Understanding drivers of forest diversity and structure in managed landscapes: Secondary forests, plantations, and agroforests in Bangladesh

Managed forests in protected area landscapes may extend the conservation functions of nature reserves, but studies comparing biodiversity between managed forest types have not examined the underlying factors that drive existing patterns. We used linear mixed effects models to test the effects of a suite of biotic and abiotic factors on structure and diversity across both plants and birds in complex agroforests, mixed plantations, and mature secondary forests of the same age in northeastern Bangladesh. We measured woody species structure and composition in 18 0.01-ha plots in each forest type across three forest ranges, and conducted bird surveys using 216 point count stations located among the vegetation plots. Tree species richness and diversity, and avian richness in agroforests were higher than, or similar to secondary forests. However, saplings in agroforests and plantations had lower densities and fewer species than secondary forests, and both managed forest types had reduced regeneration. Our results indicate that agroforests have higher potential to conserve late secondary forest species than plantations, due to specific management practices that manipulate light. This work provides quantitative evidence for the utility of traditional agroforests as a conservation tool, even under high levels of human disturbance. Inadequate evidence has been a key limitation to conservation policy planning in landscapes with both high biodiversity and high human density. We find that managed traditional agroforests are an underutilized option in the conservation of protected areas in a landscape that is characterized by human use. (C) 2016 Elsevier B.V. All rights reserved.