16:30 〜 16:45
[BBC02-05] Influence of sampling depth on the potential methane consumption of forest soils at different season and for forest stands of different species.
キーワード：Methane soil consumption, Soil depth, Temperate forest , Tree species
Methane (CH4) is one the most important greenhouse gas and is responsible for approximatively 20% of the global warming (IPCC, 2022). Soils, especially upland forest soils where aerobic environments prevail, are one of the main sinks of CH4 (Dutaur et Verchot 2007). At the soil-atmosphere interface, the net CH4 efflux consists in a net balance between the production of CH4 by methanogenic archaea mainly in deep anaerobic soil layers and the consumption in the upper aerobic soil horizons of the CH4 produced deeper or diffusing from the atmosphere into the soil by methanotrophic bacteria.
The presence of trees can influence soil edaphic features (mainly carbon content, pH, nitrogen, soil structure, water content…) which can have an impact on the abundance of methanotrophic and methanogenic communities in the soil profile and thus on CH4 consumption. The abundance of methanotrophs is the highest in the upper part of the well aerated mineral soil, but the depth of this level depends on the thickness of the organic layer and then on the rate of litter mineralisation. Depending on the season and the tree species in the plot, the intensity and the vertical pattern of CH4 consumption may change.
The objective of this project was to study the temporal dynamics of CH4 consumption in soil profiles from forest stands of different species. For this purpose, we developed a method to sample intact soil cores. We took five soil cores of three different thicknesses (5, 10 and 15 cm) in stands of spruce, beech, oak and pine at different dates during spring and summer. CH4 and CO2 fluxes were measured in the week after sampling of the soil cores incubated at 20°C.
Regardless of season, methane consumption increased with sample thickness. In the upper 5 cm, methane consumption was highest of the beech forest compared to the other stand types. However, when considering the 15 cm of soil, methane consumption no longer differed between stands. This trend seems to be related to the sharp decrease in dissolved organic carbon content extracted with KCl and the much lower water content in spruce and pine forests. It is also possible that CH4 consumption deeper in the soil of the beech stand was limited by the low availability of CH4, which was consumed at the top of the profile.
The presence of trees can influence soil edaphic features (mainly carbon content, pH, nitrogen, soil structure, water content…) which can have an impact on the abundance of methanotrophic and methanogenic communities in the soil profile and thus on CH4 consumption. The abundance of methanotrophs is the highest in the upper part of the well aerated mineral soil, but the depth of this level depends on the thickness of the organic layer and then on the rate of litter mineralisation. Depending on the season and the tree species in the plot, the intensity and the vertical pattern of CH4 consumption may change.
The objective of this project was to study the temporal dynamics of CH4 consumption in soil profiles from forest stands of different species. For this purpose, we developed a method to sample intact soil cores. We took five soil cores of three different thicknesses (5, 10 and 15 cm) in stands of spruce, beech, oak and pine at different dates during spring and summer. CH4 and CO2 fluxes were measured in the week after sampling of the soil cores incubated at 20°C.
Regardless of season, methane consumption increased with sample thickness. In the upper 5 cm, methane consumption was highest of the beech forest compared to the other stand types. However, when considering the 15 cm of soil, methane consumption no longer differed between stands. This trend seems to be related to the sharp decrease in dissolved organic carbon content extracted with KCl and the much lower water content in spruce and pine forests. It is also possible that CH4 consumption deeper in the soil of the beech stand was limited by the low availability of CH4, which was consumed at the top of the profile.