Alberta's Rocky Mountain Natural Region
Updated December 15, 2006
Mountains, high foothills, and deep glacial valleys define the Rocky Mountain Natural Region. Short, cool summers and cold, snowy winters are typical. At the highest elevations, trees cannot survive; shrubs and herbs grow only in protected places. At lower elevations, coniferous forests are dominant, with grasslands and mixedwood forests on lower elevation warm aspects and valley bottoms.
The Rocky Mountain Natural Region includes the Alpine, Subalpine and Montane Natural Subregions within and adjacent to the Front Ranges and Main Ranges of the Rocky Mountains. It spans the widest elevational range in Alberta, from a low of about 825 m in northern Montane Natural Subregion valleys to a high of over 3600 m (Mount Columbia) in the Alpine Natural Subregion. Rapid aspect changes and extreme slopes are characteristic of the Alpine Natural Subregion, with less pronounced ridged and rolling landscapes in the Subalpine and Montane Natural Subregions.
The following links provides basic information on the key characteristics at the subregion level.
- Alpine Natural Subregion
The Alpine Natural Subregion is a land of mountains, glaciers and snowfields extending north to south along the Continental Divide. Steeply inclined to vertical bedrock exposures, short, cold summers, strong winds and high snowfalls prevent tree growth and limit plant growth to lowgrowing shrubs and herbs in protected areas.
- Mountains, glaciers and snowfields.
- Trees absent except for dwarfed individuals or scattered islands in sheltered locations at lower elevations.
- Harsh climates.
- Highly variable microclimates produced by differing aspects, wind exposures, elevations, substrates, and snow deposition patterns produce complex vegetation patterns.
The Alpine Natural Subregion occupies the highest lands in Alberta, and includes all areas above tree line in the Rocky Mountain Front and Main Ranges. It occurs at elevations as low as 1900 m in the north and as high as the summit of Mt. Columbia at just under 3650 m. Its lower boundary with the Subalpine Natural Subregion decreases with latitude at a rate of about 0.5 m/km northward. A cold, harsh climate along with steep and unstable rocky substrates, active glaciers and permanent snowfields limit plant growth and soil development to sheltered locales.
- Subalpine Natural Subregion
The Subalpine Natural Subregion occurs at high elevations below the Alpine Natural Subregion on rolling to inclined shallow morainal and residual materials over bedrock. Short, cool summers and high winter snowfalls are characteristic. Open stands of Engelmann spruce and subalpine fir are dominant at higher elevations, with stunted individuals and krummholz islands near treeline; closed lodgepole pine forests are prevalent at lower elevations.
- Occurs on midslopes of the Front Ranges and lower slopes of the western Central Ranges.
- Coniferous forests are dominant throughout the Subregion; open Engelmann spruce, subalpine fir and subalpine larch forests interspersed with herb-rich meadows occur at higher elevations and young fire-successional lodgepole pine stands at lower elevations.
- Highly variable microclimates produced by differing aspects, wind exposures, elevations and substrates.
The Subalpine Natural Subregion includes all areas below the Alpine Natural Subregion and above the Montane Natural Subregion south of the Bow River, above the Upper Foothills Natural Subregion north of the Bow River, and within the lower valleys sides and bottoms of the Rocky Mountain Main Ranges. The Subalpine-Upper Foothills boundary occurs at approximately 1350 m in the Grande Prairie area, rising to approximately 1700 m along the Bow River Corridor.
South of the Bow River, the Subalpine Natural Subregion borders the Montane Natural Subregion, and this boundary occurs at about 1600 m. Its lower boundary with the Upper Foothills Natural Subregion decreases with latitude at a rate of about 0.6 m per kilometre northward; its upper boundary with the Alpine Natural Subregion decreases with latitude at a rate of about 0.5 m per kilometre northward. Climatic conditions are somewhat more moderate than the Alpine Natural Subregion, allowing the growth of trees; however, the climate is still cold year-round and tree growth rates are generally slow.
- Montane Natural Subregion
The Montane Natural Subregion, a land of striking contrasts, occurs at lower elevations along the Front Ranges. It extends west into the Main Ranges along major mountain valleys and south along the Porcupine Hills. The upper elevations of the eastern Cypress Hills also belong to this Natural Subregion.
Summers are cool, but winters are warmer than almost anywhere else in Alberta. Lodgepole pine, Douglas fir and aspen stands occur on easterly and northerly aspects and grasslands on southerly and westerly aspect at lower elevations. Closed mixedwood and coniferous forests dominated by lodgepole pine occur at higher elevations. Key
- Occurs on lower slopes and valley bottoms of the Front Ranges south of the Bow Valley, in the Porcupine Hills, within the lower valleys of major mountain river valleys north of the Bow Valley, and on the uppermost elevations of the Cypress Hills.
- Chinooks are frequent along the Front Ranges, and winters are warm with much lower snowfalls than in the Subalpine and Alpine Natural Subregions.
- Highly variable microclimates produced by differing aspects, slope positions and wind exposures produce abrupt changes in vegetation over very short distances.
The Montane Natural Subregion is composed of several separate units. The largest continuous unit spans lower elevations along the Front Ranges of the Rocky Mountains from just north of the Bow Valley to the Alberta-Montana border, including the Porcupine Hills. An outlier occurs on the highest elevations of the Cypress Hills in southeastern Alberta.
North of the Bow River Valley, the Montane Natural Subregion extends from the foothills west into the Main Ranges along major eastwest river valleys including the North Saskatchewan, Athabasca and Smoky Rivers, with a small isolated outlier on the Red Deer River at the Ya-Ha-Tinda Ranch. Its upper boundary is the lower limit of the Subalpine Natural Subregion.
South of the Bow River, the Montane Natural Subregion intergrades with the Foothills Fescue and Foothills Parkland Natural Subregions, which have similar climates, vegetation and soils along the boundary. North of the Bow River, the Montane Natural Subregion is bounded on the east by the Upper Foothills or Lower Foothills Natural Subregions.
This is the driest and warmest of the three Natural Subregions in the Rocky Mountain Natural Region, and regional and local climatic influences produce a highly diverse array of plant communities and soil types that change rapidly over very short distances.
The new Natural Regions and Subregions of Alberta Report (5.2 MB) is now available.
View the Errata Report(23 KB) for the printed and digital versions of the above report, prior to May 15 2006.