Cacao agroforestry in Belize: Effects on soil nematode community structure

Abstract

Cacao (Theobroma cacao L.) is a shade tolerant crop that can be grown beneath the rainforest canopy rather than in a conventional monoculture. Cacao agroforestry has been proposed as a more sustainable method of farming to mitigate climate change and protect above-ground biodiversity, yet impacts on soil biodiversity and function have rarely been investigated. Our goal was to study how the diversity and community structure of soil nematodes are impacted by planting the rainforest understory with cacao. At field sites in southern Belize and during two growing seasons, nematodes were extracted from soil from cacao agroforestry plots, undisturbed rainforests, and a banana plantation. Nematodes were enumerated and visually identified, and communities were analyzed using several community and diversity indices. In both the dry and wet seasons, soils from cacao plots contained similar nematode communities to the rainforest with respect to all measured variables, including the abundance of nematodes from each trophic group, the Bongers Maturity and Plant-Parasite indices, and the Shannon and Simpson’s diversity indices. In contrast, the banana plantation soils were dominated by plant-parasitic nematodes with lower Shannon and Simpson’s diversity indices. Overall, it appears that cacao agroforestry plots maintain nematode community structure relative to the undisturbed rainforest they were created from, suggesting that soil health is not compromised by this land-use strategy.