Shade tree species composition in a cacao (Theobroma cacao L.) agroecosystem in Ghana

Abstract

Shade trees are important in cocoa agroforestry systems. However, the decline in shade tree cover on cocoa farms, alongside diminishing forest cover due to deforestation and overexploitation, raises concerns about agroecosystem function and long-term sustainability in Ghana. Enhancing multifunctionality in shaded cocoa systems requires understanding the ecological attributes that drive biodiversity and productivity. This study examined how location and corresponding soil association influence the composition, abundance and diversity of shade trees in cocoa agroecosystems. A complete tree census was conducted across 40 stratified-randomly selected mature cocoa farms in four locations (L), namely Pankese (L1), Pramang (L2), Abirem-Afosu (L3) and Akoase (L4), each representing a distinct soil association. A total of 1185 trees representing 78 species were recorded within 40 (100 m × 100 m) plots. The results indicated that the most abundant species were Spathodea campanulata (6.7%), Alstonia boonei (5.5%), and Milicia excelsa (5.2%). Rényi diversity profiles revealed variation in species richness and evenness across locations, with L2 having the highest richness (α₀ = 3.97) and L3 the lowest (α₀ = 3.52). L3 had the most uneven distribution, while L1 had the highest evenness. Bray–Curtis distances and Distance-based Redundancy Analysis (db-RDA) showed that locations had some shade tree species in common. However, ecological distances were relatively high, indicating dissimilarity in species composition between locations. These findings showed that location and soil association influence shade tree diversity in cocoa agroecosystems and highlight the potential of cocoa agroforests for ex-situ conservation of native tree species.