Composition of Old Growth Ponderosa Pine Forests
The dominant species in ponderosa pine old-growth forests is, not
surprisingly, ponderosa pine. In many forest patches it forms pure stands but
is also found with other species. In dry sites it is with western juniper,
along the eastern slopes of the Cascade Range it is found with Oregon white
oak, in riparian corridors it is joined by quaking aspen, and in pumice-rich
central Oregon, it associates with lodgepole pine. These days which the encroachment
of shade tolerant species, however, it might very well have its greatest association
with grand fir and Douglas fir.
Even without fire disturbance, ponderosa pine stands are often encroached
by other species. Ingrowths of Douglas-fir and the true firs enter at moist
sites especially as elevation increases and at ingrowths of juniper occur in
dryer sites at the lower elevations.
Under this canopy, a sparse layer of grasses and shrubs grow. In Eastern
Washington, a typical understory is snowberry, western serviceberry, and roses
along with bluebunch wheatgrass. In the pumice regions of central Oregon, this
understory changes to antelope bitterbrush, greenleaf manzanita, and Idaho
Few animal species live exclusively in the ponderosa pine zone. Mule
deer, white-tailed deer, and elk enter to graze the shrubs, and predators – especially
the reclusive mountain lion - follow them. Squirrels and chipmunks are common
as well and are among the rodents that collect seeds from many of the shrubs
and trees, thereby helping to distribute plant species, including ponderosa
pine. In addition, a number of birds, such as blue grouse, find food and nesting
sites in the shrubs of ponderosa pine forest.