Evaluating Effect of Cutting Depths on Regrowth of Invasive Cattails (Typha angustifolia)

Cattail (Typha spp.) expansions into wetlands can reduce open-water habitats and negatively affect native flora and fauna diversity. Cattail removal is needed to maintain wetland quality but removal is often non-permanent requiring repeated treatments to retard reestablishment. Cutting cattails with mechanical harvesters is a common management technique; however, it is unclear what cutting depths are optimal. We conducted a controlled, replicated experiment at Cheyenne Bottoms Wildlife Area (CBWA), Kansas, USA during 2017-2018 to address this question. We hypothesized cattails cut below water would have reduced gas exchange capabilities due to flooded aerenchyma resulting in greater mortality. We conducted genetic testing in CBWA, a Ramsar Wetland of International Importance, and identified narrowleaf cattail (Typha angustifolia), which is considered an invasive species in Kansas and is the first known genetic-level confirmation of narrowleaf cattail at CBWA. Within this stand of cattail, we established a randomized complete block design experiment with four blocks, and three clipping treatments in July 2017. Clipping treatments included a control (no cattails clipped), an above-water treatment (cattails cut 15 cm above water surface) and a below-water treatment (cattails cut 15 cm below water surface). We quantified emergent stem densities in each plot in September 2017 to assess the effectiveness of simulated management actions. Mean stem densities were greatest in the control (113.0±10.7 stems). Clipping the cattails resulted in significantly fewer stem counts in both the above-water cutting treatment (44.1±10.7, P = 0.0032) and in the below-water cutting treatment blocks (11.1±12.5, P = 0.0004). The below-water treatment had fewer stems than the above-water treatment, though not statistically significant (P = 0.0789). Our experiment was inadvertently destroyed with herbicides in 2019 preventing further comparisons. Our results suggest that management efforts focused on cutting cattails below water can reduce cattail growth.