Agroforestry management as a strategy to reduce carbon footprint in coffee farms of Puerto Rico

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Javier Lugo-Pérez, Department of Natural Sciences, University of Puerto Rico at Utuado, Utuado, PR, Ivette Perfecto and John Vandermeer, School for Environment and Sustainability, University of Michigan, Ann Arbor, MI

Background/Question/Methods
Agriculture has been identified as an activity that promotes climate change, in part because of its contribution to greenhouse gas (GHG) emissions. Therefore, it is imperative to understand how alternative management practices can help mitigate this negative contribution. Due to its economic importance, coffee production occupies a significant portion of agricultural land within the tropical region. Management practices for this crop vary drastically from sun-grown monocultures to shaded agroforestry systems. Some of these practices can help mitigate GHG emissions by increasing the carbon (C) storage capacity of this system. This study addresses two main questions: (1) How much C is present in coffee farms with different management practices? and (2) what is the effect of shade trees on coffee farms C storage capacity? We measured the C stock in the woody plant biomass and the soil (0-10 cm deep) in 68 privately owned coffee farms in Puerto Rico. The data were examined using descriptive statistics and regression analysis.
Results/Conclusions
Our preliminary results show that soil organic carbon and shade trees were the main contributors to the farms C stock, followed by coffee shrubs, Citrus spp. and Musa x paradisiaca. The regression analyses show only a strong and positive relationship (r = 0.95 p < 0.001) between farm C stock and shade tree C biomass. Mean farm C stocks increased significantly from 31.1 to 74.9 Mg C ha-1 with the presence of shade trees. The influence of shade trees on farm C stock varied with crop combination. On farms with only coffee plants or coffee-Citrus intercrops, the contribution of shade trees was small and non-significant. However, in the farms that included M. paradisiaca within the intercrop combination, the inclusion of shade trees significantly increased the farms C storage capacity by a factor of 12. Soil organic carbon was not affected with the increase in aboveground biomass. This information is essential to help make decisions about the adoption of shade trees in coffee plantations. Our preliminary results suggest that the adoption of agroforestry practices on coffee farms in this region would help reduce the carbon footprint. Additionally, these agroforestry practices could incorporate other ecosystem benefits, making these agricultural systems more resilient to climate change.