Cocoa agroforestry and tree diversity in relation to past land use in the Northern Ecuadorian Amazon

Abstract

Shifting agriculture (SA) involving fallow intervals between crop cycles is common in tropical areas. It allows the recovery of soil fertility for subsequent crops. However, the diminishing of fallow intervals (referred here as intensification of SA) is a main cause of forest degradation. Agroforestry systems (AFSs) based on modification of mature forests may play an important role in buffering adverse environmental outcomes caused by short fallow intervals in SA. We investigated whether AFSs reverse the effect of intensification of SA in cocoa (Theobroma cacao) agrosystems and aimed to (1) characterize species diversity in cocoa agroecosystem under SA with short fallow periods; (2) predict the ecological impact of intensification of SA on floristic composition, particularly in endangered endemic species; and (3) identify whether changes in floristic composition and species diversity in agroecosystems under different fallow intervals are localized in certain strata or whether structural changes occur throughout the plant community. Our study revealed that shortened SA’s fallow periods on cocoa AFSs have drastic effects on levels of diversity. Tree species assembly decreases across cocoa agroforest established in reduced fallow periods. Also, absence of fallow intervals of SA affects tree conservation rates in AFSs by changing floristic composition. Nevertheless, the use of AFSs with complex arboreal structures under SA preserves and protects higher rates of native and endangered endemic species and delays forest degradation rates. The conservation of native species in this agricultural model may meet the requirements to reverse the cycle of land degradation and social deprivation.