Responses of methane effluxes and soil methane concentrations to compaction.
Abstract:Forest soils host methanotrophic bacterial communities that make them a major methane sink worldwide. Soil compaction resulting from mechanization of forest operations is first affecting soil macroporosity, and thus gas and water transfer within the soil, leading to a reduced oxygenation of the soil. This reduction of soil aeration is expected to reduce the methanotrophic activity leading thus to less CH4 oxidation and more CH4 production, affecting the overall soil CH4budget.
Compaction was applied in 2007 and had created linear ruts. We measured continuously since September 2014, in three different situations (compacted-mound, compacted hollow and control), soil CO2 and CH4 effluxes using closed chamber coupled to a cavity ring down spectrometer in an young oak plantation.
Since December 2015, in addition to these measurements, we have implanted hydrophobic tubes to measure vertical soil profiles of CH4, O2 and CO2 concentrations in the 3 situations.
The soil acts as CH4 sink, with no significant difference in net CH4uptake between control and both hollow and mound in the compacted treatment.
However, the uptake of CH4 was significantly lower for the hollows than for the mounds resulting from both a lower diffusion of CH4 within soil and a higher production of CH4 in deeper layer when the soil is water saturated.