Vegetation
Shasta Red Fir
The Shasta red fir historic plant association is at the southeastern and eastern edges of the park. This association is a transitional area from a udic (wet) soil moisture regime to a xeric (dry) regime. This association is at slightly lower elevations than the udic mountain hemlock association and at higher elevations than the xeric ponderosa pine/fir association. The understory vegetation in most of the Shasta red fir association is limited, but grasses and sedges are most common.
Because of the sparse understory vegetation, fires spread slowly in this association and seldom destroy large areas of trees. Naturally occurring fires commonly are patchy and of low intensity. Shasta red fir sustains moderate damage from low-intensity fires (Atzet and Wheeler, 1982). Stand-replacing fires in Shasta red fir stands are rare; the interval between fires is 70 to 130 years (Atzet and McCrimmon, 1990). Fire suppression practices allow the Shasta red fir stands to become older. As the older trees die and accumulate on the forest floor, the potential for stand-replacing fires increases.
If a large stand-replacing fire occurs, lodgepole pine typically is the first tree species to become re-established. As the lodgepole pine matures, Shasta red fir becomes re-established. If the fires are small and a seed source is nearby, Shasta red fir typically becomes re-established with some lodgepole pine.
Fire exclusion on this association can lead to invasion by shade-tolerant tree species. At the higher elevations, mountain hemlock invades, and at the lower elevations, white fir invades. On north aspects, the mountain hemlock association can become established.
The ecological sites in the Shasta red fir plant association are Shasta red fir/longstolon sedge (Abies x shastensis/Carex inops), Shasta red fir/pinemat manzanita/longstolon sedge (Abies x shastensis/Arctostaphylos nevadensis/Carex inops), and Shasta red fir-western white pine/pinemat manzanita (Abies x shastensis-Pinus monticola/Arctostaphylos nevadensis).
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