Oecologia

, Volume 147, Issue 1, pp 96–107

Contrasting patterns of soil N-cycling in model ecosystems of Fennoscandian boreal forests

  • Mona N. Högberg
  • David D. Myrold
  • Reiner Giesler
  • Peter Högberg
Ecosystem Ecology

DOI: 10.1007/s00442-005-0253-7

Cite this article as:
Högberg, M.N., Myrold, D.D., Giesler, R. et al. Oecologia (2006) 147: 96. doi:10.1007/s00442-005-0253-7

Abstract

The low plant productivity of boreal forests in general has been attributed to low soil N supply and low temperatures. Exceptionally high productivity occurs in toe-slope positions, and has been ascribed to influx of N from surrounding areas and higher rates of soil N turnover in situ. Despite large apparent natural variations in forest productivity, rates of gross soil N mineralization and gross nitrification have never been compared in Fennoscandian boreal forests of contrasting productivity. We report contrasting patterns of soil N turnover in three model ecosystems, representing the range in soil C-to-N ratios (19–41) in Fennoscandian boreal forests and differences in forest productivity by a factor close to 3. Gross N mineralization was seven times higher when soil, microbial, and plant C-to-N ratios were the lowest compared to the highest. This process, nitrification and potential denitrification correlated with inorganic, total and microbial biomass N, but not microbial C. There was a constant ratio between soil and microbial C-to-N ratio of 3.7±0.2, across wide ratios of soil C-to-N and fungi-to-bacteria. Soil N-cycling should be controlled by the supplies of C and N to the microbes. In accordance with plant allocation theory, we discuss the possibility that the high fungal biomass at high soil C-to-N ratio reflects a particularly high supply of plant photosynthates, substrates of high-quality C, to mycorrhizal fungi. Methods to study soil N turnover and N retention should be developed to take into account the impact of mycorrhizal fungi on soil N-cycling.

Keywords

C-to-N stoichiometryForest productivityGross N turnoverMycorrhizal fungi

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Mona N. Högberg
    • 1
  • David D. Myrold
    • 2
  • Reiner Giesler
    • 1
    • 3
  • Peter Högberg
    • 1
  1. 1.Department of Forest EcologySwedish University of Agricultural Sciences, SLUUmeåSweden
  2. 2.Department of Crop and Soil ScienceOregon State UniversityCorvallisUSA
  3. 3.Climate Impact Research Centre, Department of Ecology and Environmental ScienceUmeå UniversityUmeåSweden