. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. Figure 35. —The prolific and fast-growing Alnus ru- bra often pioneers on logged or burned lands in the Picea sitchensis Zone, offer- ing severe competition for conifers; this typical 50-year-old Alnus rubra stand has an understory dominated by Rubus spec tab His (Siuslaw National Forest, Oregon). Succession in most mature conifer forest types is toward replacement of mixed Picea, Thuja, Tsuga, and Pseudotsuga forests by Tsuga heterophylla. This species is apparently more tolerant than the Picea si
. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. Figure 35. —The prolific and fast-growing Alnus ru- bra often pioneers on logged or burned lands in the Picea sitchensis Zone, offer- ing severe competition for conifers; this typical 50-year-old Alnus rubra stand has an understory dominated by Rubus spec tab His (Siuslaw National Forest, Oregon). Succession in most mature conifer forest types is toward replacement of mixed Picea, Thuja, Tsuga, and Pseudotsuga forests by Tsuga heterophylla. This species is apparently more tolerant than the Picea sitchensis and dominates the reproduction in old-growth for- ests. Since P. sitchensis, Thuja plicata, and Pseudotsuga menziesii are all long-lived spe- cies, even very old stands usually retain at least some of the original representation of these species. On moist to wet sites, it appears T. plicata and, in some cases, P. sitchensis will be at least a part of the climax along with T. heterophylla. Much of the forest regeneration in conifer stands takes place on rotting logs, "nurse logs," which often support hundreds of Tsuga, Picea, and Thuja seedlings (fig. 36) (Sharpe 1956). Some of these survive, and their roots eventually reach mineral soil. The consequences are often readily visible in for- ests as lines of mature trees growing along the remains of the original nurse logs. Special Types Including, as it does, the ocean strand, headland, and coastal plain environments, the Picea sitchensis Zone is the locale of a rich variety of specialized communities. Sand dune and strand communities. — Sand dunes are the major locale where ocean- facing vegetation types have been studied by ecologists. In Oregon and Washington, there are extensive areas of such dunes — on 225 kilometers of 500 kilometers of shoreline in Oregon alone (Wiedemann 1966) (fig. 37). The greatest development is the Coos Bay dune sheet covering 86 kilometers of contin- uous coastline and a major
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