However, for two legume species, which were formerly classified in the genus Acacia, Vachellia etbaica and Senegalia senegal that both rely on N2 fixation, there was no (V. etbaica) or only small (S. senegal) effect of soil layer on biomass performance. Leaf N:P ratios of these three tree species in topsoil ranged between 10 and 12, and in the subsoil for S. senegal and B. papyrifera between 6 and 8, consistent with N limitation in subsoil.