Abstract

Agroforestry systems contribute to the maintenance of ecosystem functions, especially agrisilvicultural systems such as shade coffee systems. However, the role of organic crops to store carbon has been scarcely investigated. This study aimed to quantify carbon stocks in organic polyculture coffee plantations, non-organic polyculture plantations, and organic Inga spp.-shaded coffee systems in northern Chiapas, Mexico. Vegetation inventories were carried out in 1,000 and 100 m² circular plots from six agroforestry communities. Carbon stocks were estimated from living biomass and roots through allometric formulas; dead biomass and soil organic matter (0- 0.3 m- in depth) were collected, dried, weighted and processed for laboratory analysis. Firstly, results showed that living biomass contributed about 30% of total carbon; soil organic carbon particularly contributed between 56 and 70%; while dead organic matter represented between 3 and 5% of total carbon in the system. Organic polyculture coffee plantations stored significantly more carbon in soil (0.1-0.3 m in depth) and tree biomass than non-organic polyculture coffee plantations. These stocks were intermediate in organic Inga spp.-shaded coffee system. Secondly, dead organic matter was statistically similar between systems. Thus, organic polyculture coffee plantations, non-organic polyculture, and organic Inga spp.-shade system stored 194.7, 134.9, and 154.3 Mg C ha^-1 of total carbon, respectively. In the same order, these systems stored in live aboveground biomass 57.5, 53.0, and 46.9 Mg C ha^-1, respectively. Dead organic matter had similar amounts of C stored in the three studied systems (6.3 Mg C ha^-1). The amounts of total carbon stocks in organic coffee were higher than those reported for others in coffee plantations in Central America and, particularly, similar to some dry and semi-humid forests and other agrisilvicultural systems in Mexico. The results highlight the importance of coffee, especially organic coffee to provide the environmental function of carbon sequestration.

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