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Comparable canopy and soil free-living nitrogen fixation rates in a lowland tropical forest

Abstract : Biological nitrogen fixation (BNF) is a fundamental part of nitrogen cycling in tropical forests, yet little is known about the contribution made by free-living nitrogen fixers inhabiting the often-extensive forest canopy. We used the acetylene reduction assay, calibrated with 15N2, to measure free-living BNF on forest canopy leaves, vascular epiphytes, bryophytes and canopy soil, as well as on the forest floor in leaf litter and soil. We used a combination of calculated and published component densities to upscale free-living BNF rates to the forest level. We found that bryophytes and leaves situated in the canopy in particular displayed high mass-based rates of free-living BNF. Additionally, we calculated that nearly 2 kg of nitrogen enters the forest ecosystem through free-living BNF every year, 40% of which was fixed by the various canopy components. Our results reveal that in the studied tropical lowland forest a large part of the nitrogen input through free-living BNF stems from the canopy, but also that the total nitrogen inputs by free-living BNF are lower than previously thought and comparable to the inputs of reactive nitrogen by atmospheric deposition.
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https://hal.inrae.fr/hal-03063571
Contributor : Yannick Brohard <>
Submitted on : Monday, December 14, 2020 - 10:55:24 AM
Last modification on : Monday, March 29, 2021 - 2:44:13 PM

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Leandro van Langenhove, Thomas Depaepe, Lore Verryckt, Lucia Fuchslueger, Julian Donald, et al.. Comparable canopy and soil free-living nitrogen fixation rates in a lowland tropical forest. Science of the Total Environment, Elsevier, 2021, 754, pp.142202. ⟨10.1016/j.scitotenv.2020.142202⟩. ⟨hal-03063571⟩

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