Carbon stocks, tree diversity, and the role of organic certification in different cocoa production systems in Alto Beni, Bolivia

This study compares aboveground and belowground carbon stocks and tree diversity in different cocoa cultivation systems in Bolivia: monoculture, simple agroforestry, and successional agroforestry, as well as fallow as a control. Since diversified, agroforestry-based cultivation systems are often considered important for sustainable development, we also evaluated the links between carbon stocks and tree diversity, as well as the role of organic certification in transitioning from monoculture to agroforestry. Biomass, tree diversity, and soil physiochemical parameters were sampled in 15 plots measuring 48 × 48 m. Semi-structured interviews with 52 cocoa farmers were used to evaluate the role of organic certification and farmers’ organizations (e.g., cocoa cooperatives) in promoting tree diversity. Total carbon stocks in simple agroforestry systems (128.4 ± 20 Mg ha−1) were similar to those on fallow plots (125.2 ± 10 Mg ha−1). Successional agroforestry systems had the highest carbon stocks (143.7 ± 5.3 Mg ha−1). Monocultures stored significantly less carbon than all other systems (86.3 ± 4.0 Mg ha−1, posterior probability P(Diff > 0) of 0.000–0.006). Among shade tree species, Schizolobium amazonicum, Centrolobium ochroxylum, and Anadenanthera sp. accumulated the most biomass. High-value timber species (S. amazonicum, C. ochroxylum, Amburana cearensis, and Swietenia macrophylla) accounted for 22.0 % of shade tree biomass. The Shannon index and tree species richness were highest in successional agroforestry systems. Cocoa plots on certified organic farms displayed significantly higher tree species richness than plots on non-certified farms. Thus, expanding the coverage of organic farmers’ organizations may be an effective strategy for fostering transitions from monoculture to agroforestry systems.

Farm resilience in organic and nonorganic cocoa farming systems in Alto Beni, Bolivia

Cocoa production in Alto Beni, Bolivia, is a major source of income and is severely affected by climate change impacts and other stress factors. Resilient farming systems are, thus, important for local families. This study compares indicators for social–ecological resilience in 30 organic and 22 nonorganic cocoa farms of Alto Beni. Organic farms had a higher tree and crop diversity, higher yields and incomes, more social connectedness, and participated in more courses on cocoa cultivation. Resilience was enhanced by local farmers’ organizations, providing organic certification and supporting diversified agroforestry with seedlings and extension, going beyond basic organic certification requirements.

Agroecosystem resilience and farmers’ perceptions of climate change impacts on cocoa farms in Alto Beni, Bolivia

Cocoa-based small-scale agriculture is the most important source of income for most farming families in the region of Alto Beni in the sub-humid foothills of the Andes. Cocoa is grown in cultivation systems of varying ecological complexity. The plantations are highly susceptible to climate change impacts. Local cocoa producers mention heat waves, droughts, floods and plant diseases as the main impacts affecting plants and working conditions, and they associate these impacts with global climate change. From a sustainable regional development point of view, cocoa farms need to become more resilient in order to cope with the climate change related effects that are putting cocoa-based livelihoods at risk. This study assesses agroecosystem resilience under three different cocoa cultivation systems (successional agroforestry, simple agroforestry and common practice monocultures). In a first step, farmers’ perceptions of climate change impacts were assessed and eight indicators of agroecological resilience were derived in a transdisciplinary process (focus groups and workshop) based on farmers’ and scientists’ knowledge. These indicators (soil organic matter, depth of Ah horizon, soil bulk density, tree species diversity, crop varieties diversity, ant species diversity, cocoa yields and infestation of cocoa trees with Moniliophthora perniciosa) were then surveyed on 15 cocoa farms and compared for the three different cultivation systems. Parts of the socio-economic aspects of resilience were covered by evaluating the role of cocoa cooperatives and organic certification in transitioning to more resilient cocoa farms (interviews with 15 cocoa farmers combined with five expert interviews). Agroecosystem resilience was higher under the two agroforestry systems than under common practice monoculture, especially under successional agroforestry. Both agroforestry systems achieved higher cocoa yields than common practice monoculture due to agroforestry farmers’ enhanced knowledge regarding cocoa cultivation. Knowledge sharing was promoted by local organizations facilitating organic certification. These organizations were thus found to enhance the social process of farmers’ integration into cooperatives and their reorientation toward organic principles and diversified agroforestry.

Organic vs. Conventional Grassland Management: Do N-15 and C-13 Isotopic Signatures of Hay and Soil Samples Differ?

Distinguishing organic and conventional products is a major issue of food security and authenticity. Previous studies successfully used stable isotopes to separate organic and conventional products, but up to now, this approach was not tested for organic grassland hay and soil. Moreover, isotopic abundances could be a powerful tool to elucidate differences in ecosystem functioning and driving mechanisms of element cycling in organic and conventional management systems. Here, we studied the delta N-15 and delta C-13 isotopic composition of soil and hay samples of 21 organic and 34 conventional grasslands in two German regions. We also used Delta delta N-15 (delta N-15 plant - delta N-15 soil) to characterize nitrogen dynamics. In order to detect temporal trends, isotopic abundances in organic grasslands were related to the time since certification. Furthermore, discriminant analysis was used to test whether the respective management type can be deduced from observed isotopic abundances. Isotopic analyses revealed no significant differences in delta C-13 in hay and delta C-13 in both soil and hay between management types, but showed that delta C-13 abundances were significantly lower in soil of organic compared to conventional grasslands. delta C-15 values implied that management types did not substantially differ in nitrogen cycling. Only delta C-13 in soil and hay showed significant negative relationships with the time since certification. Thus, our result suggest that organic grasslands suffered less from drought stress compared to conventional grasslands most likely due to a benefit of higher plant species richness, as previously shown by manipulative biodiversity experiments. Finally, it was possible to correctly classify about two third of the samples according to their management using isotopic abundances in soil and hay. However, as more than half of the organic samples were incorrectly classified, we infer that more research is needed to improve this approach before it can be efficiently used in practice.