SOIL CO2 EFFLUX IN AGROFORESTRY SYSTEMS WITH OIL PALM IN THE EASTERN AMAZON

Soils are important carbon reservoirs in agroecosystems. However, anthropogenic disturbances such as agricultural land use have been altering its carbon balance. Therefore, evaluating how changes in land use influence the efflux of CO₂ from the soil is important to indicate how agricultural systems affect the carbon balance of agroecosystems. In the Eastern Amazon, knowledge about the effect of converting secondary forest areas to oil palm cultivation on soil CO₂ efflux is still incipient. In this context, the objective of this research was to evaluate the effect of converting secondary forest into agroforestry systems (AFS) with oil palm on soil CO₂ efflux. CO₂ efflux was estimated from February 2015 to November 2015 using a LI-6400 portable infrared wave gas analysis system (IRGA). The systems evaluated were AFS with oil palm: more diversified (AFS+) and less diversified (AFS-) and a secondary forest (SF). CO₂ efflux was higher in the period of higher humidity, higher rainfall, higher fine root production, higher microbial activity and higher C-CO2 loss via microbial respiration, compared to the period of lower rainfall and lower humidity, in all systems. The annual CO₂ efflux from the soil did not differ significantly between the systems. Therefore, agroforestry systems intercropped with oil palm could represent a viable alternative for oil palm production in the Amazon region, as the "soil metabolism" is similar to that of the most ecologically intact system (secondary forest).