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Disturbance-maintained ecosystems comprise the following BEC
zones: Dry Coastal Douglas-fir (CDF-d), Dry Interior Douglas-fir
(IDF-d), Ponderosa pine-bunchgrass (PP), and Bunchgrass (BG).
They occur at low elevations on the dry, leeward side of major
mountain ranges — in the Georgia Depression and in major
river valleys of the southern interior. On the coast the CDF-d
zone includes Garry oak-meadow communities, one of the most
endangered ecosystems in Canada and the subject of a major restoration
program. In the interior valleys similarly endangered dryland
ecological communities (PP and BG) are continuous southward
with similar communities in Washington, Idaho and Montana states.
Two maps are shown below:
Map
1 — Physiographic Regions
The first map shows the major physiographic regions of British
Columbia — mountains, depressions, plateaus and valleys.
The interaction of these topographic features and the prevailing
moist Pacific weather systems produces a sequence of wet windward
mountain slopes and drier, “rain-shadow” climates
in depressions, plateaus and major valleys. This physiographic
map will help you understand the distribution of natural disturbance
regimes in the Province, which are shown in the second map.
Map
2 — Disturbance Regimes
The second map shows the relationship between the three
disturbance regimes and the major physiographic zones. Note
especially the location of disturbance-maintained ecosystems.
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