Impact of nutrient additions on free-living nitrogen fixation in litter and soil of two French-Guianese lowland tropical forests
In tropical forests, free-living Biological nitrogen (N) fixation (BNF) in soil and litter tends to decrease when substrate N concentrations increase, whereas increasing phosphorus (P) and molybdenum (Mo) soil and litter concentrations have been shown to stimulate free-living BNF rates. Yet, very few studies explored the effects of adding N, P, and Mo together in a single large-scale fertilization experiment, which would teach us which of these elements constrain or limit BNF activities. At two distinct forest sites in French Guiana, we performed a 3-year in situ nutrient addition study to explore the effects of N, P, and Mo additions on leaf litter and soil BNF. Additionally, we conducted a short-term laboratory study with the same nutrient addition treatments (+N, +N+P, +P, +Mo, and +P+Mo). We found that N additions alone suppressed litter free-living BNF in the field, but not in the short-term laboratory study, while litter free-living BNF remained unchanged in response to N+P additions. Additionally, we found that P and P+Mo additions stimulated BNF in leaf litter, both in the field and in the lab, while Mo alone yielded no changes. Soil BNF increased with P and P+Mo additions in only one of the field sites, while in the other site soil BNF increased with Mo and P+Mo additions. We concluded that increased substrate N concentrations suppress BNF. Moreover, both P and Mo have the potential to limit free-living BNF in these tropical forests, but the balance between P versus Mo limitation is determined by site-specific characteristics of nutrient supply and demand.
Main Authors: | , , , , , , , , , , , , , , , |
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Format: | article biblioteca |
Language: | eng |
Subjects: | Fixation de l'azote, litière végétale, forêt tropicale, litière forestière, substance nutritive, Fixation biologique de l'azote, biologie du sol, substrat de culture, phosphore, http://aims.fao.org/aos/agrovoc/c_5196, http://aims.fao.org/aos/agrovoc/c_24064, http://aims.fao.org/aos/agrovoc/c_24904, http://aims.fao.org/aos/agrovoc/c_3047, http://aims.fao.org/aos/agrovoc/c_5274, http://aims.fao.org/aos/agrovoc/c_27742, http://aims.fao.org/aos/agrovoc/c_7160, http://aims.fao.org/aos/agrovoc/c_3393, http://aims.fao.org/aos/agrovoc/c_5804, http://aims.fao.org/aos/agrovoc/c_3093, http://aims.fao.org/aos/agrovoc/c_3081, |
Online Access: | http://agritrop.cirad.fr/607058/ http://agritrop.cirad.fr/607058/1/607058.pdf |
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