Oecologia

, Volume 129, Issue 1, pp 125–132

Soil nitrogen form and plant nitrogen uptake along a boreal forest productivity gradient

  • Annika Nordin
  • Peter Högberg
  • Torgny Näsholm

DOI: 10.1007/s004420100698

Cite this article as:
Nordin, A., Högberg, P. & Näsholm, T. Oecologia (2001) 129: 125. doi:10.1007/s004420100698

Abstract.

We present results from a study of soil solution concentrations of ammonium (NH4+), nitrate (NO3), and amino acid N over one growing season along a local 90-m-long plant productivity gradient in a boreal forest. Three forest types are found along the gradient: an ericaceous dwarf-shrub type between 0 and 40 m, a low-herb type between 40 and 80 m, and a tall-herb type at 90 m. Soil sampling of the mor layer was performed in June, July, August and October in the three forest types. In addition, plant uptake of NH4+, NO3 and the amino acid glycine was investigated. A mixture of the three N forms was injected into the soil; one N form at a time was labeled with 15N, and in the case of glycine also with 13C. In the dwarf-shrub forest, where plant productivity was low, the soil N pool was strongly dominated by amino acid N. There, plants took up more NH4+ than NO3. Glycine uptake did not differ significantly from either NH4+ or NO3 uptake. Along the gradient, soil concentrations of NH4+ and NO3 increased, as did plant productivity. In the low-herb forest NH4+ comprised a major portion of the soil N pool, and plants took up more NH4+ than NO3 or glycine. In the tall-herb forest, NO3 was as abundant as NH4+, and together these two N forms dominated the soil N pool. Here, plants took up nearly equal amounts of NO3 and NH4+, and this uptake exceeded that of glycine severalfold. Apart from the overall preference for NH4+ that plants exhibited throughout the gradient, the results show a correlation between soil concentrations of amino acids and NO3 and plant preferences for these N forms.

Amino acids Ammonium Glycine Nitrate Nitrogen

Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  • Annika Nordin
    • 1
  • Peter Högberg
    • 2
  • Torgny Näsholm
    • 1
  1. 1.Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden
  2. 2.Section of Forest Soils, Department of Forest Ecology, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden