Standards for Broad Terrestrial Ecosystem Classification and Mapping
for British Columbia

Table of contents

12.0 SPARSELY VEGETATED UNITS

CL Cliff

General Description

Non-alpine, steep unvegetated rock slope.

Distribution

Cliffs are typically located throughout the province, mainly concentrated in mountainous regions. Cliffs are most often associated with many of the alpine units as well as the talus and rocky outcrop units.

Typical Situation

Cliffs can be defined as steep, vertical or overhanging rock faces (Maser 1979). Characteristic features include fractures, ledges, overhangs and sheer rock faces. Fractures occur at different angles and sizes, depending on the bedrock type. The frequency with which ledges, overhangs and rock faces occur, is directly related to the angle and degree of fracturing that occurs within the given bedrock. Therefore bedrock composition is the key determining factor as to the number, extent and type of each cliff feature which is found.

Many of the cliffs found throughout the province occur as a result of past glaciation. As glaciers advanced then retreated over the province they carved out valleys and plateaus, leaving cliffs adjacent to their paths. Subsequent mechanical and chemical erosion has altered the appearance of many of these cliffs and even created some new ones.

Cliffs composed of softer materials are weathered down more easily, producing smaller fragments and numerous small fractures. Most often these types of bedrock cliffs do not reach substantial heights or degrees of steepness. Cliffs composed of more durable parent materials produce considerably larger fragments and fractures. Cliffs which are most resistant to erosional processes are usually very high, vertical cliffs.

GB Gravel Bar

General Description

Typically a level, unvegetated or partially vegetated fluvial area along an active watercourse.

Distribution

Found extensively along streams and rivers throughout the province.

Climax Vegetation

Gravel bars typically occur as unvegetated or partially vegetated areas along the perimeter of an active watercourse or along the perimeter of an island situated in the middle of an active watercourse. Gravel bars may be composed of mostly gravels, sands, silts, cobbles or any combination of these substrates. Most often these units are flooded annually for varying lengths of times, dependent on the amount of water flow.

Atypical Sites

Gravel bars associated with intermittent streams may be slightly more vegetated than perrennial streams.

GL Glacier

General Description

Typically a field or body of snow or ice formed in higher elevations in mountainous terrain where snowfall exceeds melting: these areas of snow and ice will show evidence of past or present glacier movement.

Distribution

Glaciers are generally found above 1800m in the higher elevation biogeoclimatic zones throughout the mountain ranges of the province.

Biogeoclimatic Units

AT

CWHds1

CWHws2

ESSFmw

MHmm2

SWBmk

BWBSdk1

CWHwm

ESSFmm1

ESSFxv

SWBdk

SWBvk

Physical Environment

Typically glaciers are unvegetated, permanent snowfields and icefields. These remnant icefields and cirque glaciers are now receding and are small in comparison to their former extent. There remains evidence of tremendous ice erosion surrounding many of these glaciers.

PO Lodgepole Pine Outcrop

General Description

Typically a sparse to open lodgepole pine forest, with understories dominated by moss, lichens and grasses, growing on shallow, rocky sites.

Distribution

Limited to areas with shallow soils over bedrock, within the Pacific Ranges.

Biogeoclimatic Units

CWHxm

CWHdm

MSxv

SBPSxc

   

Climax Vegetation

Typically an open forest of lodgepole pine, with minor amounts of Douglas-fir and western hemlock also present. Salal is common in the understory, along with oceanspray. The herb layer is dominated by kinnikinnick. Exposed rock is dominated by lichen and moss.

Successional Vegetation

Early successional stages are represented by oceanspray, salal and kinnikinnick.

Physical Environment

Typically found on very dry sites, with shallow soils and moderate to steep slopes. Most often located on a warm aspect.

RO Rock

General Description

Typically a mixture of gentle to steep, nonalpine bedrock escarpments and out-croppings with little soil development and relatively low vegetative cover.

Distribution

Found anywhere exposed bedrock is located in nonalpine regions of the province. Extensively occurs in mountainous areas.

Climax Vegetation

This unit does not include rock outcropping associated with either the Garry Oak - Arbutus, Douglas-fir - Arbutus or Alpine complex of broad ecosystem units. Rock outcrops are often covered with dense blankets of moss and lichen, especially at lower elevations. At higher elevations, increased precipitation and steeper slopes prevents much accumulation of eroded materials and cliffs and rocky bluffs are more common. Vegetative cover is very sparse and limited to areas with minor accumulations of soil. Cladonia and Cladina lichens are common along with Rhacomitrium mosses.

Physical Environment

Usually found on very dry, steep, exposed rocky slopes and bluffs.

Atypical Sites

Occasionally stunted trees, shrubs and/or herbs can be found in rock crevices, forming an extremely sparse canopy.

TA Talus

General Description

Typically sparsely vegetated, rubbly or blocky colluvial areas, at the base of rock outcroppings, cliffs or escarpments.

Distribution

Found throughout the province in non-alpine areas, usually on steep slopes below rock outcrops or escarpments. The weathered bedrock sheds blocks of rubble which accumulate in draws and across the base of steep slopes and cliffs.

Climax Vegetation

Typically soil moisture is very deep and only deep rooted, hardy shrubs and occasional trees are found here. The vegetative cover is sparse, but saskatoon, choke cherry, sumac, mock orange, rose and raspberry do occasionally occur. Some Cladonia and Cladina lichens are often present; as well as Rhacomitrium mosses.

Physical Environment

Moisture conditions are usually dry to very dry and sites are located on steep slopes.

Atypical Sites

Occasional trees will be found in crevices or on thin accumulations of soil.

UV Unvegetated

General Description

Typically non-alpine, unvegetated areas consisting of exposed soils and excluding unvegetated bedrock sites.

Distribution

Typically the total cover of vegetation, including trees, shrubs, herbs and lichens is less than five percent of the total surface area.

This limited habitat occurs as a result of natural erosion processes, as well as human activities. Some typical sources of exposed soils include cutbanks along watercourses and roads, beaches, gravel pits, landings for sorting and loading logs, glacial moraine, mudflats in association with dried up lakes and ponds and steep slopes where mudslides and debris torrents commonly occur.


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