Plant and Soil

, Volume 295, Issue 1, pp 79–94

Natural 15N abundance of soil N pools and N2O reflect the nitrogen dynamics of forest soils

  • Katja Pörtl
  • Sophie Zechmeister-Boltenstern
  • Wolfgang Wanek
  • Per Ambus
  • Torsten W. Berger
Regular Article

DOI: 10.1007/s11104-007-9264-y

Cite this article as:
Pörtl, K., Zechmeister-Boltenstern, S., Wanek, W. et al. Plant Soil (2007) 295: 79. doi:10.1007/s11104-007-9264-y

Abstract

Natural 15N abundance measurements of ecosystem nitrogen (N) pools and 15N pool dilution assays of gross N transformation rates were applied to investigate the potential of δ15N signatures of soil N pools to reflect the dynamics in the forest soil N cycle. Intact soil cores were collected from pure spruce (Picea abies (L.) Karst.) and mixed spruce-beech (Fagus sylvatica L.) stands on stagnic gleysol in Austria. Soil δ15N values of both forest sites increased with depth to 50 cm, but then decreased below this zone. δ15N values of microbial biomass (mixed stand: 4.7 ± 0.8‰, spruce stand: 5.9 ± 0.9‰) and of dissolved organic N (DON; mixed stand: 5.3 ± 1.7‰, spruce stand: 2.6 ± 3.3‰) were not significantly different; these pools were most enriched in 15N of all soil N pools. Denitrification represented the main N2O-producing process in the mixed forest stand as we detected a significant 15N enrichment of its substrate NO3 (3.6 ± 4.5‰) compared to NH4+ (−4.6 ± 2.6‰) and its product N2O (−11.8 ± 3.2‰). In a 15N-labelling experiment in the spruce stand, nitrification contributed more to N2O production than denitrification. Moreover, in natural abundance measurements the NH4+ pool was slightly 15N-enriched (−0.4 ± 2.0 ‰) compared to NO3 (−3.0 ± 0.6 ‰) and N2O (−2.1 ± 1.1 ‰) in the spruce stand, indicating nitrification and denitrification operated in parallel to produce N2O. The more positive δ15N values of N2O in the spruce stand than in the mixed stand point to extensive microbial N2O reduction in the spruce stand. Combining natural 15N abundance and 15N tracer experiments provided a more complete picture of soil N dynamics than possible with either measurement done separately.

Keywords

15N pool dilutionGross mineralisationGross nitrificationDenitrificationPicea abiesFagus sylvatica

Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  • Katja Pörtl
    • 1
  • Sophie Zechmeister-Boltenstern
    • 2
  • Wolfgang Wanek
    • 3
  • Per Ambus
    • 4
  • Torsten W. Berger
    • 1
  1. 1.Department of Forest and Soil Science, Institute of Forest EcologyUniversity of Natural Resources and Applied Life Sciences (BOKU)ViennaAustria
  2. 2.Department of Forest EcologyFederal Research and Training Centre for Forests, Natural Hazards and LandscapeViennaAustria
  3. 3.Department of Chemical Ecology and Ecosystem Research, Vienna Ecology CentreUniversity of ViennaViennaAustria
  4. 4.Biosystems DepartmentRisø National LaboratoryRoskildeDenmark