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.
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
