Variant restoration trajectories for wetland plant communities on a channelized floodplain

Published source details Toth L.A. (2017) Variant restoration trajectories for wetland plant communities on a channelized floodplain. Restoration Ecology, 25, 342-353.
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This study is summarised as evidence for the following.

	Action	Category
	Raise water level to restore/create freshwater swamps from other land uses Action Link
	Raise water level to restore/create freshwater marshes from other land uses Action Link

Raise water level to restore/create freshwater swamps from other land uses

A before-and-after, site comparison study in 1998–2010 in Florida, USA (Toth 2017) reported that dechannelizing the river to rewet the floodplain had mixed effects on vegetation across two sites that were historically swamps. Statistical significance was not assessed. In the year before rewetting began, one restoration site (higher elevation) was dominated by shrubs: mostly upland (46–49% cover) but some wetland-characteristic (9% cover). The other restoration site (lower elevation) was dominated by wetland-characteristic herbs (71% cover). Total cover was 68–93%. Over roughly nine years after rewetting was complete, only the higher site had substantial cover of wetland-characteristic shrubs (3–29%). Canopy cover of habitat-characteristic buttonbush Cephalanthus occidentalis was <1–6% (vs before: 1%). The other site was dominated by wetland-characteristic herbs and floating/submerged plants. In both sites, vegetation cover after rewetting was highly variable across seasons and years (e.g. wetland-characteristic herbs: 1–82%; floating/submerged plants: 0–54%; overall: 1–92%). Over the entire study period, vegetation cover was relatively stable in another part of the floodplain that remained drained: a mixture of wetland and upland herbs (32–62% cover) and shrubs (8–34% cover). Methods: Between October 1999 and February 2001, Section C of the Kissimmee River floodplain was rewetted by dechannelizing the river. Eighteen 100-m² plots were established in parts of the floodplain that were historically buttonbush swamps (more recently drained and grazed/overgrown). There were 12 plots in the dechannelized section and six in an upstream section that remained channelized. Plant species and their cover were surveyed in spring and summer before intervention (1998–1999) and for roughly nine years after (until 2010). This study used the same rewetted floodplain section as (1).

(Summarised by: Nigel Taylor)
Raise water level to restore/create freshwater marshes from other land uses

A before-and-after, site comparison study in 1998–2010 in Florida, USA (Toth 2017) reported that dechannelizing the river to rewet the floodplain reduced overall vegetation cover and cover of pasture/upland grasses in the historical marsh zone, but increased the abundance of wetland- and habitat-characteristic herbs. Statistical significance was not assessed. In restoration plots, overall vegetation cover was 96–98% in the year before rewetting began, then 10–90% roughly 1–9 years after rewetting was complete (highly variable between seasons and years). Cover of pasture/upland grasses was 75–79% before rewetting vs 0–1% after. Cover of wetland-characteristic herbs was 10–11% before rewetting vs 15–61% in all but one sample after. Broadleaf-marsh-characteristic species were absent before rewetting but colonized after (present in ≥67% of restoration plots after nine years, with 5% average cover). Over the entire study period (ignoring a year of extreme flooding), vegetation cover was relatively stable in another part of the floodplain that remained drained: 66–98% overall vegetation cover, 34–78% cover of pasture/upland grasses, 12–43% cover of wetland-characteristic herbs, and no broadleaf-marsh-characteristic species. Methods: Between October 1999 and February 2001, Section C of the Kissimmee River floodplain was rewetted by dechannelizing the river. Fifteen 100-m² plots were established in parts of the floodplain that were historically marshes (more recently used as cattle pasture). There were nine plots in the dechannelized section and six in an upstream section that remained channelized. Plant species and their cover were surveyed in spring and summer before intervention (1998–1999) and for roughly nine years after (until 2010). This study used the same floodplain section(s) as (20), (21) and (22), and shared plots with (24).

(Summarised by: Nigel Taylor)