Seed rain of fleshy and dry propagules in different habitats in the temperate rainforests of Chiloe Island, Chile

In temperate rainforests on Chiloe Island in southern Chile (42 degreesS), most canopy trees bear fleshy, avian-dispersed propagules, whereas emergent tree species have dry, wind-borne propagules. In the present study, the fo llowing hypothesis was tested: regardless of species, fleshy propagules are deposited in greater numbers in canopy gaps and in forest margins and henc e have a more heterogeneous seed shadow than wind-dispersed propagules. To test this hypothesis, the seed rains of these two types of propagules were compared in the following forest habitats: (i) tree-fall gaps (edges and ce ntre); (ii) forest margins with adjacent pastures; and (iii) under closed c anopy (forest interior). Seed collectors (30-cm diameter) were placed in tw o (15 and 100 ha) remnant forest patches (n = 60-100 seed collectors per pa tch) distributed in the four habitats. Seeds were retrieved monthly from ea ch collector during two reproductive seasons (1996, 1997). In both years, t he seed rain was numerically dominated by two species with dry propagules ( Laureliopsis philippiana and Nothofagus nitida) and three species with fles hy fruits (Drimys winteri, Amomyrtus luma, and Amomyrtus meli). The seed sh adows of the two species with dry, wind-dispersed seeds differed markedly. Seeds of L. philippiana were deposited predominantly in canopy openings, wh ereas N. nitida seeds fell almost entirely in the forest interior. The fles hy-fruited species, Drimys and Amomyrtus spp., had similar seed deposition patterns in the various habitats studied, but the between-year differences in seed rain were greater in Drimys winteri than in Amomyrtus spp. Although no more than 10% of fleshy-fruited propagules reached the margins of the p atch, approximately 7% of these were carried there by birds. Every year, ca nopy gaps (pooling data from edges and centres) concentrated approximately 60% of the total seed rain of both propagule types in both forest patches. Forest margins received less than 20% of the total seed rain, which was lar gely dominated by fleshy-fruited species. Seed shadows were a species-speci fic attribute rather than a trait associated with propagule type and disper sal mode.