Comparable canopy and soil free-living nitrogen fixation rates in a lowland tropical forest Van Langenhove, L. Depaepe, T. Verryckt, L. T. Fuchslueger, L. Donald, J. /Leroy, Céline Moorthy, S. M. K. Gargallo-Garriga, A. Ellwood, M. D. F. Verbeeck, H. Van der Straeten, D. Penuelas, J. Janssens, I. A. Canopy soil Epiphytes Leaves Litter Bryophytes N-15(2) Terrestrial LIDAR Biological nitrogen fixation (BNF) isa 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 N-15(2), 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 freeliving 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. 2021 text https://www.documentation.ird.fr/hor/fdi:010080461 fdi:010080461 Van Langenhove L., Depaepe T., Verryckt L. T., Fuchslueger L., Donald J., Leroy Céline, Moorthy S. M. K., Gargallo-Garriga A., Ellwood M. D. F., Verbeeck H., Van der Straeten D., Penuelas J., Janssens I. A.. Comparable canopy and soil free-living nitrogen fixation rates in a lowland tropical forest. 2021, 754, 142202 [ p.] EN GUYANE FRANCAISE ZONE TROPICALE