PT Journal
AU Van Langenhove, L
   Depaepe, T
   Verryckt, LT
   Vallicrosa, H
   Fuchslueger, L
   Lugli, LF
   Bréchet, LM
   Ogaya, R
   Llusia, J
   Urbina, I
   Gargallo-Garriga, A
   Grau, O
   Richter, A
   Penuelas, J
   Van Der Straeten, D
   August Janssens, IA
TI Impact of Nutrient Additions on Free-Living Nitrogen Fixation in Litter and Soil of Two French-Guianese Lowland Tropical Forests
SO JGR Biogeosciences
PY 2021
BP e2020JG006023
VL 126
IS 7
DI 10.1029/2020JG006023
AB 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.
ER