Florida freshwater herbaceous marshes are inundated approximately 6–10 mo/y, have predominantly organic soils, and are maintained by fire, which restricts invasion by woody plants. Marshes are becoming dominated by willow (Salix caroliniana Michx.) throughout Florida. Corkscrew Swamp Sanctuary and Corkscrew Regional Ecosystem Watershed Management Area treated willows in marshes from 2008 to 2016 with helicopter herbicide treatments and mechanical shredding. Our objective was to determine if treatments were shifting vegetation closer to a desirable marsh community with burnable fuels. Untreated areas were compared with (1) all herbicide and all mechanical treatments, (2) imazapyr/glyphosate mixes and other herbicides, primarily glyphosate, and (3) three imazapyr/glyphosate combination mixing rates. Mechanical treatment areas had more desirable vegetation and grasses/sedges than herbicided areas. Herbicided areas had more cattails (Typha spp., a nuisance species), and less sawgrass (Cladium jamaicense Crantz) and grasses/sedges than untreated areas. Imazapyr/glyphosate and other herbicides (mostly glyphosate) had less cover of sawgrass and grasses/sedges than untreated areas, and other herbicides also had less desirable species cover than untreated areas. Sample size was small, but the strongest imazapyr/glyphosate mix had more cattails and the weakest mix had less willow than untreated areas, while both had less grasses/sedges than untreated areas. Although more expensive and difficult, mechanical treatments better retained and/or restored desirable marsh vegetation, which was our primary objective. Sawgrass and other grasses and sedges are excellent fuels for burning. Mechanical treatments also have significantly more cover of grasses and sedges than herbicide treatments, increasing the ability to burn hot and frequently.
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19 January 2022
Vegetation Response to Mechanically and Chemically Treating Willows (Salix caroliniana) Invading Marshes in the Corkscrew Watershed, Southwest Florida
Jean McCollom,
Kathleen Smith,
Michael Duever,
Florent Bled
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Natural Areas Journal
Vol. 42 • No. 1
January 2022
Vol. 42 • No. 1
January 2022
fire exclusion
Florida
herbaceous wetland restoration
marsh restoration
willow invasion