Floristic composition and temporal dynamics of oil palm agroforests in the eastern Amazon

Abstract

Oil palm (Elaeis guineensis Jacq.) is a crop of high relevance in the global economy. In the eastern Amazon, a region with potential for the expansion of this crop, the initiative to plant oil palm together with other regional species of commercial interest, forming agroforestry systems (AFS), is considered ecologically, economically, and socially promising. We evaluated the floristic and structural dynamics of oil palm AFS in the eastern Amazon, Brazil. We analyzed the Shannon–Wiener diversity index (H'), the Importance Value Index (IVI), the Current Annual Increment (CAI), and mortality in six AFS, between 2016 and 2018. We established two types of AFS at each Site, namely, AFS-A—considered less diverse; and AFS-B—considered more diverse. Fabaceae, Arecaceae, Meliaceae, Anacardiaceae, and Malvaceae were the main botanical families occurring in the AFS. The floristic composition showed the greatest differences between AFS A and B from Site 2, whereas the most similar compositions were observed among the AFS from Site 3. The H' index ranged from 0.88 to 2.08. E. guineensis, Theobroma cacao L., and Gliricidia sepium (Jacq.) Kunth ex Walp showed the highest IVIs. In total, 38.46% of the species were wood trees, 38.46% were fruit trees, 7.69% were species planted for green manure purposes, and 15.38% were multiple-use species. Mortality in all AFS was low (< 6%). The largest diameter increments occurred in the 2016–2017 interval. Between 2017 and 2018, E. guineensis, Euterpe oleracea Mart., and T. cacao. showed low diameter increments. Between 2016 and 2018 tree growth slowed down in AFS with lower diversity, but not in AFS with higher diversity, suggesting greater resilience of AFS with higher diversity.