caa a22 4500 467886148 CHVBK 20180406152735.0 cr unu---uuuuu 170328e20060301xx s 000 0 eng 10.1007/s10021-004-0063-5 doi (NATIONALLICENCE)springer-10.1007/s10021-004-0063-5 Keystone Interactions: Salmon and Bear in Riparian Forests of Alaska [Elektronische Daten] [James Helfield, Robert Naiman] The term "keystone species” is used to describe organisms that exert a disproportionately important influence on the ecosystems in which they live. Analogous concepts such as "keystone mutualism” and "mobile links” illustrate how, in many cases, the interactions of two or more species produce an effect greater than that of any one species individually. Because of their role in transporting nutrients from the ocean to river and riparian ecosystems, Pacific salmon (Oncorhynchus spp.) and brown bear (Ursus arctos) have been described as keystone species and mobile links, although few data are available to quantify the importance of this interaction relative to other nutrient vectors. Application of a mass balance model to data from a southwestern Alaskan stream suggests that nitrogen (N) influx to the riparian forest is significantly increased in the presence of both salmon and bear, but not by either species individually. The interactions of salmon and bear may provide up to 24% of riparian N budgets, but this percentage varies in time and space according to variations in salmon escapement, channel morphology and watershed vegetation characteristics, suggesting interdependence and functional redundancy among N sources. These findings illustrate the complexity of interspecific interactions, the importance of linkages across ecosystem boundaries and the necessity of examining the processes and interactions that shape ecological communities, rather than their specific component parts. Springer Science+Business Media, Inc., 2006 salmon nationallicence bear nationallicence riparian forest nationallicence marine-derived nutrients nationallicence nitrogen nationallicence keystone species nationallicence Helfield James College of Forest Resources, University of Washington, Box 352100, 98195, Seattle, Washington, USA aut Naiman Robert School of Aquatic and Fishery Sciences, University of Washington, Box 355020, 98195, Seattle, Washington, USA aut Ecosystems Springer-Verlag; www.springer-ny.com 9/2(2006-03-01), 167-180 1432-9840 9:2<167 2006 9 10021 https://doi.org/10.1007/s10021-004-0063-5 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10021-004-0063-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Helfield James College of Forest Resources, University of Washington, Box 352100, 98195, Seattle, Washington, USA aut NATIONALLICENCE 700 1- Naiman Robert School of Aquatic and Fishery Sciences, University of Washington, Box 355020, 98195, Seattle, Washington, USA aut NATIONALLICENCE 773 0- Ecosystems Springer-Verlag; www.springer-ny.com 9/2(2006-03-01), 167-180 1432-9840 9:2<167 2006 9 10021 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer