Cocoa agroforestry systems have the potential to conserve biodiversity and provide environmental or ecological benefits at various nested scales ranging from the plot to ecoregion. While integrating organic practices into cocoa agroforestry may further enhance these potentials, empirical and robust data to support this claim is lacking, and mechanisms for biodiversity conservation and the provision of environmental and ecological benefits are poorly understood. A field study was conducted in the Eastern Region of Ghana to evaluate the potential of organic cocoa agroforests to conserve native floristic diversity in comparison with conventional cocoa agroforests. Shade tree species richness, Shannon, Simpson’s reciprocal and Margalef diversity indices were estimated from 84 organic and conventional cocoa agroforestry plots. Species importance value index, a measure of how dominant a species is in a given ecosystem, and conservation status were used to evaluate the conservation potential of shade trees on studied cocoa farms. Organic farms recorded higher mean shade tree species richness (5.10 ± 0.38) compared to conventional farms (3.48 ± 0.39). Similarly, mean Shannon diversity index, Simpson’s reciprocal diversity index and Margalef diversity index were significantly higher on organic farms compared to conventional farms. According to the importance value index, fruit and native shade tree species were the most important on both organic and conventional farms for all the cocoa age groups but more so on organic farms. Organic farms maintained 14 native tree species facing a conservation issue compared to 10 on conventional cocoa farms. The results suggest that diversified organic cocoa farms can serve as reservoirs of native tree species, including those currently facing conservation concerns thereby providing support and contributing to the conservation of tree species in the landscape.
Shade coffee agroforestry systems have the potential to support biodiversity. Sustainable certification of coffee has been promoted as a means to provide incentives to maintain these systems, but as yet there is little evidence if this is effective. We analyzed tree diversity on smallholder organic and conventional farms in buffer zones of three conservation areas in Costa Rica, Guatemala and Nicaragua (the later included some large-scale conventional and Rainforest Alliance certified farms). Organic farms had greater farm level tree species richness and Shannon diversity compared to conventional farms; estimated native tree species richness across the landscape was probably greater on organic farms than conventional in Nicaragua (48 versus 28 species respectively) and possibly in Guatemala (23 versus 15 species respectively). Organic farms had higher shade levels and more tree strata than conventional farms. In Guatemala and Nicaragua tree species composition was not closely related to whether farms were organic or conventional, although within composition clusters, organic farms tended to have greater diversity. In contrast, organic and conventional farms in Costa Rica mostly belonged to different tree species clusters. In Nicaragua most large-scale farms, and all Rainforest certified farms, formed a distinct species composition cluster with presence of old-growth forest species and within which Rainforest farms had greater diversity. Tree species composition of the shade seems to be mainly due to management history; but certification effectively differentiates those farms with greater tree diversity. Longer-term monitoring is required to determine whether certification can be an incentive to conserve or expand biodiverse coffee agroforestry systems within the buffer zones around conservation areas.
Purpose Although litter decomposition and nutrient release patterns have been studied in cocoa agroforestry systems in general, studies focusing on organic and conventional cocoa systems are lacking which is critical as organic farms are particularly dependent on nutrient returns from decomposing litter. Materials and methods Dynamics in leaf litter decomposition and the mineralisation of macro- and micro-nutrients in organic and conventional cocoa agroforestry systems were studied using the litterbag technique for 12 months. Results The average monthly mass loss was more than two times higher on organic farms (9.2–14.4 g month−1) compared to conventional farms (4.2–7.3 g month−1) in the first five months. The annual rate of decomposition (k) was higher on organic farms (1.9) compared to conventional systems (1.4). The time required for 50% (t50) and 99% (t99) decomposition of leaf litter was both lower on organic farms (t50 = 0.4 years, t99 = 2.6 years) than conventional farms (t50 = 0.5 years, t99 = 3.5 years). The estimated k values for macro- and micro-nutrients on organic cocoa systems ranged from 2.3 for calcium to 4.5 for potassium compared to 1.6 (Ca) to 2.8 (K) on conventional farms. The k values of all nutrients (except nitrogen and phosphorus) were significantly greater on organic farms than conventional systems. The estimated k values for both litter decomposition and nutrient mineralisation correlated with soil pH and moisture content, but not initial litter chemistry. Conclusions Organic management of smallholder cocoa agroforestry systems enhanced leaf litter decomposition and nutrient mineralisation through improved soil conditions. Thus, organic management of cocoa agroforestry systems may contribute to sustainable cocoa production in smallholder systems through enhanced nutrient return from litter decomposition.
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