Population dynamics of three cloud forest ferns of different growth form

Abstract

Cloud forests are highly diverse mountain ecosystems, but habitat loss and fragmentation threaten many species with extinction. Demographic parameters are essential to implement effective conservation actions and to understand the mechanisms of species coexistence, but there are very few population models with transition matrices for fern species. We evaluated the demographic dynamics of three coexisting fern species of different growth form in a cloud forest in eastern central Mexico for six years. The matrix analyses showed that the populations of a trunk-forming fern (Cyathea divergens) and a short caulescent fern (Marattia laxa) were stable while the population of a trunkless, herbaceous fern (Parablechnum schiedeanum) was decreasing. Survival was the demographic process of the life cycle that contributed the most to the population growth of the three species. As expected, with shorter longevity and high precocity, P. schiedeanum exhibited the demographic pattern of herbaceous species. In contrast, with greater longevity and a longer maturation period, the demography of C. divergens and M. laxa was more comparable with that of tree species. Our results support the hypothesis that the demography of the tropical fern species can be compared with life-history strategies of angiosperms and gymnosperms.