Effects of soil freezing on methane oxidation in deciduous vs conifer forests in Michigan's Upper Peninsula, USA
Abstract
Microbial oxidation of methane in aerated soils is the largest terrestrial methane sink, but its strength is responsive to both soil frost and vegetation cover (deciduous broadleaf vs evergreen conifer). In the northern hardwood forest zone, climate change is projected to result in decreasing snow cover and replacement of evergreen conifers by deciduous broadleaf tree species. We conducted a soil freezing (snow removal) experiment in sugar-maple (Acer saccharum) dominated and red-pine (Pinus resinosa) dominated forests growing on sandy glacial outwash in the eastern Upper Peninsula of Michigan, USA. In order to investigate the relationships between forest composition and soil frost on methane oxidation, we measured methane consumption from 6 forest stands (3 pine and 3 maple) using static chambers from May 2013 through May 2015. At each site, we had one control and one snow removal plot to induce soil freezing. Results showed that methane oxidation increased upon soil freezing in conifer (p < 0.001) and but not deciduous forests. Cumulative methane oxidation budgets for year 1 revealed that soils under conifers oxidized 47% less methane than deciduous forests, and soil freezing lead to a 30-38% increase in methane oxidation in both forests. There was little response to soil freezing for the year 2, likely due to less snowfall and colder soil temperatures, leading to similar methane oxidation rates. Converting these consumption estimates to global warming potentials also showed 41% and 27% greater climate mitigation potential for deciduous vs conifer forests for years 1 and 2, respectively (0.35-0.34 vs 0.21-0.25 Mg CO2eq ha-1 yr-1). Eddy flux tower studies of forests indicate that they sequester more than ten times as much CO2 through Net Ecosystem Productivity, suggesting that changes in methane oxidation due to changes in forest composition or soil frost will likely have minimal impacts on climate mitigation services by these forests.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B53H2487K
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES