Plant and Soil Carbon Responses to Invasive Typha Management in Great Lakes Coastal Wetlands
Johnson, O. 2018. University of Connecticut
Abstract
We quantified how control of a ubiquitous Great Lakes region invasive (Typha × glauca) shifts plant-
mediated C cycling and belowground dynamics. 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, create 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 carbon 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).
