands often intergrade to mesic sagebrush shrublands. Carex geyeri is a common understory species.

Most descriptions of mixed mountain shrublands are from northwestern Colorado. More studies are needed to describe the composition of mixed mountain shrublands in southwest Colorado and throughout the Rocky Mountain region. The variability of mixed mountain shrublands has not been adequately sampled. For example, mixed mountain shrublands near Durango are dominated by Quercus gambelii, Peraphyllum ramosissimum and Fendlera rupicola (Romme, personal communication, 1987). Two of these three dominants do not occur in northwest Colorado

1.2Aspen Forests (6.8)Occupy moist to relatively dry sites above 8000 feet in this resign. Many studies have been completed on the composition and ecology of aspen forests in Colorado. These western slope aspen forests are stable communities that occur on north-facing slopes and in fertile areas of montane sagebrush. An analysis of 42 samples indicates two types of aspen forests occur in this region: mesic and dry forests. Mesic forests are those on steep north-facing slopes whereas dry forests form islands in sagebrush.

1.3 Deciduous Riparian Forest (6.10)Occur on lower terraces and floodplains, dominated by Populus fremontii and Populus angustifolia. An analysis of 38 samples show stands on low elevation, low gradient streams are dominated by Populus fremontii and are distinct from higher elevation streams, dominated by Populus angustifolia. Invasions of Tamarix chinensis and Elaeagnus angustifolia in most low elevation riparian areas has dramatically modified the composition of these communities and limits the number of areas available for sampling.

1.3.1 Narrowleaf Cottonwood Riparian Forests (6.10.2)

Occur above 6000 feet on moderate gradient streams and are dominated by Populus angustifolia. Acer negundo or Pseudotsuga menziesii often is a secondary species in the overstory. The shrub layer is typically well developed, including Salix exigua, Rosa woodsii, Betula occidentalis, Alnus incana, and Cornus sericea. The herb layer is variable, depending on flooding regime and land use history.

1.4 Wet Meadows (6.13)Dominated by Carex and Juncus species. These communities occur in poorly drained, fine textured soils with seasonal standing water. Carex lanuginosa, C. nebraskensis, C. rostrata, and C. lasiocarpa are characteristic species (Ramaley, 1920).


1.5 Ponderosa Pine Woodlands (7.7)Occur from 5700 to 7900 feet in relatively moist sites at low elevations and drier sties at higher elevations and are dominated by Pinus ponderosa. Juniper woodlands and mixed foothill shrublands occupy drier sites and ponderosa pine forests occupy more mesic sites. Ponderosa pine woodlands are fire-derived and fire-maintained communities (Brandegee, 1891; DeVelice, 1986; Crane, 1982). Fire suppression has resulted in a denser tree canopy with an increase in Psuedotsuga and reduced grass cover of many communities. Numerous studies have been conducted on ponderosa pine communities in Colorado but more study is needed to compare geographic variation across Colorado and to investigate fire return frequencies.

Data from 28 sites were analyzed and ordination results together with information from the literature was used to develop the classification. Ponderosa pine communities above 8000 feet, in the Rocky Mountain region, were shown to be floristically distinct from sites at lower elevations, in the foothills of the Rocky Mountains.

1.6 Montane Forests (8.1)Occur in moist ravines from 7000 feet to dry sites at 11000 feet. The montane forests are widespread in the Rocky Mountain region and can be dominated by Pseudotsuga menziesii, Pinus contorta, Pinus ponderosa, Abies concolor, or Populus tremuloides.

1.6.1 Lodgepole Pine Forests (8.1.1)

Climax or persistent Pinus contorta stands are found predominantly in northern Colorado. Seral stands extend from the east slope of the Sangre de Cristo Mountains to Spanish Peaks. Lodgepole pine does not naturally occur west of the Sangre de Cristos or south of the Gunnison River (Crane, 1982). Communities considered here are those with Pinus contorta canopy density exceeding any other species.

1.6.2 Mixed Montane Forests (8.1.3)

Lower montane forests with a diverse overstory including Abies concolor. Overstory species include Abies concolor, Abies lasiocarpa, Picea engelmannii, Picea pungens, Pinus flexilis, Pinus ponderosa, and Pseudotsuga menziesii. Species composition depends on moisture and temperature characteristics of the site (DeVelice et al., 1986). Abies concolor is characteristic of relatively dry sites. Picea pungens is restricted to cool, moist situations. Pinus strobiformis replaces Pinus flexilis on south-facing slopes in the San Juan Mountains (Romme, personal communication, 1987). Mixed montane forests occur in the Sangre de Cristo Range and extend north on the Front Range to Colorado Springs and west in the San Juan Mountains. Common understory species include Juniperus communis, Pachystima myrsinites, Amelanchier utahensis, Poa fendleriana, Bromopsis ciliata, Erigeron eximius.

1.6.3 Montane Woodlands (8.2)

Woodlands dominated by either species of five-needle pine, Pinus aristata or Pinus flexilis occupying dry, windswept ridges within the region. White pine distributions in the Rocky Mountains apparently reflect competitive release (Peet, 1978). Pinus flexilis occupies xeric sites from montane to tree line where it is the only white pine present, but where Pinus aristata is present, the species is largely restricted to the low-elevation portion of its potential habitat and to locations with very rocky substrate. Pinus flexilis also appears to substitute for Pinus contorta or Pinus ponderosa where either species is


absent. Crane (1982) separated montane woodlands into Upper Montane Woodlands (8.2.1) and Lower Montane Woodlands (8.2.2).

1.7 Riparian and Wetland Forests (8.7)Forests dominated by coniferous tree species where there is a seasonally or permanently high water table. No tree species indigenous to the Rocky Mountains can withstand flooding for periods of two or more consecutive growing seasons (Walters et al., 1980). Picea engelmannii and Picea pungens can withstand flooding for most of a growing season and still produce new roots. Abies concolor, Abies lasiocarpa, Pinus contorta, Pinus ponderosa and Pseudotsuga menziesii are able to survive flooding for periods of one to three months during the growing season but will produce few roots, if any. These communities have been reviewed in Windell et al. (1986) and Peet (1978). Studies have been completed on these communities in southern Colorado (Baker, 1986; DeVelice et al., 1986; Komarkova, 1986) and in the Front Range (Hess and Alexander, 1986; Peet, 1978).

1.7.1 Wetland Forests (8.7.2)

No description provided.

1.7.1.1 Aspen Wetland Forests (8.7.2.1)

Dominated by Populus tremuloides. Populus tremuloides can withstand flooding for most of a growing season and still produce new roots (Walters et al., 1980). Thalictrum fendleri, Veratrum tenuipetalum, Pteridium aquilinum are common understory species in poorly drained areas (Bunin, 1975; Hess and Alexander, 1986). Sambucus racemosa, Cornus sericea, Salix spp. and Elymus glaucus occur along small streams and springs in the montane (Lindauer et al., 1982; Steen and Dix, 1974; Strong, 1978). Populus tremuloides surrounds plunge pools in the canyons of southeastern Colorado. Few descriptions have been reported for aspen wetlands so characterization is incomplete.

1.8 Willow Carrs (8.8)Salix dominated wetlands in the montane. Most sites are minerotrophic with a peat layer. Salix planifolia is more abundant in very wet areas. Salix geyeriana, S. monticola, and S. drummondii are more abundant on drier sites (Phillips, 1977; Rottman and Hartman, 1985). Other species such as Salix boothii, S. wolfii, and S. brachycarpa occur on wet and dry sites.

1.8.1 Upper Montane Willow Carrs (8.8.1)

Occur near timberline and are usually dominated by Salix planifolia (Baker, 1986; Rottman and Hartman, 1985; Heifner, M.A.) with an understory of Carex spp., Pedicularis groenlandica, Caltha leptosepala, Trollus laxas, and Sphagnum spp. Carex aquatilis is the most common sedge species. These communities form around small glacial lakes in poorly drained depressions formed by solifluction terraces and along subalpine streams (Smith, 1942; Heifner, 1974). Low and dwarf shrubs occur in microhabitats where shoots are covered with snow most of the winter (Bliss, 1985). Poorly drained sites approach bog-like, ombitrophic conditions (Smith, 1942; Windell et al., 1986). While low Salix shrubs are fairly common in cirques and just above timberline in the Rocky Mountains and eastern alpine areas, they are absent or minor in the Sierras, Nevada Ranges, Cascades and Olympics.

1.8.2 Lower Montane Willow Carrs (8.8.2)

Occur below 10000 feet in broad floodplains inundated by beaver dams and adjacent to meandering streams. Salix brachycarpa, S. wolfii, S. planifolia, S. caudata, S. drummondiana, S. geyeriana, and S.


monticola dominate these communities in various combinations. Betula glandulosa is present near stream margins. Carex aquatilis, Carex rostrata, Calamagrostis canadensis are common understory species. Several studies have recognized mesic and dry willow carrs (Bierly, 1972; Phillips, 1977) but the composition data do not consistently define these communities.

1.9 Montane Grasslands (8.4)Intermixed with forested stands between the upper limits of ponderosa pine woodlands and upper timberline, usually at elevations from 8000-11000 feet. Montane grasslands are most common on fine-textured colluvium in open valleys or on gentle to moderate slopes. These communities are dominated by bunch grasses including Festuca thurberi, F. arizonica, F. idahoensis, Danthonia parryi and Muhlenbergia montana. The distribution map includes South Park grasslands, which is in the Western Slope and Intermountain Valley Region. No stand data were available from South Park to compare montane grasslands of this area.

1.9.1 Lower Montane Grasslands (8.4.2)

Occur at lower elevations than the previous community and are typically dominated by Festuca idahoensis or Festuca arizonica. These two species are both considered within Festuca ovina in some taxonomic treatments (Welsh et al., 1987). The compositional data do not distinguish between communities dominated by either species. In the northern Front Range, Festuca arizonica is absent and Festuca idahoensis is infrequent. Danthonia parryi and Muhlenbergia montana predominate in these areas (Hess, 1981).

References

Galatowitsch, S. 1988. Colorado’s Natural Vegetation. Colorado Natural Areas Program.

Kittel, G. and L. Spears. 1996. Colorado Natural Heritage Program Field Survey of Riparian Vegetation of the Upper South Platte.

Malone, D. 2009. Colorado Natural Heritage Program Field Survey of Gilpin County.


Documents

GOG community descriptions May 2013