. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. Figure 44. — An understory characterized by Berberis nervosa typifies modal sites in the Tsuga heterophylla Zone; a Pseudotsuga men- ziesii-Tsuga heterophylla /Berberis ner- vosa community in western Oregon (H. J. Andrews Experimental Forest). The Tsuga heterophylla/Berberis nervosa association and its relatives typify the climatic climax for the Tsuga heterophylla Zone (fig. 44). Old-growth stands consist primarily of Pseudotsuga menziesii, Tsuga heterophylla, and Thuja plicata. Tsuga heterophylla
. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. Figure 44. — An understory characterized by Berberis nervosa typifies modal sites in the Tsuga heterophylla Zone; a Pseudotsuga men- ziesii-Tsuga heterophylla /Berberis ner- vosa community in western Oregon (H. J. Andrews Experimental Forest). The Tsuga heterophylla/Berberis nervosa association and its relatives typify the climatic climax for the Tsuga heterophylla Zone (fig. 44). Old-growth stands consist primarily of Pseudotsuga menziesii, Tsuga heterophylla, and Thuja plicata. Tsuga heterophylla is, theo- retically, the sole climax species based on size- class analyses. However, long-lived Pseudo- tsuga menziesii and Thuja plicata are often present in stands undisturbed for 500 years or more. The understory is generally balanced be- tween layers in the Tsuga/Berberis associa- tion. Major shrubs are Berberis nervosa, Acer circinatum, Vaccinium parvifolium, Rubus ursinus, and Rhododendron macrophyllum. Typical herbs are Linnaea borealis, Viola sem- pervirens, Coptis laciniata, and Goodyera ob- longifolia. The most common moss is Eurhyn- chium oreganum. Polystichum munitum and Gaultheria shallon are often present, but not as understory dominants. The Tsuga heterophylla /Polystichum mu- nitum association characterizes the herb-rich communities found on moister habitats. The overstory usually includes Pseudotsuga men- ziesii, Tsuga heterophylla, and Thuja plicata. Very large Pseudotsuga are encountered in old-growth stands, as growth conditions are near optimum for the species. Size-class analy- ses indicate Tsuga heterophylla will be the major climax species, but Thuja plicata also reproduces in sufficient quantity to perpetu- ate itself. The understory is dominated by a lush growth of herbs (fig. 45), including Po/y-. Figure 45. —Polys tic hum munitum dominates the lush herbaceous understory on moist sites in the Tsuga heterophylla Zone (H. J. Andrews Experimental Fo
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