Bark and latex harvesting short-term impact on native tree species reproduction

The bark and the latex of plants constitute non-timber forest products (NTFPs) of medicinal and economic value that are widely harvested throughout the world. Bark and latex harvesting impacts on plant reproduction are controversial in the literature. Some species are negatively impacted, some do not show any response, and others may exhibit higher flower and fruit production after harvesting. In areas of rainforests and cerrado (tropical savanna) in northeastern Brazil, local people intensely remove the bark of Himatanthus drasticus (for latex collection) and Stryphnodendron rotundifolium for medicinal purposes. We aimed to investigate the short-term impact of harvesting upon reproductive effort of tree species, using those species as models. We assumed that bark harvesting negatively interferes in the reproductive capacity of plant species. Individuals of both species were harvested 2 months before blooming (treated) and the production of reproductive structures, physical characteristics of fruits and seeds, and the pre-emergent reproductive success were compared between treated and control (intact) individuals. All parameters of H. drasticus declined after bark removal, except pollen and ovule production. The only reproductive parameters of S. rotundifolium that were negatively affected were pollen and ovule production, and the pre-emergent reproductive success was higher in treatment individuals. We discuss the differences found between the species regarding responses to harvesting. Our results show that harvesting have short-term effects upon reproduction and may impair gene flow by affecting pollination and seed dispersal of tree species.