Biomass harvest of invasive Typha promotes plant diversity in a Great Lakes coastal wetland

Abstract

Ecological and financial constraints limit restoration efforts, preventing the achievement of desired ecological outcomes. Harvesting invasive plant biomass for bioenergy has the potential to reduce feedback mechanisms that sustain invasion, while alleviating financial limitations. Typha × glauca is a highly productive invasive wetland plant that reduces plant diversity, alters ecological functioning, its impacts increase with time, and is a suitable feedstock for bioenergy. We sought to determine ecological effects of Typha utilization for bioenergy in a Great Lakes coastal wetland by testing plant community responses to harvest‐restoration treatments in stands of 2 age classes and assessing community resilience through a seed bank study. Belowground harvesting increased light penetration, diversity, and richness and decreased Typha dominance and biomass in both years post‐treatment. Aboveground harvesting increased light and reduced Typha biomass in post‐year 1 and in post‐year 2, increased diversity and richness and decreased Typha dominance. Seed bank analysis revealed that young stands (<20 years) had greater diversity, richness, seedling density, and floristic quality than old stands (>30 years). In the field, stand‐age did not affect diversity or Typha dominance, but old stands had greater Typha biomass and slightly higher richness following harvest. Harvesting Typha achieved at least 2 desirable ecological outcomes: reducing Typha dominance and increasing native plant diversity. Younger stands had greater potential for native recovery, indicated by more diverse seed banks. In similar degraded wetlands, a single harvest of Typha biomass would likely result in significant biodiversity and habitat improvements, with the potential to double plant species richness.

Herbicide management of invasive cattail (Typha × glauca) increases porewater nutrient concentrations

“…Although harvesting biomass increased light penetration to the soil surface in the first growing season, we did not observe enhanced native plant density or biomass relative to controls, possibly indicating depauperate seed banks within the mesocosm soils. In a northern Michigan field experiment however, harvest of aboveground Typha biomass increased native plant diversity and richness for at least 2 years relative to unmanipulated controls (Lishawa et al 2015), and resulted in greater plant richness than mowing (Lawrence et al unpublished data). Hall et al (2008) also observed greater plant richness and diversity with harvest of T. dominegensis in central Mexican wetlands compared with unmanipulated controls.…”

“…For example, assuming similar N and P content of leaf and litter biomass that we measured in the current study (%N = 0.9 %, %P = 0.2 %), a one-time harvest of Typha-invaded portions (16 ha) of Cheboygan Marsh in northern Michigan (USA) would remove approximately 4100 kg of N and 910 kg of P (assuming 2846 g dry biomass/m 2 ; Lishawa et al 2015), helping achieve pollutant load reduction goals of nutrient-impaired Lake Huron. Similarly, Boyd et al (2015) quantified biomass and leaf nutrient content of a Phragmites-invaded wetland in central Florida and estimated that biomass harvest would address *25 % of Lake Jesup's pollutant load reduction goal.…”

“…Leaf litter deposited on wetland surfaces during mowing should release nutrients as it decays, though nutrient uptake during plant regrowth after cutting may prevent elevated N and P concentrations. Harvesting (removing) cut biomass and accumulated Typha litter has several potential advantages including: decreasing litter accumulation which drives terrestrialization (Rooth et al 2003), increasing plant diversity (Farrer and Goldberg 2014;Hall et al 2008;Lishawa et al 2015;Osland et al 2011), and reducing N and P from wetlands by removing nutrient-rich biomass (Boyd 1970;Hansson and Fredriksson 2004;Hosoi et al 1998), thereby reducing the invasion-stimulating effects of increased nutrient availability (Larkin et al 2012b;Woo and Zedler 2002). Mechanical harvest of wetland plants is common in European wetlands, where biomass is used for compost, fodder, building materials, or as a bioenergy source (Hansson and Fredriksson 2004;Köbbing et al 2013), and Typha harvest has been implemented at large spatial scales near Lake Winnipeg to remove nutrients and provide a bioenergy source (Cicek et al 2006, R. Grosshans pers.…”

Mechanical Harvesting Effectively Controls Young Typha spp. Invasion and Unmanned Aerial Vehicle Data Enhances Post-treatment Monitoring

“…dominance (Mulhouse and Galatowitsch, 2003; Hall and Zedler, 2010) due to relatively short term seed viability (van der Valk et al, 1999) and high light requirements for germination (Kettenring et al, 2006). Further, Lishawa et al (2015) found that in a northern Great Lakes coastal wetland, Carex spp. diversity and abundance took 2 years following Typha biomass removal to increase from pre-treatment levels.…”

Invasive species removal increases species and phylogenetic diversity of wetland plant communities

“…This effect was further illustrated by the response of Juncus nodosus and J. alpinoarticulatus, which were indicator species significantly associated with harvesting in wet meadow plots. In the emergent marsh, cutting biomass below standing water (all treatments) effectively reduced Typha abundance, likely by preventing aeration and causing rhizome mortality (Jordan & Whigham, 1988;Murkin & Ward, 1980 (Lishawa et al, 2015). are prolific in GL coastal wetland seed banks (Keddy & Reznicek, 1986), and these early seral species can become the dominant emergent plants following water-level reduction and mudflat exposure (Tuchman unpublished), but they quickly disappear from the emergent community with succession or Typha invasion (Larkin et al, 2012;Tuchman et al, 2009).…”