Letters to Nature

Nature 419, 917-920 (31 October 2002) | doi:10.1038/nature01051; Received 19 April 2002; Accepted 15 July 2002

Quantifying nitrogen-fixation in feather moss carpets of boreal forests

Thomas H. DeLuca1,2, Olle Zackrisson2, Marie-Charlotte Nilsson2 & Anita Sellstedt3

  1. School of Forestry, The University of Montana, Missoula, Montana 59812, USA
  2. Department of Forest Vegetation Ecology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden
  3. Umeå Plant Science Center, Department of Plant Physiology, Umeå University, SE-901 87 Umeå, Sweden

Correspondence to: Thomas H. DeLuca1,2 Correspondence and requests for materials should be addressed to T.H.D. (e-mail: Email: thd@forestry.umt.edu).

Biological nitrogen (N) fixation is the primary source of N within natural ecosystems1, yet the origin of boreal forest N has remained elusive. The boreal forests of Eurasia and North America lack any significant, widespread symbiotic N-fixing plants1, 2, 3, 4, 5, 6. With the exception of scattered stands of alder in early primary successional forests7, N-fixation in boreal forests is considered to be extremely limited. Nitrogen-fixation in northern European boreal forests has been estimated2 at only 0.5 kg N ha-1 yr-1; however, organic N is accumulated in these ecosystems at a rate of 3 kg N ha-1 yr-1 (ref. 8). Our limited understanding of the origin of boreal N is unacceptable given the extent of the boreal forest region, but predictable given our imperfect knowledge of N-fixation1, 9. Herein we report on a N-fixing symbiosis between a cyanobacterium (Nostoc sp.) and the ubiquitous feather moss, Pleurozium schreberi (Bird) Mitt. that alone fixes between 1.5 and 2.0 kg N ha-1 yr-1 in mid- to late-successional forests of northern Scandinavia and Finland. Previous efforts have probably underestimated N-fixation potential in boreal forests.