Cocoa agroforest multifunctionality and soil fertility explained by shade tree litter traits

Abstract

Manipulating plant functional diversity to improve agroecosystem multifunctionality is a central challenge of agricultural systems world‐wide. In cocoa agroforestry systems (cAFS), shade trees are used to supply many services to farmers, yet their impact on soil functioning and cocoa yields is likely to vary substantially among tree species. Here we compared the impact of five shade tree species (Canarium schweinfurthii (Canarium), Dacryodes edulis (Safou), Milicia excelsa (Iroko), Ceiba pentandra (Kapok tree), Albizia adianthifolia (Albizia)) and unshaded conditions on the functioning of poor sandy savanna soils within eight cocoa farms in Central Cameroon. We assessed the effects of plant functional traits, leaf litterfall and fine root biomass on a range of soil functions and on cocoa yield. Shade trees generally improved soil pH, NH4+, NO3- and Olsen P content, biomass production of bioassays and soil total C and N content, while leaving cocoa yields unchanged. However, these effects varied largely among species. Improvements of soil functions were low under the two fruit trees (Canarium and Dacryodes), medium under the legume tree Albizia and high under the two timber trees (Milicia and Ceiba). Low litter recalcitrance was most strongly associated with increases in soil fertility indicators such as N and P availability, whereas soil C and N content increased with litter Ca restitution. Synthesis and applications. We demonstrate that cocoa agroforest multifunctionality is substantially influenced by the functional traits of shade tree species. Shade tree species with the most dissimilar traits to cocoa (cocoa showing the lowest leaf litter quality) showed the largest improvement of soil functions. Therefore, selection of shade trees based on their functional traits appears as a promising practice to adequately manage soil functioning. In order to fully assess the beneficial role of shade trees in these agroecosystems. Future research will need to extend this approach to other below‐ground traits and other aspects of multifunctionality such as long‐term cocoa health and yield.

Litterfall seasonal dynamics and leaf-litter turnover in cocoa agroforests established on past forest lands or savannah

“…C storage, cocoa yield, tree species conservation; Nijmeijer et al 2019a). CAFS associated species help smallholder cocoa producers diversify their production (Jagoret et al 2014) and generally have a positive effect on soil quality by amplifying root development and increasing litter production and quality (Sauvadet et al 2020;Schroth et al 2001). This last point is of special interest for tropical ecosystems whose soils are highly weathered and often poor, making litter one of the main resources of nutrient return (Lian and Zhang 1998;Martius et al 2004;van Vliet et al 2015).…”

Rebuilding Tree Cover in Deforested Cocoa Landscapes in Côte d’Ivoire: Factors Affecting the Choice of Species Planted

“…We, therefore, recommend that cocoa-based agroforestry projects in Côte d'Ivoire should seek to optimize the integration of trees within cocoa farms by optimizing both the number of trees and the products and services provided by different tree species in ways that maximize economically, agronomic (i.e., cocoa yield), and environmental (i.e., sustainable production) benefits. Further studies are therefore needed to determine how tree diversity increases yield and the overall production in cocoa systems through (i) the management of soil fertility and ecological health [61][62][63][64] and (ii) the production of useful and marketable products from a range of different tree species [7].…”

Descomposición y liberación de nutrientes en biomasa por poda de cacao (Theobroma cacao L.) en Rionegro, Santander, Colombia

“…Se ha reportado que, durante el proceso de movilización de nutrientes en descomposición de hojarasca, se producen interacciones entre las capas del cultivo en el suelo, como la deposición de residuos, la infiltración, la absorción y la mineralización, por lo cual, pueden presentarse tanto pérdidas como ganancias de peso por nutriente (Petit-Aldana et al, 2019). En el proceso de descomposición de las ramas secundarias y ramas primarias, se observó reabsorción de P, un comportamiento reportado en un estudio sobre la multifuncionalidad de la agroforestería en cacao y la fertilidad del suelo desarrollado (Sauvadet et al, 2020).…”