Stream Ecosystem Restoration: Is Watershed-Scale Treatment Effective Without Instream Habitat Rehabilitation?

摘要

Many researchers have written that the integrity of stream ecosystems is governed by watershed-level landscape variables, such as geology and land use (Hynes 1975, Roth and others 1996, Allan and others 1997, Schlosser 2002), while others have coined the term "river-scape" to emphasize the role of landscape-scale variables in stream ecosystems (Fausch and others 2002). Accordingly, some researchers and practitioners prefer a "passive approach" to stream restoration. This method consists of halting anthropogenic practices and process disturbances that prevent recovery, while suggesting that reach-scale manipulations are typically ineffective (Beschta and others 1994). Others admit the dual importance of reach- and watershed-scale influences, but emphasize the importance of processes acting at larger spatial scales (Roth and others 1996, Wissmar and Beschta 1998). They favor the restoration of functional processes rather than forms (for example, restoring conditions leading to island formation as opposed to constructing islands with equipment) (Ward and others 2002).