Methane and nitrous oxide fluxes from clonal eucalyptus forests in different spacing arrangements

Although Eucalyptus is the most commonly cultivated genus in Brazil, more information is needed on how these forests can act as a sink for greenhouse gases. This study assessed the potential greenhouse gas (GHG) mitigation of eucalyptus forests by quantifying both the seasonal rates of exchange of methane (CH4) and nitrous oxide (N2O) gases at the soil-atmosphere interface and their relationships with soil variables (moisture, temperature and physicochemical attributes). Soil organic carbon sequestration rate was used together with soil GHG emission to estimate net global warming potential. This study was conducted at an experimental forestry station in the south-central region of the state of Sao Paulo, Brazil. No differences were found between treatments in the seasonal fluxes of N2O and CH4, which may have resulted from similar soil properties, particularly bulk density and nitrate (NO3-) contents. CH4 flux dynamics were mainly controlled by the concentrations of ammonium (NH4+) in the soil. In all treatments, the soil acted as a continuous sink for CH4, absorbing it at an average rate of -65 mu g C m(-2) h(-1), which was higher than the results of other studies conducted in native areas of the Cerrado biome and planted forests. However, although CH4 removal helped offset greenhouse gas emissions, net emissions were seen in most treatments due to N2O emissions in greater magnitude and soil carbon losses.