Root traits of shade trees in cocoa agroforestry systems are associated with functional leaf phenology

Context Analysing root traits to identify below ground acquisition mechanisms and relating them to above ground traits, such as leaf phenology, can improve the understanding and design of resource use efficient and drought resilient agroforestry systems. Objectives To determine how fine root traits are associated with different shade tree functional groups and their influence on climate resilience Methods Two key roots traits, i.e. fine root length density and fine root diameter of shade trees and cocoa are evaluated for the 13 most common shade tree species belonging to six functional (leaf phenology) groups under farmer field conditions. Fine root samples were acquired for four replicates of each shade tree species through extensive root coring up to 60 cm depth and at three horizontal shade tree impact zones. Results All cocoa plants irrespective of their associated shade tree functional group exhibited resource acquisitive fine root traits, i.e. higher root length density and smaller diameter. Similarly, shade trees in the ‘brevi deciduous during dry season’ functional group, i.e. characterized by higher, leaf area-related, water uptake in the dry season exhibited acquisitive fine root traits. Evergreen and complete deciduous functional groups showed a conservative fine root trait, i.e. with lower fine root length density and larger diameter. Conclusion Pairing acquisitive root traits in cocoa with conservative fine root trait shade trees optimize agroforestry systems.