Understory diversity in agroforestry ecosystems

Abstract. Agroforestry ecosystems, because of their wide and growing prevalence, will play a large role in preserving or destroying biological diversity in the tropics. The agroforestry plantations at La Selva Biological Station, Costa Rica, offer an opportunity to examine the effects of various plantation designs on the diversity of understory plants in the plantations. In these plantations, three timber species, Cedrela odorata, Cordia alliodora, and Hyeronima alchoreoides, are planted alone and in combination with one another and with a palm, Euterpe oleracea, and a heliconia, Heliconia imbricata. Using three measures of diversity (species richness, Simpson’s Index, and the Shannon Diversity Index), I found that both the plantation species and the number of species planted in the plantation had significant effects on understory diversity. When planted alone, Cedrela odorata supported higher diversity than other species, and monospecific plantations supported higher diversity than polyspecific plantations. Though the reasons for these differences are unclear, it is apparent that different kinds of agroforestry systems will support different levels of diversity. Therefore, these systems should be planned carefully, in order to preserve as much diversity as possible.