Land‐use history determines stand structure and tree diversity in vanilla agroforests of northeastern Madagascar

Abstract

Abstract Question In human‐modified tropical landscapes, agroforestry is considered a promising land use to reconcile biodiversity conservation with production goals. The role of agroforests regarding conservation may be strongly influenced by land‐use history; however, few studies have explicitly investigated this. We therefore tested the importance of land‐use history for habitat structure and tree diversity in vanilla agroforests situated in a human‐modified tropical landscape. Location Smallholder mosaic landscape of northeastern Madagascar. Methods We studied tree stand structure, diversity and composition in vanilla agroforests of contrasting land‐use history, old‐growth forests, forest fragments and woody fallows after slash‐and‐burn agriculture, which all contribute to the smallholder mosaic landscape of northeastern Madagascar. The vanilla agroforests were either derived directly from forest or otherwise from woody fallows after slash‐and‐burn agriculture. Results Land‐use history strongly influenced tree species diversity and composition in vanilla agroforests and also affected stand structure. Forest‐derived agroforests maintained high levels of tree species diversity and differed in community composition from fallow‐derived agroforests, which had relatively low levels of tree diversity. Additionally, forest‐derived vanilla agroforests harboured a significantly higher percentage of endemic species than fallow‐derived agroforests, and forest‐derived agroforests also shared many species with old‐growth forests and forest fragments. Fallow‐derived vanilla agroforests harboured a lower percentage of endemic species than woody fallows. Conclusion Considering the land‐use history of agroforests is important to unfold their full potential as elements in a multifunctional human‐modified landscape. Forest‐derived agroforests are an alternative to forest conversion through slash‐and‐burn agriculture and have the potential to sustain high levels of species diversity and important habitat structures. In contrast, fallow‐derived agroforests regain stand structure on degraded historically forested land and thereby have the potential to increase canopy cover and connectivity at the landscape scale.

Vanilla agroforests differ in land‐use history and this difference determines their stand structure and tree diversity. We show that forest‐derived agroforests are important for maintaining habitat structure and tree diversity, whereas fallow‐derived agroforests offer restoration opportunities that also contribute to farmers' livelihood. We therefore consider it important to take the land‐use history of agroforests into account when devising conservation strategies. image