Ecosystem Feedbacks and Nitrogen Fixation in Boreal Forests
Thomas H. DeLuca,1,2*
Olle Zackrisson,2
Michael J. Gundale,2
Marie-Charlotte Nilsson2
Biological feedback mechanisms regulate fundamental ecosystem processes and potentially regulate ecosystem productivity. To date, no studies have documented the down-regulation of terrestrial nitrogen (N) fixation via an ecosystem-level feedback mechanism. Herein, we demonstrate such a feedback in boreal forests. Rapid cycling of N in early secondary succession forests yielded greater throughfall N deposition, which in turn decreased N fixation by cyanobacterial associates in feather moss carpets that reside on the forest floor. The forest canopy exerts a tight control on biotic N input at a period of high productivity.
1 Ecology and Economics Research Department, The Wilderness Society, 503 West Mendenhall, Bozeman, MT 59715, USA.
2 Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 901-83 Umeå, Sweden.
* To whom correspondence should be addressed. E-mail: tom_deluca{at}tws.org
