The Salmon Forest Project
Nutrients tend to flow from the land to the sea but recent studies by researchers in Alaska, British Columbia and Washington have focussed attention on the immense schools of migrating salmon that return nutrients from the open Pacific Ocean to coastal rivers and terrestrial habitats. Our research group has observed that black bears and grizzly bears throughout the British Columbia coast transfer large quantities of salmon carcasses from rivers into forests and these nutrients are incorporated into a broad diversity of plant and animal taxa.  We are using nitrogen and carbon isotopes to quantify the uptake of salmon-derived nutrients by mosses, herbs, shrubs, trees, insects (Wilkinson et al 2002, Hocking  and Reimchen 202,  Reimchen et al. 2003, Mathewson et al. 2003, songbirds (Christie and Reimchen, 2008, Christie et al. 2008),  bears  (Klinka and Reimchen 2002,  2009a, 2009b),  wolves (Darimont and Reimchen  2002, Darimont et al. 2003, 2007, 2008)(see additional projects on Lab Members Page and Publications) .

Toggle flow diagram for video clip.

One of the results to emerge from our studies has been the detection of salmon signatures in the yearly growth rings of ancient trees. Conifer trees adjacent  to salmon rivers on the west coast of North America incorporate marine-derived nitrogen from the carcasses of salmon carried into the forest by bears and other scavengers. We demonstrated (Reimchen et al. 2003) that small samples of wood  (30 mg) extracted from cores of ancient trees contain detectable levels of 15N. Comparisons among  watersheds differing in number of salmon show that 15N levels in wood of trees are directly proportional to the present numbers of salmon entering the streams. Comparisons within watersheds along a sharp gradient in salmon density also show a strong positive correlation with 15N levels in trees and salmon density.  Historical fluctuations in 15N levels extracted from yearly growth rings of trees show significant tracking with salmon escapement over the last 50 years for some trees yet no association for other trees that occur within the same microhabitat.  Within watersheds, larger and older trees exhibit higher 15N levels than small trees from the same habitat. Among trees with major access to salmon carcasses, up to 75% of the total nitrogen in the tree appears to be derived from salmon nutrients.  Our detection of 15N levels in yearly growth rings of trees using small quantities of wood from standard increment cores offers a novel tool for assessing the occurrence and potentially the relative abundance of salmon and other anadromous fish in past centuries from watersheds of North America, Europe and Asia (Reimchen and Fox 2013)  and has applications for any regions with ancient trees near marine habitats including those on seabird colonies (Reimchen, McGehee, Glickman  2013) .

This research is funded primarily by the David Suzuki Foundation (www.davidsuzuki.org), the Friends of Ecological Reserves(www.ecoreserves.bc.ca) ,  NSERC (http://www.nserc-crsng.gc.ca/index_eng.asp) and the Hakai Institute (https://www.hakai.org/).