Mirroring nature: The biodiversity of traditional betel-leaf agroforests, teak plantation, and secondary forests in Northeast Bangladesh.

摘要

Nature reserves are increasing in number worldwide, but they are often fragmented, small, and poorly managed. Land uses contrasting strongly with reserves may reduce their effective size. Complex agroforests and mature plantations, however, may extend forest functions beyond park boundaries. In northeastern Bangladesh, betel agroforestry is a traditional practice often blamed for biodiversity loss. Absent any evidence, it is a source of contention between local stakeholders and the state. To evaluate the conservation value of betel agroforestry, I compared mature secondary forests to agroforests and teak plantations of similar ages in terms of vegetation structure, vegetation composition, and avian diversity. I found agroforests have higher canopy betadiversity than secondary forests, but saplings are significantly reduced in betel agroforests due to understory clearing. Canopy trees in secondary forests are more similar to agroforests than plantations, largely due to shared species of animal-dispersed lightdemanding trees. There were no differences in avian species composition between forest types; avian richness was highest in secondary forest. Species patterns across different taxonomic groups thus are poorly correlated. These results suggest that: (1) With appropriate understory management, betel agroforests may play an important role in conservation of canopy species (2) Agroforests and plantations provide important but limited avian habitat. (3) Agroforests can be modified through vegetation structure to improve their conservation value for both vegetation and avifauna. These findings are important for the study region and Asia, where the world's highest rates of deforestation and land-use change are now taking place.