The predominant role of soil in determining species composition of fern communities in subtropical coastal forest ecosystems

EnglishFerns are an important component in the understorey of tropical forests and their distribution is influenced by several biotic and abiotic factors. At a regional scale, soil characteristics and canopy openness play an important role in fern species composition and richness, as well as in the abundance of individuals. Our objective was to compare the influence of edaphic conditions and vegetation structure on the abundance and distribution of fern communities in Atlantic forest and restinga forest. Our hypotheses were that fern species richness and diversity are higher in Atlantic forest than in restinga due to limiting conditions in this habitat and the composition of fern species in Atlantic forest differs from restinga, especially due to differences in edaphic conditions. A principal coordinates analysis was applied to ordinate sampling units in relation to the environmental variables and a permutational multivariate analysis of variance was used to test that environmental variables did not differ between the two vegetation types. Species richness was compared using rarefaction curves. The influence of abiotic variables in species composition and abundance was verified using canonical correspondence analysis. No differences were observed in species richness, diversity or dominance between vegetation types, although abundance was higher in restinga. Fern communities respond to edaphic conditions and vegetation structure variations between vegetation types, the soil playing a major role. A greater variety of habitats resulting from differences in soil drainage in restinga facilitates the co-existence of species with different ecological tolerance, increasing local diversity and compensating for limiting conditions in restinga. portuguesSamambaias sao um importante componente do subosque das florestas tropicais e sua distribuicao esta condicionada a diversos fatores bioticos e abioticos. Em escala regional, caracteristicas do solo e da abertura do dossel exercem importante papel na composicao e riqueza de especies de samambaias, bem como na abundância dos individuos. O objetivo do estudo foi comparar a influencia das condicoes edaficas e da estrutura da vegetacao na abundância e distribuicao de comunidades de samambaias na floresta Atlântica e na floresta de restinga. As hipoteses foram que a riqueza de especies e a diversidade de samambaias sao maiores na floresta Atlântica do que na restinga devido as condicoes limitantes neste habitat e, a composicao de especies de samambaias na Mata Atlântica difere da restinga especialmente devido a diferencas nas condicoes edaficas. Uma analise de coordenadas principais foi aplicada, para ordenar unidades amostrais em relacao as variaveis ambientais, e uma analise de variância multivariada permutacional foi usada para testar se as variaveis ambientais nao diferiram entre os dois tipos de vegetacao. A riqueza de especies foi comparada usando curvas de rarefacao. A influencia das variacoes abioticas na composicao e abundância das especies foi verificada por meio da analise de correspondencia canonica. Nao foram observadas diferencas na riqueza, diversidade ou dominância entre os tipos de vegetacao, embora a abundância tenha sido maior na restinga. As comunidades de samambaias respondem as condicoes edaficas e as variacoes da estrutura da vegetacao entre os dois tipos de vegetacao, tendo o solo um papel importante. A maior variedade de habitats decorrentes das diferencas na drenagem do solo na restinga facilita a coexistencia de especies com diferentes tolerâncias ecologicas, aumentando a diversidade local e compensando as condicoes limitantes na restinga.