Using artificial canopy gaps to restore Puerto Rican Parrot (Amazona vittata) habitat in tropical timber plantations.

摘要

Timber plantations have the potential to catalyse regeneration of natural forest on degraded land. However, effective management methods to restore native tree diversity and wildlife habitat in areas planted with non-native timber species are needed. This study investigated the effectiveness of creating artificial canopy gaps within timber plantations to increase germination, growth, and survival of native tree species that may be important food plants for the Puerto Rican Parrot (Amazona vittata). The study was conducted in Rio Abajo, in the karst region of north central Puerto Rico, with blue mahoe plantations Hibiscus elatus. Seedling growth increased significantly in gaps; however, there were no differences in percent germination or survival between gap and closed (control) plots. Percent cover of grasses, shrubs, and vines increased in gaps, but the increased growth of competitors did not prevent tree seedlings from growing significantly more rapidly in gaps. Removing leaf litter at time of sowing had no effect on germination, growth, or survival of direct seeded species. Creation of canopy gaps by girdling timber trees reduced basal area of non-native tree species to levels comparable with those of native trees. Both local and landscape level diversity were predicted to increase in canopy gaps; however, plantations will continue to be dominated by non-native and timber tree species because advance regeneration of these species is common in plantation understories. The results suggest that restoration of native tree diversity and wildlife habitat in plantations will require continued management to remove non-native species and to promote growth of tree species with high wildlife habitat value..