Using association tables and a two-dimensional ordination procedure, two topo-edaphic climaxes (associations) have been identified. These are: (1) the Tsuga heterophylla/Po1ystichum mumitum-OxaIis oregana association occurring on terraces with fine, sandy loom to silt loam soils derived from silty river alluvium; and (2) The Tsuga heterophyfla/Berberis nervosa-Gaultheria shallon association occurring on rockier soils with coarser alluvium or glacial outwash. Two early seral associes, each dependent on sedimentation, plus later seral associes, at least one dependent on recent fires, are also identified. A major factor leading to vegetation differences appears to be moisture availability in late summer. (The soils in the Tsuga heterophylla/Berberis nervosa Gaultheria shallon habitat type are shallower, coarser, and rockier than those in the Tsuga heterophvlla/ PoIystichum munitum-0xalis oregana habitat type). This hypothesis is supported by plant moisture stress-measurements on saplings growing in each of the topo.edaphic associations.