PONDEROSA-LODGEPOLE PINE ON PUMICE (59)

Geographic Distribution. The most common forest and/or woodland cover type in the southern half of the eastern Cascades ecoregion. The long taproots of lodgepole (Pinus contorta) and ponderosa (P. ponderosa) make them especially well adapted to the droughty pumice soils of this region. Pumice soils are derived from the volcanic eruptions of prehistoric Mount Mazama and numerous cinder cones throughout the region. This forest type forms a nearly continuous cover from LaPine to the northern edge of the Klamath Marsh.

Structure and Appearance. Ponderosa and lodgepole dominate the overstory canopy and regeneration layers in these forests. In its mature, undisturbed form, these forests are distinctly two story canopies with large ponderosa over the shorter lodgepole. Due to extensive selective logging in this type most of the large ponderosa have been removed leaving large tracts of single story lodgepole forests. Regeneration and tree growth are slow in these infertile forests. These forests have an active fire history and have evolved with frequent fires.

Shrub and herb layers are poorly developed in this forest type.

Composition. Ponderosa and lodgepole are the most commonly encountered trees. In wet places and riparian strips, Engelmann spruce (Picea engelmannii), quaking aspen (Populus tremuloides), and white fir (Abies concolor) can be found.

The shrub layer in this cover type is poorly developed. The most commonly associated shrubs are bitterbrush (Purshia tridentata), greenleaf manzanita (Arctostaphylos patula), kinnikinnik (A. uva-ursi), and serviceberry (Amelanchier alnifolia).

The herb layer in most stands has sparse cover with few species. Several grasses, western needlegrass (Stipa occidentalis), squirreltail (Sitanion hystrix), Wheeler's bluegrass (Poa nervosa), and Idaho fescue (Festuca idahoensis) are commonly found. Other forbs can be: wooly wyethia (Wyethia mollis), white hawkweed (Hieracium albiflorum), and Ross' sedge (Carex rossii).

Landscape Setting. The distribution of the ponderosa-lodgepole pine on pumice cover type closely corresponds to the distribution of deep tephra layers from the regions volcanic activity. As such, it doesn't necessarily relate to environment or climatic conditions.

References. Volland 1988, Kovalchik 1987, Hopkins 1979.