[1] IRD Embrapa Cerrados, UMR Biodivers & Fonctionnement Sols 137, BR-71619970 Brasilia, DF, Brazil
[2] Univ Paris 11, CNRS, UMR IDES 8418, F-91405 Orsay, France
[3] Univ Nancy 1, CNRS, UMR 7137, LiMos, F-54506 Vandoeuvre Les Nancy, France
[4] Univ Nancy 1, Serv Commun Microscopie Elect Transmiss, F-54506 Vandoeuvre Les Nancy, France
[5] Univ Catholique Louvain, Unite Sci Sol, B-1348 Louvain, Belgium