Collected Evidence: Collected Evidence: Change season/timing of livestock grazing: brackish/salt marshes Two studies evaluated the effects, on vegetation, of grazing brackish/salt marshes in different seasons or at different times. One study was in the USA and one was in the Netherlands. In both studies, the focal livestock were cattle. VEGETATION COMMUNITY Community composition (1 study): One replicated, randomized, paired, controlled, before-and-after study on a salt marsh in the Netherlands found that plots grazed annually by 0.5 cattle/ha and plots grazed biennially by 1.0 cattle/ha experienced a similar turnover of plant species over six years, and had a similar overall plant community composition after six years. Overall richness/diversity (1 study): The same study found that plots grazed annually by 0.5 cattle/ha and plots grazed biennially by 1.0 cattle/ha experienced similar increases in plant species richness over six years, and had similar species richness after six years. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, randomized, paired, controlled, before-and-after study in alkali marshes in the USA found that summer- and autumn-grazed plots experienced similar changes in live vegetation biomass, over one year. Individual species abundance (1 study): One replicated, randomized, paired, controlled, before-and-after study on a salt marsh in the Netherlands found that grazing annually with 0.5 cattle/ha stimulated greater increases in cover of sea aster Aster tripolium than grazing biennially with 1.0 cattle/ha. There was no significant difference between the grazing regimes for cover of sea couch grass Elytrigia atheria. Vegetation was monitored over six years. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2975https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2975Thu, 25 Mar 2021 14:17:58 +0000Collected Evidence: Collected Evidence: Plug/dam canals or trenches: brackish/salt marshes Two studies evaluated the effects, on vegetation, of plugging/damming canals or trenches in brackish/salt marshes. Both studies were in the USA. There was overlap in the canals used in the studies. Both studies included some freshwater areas in some analyses, but all results are based predominantly on canals in brackish or saline marshes. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Overall abundance (2 studies): Two replicated, site comparison studies studied emergent vegetation of backfilled canals in the USA. One study reported that plugged canals had greater coverage of emergent marsh vegetation than unplugged canals after 6–60 months. One study found that emergent vegetation coverage on former spoil heaps did not significantly differ alongside plugged and unplugged canals after 6–11 years. The first study also reported that plugged canals were more likely to contain floating/submerged vegetation than unplugged canals. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2992https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2992Mon, 29 Mar 2021 12:08:35 +0100Collected Evidence: Collected Evidence: Raise water level to restore degraded brackish/salt marshes Two studies evaluated the effects, on vegetation, of raising the water level to restore degraded brackish/salt marshes. One study was in the Netherlands and one was in Tunisia. VEGETATION COMMUNITY Community types (2 study): One before-and-after study of a lakeshore brackish/salt marsh in Tunisia reported an increase in coverage of bulrush-dominated vegetation relative to salt marsh vegetation over three years after modifying a canal to retain water in the marsh. One study of a salt marsh in the Netherlands reported increased coverage of pioneer succulent plant communities, and reduced coverage of short-grass communities, over approximately 10 years following abandonment of the drainage system (along with other interventions). Overall richness/diversity (1 study): One study of a salt marsh in the Netherlands reported that overall plant species richness increased over 14 years after abandoning drainage systems (along with other interventions). VEGETATION ABUNDANCE Individual species abundance (1 study): One study of a salt marsh in the Netherlands reported that some individual plant species became more common over 14 years after abandoning drainage systems (along with other interventions). These included saltbush Atriplex prostrata and seablite Suaeda maritima. Some other species became less common, including creeping bentgrass Agrostis stolonifera and common cordgrass Spartina anglica. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3027https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3027Wed, 31 Mar 2021 14:47:25 +0100Collected Evidence: Collected Evidence: Lower water level to restore degraded freshwater marshes Two studies evaluated the effects, on vegetation, of lowering the water level to restore degraded freshwater marshes. One study was in the USA and one was in Canada. VEGETATION COMMUNITY Overall extent (1 study): One before-and-after study of a lakeshore marsh in the USA reported that following a drawdown of water levels, emergent vegetation coverage increased in areas that were previously open water. Community types (1 study): One replicated, controlled, before-and-after study of freshwater marshes in Canada reported changes in the area of some vegetation classes over three years of partial drawdown. There was a temporary increase in coverage of dead vegetation at the expense of some live vegetation classes. Two classes – horsetail-dominated and bur-reed-dominated – had greater coverage after three years of drawdown than before. VEGETATION ABUNDANCE   VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3030https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3030Wed, 31 Mar 2021 15:20:12 +0100Collected Evidence: Collected Evidence: Actively manage water level: freshwater swamps Two studies evaluated the effects, on vegetation, of active water level management in freshwater swamps. Both studies were in the USA. VEGETATION COMMUNITY Overall richness/diversity (1 study): One before-and-after study of a swamp/marsh in the USA found that overall plant diversity was higher in the autumn following a managed flood/drawdown than in the autumn before. VEGETATION ABUNDANCE Tree/shrub abundance (1 study): One site comparison study of floodplain swamps in the USA found that an artificial flood had no significant effect on tree seedling density in a low and very wet swamp, but increased tree seedling density in a drier swamp higher on the floodplain. Individual species abundance (1 study): One before-and-after study of a swamp/marsh in the USA reported mixed responses of individual plant species’ cover to active water level management. However, the study found that cover of the dominant woody species, Pacific willow Salix lucida, was higher in the autumn following a managed flood/drawdown than in the autumn before. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3040https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3040Thu, 01 Apr 2021 10:03:39 +0100Collected Evidence: Collected Evidence: Use prescribed fire to maintain or restore disturbance: freshwater swamps Two studies evaluated the effects, on vegetation, of using prescribed fire to maintain or restore disturbance in freshwater swamps. Both studies were in the USA. VEGETATION COMMUNITY Tree/shrub richness/diversity (1 study): One replicated, site comparison study in the USA found that shrub-dominated wetlands burned every three years contained fewer species of mature tree than unburned wetlands, but a similar number of shrub and sapling species. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, site comparison study of bottomland swamps in the USA found that swamps burned every 2–3 years had a similar overall density of midstory and understory vegetation to unburned swamps. Herb abundance (2 studies): One replicated, site comparison study of shrub-dominated wetlands in the USA found that wetlands burned every three years had greater cover of grasses than unburned wetlands, but statistically similar cover of forbs and ferns. Another replicated, site comparison study of bottomland swamps in the USA found that swamps burned every 2–3 years had a similar density of understory grasses to unburned swamps. Tree/shrub abundance (2 studies): One replicated, site comparison study of shrub-dominated wetlands in the USA found that wetlands burned every three years had greater cover of shrubs than unburned wetlands. Another replicated, site comparison study of bottomland swamps in the USA found that swamps burned every 2–3 years had a similar density of shrubs, vines and other woody plants to unburned swamps. VEGETATION STRUCTURE Height (2 studies): One replicated, site comparison study of bottomland swamps in the USA found that swamps burned every 2–3 years had a shorter tree canopy than unburned swamps – but a similar-height midstory and understory. Another replicated, site comparison study of shrub-dominated wetlands in the USA found that the tree canopy was a similar height in wetlands burned every three years and unburned wetlands. Basal area (1 study): One replicated, site comparison study of bottomland swamps in the USA found that swamps burned every 2–3 years had a similar basal area of trees to unburned swamps. Canopy cover (1 study): One replicated, site comparison study of shrub-dominated wetlands in the USA found that wetlands burned every three years had less canopy cover than unburned wetlands. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3056https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3056Fri, 02 Apr 2021 08:57:49 +0100Collected Evidence: Collected Evidence: Physically damage problematic plants: freshwater swamps Two studies evaluated the effects, on vegetation, of physically damaging problematic plants in freshwater swamps. Both studies were in the USA. VEGETATION COMMUNITY Overall richness/diversity (1 study): One controlled study aiming to restore a swamp in the USA found that ploughing a canarygrass-invaded plot after spraying it with herbicide increased overall plant richness and diversity, two growing seasons later, compared to spraying alone. Native/non-target richness/diversity (1 study): The same study found that ploughing a canarygrass-invaded plot 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 (2 studies): Two controlled studies in the USA evaluated the effects, on tree/shrub abundance, of physically damaging canarygrass-invaded vegetation. One study found that ploughing a canarygrass-invaded plot 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. 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 disking, along with cutting 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 controlled study aiming to restore a swamp in the USA reported that ploughing a canarygrass-invaded plot after spraying it 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%2F3097https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3097Sat, 03 Apr 2021 16:05:55 +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 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: Control populations of wild vertebrates: freshwater marshes Two studies evaluated the effects, on vegetation, of controlling populations of wild vertebrates in freshwater marshes. Both studies were in the USA. In one study, the problematic animals were mammals and in the other study they were birds. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Overall abundance (1 study): One before-and-after study of marshy vegetation in the USA reported that over two years of trapping and shooting feral swine Sus scrofa, overall vegetation cover increased. Characteristic plant abundance (1 study): One before-and-after study in the USA reported that over two years of trapping and shooting feral swine Sus scrofa, cover of two plant species characteristic of target seepage slope vegetation increased. Herb abundance (1 study): One before-and-after study of marshy vegetation in the USA reported that over two years of trapping and shooting feral swine Sus scrofa, total forb cover increased. Individual species abundance (2 studies): One paired, controlled, before-and-after study in freshwater marshes in the USA reported that killing and scaring Canada geese Branta canadensis reduced their impacts on the density of wild rice Zizania aquatica: its density became similar in plots open to geese and plots fenced to exclude geese. One before-and-after study of marshy vegetation in the USA reported mixed responses of individual plant species to two years of trapping and shooting feral swine Sus scrofa. VEGETATION STRUCTURE Height (1 study): One paired, controlled, before-and-after study in freshwater marshes in the USA reported that killing and scaring Canada geese Branta canadensis reduced their impacts on the height of wild rice Zizania aquatica: its height became similar in plots open to geese and plots fenced to exclude geese. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3136https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3136Mon, 05 Apr 2021 14:09:16 +0100Collected Evidence: Collected Evidence: Remove debris from brackish/salt marshes Two studies evaluated the effects, on vegetation, of removing debris from brackish/salt marshes. Both studies were in the USA. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, paired, site comparison study in a salt marsh in the USA found that overall vegetation cover in patches where debris had been removed remained lower than in undisturbed marsh for one growing season, but had recovered to match undisturbed marsh after two growing seasons. Individual species abundance (2 studies): Two studies quantified the effect of this action on the abundance of individual plant species. For example, the two replicated, site comparison studies in salt marshes in the USA found that the abundance of dominant herb species in impacted vegetation patches was typically lower than in undisturbed marsh one growing season after removing debris, but was sometimes similar to undisturbed marsh. The results depended on the species, metric and type of debris removed. One of the studies also monitored until the second growing season after removing debris; at this point, the cover of both dominant herb species had recovered to match undisturbed marsh. VEGETATION STRUCTURE Height (1 study): One replicated, before-and-after, site comparison study in a salt marsh in the USA found that the maximum height of smooth cordgrass recovered, to match undisturbed marsh, within 45 weeks of removing debris. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3162https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3162Tue, 06 Apr 2021 12:49:05 +0100Collected Evidence: Collected Evidence: Cut or burn oil-contaminated vegetation: brackish/salt marshes Two studies evaluated the effects, on vegetation, of cutting or burning oil-contaminated vegetation in brackish/salt marshes. One study reviewed multiple cases from the UK and the USA. The other study was in Brazil. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Overall abundance (1 study): One review of studies in oil-contaminated salt marshes in the UK and the USA reported that in eight of eight cases with quantitative comparisons between cut and uncut areas, cutting had no clear benefit for vegetation abundance (density, biomass or cover) over 8–29 months of recovery. Individual species abundance (1 study): One replicated, paired, controlled, site comparison study in oil-contaminated brackish/salt marshes in Brazil found that smooth cordgrass Spartina alterniflora density and biomass were never greater in cut than uncut plots (and typically similar under each treatment), over nine months after cutting. VEGETATION STRUCTURE Height (1 study): One replicated, paired, controlled, site comparison study in oil-contaminated brackish/saline marshes in Brazil found that smooth cordgrass Spartina alterniflora was never taller in cut than uncut plots (typically similar height under each treatment) over nine months after cutting. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3175https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3175Tue, 06 Apr 2021 13:41:15 +0100Collected Evidence: Collected Evidence: Raise water level to restore/create brackish/salt marshes from other land uses Two studies evaluated the effects, on vegetation, of raising the water level to restore/create brackish/salt marshes from other land uses or habitat types. Both studies were in the same area of Iraq, but used different study sites. VEGETATION COMMUNITY Community types (1 study): One before-and-after study of a slightly brackish marsh in Iraq reported that fewer plant community types were present three years after reflooding than before drainage. Overall richness/diversity (2 studies): Two before-and-after studies of brackish marshes in Iraq reported that fewer plant species were present three years after reflooding than before drainage. One of these studies also reported that individual plant communities typically had lower diversity after reflooding than before drainage. VEGETATION ABUNDANCE Overall abundance (1 study): One before-and-after study of a slightly brackish marsh in Iraq reported that six of seven studied plant communities had lower spring and/or summer biomass three years after reflooding than before drainage. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3199https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3199Fri, 09 Apr 2021 07:45:05 +0100Collected Evidence: Collected Evidence: Raise water level to restore/create freshwater swamps from other land uses Two studies evaluated the effects, on vegetation, of raising the water level to restore/create freshwater swamps from other land uses or habitat types. Both studies monitored the effects of one river dechannelization project in the USA. VEGETATION COMMUNITY Overall extent (1 study): One before-and-after study of a floodplain in the USA reported that after dechannelizing a river to raise the water level, the area of shrubby and forested wetlands increased – reaching greater coverage than before intervention, but also than before degradation. Community types (1 study): The same study broke down overall swamp coverage into specific community types. For example, most of the shrubby wetlands that developed after raising the water level were dominated by a non-native species – which was not present historically. VEGETATION ABUNDANCE                                                                             Overall abundance (1 study): One before-and-after, site comparison study of historical shrubby wetlands on a floodplain in the USA reported that dechannelizing a river to raise the water level reduced overall vegetation cover in the following nine years. Characteristic plant abundance (1 study): The same study reported that after dechannelizing a river to raise the water level, only one of two sites became dominated by wetland-characteristic shrubs. The other site remained dominated by wetland-characteristic herb species. Individual species abundance (1 study): The same study reported that dechannelizing a river to raise the water level slightly increased cover of buttonbush Cephalanthus occidentalis in one of two sites (no data for other site). VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3200https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3200Fri, 09 Apr 2021 07:45:18 +0100Collected Evidence: Collected Evidence: Lower water level to restore/create freshwater marshes from other land uses Two studies evaluated the effects, on vegetation, of lowering the water level to restore/create freshwater marshes from other land uses or habitat types. One study was in the USA and one was in the Netherlands. VEGETATION COMMUNITY Overall extent (1 study): One replicated, before-and-after study of a freshwater wetland in the USA reported that following a drawdown of water levels, emergent vegetation coverage increased in areas that were previously open water. VEGETATION ABUNDANCE Overall abundance (1 study): One before-and-after study at the edge of a freshwater lake in the Netherlands reported that following a drawdown of the lake water level, vegetation cover developed in areas that were previously open water. Cover varied between years and elevations. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3202https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3202Fri, 09 Apr 2021 07:46:42 +0100Collected Evidence: Collected Evidence: Facilitate tidal exchange to restore/create brackish/saline swamps from other land uses Two studies evaluated the effects, on vegetation, of facilitating tidal exchange to restore/create brackish/saline swamps from other land uses or habitat types. One study was in Australia and one was in Thailand. VEGETATION COMMUNITY                              Overall extent (1 study): One before-and-after study in an estuary in Australia reported that the area of mangrove forest on an island was greater 3–9 years after restoring full tidal exchange than in the years before. Tree/shrub richness/diversity (1 study): One study in a former shrimp pond in Thailand reported the number of mangrove tree species that spontaneously colonized in the six years after restoring full tidal exchange (along with other interventions). VEGETATION ABUNDANCE Individual species abundance (1 study): One study in a former shrimp pond in Thailand reported the number of mangrove trees, by species, that spontaneously colonized in the six years after restoring full tidal exchange (along with other interventions). VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3209https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3209Fri, 09 Apr 2021 07:49:33 +0100Collected Evidence: Collected Evidence: Reprofile/relandscape: freshwater swamps Two studies evaluated the effects, on vegetation, of reprofiling or relandscaping to restore or create freshwater swamps. Both studies were in the USA. VEGETATION COMMUNITY Community composition (1 study): One replicated, site comparison study in the USA found that swamps created by reprofiling uplands (along with planting trees/shrubs) contained a similar proportion of tree species in different plant groups, after 7–11 years, to nearby swamps recovering naturally from logging. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, site comparison study in the USA found that swamps created by reprofiling uplands (along with planting trees/shrubs) had similar ground and canopy cover, after 7–11 years, to nearby swamps recovering naturally from logging. Herb abundance (1 study): One study in a former firing range in the USA simply quantified herb cover approximately 1–2 years after reprofiling the site (and planting trees/shrubs). Tree/shrub abundance (1 study): One study in a former firing range in the USA simply quantified woody plant cover approximately 1–2 years after reprofiling the site (and planting trees/shrubs). VEGETATION STRUCTURE Visual obstruction (1 study): One replicated, site comparison study in the USA found that swamps created by reprofiling uplands (along with planting trees/shrubs) had less horizontal vegetation cover, after 7–11 years, than nearby swamps recovering naturally from logging. Height (1 study): The same study found that swamps created by reprofiling uplands (along with planting trees/shrubs) contained shorter woody vegetation, after 7–11 years, than nearby swamps recovering naturally from logging. Herbaceous vegetation, however, was of similar height in both created and naturally recovering swamps. Basal area (1 study): The same study found that swamps created by reprofiling uplands (along with planting trees/shrubs) had a lower vegetation basal area, after 7–11 years, than nearby swamps recovering naturally from logging. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3215https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3215Fri, 09 Apr 2021 09:10:34 +0100Collected Evidence: Collected Evidence: Disturb soil/sediment surface: freshwater marshes Two studies evaluated the effects, on vegetation, of disturbing the surface of freshwater marshes. Both studies were in the USA – in the same region but different sites. VEGETATION COMMUNITY Community composition (1 study): One replicated, paired, controlled study in rewetted marshes in the USA found that ploughed plots contained a plant community characteristic of wetter conditions than unploughed plots after one growing season – but not after two. Overall richness/diversity (2 studies): Two replicated, controlled studies in rewetted marshes in the USA found that ploughed plots typically contained more wetland plant species than unploughed plots after one growing season – but not after two. VEGETATION ABUNDANCE Overall abundance (2 studies): Two replicated, controlled studies in rewetted marshes in the USA found that ploughed plots had greater cover of wetland plants than unploughed plots after one growing season – but not after two. Individual species abundance (1 study): One replicated, controlled study in rewetted marshes in the USA found that ploughed plots had much greater cover of cattails Typha than unploughed plots after two growing seasons. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3226https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3226Fri, 09 Apr 2021 14:04:02 +0100Collected Evidence: Collected Evidence: Deposit soil/sediment to form physical structure of freshwater marshes Two studies evaluated the effects, on vegetation, of depositing soil/sediment to form the physical structure of freshwater marshes (without introducing vegetation). One study was in the USA and one was in the Netherlands. VEGETATION COMMUNITY Community types (1 study): One replicated, paired, site comparison study in the Netherlands reported that marshes created by depositing sand at lake margins contained fewer plant community types, after 8–16 years, than mature natural marshes. VEGETATION ABUNDANCE Overall abundance (2 studies): One site comparison study in the USA reported that plant stem density was similar, after 4–10 years, in marshes created by depositing sediment and in natural marshes, but that vegetation cover was lower in the created marshes. One replicated, paired, site comparison study in the Netherlands reported that marshes created by depositing sand at lake margins contained similar vegetation biomass to nearby natural marshes after 8–16 years. VEGETATION STRUCTURE Height (1 study): One site comparison study in the USA reported that a freshwater marsh created by depositing sediment contained vegetation of a similar height to nearby natural marshes after 4–10 years. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3235https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3235Fri, 09 Apr 2021 15:01:56 +0100Collected Evidence: Collected Evidence: Create mounds or hollows before planting trees/shrubs: freshwater wetlands Three studies evaluated the effects, on vegetation, of creating mounds or hollows in freshwater wetlands before planting trees/shrubs. All three studies were in the USA. VEGETATION COMMUNITY Community composition (1 study): One replicated, site comparison study of 10-year-old restored/created freshwater wetlands in the USA reported that adding coarse woody debris to wetlands before planting trees/shrubs affected the composition of the ground vegetation layer, but not the tree layer. Overall richness/diversity (2 studies): Two studies in freshwater wetlands in the USA reported that creating mounds or hollows before planting trees/shrubs had no clear or significant effect on plant species richness and diversity 10–12 years later. In one of the studies, the same was true for bryophyte, herb and woody plants richness separately. VEGETATION ABUNDANCE   VEGETATION STRUCTURE Height (1 study): One replicated, paired, controlled study in created freshwater wetlands in the USA found that the average height of white cedar Thuja occidentalis saplings typically increased more, between two and five years after planting, in created mounds than on lower (occasionally flooded) ground. OTHER                                         Survival (1 study): One replicated, paired, controlled study in created freshwater wetlands in the USA found that white cedar Thuja occidentalis seedlings had higher survival rates when planted into created mounds than on lower (occasionally flooded) ground. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3288https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3288Sat, 10 Apr 2021 17:35:08 +0100Collected Evidence: Collected Evidence: Add upland topsoil before/after planting non-woody plants: freshwater wetlands Three studies evaluated the effects, on vegetation, of adding upland topsoil to freshwater wetlands planted with emergent, non-woody plants. Two studies were in the USA and one was in Canada. One study was in a greenhouse. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Individual species abundance (1 study): One replicated, randomized, paired, controlled study in freshwater trenches in Canada found that adding a mixture of mineral soil and peat to pots of mine tailings before planting water sedge Carex aquatilis typically increased its above-ground biomass two growing seasons later. VEGETATION STRUCTURE Individual plant size (2 studies): One replicated, controlled study in a greenhouse in the USA found that mixing topsoil into pots of mineral soil/compost before planting tussock sedge Carex stricta seedlings typically increased the biomass and number of shoots they developed over three months. However, one replicated, paired, controlled study in a wet meadow restoration site in the USA reported that mixing topsoil into the mineral soil/compost substrate before planting tussock sedge seedlings had no clear effect on the number of shoots they developed over two months. OTHER Survival (1 study): One replicated, randomized, paired, controlled study in freshwater trenches in Canada found that adding a mixture of mineral soil and peat to pots of mine tailings either increased or had no significant effect on survival of planted water sedge Carex aquatilis over two growing seasons. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3296https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3296Sun, 11 Apr 2021 08:11:14 +0100Collected Evidence: Collected Evidence: Add lime or similar chemicals before/after planting non-woody plants: brackish/saline wetlands Three studies evaluated the effects, on vegetation, of adding neutralizing chemicals to brackish/saline wetlands planted with emergent, non-woody plants. Two studies were in Canada. One study was in the USA. One study was in a greenhouse. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Characteristic plant abundance (1 study): One replicated, paired, controlled, before-and-after study in salt-contaminated bogs in Canada reported that liming reduced the above-ground biomass of planted salt marsh vegetation after one year. Individual species abundance (2 studies): One controlled study in former borrow pits in the USA found that limed and unlimed plots supported similar biomass of a planted herb species after 1–2 growing seasons. In contrast, one replicated, randomized, paired, controlled study in salt-contaminated peat in Canada found that limed pots supported lower biomass of two sown herb species than unlimed pots, after four months. VEGETATION STRUCTURE   OTHER Germination/emergence (1 study): One replicated, randomized, paired, controlled study in salt-contaminated peat in Canada found that for each of two sown herb species, germination rates were similar in limed and unlimed pots. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3301https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3301Sun, 11 Apr 2021 08:46:32 +0100Collected Evidence: Collected Evidence: Remove vegetation that could compete with planted non-woody plants: freshwater wetlands Three studies evaluated the effects, on emergent non-woody vegetation planted in freshwater wetlands, of removing competing plants. All three studies were in the USA. Two studies used the same experimental wet basins but planted different species. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Herb abundance (1 study): One replicated, randomized, paired, controlled study in wet meadows in the USA found removing an invasive species with herbicide before sowing mixed grass and forb seeds increased the total biomass of sown species after 1–2 growing seasons, but that burning to remove the invasive species had no significant effect on sown species biomass. Individual species abundance (1 study): One replicated, paired, controlled study in wet basins in the USA found that the effect of weeding to remove competitors on lake sedge Carex lacustris biomass and density, in the three years after planting, depended on the year and water level. VEGETATION STRUCTURE Height (2 studies): Two replicated, paired, controlled studies in wet basins in the USA examined the effect of weeding to remove competitors on the height of planted sedges. One of the studies found that weeding had no significant effect on the height of planted tussock sedge Carex stricta in three of three years. The other study found that weeding reduced the average height of lake sedge Carex lacustris in the first year after planting, but had no significant effect in the following two years. OTHER Survival (2 studies): Two replicated, paired, controlled studies in wet basins in the USA examined the effect of weeding to remove competitors on the survival of planted sedges Carex spp. Both studies found that weeding had no significant effect on sedge survival in at least two of three years. One of the studies found that weeding affected tussock sedge Carex stricta survival in the second year after planting, but that the direction of the effect depended on plot elevation. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3332https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3332Sun, 11 Apr 2021 14:05:56 +0100Collected Evidence: Collected Evidence: Physically damage seeds of non-woody plants before sowing: freshwater wetlands Three studies evaluated the effects – on emergent, non-woody plants typical of freshwater wetlands – of physically damaging their seeds before sowing. All three studies were in greenhouses or laboratories in the USA. VEGETATION COMMUNITY   VEGETATION ABUNDANCE   VEGETATION STRUCTURE   OTHER Germination/emergence (3 studies): Two replicated, controlled studies (one also randomized) in greenhouses in the USA found that rubbing seeds of herbaceous plants with sandpaper before sowing had no significant effect on their germination rate. One replicated, randomized, paired, controlled study in a laboratory in the USA found that removing the sac-like seed coating before sowing typically increased, and did not reduce, the germination rate of sedges Carex spp. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3376https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3376Mon, 12 Apr 2021 08:22:24 +0100Collected Evidence: Collected Evidence: Provide general protection for marshes or swamps Three studies evaluated the overall effects, on vegetation or human behaviour, of providing general protection for marshes or swamps. There was one study in each of Puerto Rico, China and Canada. VEGETATION COMMUNITY Overall extent (3 studies): Two studies in China and Canada reported that the area of wetlands (including habitats other than marshes or swamps) in their study regions declined over 10–29 years, despite general protection of wetlands. However, in China, the decline was slower than in a previous period without protection. One before-and-after study of mangrove forests in Puerto Rico reported that their area increased following legal protection. VEGETATION ABUNDANCE   VEGETATION STRUCTURE Overall structure (1 study): One before-and-after study in China reported degradation in wetland landscape structure over 29 years when wetlands were generally protected. However, the decline was slower than in a previous period when wetlands were not protected. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3385https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3385Mon, 12 Apr 2021 09:30:20 +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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