Links between environmental factors and hemiepiphytes along a slope of subtropical Atlantic forest

Several basic ecological aspects of hemiepiphytes, such as abundance, diversity and distribution, are still scarcely addressed in scientific papers and thus remain poorly documented. The main aim of this study was to analyse the relative importance of different environmental factors on the abundance and richness of primary hemiepiphytes, secondary hemiepiphytes and root-climbing lianas, at three altitudinal levels in one slope of the south Brazilian Atlantic forest. Fifteen 400-m(2) square sample plots within the altitudinal levels at the slope of Serra Geral in northeastern Rio Grande do Sul were defined. Abundance of species, the percentage of host trees colonized by each life form, canopy openness, soil composition and tree density were recorded for each sample plot, besides climatic variables for each altitudinal level. We sampled a total of 1994 occurrences belonging to 16 species. The three life forms showed different compositions in the three altitudinal levels and presented different intensities in their response to the analysed variables. The abundance of secondary hemiepiphytes increased up to four times from the lower to upper altitudinal levels, while root-climbing lianas increased almost twice in the same direction, following an increase in precipitation. The species richness decreased toward the upper level for the three life forms. Our study also identifies, for the first time, significant correlations between abundance of secondary hemiepiphytes and soil composition, and also with support availability (tree density).