Phragmites australis invasion and herbicide-based control changes primary production and decomposition in a freshwater wetland

Abstract

Wetlands are important global carbon sinks, an increasingly important ecosystem service. Invasive plants can disrupt wetland carbon budgets, although efforts to suppress invasive plants may also have unintended effects. Invasive Phragmites australis subsp. australis (European common reed) produces extensive monocultures that displace resident plant communities. In Long Point (Ontario, Canada), a glyphosate-based herbicide was used to control over 900 ha of P. australis. We determined how this ongoing management, and different environmental conditions, influence net primary productivity and decomposition rates. We compared above- and below-ground biomass, belowground:aboveground biomass ratios, standing dead stems, and litter in un-treated P. australis stands, in herbicide-treated areas, and in reference vegetation. We also conducted a reciprocal transplant experiment to measure the decomposition rates of plant litter. One-year post-treatment, control efforts dramatically reduced aboveground biomass (122 g/m2 ± 133 SD) compared to un-treated P. australis (1254 g/m2 ± 449 SD) and reference habitat (821 g/m2 ± 335 SD). An interaction between the plant community of the site and water depth predicted litter decomposition rates, with litter loss ranging from 5.75 to 74.65% across all species, and submerged litter decomposing faster. These results emphasize that secondary treatment, such as rolling, burning, or cutting, encourages the decomposition of dead P. australis stems, opening up space for the recovery of native plants. While herbicide-treated sites had low biomass immediately following treatment, aquatic vegetation began rapidly colonizing treated areas, suggesting that plant community recovery may restore the wetland carbon uptake in subsequent years.

Natural disturbance allows multiple anuran taxa to persist in a dynamic wetland complex

“…The standing vegetation was then rolled over during winter 2020-2021 and the dead organic matter left to decompose to promote a swift decomposition rate (Yuckin et al 2022). The shore and the lakeside dune system are dynamic, with an extensive erosion and disposition processes actively occurring through the year (Davidson-Arnott and Fisher 1992).…”

“…In autumn 2020, prior to our study, dense stands of common reed in the Long Point marsh were selectively treated with the glyphosate‐based herbicide, Roundup® Custom for Aquatic & Terrestrial Use (Canadian regulation number 32356; Bayer Cropscience, Saint Louis, MO, USA), combined with the aquatic‐safe surfactant Aquasurf® (Canadian regulation number 32152; Norac Concepts, Guelph, ON, Canada), prioritizing large stands. The standing vegetation was then rolled over during winter 2020–2021 and the dead organic matter left to decompose to promote a swift decomposition rate (Yuckin et al 2022). The shore and the lakeside dune system are dynamic, with an extensive erosion and disposition processes actively occurring through the year (Davidson‐Arnott and Fisher 1992).…”