Stream channel configuration, landform, and riparian forest structure in the Cascade Mountains, Washington

The hierarchical relationship of five key elements, valley constraint, ripa rian landform, riparian plant community, channel type, and channel configur ation, are described for 21 sites in mature to old-growth riparian forests of the western Cascades Mountains, Washington, U.S.A. Channel type (bedrock , plane-bed, and forced pool-riffle) was closely related to channel configu ration (especially large woody debris (LWD) volume, density, and LWD-formed pools) at the smallest spatial scale and valley constraint at the largest. Valley constraint significantly influenced off-channel habitat (r(2) = 0.7 1) and LWD volume within forced pool-riffle channels (r(2) = 0.58). Riparia n plant community composition was differentiated by four landform classes: three alluvial landforms based on height above the channel and one based on hillslope. Just above the active channel, floodplain landforms contained m ore deciduous stems than conifer and greater conifer basal area than decidu ous. Conifers dominated other landforms. The diameter of in-channel LWD inc reased with the age of the riparian forest (r(2) = 0.34). In old-growth for ests, LWD diameter was equivalent to or greater than the average riparian t ree diameter for all sites. In younger forests, the mixed relationship betw een LWD and riparian tree diameter may reflect a combination of LWD input f rom the previous old-growth stand and LWD input from the existing stand.