Short term effects of burning on soil microbial processes involved in greenhouse gas fluxes from soil

Effects of fire on mineral N, nitrification, denitrification enzyme activity and soil methane consumption, were investigated for one year in a Mediterranean maquis area, where three subplots were treated with light fire (LF), three with intense fire (IF), and three were unburned and used as control (C). Results demonstrated a significant increase of soil NH4+ in the first 4 months after fire, not followed by an increase in net NO3- content, with the exception of the first sampling. Only after 4 months, nitrification rates in the burned sites were significantly higher than in the control, despite a constant higher NH4+ content. The lowest denitrification activity was measured in the IF plots, and seemed to be influenced by substrate availability. However, other factors concurred as well to limit denitrification in the burned sites. CH4 oxidation was not significantly affected by soil burning. Data suggest that isolated fire events do not have relevant and long lasting effects on nitrification, denitrification and methane consumption.