Salinity and fertility are the main factors cited in Within the restinga (coastal woodland) biome in Brazil, the positioning of Canavalia rosea and Passiflora mucronata occur, respectively, near the shore-in the creeping psammophyte formation (CPF) - and far from the shore - in the Palmae formation (PF). The hypothesis that such positioning is related to salinity and fertility was tested by applying a salt gradient (increasing solutions of NaCl) and a nutritional gradient (different proportions of Hoagland solution). Neither species survived in solutions over 200 mM of NaCl. The shoots of P. mucronata showed negative growth (lower dry mass) in the first week of exposure to saline solutions. The roots of C. rosea showed great sensitivity to salinity, which resulted in greater growth reduction, with increasing plant age, in comparison with P. mucronata. C. rosea grew best in the nutrient-deficient solution, whereas P. mucronata responded best to the nutrient-rich solution, suggesting that C. rosea is better able to populate less fertile sites, such as the CPF, whereas P. mucronata is more suited to sites that are more fertile, such as the PF. Therefore, we can speculate that fertility is the only factor limiting the positioning of species in the restinga.

As hipóteses sobre o posicionamento das formações de restinga são diversas sendo o gradiente salino e a fertilidade do solo as mais difundidas. Buscando elucidar essas questões, foram analisadas as propriedades dos solos das formações psamófila-reptante (FPR) e Palmae (FP) bem como a constituição química foliar de C. rosea (Sw.) DC. restrita à FPR e P. mucronata Lam., na FP. O solo da FP destacou-se pela maior fertilidade. Maiores teores dos metais Fe, Zn e ISNa foram encontrados em solos da FPR. Não foi detectada a presença de Al nas duas formações. O pH dos solos é alcalino sem diferenças entre as duas formações. Os elementos químicos P, S, Cu e Zn acumulam-se em maiores concentrações em folhas de P. mucronata. C. rosea destacou-se pelos maiores teores foliares de N, Fe e B. Essa Fabaceae mostrou valores superiores do fator de concentração para o Ca, Mg, Fe, Cu e B enquanto que P. mucronata, para o P e Zn. Os resultados obtidos sugerem que as características pedológicas têm papel chave no estabelecimento de C. rosea na FPRe de P. mucronata na FP.

Hypotheses as to the position of restinga formations are many, the most widespread being the salinity gradient and soil fertility. In order to elucidate these questions, soil properties of the creeping psammophyte (CPF) and Palmae formations (PF) as well as leaf chemistry of C. rosea (Sw.) DC. restricted to the former and P. mucronata Lam. in the latter were analyzed. The PF soil was more fertile. Higher content of Fe, Zn and ISNa was found in CPF soil. The presence of Al in these two formations was not detected. Soil pH is alkaline, with no difference found between the two formations. The chemical elements P, S, Cu and Zn accumulate in greater concentrations in P. mucronata leaves. C. rosea was distinguished by a higher leaf content of N, Fe and B. This legume showed greater factor of concentration values for Ca, Mg, Fe, Cu and B whereas P. mucronata, for P and Zn. The results suggest that soil characteristics play a major role in the development of C. rosea in the CPF and of P. mucronata in the PF.