Vascular epiphyte communities in secondary and mature forests of a subtropical montane area

摘要

Vascular epiphytes were traditionally studied in pristine forests, and few studies were performed to understand their colonization in secondary forests, particularly in subtropical areas. Many secondary forests are invaded by exotic tree species that threaten biodiversity, and the impact of invaders on epiphytes remains unknown. The structure, diversity and composition of epiphytes were analyzed along a successional gradient of native forests in a subtropical montane area of Tucuman, Argentina. Changes in epiphyte communities were also analyzed along density gradients of the exotic invaders Ligustrum lucidum and Morus alba in secondary forests. The epiphyte communities of trees with a diameter >= 10 cm were surveyed in 20 x 20 m quadrats in a successional gradient (30-y and 60-y secondary forests, and mature forests) and in 30-45-y secondary forests with different densities of the invaders. In the successional gradient, increasing cover and number of records of epiphytes (i.e. the sum of epiphytes records on all trees) were explained by the pooled basal area of trees, and older patches (60-y secondary forests and mature forests) had higher epiphyte species richness. Epiphyte species richness and the percentage of trees colonized by epiphytes decreased steadily towards higher densities of Ligustrum lucidum and Morus alba in 30-45-y secondary forests. Vascular epiphyte communities were impoverished in secondary forests dominated by Ligustrum lucidum or Morus alba possibly because they represent low quality habitats for these plants. The patterns emerged in this study showed the importance of secondary forests dominated by native trees for epiphyte diversity conservation, and the necessity to control the invasion of exotic tree species.