LAUSR

Abstract It has been reported that biochar changes the properties of soil and has beneficial environmental and agrotechnical consequences, especially in degraded lands, including those affected by climate change. We added wood biochar (produced from fir sawdust by pyrolysis at 650 °C) to soil collected from a forest and an adjacent long-term cultivated orchard to test the short-term response of soil respiration and methanotrophy under moisture levels of 100% and 55% water holding capacity (WHC). In the controls of the respiration studies (without biochar), CO2 emission was generally higher under 55% than 100% WHC in both soils. Biochar application to the forest soil resulted in a significant reduction of the CO2 emission rate under both WHC levels. This is in contrast with the orchard soil, where the CO2 emission rate was not significantly changed (55% WHC) or even stimulated (100% WHC). Regardless of the moisture level, the CO2 emission and O2 consumption was higher in the forest soil than in orchard soil. In the controls of the methanotrophic study, only slight CH4 consumption was observed in both the tested water-content conditions. The biochar effect was dependent on the WHC level. Under 100% WHC, CH4 was completely consumed in both soils with different lag durations. However, under 55% WHC, methanotrophy was stimulated by biochar only in the orchard soil. We concluded that the short-term response of soil respiration and methanotrophy to biochar amendment is influenced by land use and strongly depends on soil moisture conditions. We showed the effectiveness of biochar addition as a method to limit CO2 emission in non-saturated forest soil, and to increase CH4 uptake in saturated soils, regardless of land use, which confirms its efficiency in reducing the greenhouse effect.