Above and Below Ground Carbon Stock along a Cashew Chronosequence in the Central Côte d’Ivoire

The conversion of forests into agrosystems is characterised by changes in the biophysical parameters of vegetation. In recent years, we have noted a significant expansion of cashew plantations in Côte d'Ivoire, characterised by an increase in cultivated areas and mainly driven by strong global demand for cashew nuts. Cashew cultivation presents both opportunities and environmental challenges in the context of climate change. For a better understanding of these changes, An investigation was conducted along the cashew chronosequence in central Côte d'Ivoire, where the principal aim was to assess the amount of carbon stock. The paper hypothesised that (i) the biophysical parameters of vegetation and soil chemical properties decline after the conversion of secondary forests into cashew plantations, and (ii) the same ones increase with the ageing of the cashew plantations. After data collection in the subplots 16 m × 16 m of secondary forests, young, mature and old cashew plantations, the results showed that the total carbon stock per soil-vegetation association declined significantly after the secondary forests’ conversion, and increased with the aging of the cashew plantations (young plantations: 71.60 ± 6.72 t C ha–1; old plantations: 82.84 ± 1.21 t C ha–1). The contribution of soil carbon to total carbon stocks was higher in cashew plantations. Additionally, the total carbon dioxide sequestered dropped significantly after the secondary forests’ transformation, and increased with the increasing age of the cashew plantations (young plantations: 262.59 ± 24.65 Teq CO2 ha–1; old plantations: 304.68 ± 4.46 Teq CO2 ha–1). Our findings suggest that the sustainable management of the cashew plantations in Côte d’Ivoire could generate benefits up to 46,583,882,200 euros in terms of carbon budget. In conclusion, the research conducted along the cashew chronosequence highlighted a decrease in the biophysical parameters of vegetation, such as tree density, plant biomass, and carbon stocks, after the conversion of secondary forests into agricultural land. Nonetheless, the total carbon stock increased with the ageing of the plantations, indicating the key role of these orchards in greenhouse gas reduction and climate change mitigation.