Seed movement between the native forest and monoculture tree plantations in the southern Atlantic forest: A functional approach

Abstract

The native vegetation within tree plantations increases the suitability for native biodiversity; however, the regeneration of this vegetation depends on the movement of seeds from the native forest by vertebrates and wind. In the present study, we examined functional patterns of seed dispersal between the native forest and tree plantations with different degrees of contrast. We expected that the movement of seeds between the native forest and plantations would depend on the degree of edge contrast, the dispersal syndrome, and the size/weight of seeds. We sampled the seed rain by using seed traps, and measured vegetation structure in the ecotone between four different plantations and the native forest (300 m inside both the native forest and the plantations) in the Atlantic forest of Argentina during a 12-month period. We weighed wind-dispersed seeds and measured vertebrate-dispersed seeds. Edge effects acted as a filter for seed size/weight of both vertebrate- and wind-dispersed seeds. The abundance and functional diversity of seeds arriving at tree plantations increased with plantation age; large seeds were more sensitive to habitat disturbance than small seeds, independently of the dispersal syndrome. Our results highlight that seed movements between the native forest and human-created habitats largely depend on the interaction between dispersal syndrome, seed size, distance to the edge and habitat contrast. Our results also showed that long-term plantation cycles will increase the functional diversity of seeds in the seed bank and facilitate the regeneration of the native vegetation, and that small mature stands close to the native forest will largely facilitate the arrival of seeds and increase the suitability for native fauna.