Forest plantations and agricultural land use are gradually replacing natural forests. Biodiversity conservation in the Anthropocene must include the diversity of species in these novel ecosystems and human-modified landscapes. Evaluating the role of forest plantations as potential biodiversity refuges requires understanding how these plantations influence species interactions and processes that shape species coexistence. We used structural equation modeling to investigate the mediating role of understory plant diversity in African mahogany plantations on the effect of plantation traits (size, age, etc.) on arthropod diversity and plant herbivory rate. We found lower herbivory rates in larger plantations but no direct effect of plantation age and isolation on herbivory rates. However, we found indirect effects of plantation traits on understory plant herbivory rates, mediated by effects on species richness and its influence on phylogenetic diversity. Plantation age, size, and isolation indirectly reduced herbivory rates by increasing species richness. Phylogenetic diversity was positively associated with species richness and thus was also directly negatively associated with herbivory rates. Altogether, our findings underscore the importance of considering plantation traits and their spatial context in managing biodiversity and ecosystem services in human-modified tropical ecosystems. The biotic processes demonstrated in the understory communities of forest plantations are similar to those found in native forests. Given the ecological effects of plantation traits on species interactions in the understory, the efficient design of a network of forest plantations for biodiversity conservation needs to prioritize larger plantations with the expectation of a time-dependent increase in their ecological value.
Houehanou et al. (Wed,) studied this question.