Collected Evidence: Collected Evidence: Use cutting/mowing to control problematic herbaceous plants: freshwater marshes Eight studies evaluated the effects, on vegetation, of cutting/mowing problematic herbaceous plants or small shrubs in freshwater marshes. Six studies were in the USA, one was in Mexico and one was in Canada. VEGETATION COMMUNITY Community composition (1 study): One replicated, randomized, paired, controlled, before-and-after study in a cattail-dominated marsh in the USA found that cutting altered the overall plant community composition over the following two years. Relative abundance (1 study): One replicated, randomized, paired, controlled study in a grass-invaded marsh in Mexico found that cut and uncut plots supported a similar relative abundance of six common plant species after 4–8 months. Overall richness/diversity (4 studies): Two replicated, randomized, paired, controlled studies in invaded marshes/wet meadows in the USA found that cut plots typically had greater overall plant species richness and/or diversity than uncut plots, after 1–3 growing seasons. One of the studies carried out other interventions along with cutting. Two replicated, controlled studies in freshwater marshes in the USA and Mexico found that cut and uncut plots had similar overall plant richness and/or diversity, after 1–2 growing seasons. Native/non-target richness/diversity (2 studies): One controlled, before-and-after study in a reed-dominated freshwater marsh in the USA found that cutting/mowing (along with applying herbicide) increased non-reed species richness three years later. One replicated, controlled, before-and-after study in cattail-invaded marshes in the USA found that mown and unmown marshes had similar native plant species richness after 1–12 months VEGETATION ABUNDANCE Overall abundance (3 studies): Two replicated, controlled studies in freshwater marshes in the USA and Mexico found that cut and uncut plots contained a similar amount of vegetation after 1–2 growing seasons. This was true for cover of wetland plants and density of all plants. One replicated, randomized, paired, controlled, before-and-after study in iris-invaded lakeshore marshes in Canada reported that cutting reduced overall vegetation cover, one year later, in a permanently flooded marsh but had no clear effect on cover in an intermittently flooded marsh. Herb abundance (1 study): One replicated, randomized, paired, controlled study in a cattail-invaded wet meadow in the USA found that plots in which cattail was cut four times over two growing seasons developed greater cover of sedges Carex than uncut plots, but that cutting cattail only twice had no significant effect on sedge cover. Native/non-target abundance (3 studies): Two controlled studies (one also replicated, randomized, paired; one also before-and-after) in reed- or canarygrass-dominated wetlands in the USA found that cut plots typically contained more native or non-target vegetation than uncut plots, after 1–3 growing seasons. Both studies carried out other interventions along with cutting. One replicated, controlled, before-and-after study in cattail-invaded marshes in the USA found that mown and unmown marshes supported a similar native vegetation density after 1–12 months, and similar native vegetation biomass after 12 months. Individual species abundance (2 studies): Three studies quantified the effect of this action on the abundance of individual plant species, other than the species being controlled. For example, one replicated, randomized, paired, controlled study in a grass-invaded marsh in Mexico found that five of five monitored native species had similar cover in cut and uncut plots after 4–8 months. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3104https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3104Sun, 04 Apr 2021 09:58:57 +0100Collected Evidence: Collected Evidence: Use cutting/mowing to control problematic herbaceous plants: brackish/salt marshes One study evaluated the effects, on vegetation, of cutting/mowing problematic herbaceous plants or small shrubs in brackish/salt marshes. The study was in the USA. VEGETATION COMMUNITY Overall richness/diversity (1 study): One replicated, randomized, paired, controlled study in a saltgrass-dominated marsh in the USA found that mown and unmown plots had similar overall plant species richness after one year. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, randomized, paired, controlled study in a saltgrass-dominated marsh in the USA found that mown and unmown plots had similar overall vegetation cover after one year. Individual species abundance (1 study): The same study found that six dominant herb species, other than the species being controlled, had similar cover in mown and unmown plots after one year. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3105https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3105Sun, 04 Apr 2021 09:59:17 +0100Collected Evidence: Collected Evidence: Use cutting/mowing to control problematic herbaceous plants: freshwater swamps Two studies evaluated the effects, on vegetation, of cutting/mowing problematic herbaceous plants or small shrubs in freshwater swamps. Both studies were in the USA. VEGETATION COMMUNITY Overall richness/diversity (1 study): One replicated, controlled study aiming to restore a swamp in the USA found that mowing canarygrass-invaded vegetation before spraying it with herbicide had no significant effect on overall plant richness or diversity, two growing seasons later, compared to spraying alone. Native/non-target richness/diversity (1 study): The same study found that mowing canarygrass-invaded vegetation before spraying it with herbicide had no significant effect on native plant species richness, two growing seasons later, compared to spraying alone. VEGETATION ABUNDANCE Tree/shrub abundance (2 studies): Two replicated, controlled studies in the USA evaluated the effects, on tree/shrub abundance, of managing canarygrass-invaded vegetation by cutting. One study found that mowing canarygrass-invaded vegetation before spraying it with herbicide had no significant effect on the density of non-planted tree seedlings, two growing seasons later, compared to spraying alone. The other study found that managed plots (cut, disked and sprayed with herbicide) contained more non-planted tree seedlings than unmanaged plots, after 1–3 years. Native/non-target abundance (1 study): One replicated, controlled study aiming to restore a swamp in the USA found that plots in which canarygrass-invaded vegetation was managed (by cutting, along with disking and applying herbicide) contained at least as much non-canarygrass herb cover, after 1–3 years, to plots in which vegetation was not managed. Individual species abundance (1 study): One replicated, controlled study aiming to restore a swamp in the USA reported that mowing canarygrass-invaded vegetation before spraying it with herbicide affected the abundance of some individual plant species two growing seasons later. VEGETATION STRUCTURE  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3106https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3106Sun, 04 Apr 2021 09:59:35 +0100Collected Evidence: Collected Evidence: Use cutting/mowing to control problematic herbaceous plants: brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of cutting/mowing problematic herbaceous plants or small shrubs in brackish/saline swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3107https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3107Sun, 04 Apr 2021 10:00:38 +0100Collected Evidence: Collected Evidence: Use cutting to control problematic large trees/shrubs: freshwater marshes Two studies evaluated the effects, on vegetation, of cutting down problematic large trees/shrubs in freshwater marshes. One study was in the UK and one was in the USA. VEGETATION COMMUNITY Overall extent (1 study): One study of a dune slack in the UK reported an increase in total vegetation coverage between one and two years after clearing scrub (by cutting and applying herbicide). Overall richness/diversity (1 study): The same study reported a small increase in total plant richness between one and two years after clearing scrub (by cutting and applying herbicide). Characteristic plant richness/diversity (1 study): The same study reported an increase in the number of slack-characteristic plant species present between one and two years after clearing scrub (by cutting and applying herbicide). Native/non-target richness/diversity (1 study): The same study reported an increase in native plant richness between one and two years after clearing scrub (by cutting and applying herbicide). VEGETATION ABUNDANCE Individual species abundance (1 study): One study quantified the effect of this action on the abundance of individual plant species, other than the species being controlled. The site comparison study in the USA found that tussock sedge Carex stricta was less dense in a wet meadow restored by removing trees (along with other interventions, including planting sedges) than in nearby natural meadows, after 11–14 years. VEGETATION STRUCTURE Height (1 study): One site comparison study in the USA reported that sedge tussocks were shorter in a wet meadow restored by removing trees (along with other interventions, including planting sedges) than in nearby natural meadows, after 11–14 years. Diameter/perimeter/area (1 study): The same study reported that sedge tussocks had a smaller perimeter in a wet meadow restored by removing trees (along with other interventions, including planting sedges) than in nearby natural meadows, after 11–14 years. Basal area (1 study): The same study reported that the basal area of sedge tussocks was smaller in a wet meadow restored by removing trees (along with other interventions, including planting sedges) than in nearby natural meadows, after 11–14 years. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3108https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3108Sun, 04 Apr 2021 14:31:56 +0100Collected Evidence: Collected Evidence: Use cutting to control problematic large trees/shrubs: brackish/salt marshes One study evaluated the effects, on vegetation, of cutting down problematic large trees/shrubs in brackish/salt marshes. The study was in the USA. VEGETATION COMMUNITY Community composition (1 study): One controlled, before-and-after study in a salt marsh in the USA reported that in seven of nine cases, the overall plant community composition varied more across plots from which mangrove trees had been removed than a plot from which mangrove trees had not been removed. Vegetation was surveyed after two years of continual tree removal. VEGETATION ABUNDANCE Overall abundance (1 study): One controlled, before-and-after study in a salt marsh in the USA reported that removing >50% of invading mangrove trees increased total cover of salt marsh vegetation two years later, but that removing <50% of invading mangrove trees had no clear effect. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3109https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3109Sun, 04 Apr 2021 14:32:13 +0100Collected Evidence: Collected Evidence: Use cutting to control problematic large trees/shrubs: freshwater swampsWe found no studies that evaluated the effects, on vegetation, of cutting down problematic large trees/shrubs in freshwater swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3110https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3110Sun, 04 Apr 2021 14:32:24 +0100Collected Evidence: Collected Evidence: Use cutting to control problematic large trees/shrubs: brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of cutting down problematic large trees/shrubs in brackish/saline swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3111https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3111Sun, 04 Apr 2021 14:32:37 +0100Collected Evidence: Collected Evidence: Use grazing to control problematic plants: freshwater marshes Three studies evaluated the effects, on vegetation, of using grazing to control problematic plants in freshwater marshes. Two studies were in the USA. One study was in Costa Rica. VEGETATION COMMUNITY Community composition (1 study): One replicated, randomized, paired, controlled study in Costa Rica found that amongst plots where cattail-dominated vegetation had been crushed, grazing had no significant effect on the overall plant community composition over 15 months. Relative abundance (1 study): One replicated, paired, controlled, before-and-after study in a canarygrass-invaded marsh in the USA found that grazing had no significant effect on the relative abundance of the invader: over two years, it declined similarly in grazed and ungrazed plots. Overall richness/diversity (3 studies): Of three replicated, paired, controlled studies in invaded marshes/wet meadows in the USA and Costa Rica, two found that grazing typically had no significant effect on plant species richness and/or diversity over approximately two years. The other study found that grazed areas had higher plant species richness than ungrazed areas after two months. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, paired, controlled, before-and-after study in a canarygrass-invaded marsh in the USA found that grazing had no significant effect on total vegetation cover at the ground surface, over two years. Native/non-target abundance (1 study): One replicated, paired, controlled, before-and-after study in an invaded wet meadow in the USA found that two months of grazing increased cover of non-invasive grass-like plants. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3112https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3112Sun, 04 Apr 2021 15:42:11 +0100Collected Evidence: Collected Evidence: Use grazing to control problematic plants: brackish/salt marshesWe found no studies that evaluated the effects, on vegetation, of using grazing to control problematic plants in brackish/salt marshes.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3113https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3113Sun, 04 Apr 2021 15:42:40 +0100Collected Evidence: Collected Evidence: Use grazing to control problematic plants: freshwater swampsWe found no studies that evaluated the effects, on vegetation, of using grazing to control problematic plants in freshwater swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3114https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3114Sun, 04 Apr 2021 15:47:05 +0100Collected Evidence: Collected Evidence: Use grazing to control problematic plants: brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of using grazing to control problematic plants in brackish/saline swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3115https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3115Sun, 04 Apr 2021 15:47:21 +0100Collected Evidence: Collected Evidence: Use prescribed fire to control problematic plants: freshwater marshes Four studies evaluated the effects, on vegetation, of using prescribed fire to control problematic plants in freshwater marshes. Two studies were in the USA. There was one study in each of Australia and Costa Rica. VEGETATION COMMUNITY Overall extent (1 study): One controlled, before-and-after study in a freshwater marsh in Costa Rica reported that burning (and physically damaging) cattail stands reduced the area of live vegetation present 5–22 months later. Overall richness/diversity (2 studies): One controlled study in a freshwater marsh in Costa Rica found that plots in which cattail stands were managed (burned and physically damaged) had greater overall plant species richness than unmanaged plots, 11–22 months after intervention. One replicated, randomized, controlled study in a marsh in the USA found that the effect of prescribed burning on plant species richness in the following autumn depended on the season of burning. VEGETATION ABUNDANCE Overall abundance (2 studies): One controlled, before-and-after study in a freshwater marsh in Costa Rica reported that burning (and physically damaging) cattail stands reduced live vegetation cover 5–22 months later. One replicated, randomized, controlled study in a marsh in the USA found that the effect of prescribed burning on overall vegetation cover in the following autumn depended on the season of burning. Herb abundance (1 study): One study of a floodplain marsh in Australia simply reported grass/sedge cover for up to four years after burning mimosa-invaded vegetation (along with other interventions). Native/non-target abundance (2 studies): One replicated, randomized, paired, controlled study in canarygrass-invaded wet meadows in the USA found that prescribed burning had no significant effect on the biomass of plants other than the invasive species, 2–3 growing seasons later. One study of a floodplain marsh in Australia simply reported non-target vegetation cover for up to four years after burning mimosa-invaded vegetation (along with other interventions). Individual species abundance (1 study): One study quantified the effect of this action on the abundance of individual plant species, other than the species being controlled. The replicated, randomized, controlled study in a marsh in the USA found that the effect of prescribed burning on the cover of dominant species in the following autumn depended on the season of burning. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3116https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3116Sun, 04 Apr 2021 16:05:02 +0100Collected Evidence: Collected Evidence: Use prescribed fire to control problematic plants: brackish/salt marshes Four studies evaluated the effects, on vegetation, of using prescribed fire to control problematic plants in brackish/salt marshes. All four studies were in the USA. Two studies were based on the same experimental set-up. VEGETATION COMMUNITY Overall richness/diversity (4 studies): Two replicated, randomized, paired, controlled studies in brackish and salt marshes in the USA reported that burned and unburned plots had similar plant species richness over the following 1–3 years. Two studies in saltgrass- or reed-dominated marshes in the USA reported that burned areas had greater plant species richness than unburned areas, after approximately 1–3 years. In one of the studies, burned areas had also been sprayed with herbicide for nine years – and contained more plant species than a nearby natural marsh. VEGETATION ABUNDANCE Overall abundance (3 studies): Three replicated, randomized, paired, controlled studies in brackish and salt marshes in the USA evaluated the effect of prescribed burning on vegetation cover. One study found that autumn-burned plots had lower overall vegetation cover than unburned plots after 11 months, but one found that winter-burned plots had similar overall vegetation cover to unburned plots after one year. Two of the studies reported that winter-burned plots had less standing dead vegetation cover than unburned plots in the following summer or winter. Individual species abundance (4 studies): All four studies quantified the effect of this action on the abundance of individual plant species, other than a species being controlled. For example, three replicated, randomized, paired, controlled studies in brackish and salt marshes in the USA reported mixed effects of burning on cover of saltgrass Distichlis spicata: higher in burned than unburned plots in the following summer, lower in burned than unburned plots in the following winter, or mixed effects amongst marsh types. Two replicated, randomized, paired, controlled studies in brackish and salt marshes in the USA reported that burning did not reduce cover of saltmeadow cordgrass Spartina patens, compared to cover in unburned plots, over the following 1–3 years. One site comparison study of brackish marshes in the USA reported that a marsh that had been burned for three years (and sprayed with herbicide for nine) contained more smooth cordgrass Spartina alterniflora than an unburned and unsprayed marsh, and a similar amount of smooth cordgrass to a nearby natural marsh. VEGETATION STRUCTURE Visual obstruction (1 study): One replicated, randomized, paired, controlled study in brackish and salt marshes in the USA found that the visual obstruction caused by vegetation (combination of height and horizontal cover) was similar in burned and unburned plots, after 11 months. Height (1 study): One site comparison study of brackish marshes in the USA found that in a marsh burned for two years (and sprayed with herbicide for nine), the dominant plant species (smooth cordgrass Spartina alterniflora) grew to a similar height as in a nearby natural marsh. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3117https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3117Sun, 04 Apr 2021 16:05:16 +0100Collected Evidence: Collected Evidence: Use prescribed fire to control problematic plants: freshwater swamps One study evaluated the effects, on vegetation, of using prescribed fire to control problematic plants in freshwater swamps. The study was in the USA. VEGETATION COMMUNITY Overall richness/diversity (1 study): One replicated, randomized, controlled study aiming to restore a swamp in the USA found that burning canarygrass-invaded vegetation after spraying it with herbicide increased overall plant diversity, two growing seasons later, compared to spraying alone. However, burning had no significant effect on plant species richness. Native/non-target richness/diversity (1 study): The same study found that burning canarygrass-invaded vegetation after spraying it with herbicide had no significant effect on native plant species richness, two growing seasons later, compared to spraying alone. VEGETATION ABUNDANCE Tree/shrub abundance (1 study): One replicated, randomized, controlled study aiming to restore a swamp in the USA found that burning canarygrass-invaded vegetation after spraying it with herbicide had no significant effect on the density of non-planted tree seedlings, two growing seasons later, compared to spraying alone. Individual species abundance (1 study): The same study reported that burning canarygrass-invaded vegetation after spraying it with herbicide affected the abundance of some individual plant species two growing seasons later. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3118https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3118Sun, 04 Apr 2021 16:05:25 +0100Collected Evidence: Collected Evidence: Use prescribed fire to control problematic plants: brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of using prescribed fire to control problematic plants in brackish/saline swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3119https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3119Sun, 04 Apr 2021 16:05:37 +0100Collected Evidence: Collected Evidence: Use herbicide to control problematic plants: freshwater marshes Seventeen studies evaluated the effects, on vegetation, of using herbicide to control problematic plants in freshwater marshes. Twelve studies were in the USA. Two studies were in Australia. There was one study in each of Canada, Mexico and the UK. There was overlap in the sites used in two studies. Two pairs of studies in Australia and the USA used the same general study area, but different plots or experimental set-ups. VEGETATION COMMUNITY Overall extent (3 studies): Two replicated, randomized, controlled, before-and-after studies in the USA found that marshes sprayed with herbicide had lower live vegetation coverage but greater dead vegetation coverage than unsprayed marshes, after 1–2 years. Overall vegetation coverage was lower in sprayed than unsprayed marshes in one study, but similar in sprayed and unsprayed marshes in the other. One study of a dune slack in the UK simply reported an increase in overall vegetation coverage between one and two years after clearing scrub (by cutting and applying herbicide). Overall richness/diversity (6 studies): Three studies (including one replicated, randomized, paired, controlled) in ephemeral marshes/wet meadows in the USA reported that spraying invaded vegetation with herbicide (sometimes along with other interventions) typically increased total plant species richness 1–5 growing seasons later. Two replicated, randomized, paired, controlled studies (one also before-and-after) in freshwater marshes/wet meadows in the USA and Mexico found that plots treated with herbicide (sometimes along with other interventions) had similar overall plant species richness and diversity to untreated plots, after 4–8 months or three years. One study of a dune slack in the UK simply reported a small increase in total plant richness between one and two years after clearing scrub (by cutting and applying herbicide). Characteristic plant richness/diversity (3 studies): Two before-and-after studies of floodplain marshes in the USA reported that cover of wet-prairie indicator species was higher 1–4 years after applying herbicide than before. However, one of these studies reported that the total cover of non-invasive, wetland-characteristic herbs was similar or lower 2–3 years after applying herbicide than before. One study of a dune slack in the UK simply reported an increase the number of slack-characteristic plant species present between one and two years after clearing scrub (by cutting and applying herbicide). Native/non-target richness/diversity (3 studies): One controlled, before-and-after study in a reed-dominated freshwater marsh in the USA found that applying herbicide (along with cutting/mowing) increased non-reed species richness three years later. One replicated, controlled, before-and-after study in cattail-invaded marshes in the USA reported that marshes sprayed with herbicide contained no living native plants one year later: fewer than were present before spraying and in unsprayed marshes. One study of a dune slack in the UK simply reported an increase in native plant richness between one and two years after clearing scrub (by cutting and applying herbicide). VEGETATION ABUNDANCE Overall abundance (4 studies): Three replicated studies (two also randomized, paired, controlled) in freshwater marshes/wet meadows in the USA and Mexico found that applying herbicide (sometimes along with other interventions) had no clear or significant effect on overall vegetation abundance four months to three years later. Cover and density were similar to untreated plots and/or pre-treatment levels. One replicated, randomized, paired, controlled study in the USA found that wet meadows sprayed with herbicide contained less total vegetation biomass than unsprayed marshes, 2–3 growing seasons later. Native/non-target abundance (7 studies): Four studies (including one replicated, randomized, paired, controlled, before-and-after) in marshes/wet meadows in the USA and Australia found that spraying invaded plots with herbicide (sometimes along with other interventions) did not reduce – and often increased – the abundance of native or non-target vegetation 1–3 growing seasons later. One replicated, controlled, before-and-after study in cattail-invaded marshes in the USA reported that marshes sprayed with herbicide contained no living native plants one year later: density and biomass were lower than before spraying and in unsprayed marshes. One replicated, randomized, paired, controlled study in an alligatorweed-invaded marsh in the USA found that spraying vegetation with herbicide had no significant effect on native plant biomass after 1–2 growing seasons. One study of a floodplain marsh in Australia simply reported non-target vegetation cover for up to four years after treating mimosa-invaded vegetation with herbicide (along with other interventions). Herb abundance (4 studies): Two replicated, randomized, paired, controlled studies in wet meadows in the USA found that treating a problematic plant species with herbicide (sometimes along with physical removal) had no significant effect on cover of forbs, grass-like plants or sedges after 2–3 growing seasons. One replicated, randomized, paired, controlled study in a loosestrife-invaded marsh in Canada found that the density of sedges and grasses was not lower in herbicide-sprayed plots, than in unsprayed plots, after 2–3 years. The precise effect depended on dose of herbicide used. One study of a floodplain marsh in Australia simply reported grass/sedge cover for up to four years after treating mimosa-invaded vegetation with herbicide (along with other interventions). Algae/phytoplankton abundance (1 study): One replicated, randomized, controlled study in a reed-invaded marsh in the USA reported that free-growing filamentous algae were more common in plots sprayed with herbicide than unsprayed plots, approximately one year later. However, spraying with herbicide had no significant effect on the density or biomass of biofilm algae. Individual species abundance (3 studies): Three studies quantified the effect of this action on the abundance of individual plant species, other than the species being controlled. For example, one replicated, randomized, paired, controlled study in a grass-invaded marsh in Mexico found that five of five monitored native species had similar cover in herbicide-sprayed and unsprayed plots after 4–8 months. Two of the studies do not distinguish between the effects of applying herbicide and other interventions. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3120https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3120Sun, 04 Apr 2021 17:19:04 +0100Collected Evidence: Collected Evidence: Use herbicide to control problematic plants: brackish/salt marshes Seven studies evaluated the effects, on vegetation, of using herbicide to control problematic plants in brackish/salt marshes. Six studies were in the USA. One study was in South Africa. Two studies shared part of the same experimental set-up. VEGETATION COMMUNITY Relative abundance (1 study): One site comparison study of brackish marshes in the USA found that a marsh sprayed with herbicide for nine years (and burned for three) and a nearby natural marsh supported a similar relative abundance of the dominant plant species, smooth cordgrass Spartina alterniflora. Overall richness/diversity (1 study): One site comparison study of brackish marshes in the USA reported that a marsh sprayed with herbicide for nine years (and burned for three) contained more plant species than an unburned and unsprayed marsh – but also more plant species than a nearby natural marsh. Native/non-target richness/diversity (2 studies): One replicated, randomized, paired, controlled, before-and-after study in a pepperweed-invaded marsh in the USA found that applying herbicide did not increase the richness of non-pepperweed species over two years after intervention. The precise effect depended on the herbicide used. One study of an intertidal area in the USA simply counted the number of native salt marsh plant species that colonized after treating smooth cordgrass Spartina alterniflora stands with herbicide. VEGETATION ABUNDANCE Native/non-target abundance (5 studies): Three replicated, randomized, paired, controlled, before-and-after studies in pepperweed-invaded marshes in the USA found that applying herbicide typically did not increase cover of non-pepperweed vegetation, in the two years following intervention. The precise effect depended on the herbicide used. Two studies on the coasts of South Africa and the USA simply quantified the abundance of native salt marsh vegetation that colonized after treating smooth cordgrass Spartina alterniflora stands with herbicide. Individual species abundance (4 studies): Four studies quantified the effect of this action on the abundance of individual plant species, other than the species being controlled. For example, one site comparison study of brackish marshes in the USA reported that a marsh sprayed with herbicide for nine years (and burned for three) contained more smooth cordgrass Spartina alterniflora than an unburned and unsprayed marsh, and a similar amount of smooth cordgrass to a nearby natural marsh. One replicated, paired, controlled, before-and-after study in a pepperweed-invaded marsh in the USA reported that applying herbicide typically reduced cover of dominant native species over two years. The precise effect depended on the herbicide used. VEGETATION STRUCTURE Height (1 study): One site comparison study of brackish marshes in the USA found that in a marsh sprayed with herbicide for nine years (and burned for three), the dominant plant species (smooth cordgrass Spartina alterniflora) grew to a similar height as in a nearby natural marsh. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3121https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3121Sun, 04 Apr 2021 17:19:16 +0100Collected Evidence: Collected Evidence: Use herbicide to control problematic plants: freshwater swamps Four studies evaluated the effects, on vegetation, of using herbicide to control problematic plants in freshwater swamps. All four studies were in the USA. VEGETATION COMMUNITY Overall richness/diversity (2 studies): One replicated, randomized, paired, controlled study aiming to restore canarygrass-invaded swamps in the USA found that plots sprayed with herbicide typically had greater plant species richness and diversity than unsprayed plots, after 1–2 growing seasons. One replicated, randomized, controlled study in a petunia-invaded floodplain swamp in the USA found that plots sprayed with herbicide had similar overall plant species richness to unsprayed plots over 15 months after spraying. Native/non-target richness/diversity (3 studies): Three replicated, controlled studies (also paired and/or randomized) in invaded freshwater swamps in the USA found that applying herbicide typically had no significant effect on native plant species richness, over 3–24 months after spraying. VEGETATION ABUNDANCE Tree/shrub abundance (2 studies): Two replicated, controlled studies in the USA evaluated the effects, on tree/shrub abundance, of managing canarygrass-invaded vegetation by applying herbicide. One study found that plots sprayed with herbicide contained more non-planted tree seedlings than unsprayed plots, after 1–2 growing seasons. The other study found that managed plots (cut, disked and sprayed with herbicide) contained more non-planted tree seedlings than unmanaged plots, after 1–3 years. Native/non-target abundance (2 studies): Two replicated, controlled studies in swamps in the USA reported that spraying invaded vegetation with herbicide (sometimes along with other interventions) typically had no clear or significant effect on native/non-target vegetation cover 1–3 years later. Cover was typically similar to unmanaged plots or before intervention. Individual species abundance (1 study): One replicated, randomized, paired, controlled study aiming to restore a canarygrass-invaded swamp in the USA reported that spraying the vegetation with herbicide affected the abundance of some individual plant species – other than the target problematic species – two growing seasons later. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3122https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3122Sun, 04 Apr 2021 17:19:27 +0100Collected Evidence: Collected Evidence: Use herbicide to control problematic plants: brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of using herbicide to control problematic plants in brackish/saline swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3123https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3123Sun, 04 Apr 2021 17:19:48 +0100Collected Evidence: Collected Evidence: Use covers/barriers to control problematic plants: freshwater marshes One study evaluated the effects, on vegetation, of using covers or barriers to control problematic plants in freshwater marshes. The study was in Canada. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, randomized, paired, controlled, before-and-after study in iris-invaded lakeshore marshes in Canada reported that covering plots with rubber sheeting after cutting back yellow iris Iris pseudacorus prevented most vegetation regrowth in an intermittently flooded marsh, but had no clear effect in a permanently flooded marsh. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3124https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3124Mon, 05 Apr 2021 09:58:41 +0100Collected Evidence: Collected Evidence: Use covers/barriers to control problematic plants: brackish/salt marshesWe found no studies that evaluated the effects, on vegetation, of using covers or barriers to control problematic plants in brackish/salt marshes.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3125https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3125Mon, 05 Apr 2021 09:58:54 +0100Collected Evidence: Collected Evidence: Use covers/barriers to control problematic plants: freshwater swampsWe found no studies that evaluated the effects, on vegetation, of using covers or barriers to control problematic plants in freshwater swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3126https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3126Mon, 05 Apr 2021 09:59:05 +0100Collected Evidence: Collected Evidence: Use covers/barriers to control problematic plants: brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of using covers or barriers to control problematic plants in brackish/saline swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3127https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3127Mon, 05 Apr 2021 09:59:17 +0100Collected Evidence: Collected Evidence: Introduce organisms to control problematic plants: freshwater marshes One study evaluated the effects, on vegetation, of introducing organisms (other than large vertebrate grazers) to control problematic plants in freshwater marshes. The study was in the USA. It involved introducing plants to compete with problematic plants. VEGETATION COMMUNITY Overall richness/diversity (1 study): One replicated, randomized, paired, controlled study in canarygrass-invaded wet meadows in the USA found that plots planted with upland vegetation (after mowing and applying herbicide) had greater overall plant species richness than untreated plots, after 1–3 growing seasons. VEGETATION ABUNDANCE Native/non-target abundance (1 study): One replicated, randomized, paired, controlled study in canarygrass-invaded wet meadows in the USA found that plots planted with upland vegetation (after mowing and applying herbicide) typically had greater cover of unplanted native vegetation than untreated plots, after 1–3 growing seasons. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3128https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3128Mon, 05 Apr 2021 11:55:51 +0100
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What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

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