Methods for restoring sedge/grass meadow community in a Typha-invaded Lake Ontario drowned-river-mouth wetland

Abstract

Water-level regulation has resulted in vegetation changes in Lake Ontario coastal wetlands. The vegetation has shifted from structurally complex sedge/grass meadow communities to communities dominated by invasive Typha, specifically the hybrid cattail Typha x glauca. This study aims to identify control techniques for Typha x glauca to be used in wetlands hydrologically connected to Lake Ontario. The tested control techniques were implemented in a Lake Ontario drowned river-mouth wetland in 2010 and 2011 and were administered along the active invasion zone between a dense Typha stand and remaining sedge/grass meadow. Multiple physical and chemical treatment techniques were implemented over a two-year period at Kents Creek, in northern New York. Treatments included cutting (C), spraying (S) glyphosate (Rodeo) onto cut stalks, and wicking (W) cattail re-sprouts with glyphosate later in the growing season (August). Each treatment method had the following year options: the cut, spray, and wick treatments were applied in year 1 or in both years 1 and 2 (C1S1W1 or C12S12W12). All possible treatments yielded 12 treatment combinations, plus two control plots. Each treatment option was randomly assigned within each of five treatment replicates. All five treatment replicates were located in the invasion zone that had ~25% cover invading Typha and ~75% remaining sedge/grass meadow community. Vegetation sampling occurred in early summer (late June) and again in late summer (August) before treatment in both years. Cattail stem counts and species percent cover data were collected to analyze the effects of each treatment combination. Environmental variables (soil moisture, sediment depth, water-table elevation, soil organic matter, and bulk density) were measured to assist in explaining treatment success or failure and to assess differences among replicates. In addition to looking at the effects that the treatments had on reducing Typha stem density and percent cover, I assessed whether the treatments had an effect on the growth and expansion of existing sedge/grass meadow species, specifically Calamagrostis canadensis and Carex lacustris. Vegetation was sampled again in August 2012 following one full growing season after the second year treatments were applied. Seven treatment combinations: C12, C12W12, C12S, C12SW1, C1W1, C1W12, and C1SW12 significantly reduced cattail stem counts from June 2010 to August 2012. The wick (W) treatment, which was applied to the re-sprouted cattail stems in late August, was the most important treatment, when combined with other treatments (cutting and spraying). Five treatment combinations: C1SW12, C12W12, C12S, C1W12, and C12W1significantly reduced cattail percent cover from June 2010 to August 2012. Although application of the wick treatment in August was the most successful treatment method, the addition of other treatments earlier in the growing season increased Typha stress and led to increased reductions in Typha stems and percent cover. The success of cattails is strongly correlated with stable, high water levels that increase soil moisture. Four of the five replicates were statistically similar in terms of soil moisture throughout the study. Replicate 5 had significantly drier oils than the remaining replicates and had substantially fewer initial Typha stems and lower percent cover, which led to slightly different results in this replicate. For management practices, I suggest using the early summer cutting and late summer wicking treatments, as these two treatments (in combination) were the most effective at reducing Typha stems and percent cover.