University of Zurich, Pacific Northwest National Laboratory
Wetlands provide a range of ecosystem services such as soil carbon sequestration and water filtration but are also globally significant emitters of greenhouse gases (GHGs). Wetlands face pressures from climate change and human land use, and their global change responses remain uncertain, especially belowground. Mechanistic insights regarding wetland roots are particularly hard to infer from other ecosystems because wetland roots are uniquely adapted to soils that can be water-saturated, saline, extremely low pH, etc.
How do wetland roots respond to climate and management changes? What implications do these root system changes have on ecosystem function? To answer these questions, we will present two case studies from different wetland types undergoing management or environmental changes, with a focus on root system responses and their implications for GHGs.
First, in an unmanaged boreal peatland, we found that fine roots are one of the first ecosystem components to respond to soil warming and drying. Fine-root production increased by 130% for a degree Celsius increase in experimental soil warming and this response was much stronger than previous observations from similar upland studies. Based on isotopically labelled-root litter additions into a peat soil incubation experiment, we further found that increasing root-carbon inputs increased peatland CO2 emissions under aerobic conditions and CH4 under anaerobic conditions. Second, in a managed wetland with degraded organic soils, root systems responded both to water level drawdown and soil amendments. Total root biomass halved with mineral soil additions and this decreased root biomass was also associated with lower CH4 emissions. Across both case studies, soil moisture was a key regulator of root system response and its GHG outcome.
We conclude that wetland roots can be highly plastic in response to a changing environment and can have major implications for wetland GHG emissions.
