Reply to comment by Jackson and Martin on "does timber harvest influence the dynamics of marine-derived nutrients in Southeast Alaska streams?"

• Published in: Canadian journal of fisheries and aquatic sciences Vol. 69; no. 11; pp. 1898 - 1901
• Main Authors: Levi, Peter S, Tank, Jennifer L, Tiegs, Scott D, Ruegg, Janine, Chaloner, Dominic T, Lamberti, Gary A
• Format: Journal Article
• Language: English
• Published: Ottawa NRC Research Press 01.11.2012; Canadian Science Publishing NRC Research Press
• Subjects: Creeks & streams; Distribution; Ecological research; Environmental aspects; Freshwater; Geomorphology; Marine ecology; Nutrients; Oncorhynchus; Salmon; Salmonidae; Timber; Alaska; USA, Alaska
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/f2012-106

The stated goal of Levi et al. (2011, Can. J. Fish. Aquat. Sci. 68: 1316-1329) was to determine the influence of geomorphic complexity on the dynamics of salmon-derived nutrients. We studied seven streams in Southeast Alaska with varying degrees of historical (mid-1900s) timber harvest and, as a result, differences in stream geomorphology. In a comment on our study, Jackson and Martin (2012, Can. J. Fish. Aquat. Sci. 69: this issue) suggest that the geomorphic complexity we ascribe to timber harvest may be due to natural variation in watershed characteristics and offer alternative hypotheses. We sought to reduce the natural variation among our study streams by using a stratified sampling design (i.e., selecting reaches classified as floodplain 4 or 5 by the USDA Forest Service), but acknowledge that, as with any ecological field study, alternative hypotheses may exist to explain observed patterns in ecological responses. We maintain that our study design was sufficiently robust (i.e., 300 m reaches studied in seven streams for 3 years, totaling 21 stream-years) to draw inferences about the influence of salmon on streamwater nutrients and, secondarily, the role of geomorphic variation in mediating nutrient dynamics. Our data also support our finding that the legacy of timber harvest altered nutrient dynamics in salmon-bearing streams via alterations to stream geomorphology that were quantifiable.