(7) Subalpine Fir/Goldenweed/Aster-Blue Wildrye
This relatively lush seral community is found between 1540 and 1920 m in the vicinity of streams and at the base of steep ridges. The most extensive stands are on the west slope of Mount Mazama, Munson Valley, and along upper Sand Creek. Smaller stands occur near Sphagnum Bog, Crater Springs and Pole Bridge Creek. Floristically, this type differs from others in the presence of Cascade aster, blue wildrye, Green’s rabbitbrush and/or Rydberg’s penstemon. Subalpine fir is also present in almost all areas. Rather than being a true forest, the community is a forest-meadow mosaic. Patches of relatively dense trees of all sizes are separated by relatively lush meadows of lupines, grasses and sedges. The islands of tree reproduction appear to be slowly spreading into the meadow areas. Heavy litter accumulations occur only in the tree islands. In older, nearly closed stands, such as those found in upper Munson Valley, tree mortality from mountain pine beetle has been and continues to be quite high among older, larger trees.
Most of these areas were burned before 1900 by ranchers, to improve grazing for their herds. Age analysis indicates that most of the west slope stands are of post-white man origin while those in Munson Valley contain pre-white man age classes. Charcoal data indicate that some earlier stands contained predominantly fir and hemlock. Fires in this type, at present, would probably be limited to a few tree ” islands'” and the intervening meadow-like areas. In the primeval forest, intense fires through nearly closed forests of this type probably resulted in very open forest-meadow mosaics. These mosaics gradually closed over several generations of trees, with closure retarded or temporarily reversed by periodic light or small fires. The closed forests either burned again or developed to pure fir-hemlock stands.
(8) Shasta Fir-Mountain Hemlock/Sedge-Lupine
This widespread seral community is found between 1690 m and 2080 m through out the Park. Extensive stands may be found in the northwest quarter of the Park, on the slopes of Timber Crater and in Castle Creek Valley. This community is recognized by the presence of pine and/or broadleaf lupine in an understory of conspicuous and apparently vigorous fir and hemlock reproduction.
Bark beetle activity and breakage at galls on the main stems of trees have contributed to a heavy accumulation of lodgepole pine litter. Fires in this community would probably result in nearly 100% tree mortality and a post-fire forest of lodgepole pine. However, litter loads would again be high within a decade or two after the fire as fire-killed trees fell.
Age analysis of stands comprising this community reveals that only half of the stands contain trees which germinated before 1855. Charcoal from some of the stands indicates that the sites were occupied earlier by fir and hemlock forests. In addition, many stands contain old, unburned logs and stumps that were obviously quite old firs and hemlocks from a previous forest. Some stands contain surviving large trees of these species. Other stands of almost pure medium-sized fir and hemlock contain a few very large lodgepole pines and have considerable lodgepole mortality on the forest floor.
These data and observations in this community suggest that:
1) A natural cycle exists where lodgepole pine forests are created from mature fir-hemlock forests by fire. Lodgepole pine forests created in this manner may be maintained as lodgepole by repeated fire for a period of time before developing to fir-hemlock again (Fig. 1).
