Buffering the Buffer 1

Riparian buffer strips are a widely accepted tool for helping to sustain aquatic ecosystems and to protect downstream resources and values in forested areas, but controversy persists over how wide a buffer strip is necessary. The physical integrity of stream channels is expected to be sustained if the characteristics and rates of tree fall along buffered reaches are similar to those in undisturbed forests. Although most tree-fall-related sediment and woody debris inputs to Caspar Creek are generated by trees falling from within a tree’s height of the channel, about 30 percent of those tree falls are triggered by trees falling from upslope of the contributing tree, suggesting that the core zone over which natural rates of tree fall would need to be sustained is wider than the one-treeheight’s-width previously assumed. Furthermore, an additional width of “fringe” buffer is necessary to sustain appropriate tree-fall rates within the core buffer. Analysis of the distribution of tree falls in buffer strips and un-reentered streamside forests along the North Fork of Caspar Creek suggests that rates of tree fall are abnormally high for a distance of at least 200 m from a clearcut edge, a distance equivalent to nearly four times the current canopy height. The appropriate width of fringe buffer needed to protect the core zone will need to be determined using an analysis of the long-term effects and significance of accelerated tree-fall rates after logging. Riparian buffer strips provide an efficient and widely accepted way to help protect aquatic ecosystems and downstream values from the effects of upslope land-use activities. Buffer strips are also the focus of a major controversy concerning the appropriate balance between rights and responsibilities, between resource extraction and resource protection. The question at the center of the controversy: how wide should a buffer strip be? Here we first discuss the roles intended for riparian buffer strips and then describe preliminary results of a study that examines the stability of riparian buffer strips. The Role of Riparian Buffers Riparian buffer strips are intended to allow natural interactions between riparian and aquatic systems to be sustained, thus providing some assurance that appropriate in-stream ecosystems, sediment regimes, and channel forms can be maintained. Specific roles of riparian zones—and particularly of riparian trees—with respect to the in-stream environment include: • Maintenance of the aquatic food web through provision of leaves, branches, and insects • Maintenance of appropriate levels of predation and competition through support of appropriate riparian