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L ,4N.A-;TtR . Robert J. Naiman Robert E. Bilby Editors River Ecology and Management Lessons from the Pacific Coastal Ecoregion Sylvia Kantor Associate and Managing Editor With 202 Ilustrations Springer Robert J. Naiman Robert E. Bilby School of Fisheries Weyerhaeuser Company University of Washington Tacoma. W A 98477 Seattle, W A 98195 USA USA Cover: Queets River, Olympic National Park. Washington (Photo by Tim Hyatt) Library of Congress Cataloging-in-Publication Data River ecology and management: lessons from the Pacific coastal ecoregion (edited-by) Robert J. Naiman, Robert E. Bilby. p. cm. Includes index. ISBN 0-387-98323-6 (hc: alk. paper) 1. Stream ecology-Pacic Coast Region (North America) 2. Stream conservation-Pacific Coast Region (North America) I. Naiman. Robert J. II. Bilby, Robert E. QHI04.5.P32R57 1998 577.6' 4' 0979-dc21 97-44766 Prted on acid-free paper. 1998 Springer-Verlag New York. Inc. All rights reserved. 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Prted in the United States of America. 987654321 ISBN 0-387-98323-6 Spriger-Verlag New York Berlin Heidelberg SPIN 10523806 :';.' , , . Dynamic Landscape Systems Lee E. Benda, Daniel J. Miler, Thomas Dunne, Gordon H. Reeves and James K. Agee Overview prises a population of diverse hilopes that creates spatial varabilty in the sediment and Dynamc landscape processes inuence wood supplied to chanels; (3) chanel net- the supply, storage and transport of water, works, which govern how sediment and wood sediment, and wood, thereby shaping many are routed through a population of lied aspects of riparan and aquatic habitats. These stream reaches and unevenly reditrbuted in processes comprise the disturbance regime of a time and space; and (4) basin history, which watershed. effects the volume of sediment and wood stored The study of natural disturbance (and cu- on hiUslopes and in stream chanels, and which mulative effects) in riverie and riparian areas inuences how sediment and woody debri are . "requires a fundamental shif in focus from redistributed durng storm, fies, wid, and individual landscape elements (such as a forest floods, )3. hislope, and a stream reach) over short . The study of landscapes as systems, focus- ing on the collective behavior of populations of tiescales (year) to populations of landscape e1ements over long time scales (decades to cen- landscape elements over tie, provides the Wres). The study of landscapes as a system necessar framework for investigating natural ands the focus from predictions about exact disturbance and cumulative effects. The field futue states to predictions about the relation- application of thi framework provides inights lbps between large-scale properties of land- into how chanel and riparan morphologies l1pes (i. , cliate, topography, and channel are related to the recent environmental history Detworks) and the long-term behavior of of a watershed. i'quatic systems. Temporal patterns of landscape behavior best described by frequency distributions Introduction :ch estimate the probability of a specific nt occurng. Likewise, describing spatial Powerfl climatic and geomorphic processes ems amongst a population of landscape el- shape the landscape of the Pacifc coastal in any year requires proportionig their ecoregion. Cliatic conditions produce wild- cteristics amongst the range of aUpossible fires and windstorm that modif large tracts 9nmental conditions, and this also is best of forests, enabling new species to contribute to bed by frequency distributions. a diversity of forest ages and structures. Fires Characteristics of landscapes that var in paricular, controlled the age distribution ,.y over time can be described by four of natural forests prior to fie suppression 9nents: (1) climate, which drives environ- throughout most of the mid- and southern pars r., varabilty; (2) topography, which com of the Pacifc coastal ecoregion (Teensma 1987 261 ', ;; L.E. Benda et al. 262 1990), wind (Borman Morrison and Swanson 1990. Agee 1993). Fires Morrison and Swanson and storms trigger geomorphic processes such et al. 1995). snow avalanches (Hemstrom and rockfalls (Oliver 1981). as bank erosion, surface erosion and gullying, Franklin 1982), and and shallow and deep landslides; processes Although some of the disturbances influencing aquatic systems have been recognized, they which control the supply of sediment and wood quantified (Everest and to streams (Dietrich and Dunne 1978, Swanson have not been well 1981. Sedell and Swanson 1984 1981. Swanston 1991). Once in stream channels, Meehan , Frissell et al. 1986, Resh et sediment and wood are transported episodi- Minshall et al. 1985 cally and redistributed unevenly through the al. 1988. Naiman et al. 1992). As a consequence channel network by floods. descriptions of streams in the context of their spatial deter- Collectively, these climatic and geomorphic watersheds have emphasized minism (which include classification systems processes comprise the disturbance regime of stream biota) a watershed. The term disturbance refers to a of channel morphology and environment that leads to a (Vannote et al. 1980, F rissell et al. 1986. Rosgen disruption in an 1997. Chap- biological response (Pickett and White 1985). 1995, Montgomery and Buffington Fully understanding the role of disturbance ters 2 and 5). Given the importance of distur- in shaping aquatic ecosystems requires estimat- bance in aquatic systems. why has disturbance ing its regime frequencies. magnitudes. and been difficult to define? spatial distributions of landscape processes. Most quantitative theories of landscape pro- Likewise. cumulative effects (because they in- cesses. and their derivative predictive models volve a history of human activities dispersed address the behavior of a single landscape pro- in time and space) can beviewed as a modi- cess (such as fire. flooding, sediment transport, fication of a regime-a shift in frequency. and slope stabilty). or a single landscape magnitude and spa tical distribution of element (such as an individual forest stand hilslope, or stream reach). over short time processes. fire, Disturbance is embodied in the temporal be- scales; for example, responses to a single havior of a single (or set of interacting) land- storm, or flood. Disturbance regimes (and cu- scape element(s). such as forests, hilsides. and mulative effects which can be viewed as an al- streams over decades to centuries. However teration of a regime) in aquatic systems remain in any year. the history of a dynamic climate unquantified largely because theories and mod- els designed to predict numerical solutions or the history of disturbance is represented by processes at the environmental condition of a population about exact future states of single , a few years) are inappropriate of landscape elements (e.g.. hundreds to thou- small scales (e. stream for understanding behavior of populations of sands of forest stands. hilsides. or g.. de- reaches). Therefore, the study of disturbance processes occurring at larger scales (e. I:: cades to centuries). Limitations in data and II' fundamentally involves changes over time and populations of landscape elements. computing power. and the unpredictabilty of the weather. further confound applications I . 11 Natural disturbance is of great interest to resource managers of data-intensive, small-scale theories and . t researchers and natural term because dynamic (temporal) aspects of land- models to the problem of predicting long- ecosystem behavior. scapes are an inherent characteristic of ecosys- distur- t'5 ; :i: . tems in the region (Swanson et al. 1988), and Understanding the consequences of because natural disturbance can be contrasted bance (or cumulative effects) in aquatic sys- reveal tems requires a fundamental shift in focus from with human impacts or disturbances to . ele- the long-term consequences of resource man- individuals to populations (of landscape time scales. For agement. The study of disturbance in land- ments) and from short- to long- scapes of the Pacific coastal ecoregion has example, the behavior of a population of land- sources of focused primarily on processes in terrestrial en- scape elements (such as all point watershed), and the vironments such as revegetation following vol- sediment and wood in a canism (Franklin 1990), fires (Teensma 1987. interaction of that population with other popu- , ; L.E. Bendel et al. 11. Dynamic Landscape Systems 263 I, wine: (Borman lations (such as a set of linked stream reaches A new system-scale framework is described us- (Hemstrom and comprising a whole network) involves routing ing