, Volume 122, Issue 2–3, pp 281–294 | Cite as

Free-living nitrogen fixation responds to elevated nutrient inputs in tropical montane forest floor and canopy soils of southern Ecuador

  • Amanda L. MatsonEmail author
  • Marife D. Corre
  • Juan I. Burneo
  • Edzo Veldkamp


Although often overlooked in forest research, the canopy can play an important role in forest nutrient cycling. Since the canopy is spatially isolated from the forest floor, nutrient cycling in the two areas may differ as terrestrial nutrients accumulate. We measured rates of free-living N2 fixation along an elevation gradient (1,000, 2,000 and 3,000 m) of tropical montane canopy soils, compared these to rates measured in the top 5 cm of forest floor soils (excluding fresh litter), and assessed the effects of elevated nutrient inputs to the forest floor. N2 fixation was measured using the acetylene reduction assay. Measurements occurred in the field, in the wet and dry seasons, using intact cores of soil. The forest floor had been fertilized biannually with moderate amounts of nitrogen (N) and phosphorus (P) for 4 years; treatments included control, N, P and N + P. N2 fixation rates exhibited little variation with elevation but were higher in the dry season than the wet season. Fixation was inhibited in forest floor N plots compared to control and P plots, and stimulated in canopy P plots compared to control. At 2,000 m, the canopy contributed 12 % of measured canopy and forest floor N2 fixation (1.2 kg N ha−1 year−1). Results suggest that N2 fixation is an active process in canopy soils, which is variable across seasons and sensitive to changes in terrestrial nutrient availability. Long-term terrestrial accumulation of N and/or P has the potential to significantly change the dynamics of soil N cycling in these canopies.


N2 fixation Arboreal soil Canopy organic matter Tropical Andes Nutrient addition 



Funding was provided by a postgraduate scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC) and by the German Research Foundation (DFG), as part of Project A7 (Ve 219/8-2) of Research Group 816 (Biodiversity and sustainable management of a mega diverse mountain ecosystem in southern Ecuador). We would like to thank Dr. Thorsten Peters, who gave us access to the climate station data and Marc Adams, who provided much-appreciated statistical advice. We also thank Anke Mueller, Karina Feijoo and Patricio Salas for their help in the field, the soil science staff at both the Universidad Técnica Particular de Loja (Ecuador) and Georg-August-Universität Göttingen (Germany) for their invaluable laboratory assistance, the Ministerio del Ambiente in Ecuador for granting research permits, and Nature and Culture International (NCI) in Loja, Ecuador for providing access to the field station and study areas. Finally, we thank the anonymous reviewers for feedback and suggestions that greatly improved the manuscript.


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Copyright information

© Springer International Publishing Switzerland 2014

Authors and Affiliations

  • Amanda L. Matson
    • 1
    Email author
  • Marife D. Corre
    • 1
  • Juan I. Burneo
    • 2
  • Edzo Veldkamp
    • 1
  1. 1.Buesgen Institute, Soil Science of Tropical and Subtropical EcosystemsGeorg-August UniversityGöttingenGermany
  2. 2.Departamento de Ciencias Agropecuarias y AlimentosUniversidad Técnica Particular de LojaLojaEcuador

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