MetGrass2 - Understanding the determinants and long-term dynamics of land use management on the methane sink microbiome biodiversity in grassland, forest and arable soils

• Applicants: Professor Dr. Steffen Kolb; Dr. Sven Marhan; Professor Dr. Tim Urich
• Subject Area: Microbial Ecology and Applied Microbiology ; Soil Sciences ; Ecology of Land Use
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 512405836

Methane is the second most important greenhouse gas and a major contributor to global warming. Two fundamentally different groups of microbes are crucial for methane cycling: Methanotrophic bacteria act as a biological sink by oxidising atmospheric methane, while methanogens produce methane. In the previous projects, we showed the negative impact of high land use intensity on methanotrophic bacteria in grassland soils and that the recovery of the methane sink function after reduction of land use intensity started after three years. In MetGrass2 we will continue our investigations on the effects of grassland extensification on the methane sink function and associated methane-cycling microorganisms in REX grasslands (WP1). We hypothesise that after 6 years the abundance of methanogens will continue to decrease and the reduced soil bulk density will favour methanotrophs, resulting in an increased potential atmospheric methane uptake. Increasing numbers of grassland sites are managed by mowing but leaving the hay on the ground, creating a mulch layer. As the diffusion of atmospheric methane into the soil is a rate-limiting factor for the activity of methanotrophs, we will investigate (WP2) whether a mulch layer reduces the fluxes of atmospheric methane, thereby reducing the methane sink function for a certain period of the year, or whether the resources released during litter decomposition positively influence soil microorganisms, including methanotrophs, potentially increasing the methane sink function at other times of the year. In WP3 we will investigate the previously unknown effects of land management practices (tillage, fertilisation, organic - conventional) on methane sink activity and the methanotrophic and methanogenic microbiome. Copper is a known and necessary micronutrient for methanotrophs to oxidise methane, as the active enzyme that oxidises methane requires copper. We will investigate total and biologically available copper and other micronutrient levels in all 150 grassland soils (WP4) and correlate these data with potential methane oxidation rates and methane-cycling microbial abundances. Here, we will further identify the key players of methanotrophic bacteria by metagenome analyses. In WP5 we will use the unique long-term (15 years) soil microbial taxa datasets together with the climate and land use data from the Biodiversity Exploratories to disentangle the effects of long-term changes in weather and land-use intensity on methane sink microbiomes in 150 grassland and 150 forest soils. We will use a unique combination of state-of-the-art approaches, reflecting the interdisciplinary nature of the MetGrass2 team. The project will generate data that address pressing questions about the influence of land use intensity, its extensification and the role of climate change on the functional diversity and activity of methanotrophic and methanogenic microorganisms in grassland, forest and arable soils.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1374: Biodiversity Exploratories