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Eastern Cascades Slopes and Foothills

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NameColor on MapEPA Code‡
Yakima Plateau and Slopes9a
Grand Fir Mixed Forest9b
Oak/Conifer Foothills9c
Ponderosa Pine/Bitterbrush Woodland9d
Pumice Plateau9e
Pumice Plateau Basins9f
Klamath/Goose Lake Basins9g
Fremont Pine/Fir Forest9h
Southern Cascades Slope9i
Klamath Juniper Woodland/Devils Garden9j
Shasta Valley9k
Pit River Valleys9l
Warner Mountains9m
High Elevation Warner Mountains9n
Likely Tableland9o
Modoc/Lassen Juniper-Shrub Hills and Mountains9p
Adin/Horsehead Mountains Forest and Woodland9q
Adin/Dixie Low Hills9r
Modoc Lava Flows and Buttes9s
Old Cascades9t

† Status: ✓ = Complete ○ = Needs Image … = Incomplete ∅ = Stub Only

This code refers to the US EPA's Level 4 ecoregion codes for the continental U.S., see here.


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About the Eastern Cascades Slopes and Foothills

The Eastern Cascades Slopes and Foothills is a region of mountains to hills and plateaus on the east side of the Cascade Range, where precipitation is lower due to rain shadow. This region is narrow over most of its width, and does not extend to the northernmost reaches of the Cascade Range. In the south, it widens, reflecting the lower elevations of the southern end of the Cascades, as well as greater rain shadow from the taller Klamath mountains to the west. This region corresponds more to ecologically-similar zones rather than geological formations.

The terrain here consists of gently sloping mountains, mostly in the west, to high plateaus ranging from flat to hilly. There are volcanic cones and buttes throughout, as well as some relatively recent lava flows. Because of the lower rainfall, the terrain is only weakly dissected, with plateaus featuring isolated canyons through a mostly undissected landscape. The south is largely unglaciated but moving north there are more glaical features as well. The bedrock is volcanic, consisting mostly of basalt, andesite, and tuff, with surface deposits of ash, pumice, and cinders that can be thick in some areas. Stream density tends to increase to the north, and there tend to be fewer streams in areas underlain by pumice.

The climate here is more arid and has greater continental influence than regions to the west; it has attributes of humid continental and Mediterranean climates. Precipitation is strongly seasonal, with wet winters and dry summers, but in spite of the lower total precipitation, summers do receive slightly more rainfall than areas closer to the coast.

This region is covered primarily in open forests of mostly ponderosa pine (Pinus ponderosa), with some lodgepole pine (Pinus contorta). The higher elevations feature douglas-fir (Pseudotsuga menziesii), grand fir (Abies grandis) and white fir (Abies concolor), more characteristic of areas to the west, whereas the lower elevations support sagebrush and steppe, more typical of areas to the east. Wildfire is common throughout much of the region, and frequency and severity of fire is an important mechanism at maintaining the borders between different cover types.

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