01966naa a2200205 a 450000100080000000500110000800800410001902200140006010000250007424501210009926000090022052013630022965000160159270000280160870000230163670000250165970000160168470000190170077300410171920592602016-12-24       2015    bl uuuu     u00u1 u    #d  a1573-50361 aFREITAS, A. D. S. de  aNitrogen isotopic patterns in tropical forests along a rainfall gradient in Northeast Brazil.h[electronic resource]  c2015  aBackground and aims The interpretation of ecosystem nitrogen isotopic patterns is subject to controversies since there are few surveys of signals along climate gradients within the same region. We determined the effects of a rainfall gradient, under high temperatures, on the soil and plant δ15N signals in Northeast Brazil. Methods Nitrogen, carbon and δ15N signals were determined from coastal perennial to subhumid and semiarid deciduous forests to savanna ? deciduous forest transition. Results Soil C and N concentrations were linearly related and both related quadratically with mean annual rainfall while δ15N concentrations decreased with higher rainfall (16 to 4?). Plant δ15N was 1?3? lower than soil δ15N (Δδ15N) in all areas. Only in the deciduous forests, leaves of target species had significantly lower 15 N signals than those of non-fixing species, allowing estimation of fixation. Conclusions In the perennial forests the low signals indicated that the 15 N natural abundance method was not suitable to estimate fixation, while in the savanna ? deciduous forest transition, high signals indicated that the legume species were not fixing. The smaller Δδ15N than those reported in cooler areas and the absence of rainfall effect indicates that, when high, temperature overrides the rainfall effect.  aNitrogênio1 aSAMPAIO, E. V. de S. B.1 aRAMOS, A. P. de S.1 aBARBOSA, M. R. de V.1 aLYRA, R. P.1 aARAÚJO, E. L.  tPlant Soilgv. 391, p.109?122, 2015.