Large-seeded, animal-dispersed (LSAD) trees include some of the most valuable and threatened species in the tropics, but they are chronically under-represented in regenerating forests. Toucans disperse many LSAD species’ seeds, so attracting toucans to regenerating forests should help re-establish diverse LSAD tree communities. Here we address two unanswered questions about toucan-mediated seed dispersal in tropical forest restoration. First, how much is toucan visitation affected by small-scale restoration strategies compared to large-scale landscape suitability? Second, how well does toucan activity predict the richness of LSAD tree species recruiting into regenerating forests? To answer these questions, we combined habitat suitability models with long-term toucan observations and comprehensive LSAD tree recruitment surveys in a replicated forest restoration experiment in southern Costa Rica. Experimental treatments included 0.25-ha cattle pastures restored via tree plantations, natural regeneration, or applied nucleation (i.e., planting patches of trees).
Results/Conclusions
Habitat suitability for three sympatric toucan species was predicted by elevation and the age and extent of landscape forest cover. Within suitable landscapes, toucans visited tree plantations 1-6 (or more) years sooner and at least twice as often than plots restored via applied nucleation or natural regeneration. Tree plantations in suitable toucan habitat had LSAD tree recruitment communities that were 2-3× richer than plantations located in poor toucan habitat. Indeed, 65% (15/23) LSAD tree species were found only in tree plantations where habitat was suitable for the largest toucan, Ramphastos ambiguus. Results suggest a multi-scale explanation for how and where small-scale forest restoration can influence toucan-mediated dispersal of LSAD trees. Active tree planting concentrates toucan-mediated seed dispersal, but only within broader landscapes that represent suitable toucan habitat. In contrast, toucans are unlikely to visit or disperse seeds to less-intensively restored areas or regenerating forests embedded in unsuitable landscapes.