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Author  |
Schimann, H.; Ponton, S.; Hattenschwiler, S.; Ferry, B.; Lensi, R.; Domenach, A.M.; Roggy, J.C. |
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Title |
Differing nitrogen use strategies of two tropical rainforest late successional tree species in French Guiana: Evidence from N-15 natural abundance and microbial activities |
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Journal Article |
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Year |
2008 |
Publication |
Soil Biology & Biochemistry |
Abbreviated Journal |
Soil Biol. Biochem. |
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Volume |
40 |
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2 |
Pages |
487-494 |
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Keywords |
soil; litter; nitrate; nitrification; tree rooting; N-15; Eperua falcata; Dicorynia guianensis; tropical forest |
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Abstract |
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. |
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Address |
[Schimann, Heidy; Ponton, Stephane; Domenach, Anne-Marie; Roggy, Jean-Christophe] UMR Ecol Forets Guyane, F-97387 Kourou, French Guiana, Email: heidy_schimann@cirad.fr |
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PERGAMON-ELSEVIER SCIENCE LTD |
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ISSN |
0038-0717 |
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Notes |
ISI:000251655800021 |
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Call Number |
EcoFoG @ eric.marcon @ |
Serial |
146 |
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