Plant and Soil Carbon Responses to Invasive Typha Management in Great Lakes Coastal Wetlands

We quantified how control of a ubiquitous Great Lakes region invasive (Typha × glauca) shifts plant-mediated C cycling and belowground properties and processes. Two field experiments implemented large scale treatment plots (~1-ha to 3-ha) of harvesting (i.e., cut above water surface, removed biomass), crushing (i.e., ran over biomass), and creating connectivity channels (i.e., cut at the soil surface, created open-water within Typha-dominated stands). In one experiment, we observed immediate C release via gas flux and aqueous C; harvesting and crushing caused net emission of carbon dioxide (CO2), and crush increased dissolved organic carbon in the surface water and particulate organic carbon in soil pore water. Within one year, all treated Typha stands regrew with reduced stem height, which increased light penetration to the water surface. Harvested stands had greater CO2 uptake relative to un-manipulated controls, but also had greater methane (CH4) emissions, decreasing the wetland’s capacity to sequester C. In another experiment, Typha remained absent from channels, leading to greater light transmission through the water column to the soil surface, and channels had increased soil pore water availability of phosphorus and potassium. CO2 and CH4 soil production rates were positively related to iron availability, so the interaction between C turnover and soil redox may counteract the effect of treatment. Our study suggests mechanical invasive macrophyte control can alter aboveground structure, carbon flux, and soil availability of certain nutrients, and these factors should be included in evaluation of management tradeoffs (i.e., plant diversity and wildlife habitat vs. carbon mitigation and nutrient removal)