ADVENTITIOUS ROOTS EFFECTS ON MANAGEMENT OF INVASIVE PHRAGMITES AUSTRALIS IN HIGH WATER

Abstract

The prevalence of invasive Phragmites australis (common reed), has threatened biodiversity and displaced native plant species throughout North America. Along shorelines, Phragmites survives in high water by growing above the water and transporting oxygen from above to below water. Phragmites plants may develop adventitious roots in response to high water, which could aid in dissolved oxygen uptake. Cut-to-drown management is a strategy whereby Phragmites stems are cut below the water to inhibit regrowth by depriving the plant of oxygen. This strategy can be effective, however adventitious roots could help the plants withstand cut-to-drown by providing oxygen access to the plants after they have been cut under water. Understanding the role of adventitious roots for Phragmites is vital for effective management strategies in the Great Lakes. To examine the function of adventitious roots on Phragmites, we tested the effects of submergence, dissolved oxygen and presence of adventitious roots on belowand aboveground performance in a controlled greenhouse experiment. Plants receiving full cuts (cut at the soil line below water) and partial cuts (just below water) produced significantly less belowground biomass, new rhizome biomass and rhizosphere carbohydrates than controls. There was a significant negative effect of adventitious roots for rhizome biomass in the no cut treatment when the bubbler was present, but not when it was absent. Additionally, plants receiving partial cuts had significantly more new stems than no cuts and full cuts. The presence of adventitious roots produced a trend towards increased new stem growth when grown without bubblers. Together, our results suggest that full cuts are most effective in controlling Phragmites partly due to the removal of adventitious roots. The effect of adventitious roots may depend on dissolved oxygen presence. This information could be incredibly valuable to land managers, increasing effectiveness of cut-to-drown management.