TY  - JOUR
AU  - Schimann, H.
AU  - Ponton, S.
AU  - Hattenschwiler, S.
AU  - Ferry, B.
AU  - Lensi, R.
AU  - Domenach, A.M.
AU  - Roggy, J.C.
PY  - 2008//
TI  - Differing nitrogen use strategies of two tropical rainforest late successional tree species in French Guiana: Evidence from N-15 natural abundance and microbial activities
T2  - Soil Biol. Biochem.
JO  - Soil Biology & Biochemistry
SP  - 487
EP  - 494
VL  - 40
IS  - 2
PB  - PERGAMON-ELSEVIER SCIENCE LTD
KW  - soil
KW  - litter
KW  - nitrate
KW  - nitrification
KW  - tree rooting
KW  - N-15
KW  - Eperua falcata
KW  - Dicorynia guianensis
KW  - tropical forest
N2  - Previous studies in lowland tropical rainforests of French Guiana showed that, among non-N-2-fixing trees, two groups of late successional species contrasting in their leaf N-15 natural abundance coexist, suggesting two different main ways of nitrogen acquisition. Two abundant late-successional species typically co-occurring in rainforests in French Guiana, namely Eperua falcata and Dicorynia guianensis, were chosen as representative of each group. Stable isotope techniques and measurements of potentials of microbial N transformation were performed to assess to what extent leaf N-15 natural abundance of these species could be related to (i) delta N-15 signatures of soil mineral N sources and (ii) the capacity of soil to express nitrification and denitrification (both processes being directly involved in the balance between NH4+ and NO3-). Soil delta N-15-NH4+ was roughly similar to leaf delta N-15 of D. guianensis (around 3.5 parts per thousand), suggesting a preferential use of NH4+, whereas in E. falcata, leaf delta N-15 values were closer to root delta N-15-NO3- values (0.2 and -2.0 parts per thousand, respectively), suggesting a preferential use of NO3-. These differences in N source utilization were not accompanied by differences in availability in soil NO3- or in intensity of microbial functions responsible for soil N mineral evolution. However, (i) under both tree species, these functions showed clear spatial partitioning, with denitrification occurring potentially in soil and nitrification in the litter layer, and (ii) E falcata fine roots colonized the litter layer much more strongly than D. guianensis fine roots. This strongly suggests that (i) the contrasted leaf delta N-15 values found in the two late-successional species reveal distinct N acquisition strategies and (ii) the ability of roots to predominantly exploit the litter layer (E falcata) or the soil (D. guianensis) may constitute an important explanation of the observed differences. A complementarity between tree species, based on mineral N resource partitioning (itself resulting from a spatially structured location of the microbial functions responsible for the balance between NH4+ and NO3-), n thus be supposed. (c) 2007 Elsevier Ltd. All rights reserved.
SN  - 0038-0717
N1  - ISI:000251655800021
ID  - Schimann_etal2008
ER  -