Estimating biomass and carbon stock in orange trees (Citrus sinensis L. Osbeck) of the São Paulo and southwestern Minas Gerais citrus belt, Brazil

The living biomass and carbon stock of Citrus sinensis (L. Osbeck) orchards from the citrus belt in the states of São Paulo and southwestern Minas Gerais, Brazil, is receiving increasing attention due to its role in the carbon balance of citrus production and in climate change mitigation. Orange trees were analyzed to develop allometric equations to estimate the carbon stock of living biomass at citrus orchards in Brazilian citrus belt. Above- and belowground living biomass and biometric variables were measured directly for 80 harvested orange trees, considering the Pera and Valencia orange varieties and four age classes (3–5, 6–10, 11–15, >15-year old). Considering the 80 orange trees evaluated by direct method, the biomass ranged between 22 and 224 kg tree⁻¹, with the branches (54%) being the main compartment, followed by the roots (28%), leaves (10%), and trunk (8%). Allometric equations were developed using stepwise backward regression analysis. For carbon stock estimation, the allometric equation was applied in a sample of 1321 orange trees distributed inside the citrus belt studied. This sample represents the 162 million orange trees that are more than 3 years old in 337,091 ha, and has stocked more than 8.4 million Mg C in the living biomass. We show for the first time that orange tree biomass can be estimated by allometric equations and that these equations can be used to estimate the biomass of orange trees, and can be recommended for carbon biomass inventories for similar regions, orchards, tree size ranges, and site characteristics.