Conservation Evidence: Evidence Data

Collected Evidence: Collected Evidence: Reprofile/relandscape: freshwater marshes Thirteen studies evaluated the effects, on vegetation, of reprofiling/relandscaping to restore or create freshwater marshes. Ten studies were in the USA. There was one study in each of France, the UK and Italy. Two pairs of studies used the same or similar sites in Connecticut and Nebraska. VEGETATION COMMUNITY Overall extent (1 study): One replicated, site comparison study in the USA reported that emergent vegetation stands covered a smaller area within excavated than natural marshes, 4–5 years after intervention. Community composition (3 studies): Two site comparison studies (one before-and-after, one replicated) in France and the USA reported that reprofiling affected the overall plant community composition. In the USA, the community differed from, but was not intermediate between, natural marshes and degraded marshes. One study in the USA simply quantified the wetness of the overall plant community in an excavated wetland, 1–2 growing seasons after intervention. Overall richness/diversity (9 studies): Three replicated, site comparison studies in the USA found that plant species richness (overall or wetland species) was similar in reprofiled and natural marshes, 1–13 years after intervention. One before-and-after, site comparison study in the UK reported that overall plant species richness was not higher in excavated (and planted) reedbeds, than in a nearby natural reedbed, after seven years. One before-and-after study in France reported that there were more plant species present in a marsh in the two summers after reprofiling than in the summer before. Four studies in the USA and Italy simply reported the number of plant species on wetlands that had been reprofiled or excavated (sometimes along with other interventions), after three months to 23 years. Characteristic plant richness/diversity (1 study): One study in the USA simply reported the number of wetland-characteristic plant species in excavated wetlands, for up to 18 years after intervention. VEGETATION ABUNDANCE Overall abundance (8 studies): Two replicated, site comparison studies in the USA reported that overall vegetation cover was similar in reprofiled and natural marshes, 2–13 years after intervention. One of the studies also found that vegetation cover was similar in reprofiled and degraded marshes. Another replicated, site comparison study in the USA reported that vegetation cover within emergent vegetation stands was lower in excavated than natural marshes, 4–5 years after intervention. Five studies in the USA simply quantified overall vegetation abundance on wetlands that had been reprofiled or excavated (sometimes along with other interventions), after three months to 18 years. One of these studies reported an absence of vegetation after two years. Characteristic plant abundance (1 study): One study in the USA simply quantified the abundance of wetland-characteristic plants in an excavated wetland, after 1–2 growing seasons. Bryophyte abundance (1 study): One replicated, site comparison study in the USA reported that excavated marshes contained a lower abundance (frequency and biomass) of bryophytes than natural marshes, 2–15 years after intervention. Trees/shrub abundance (1 study): One replicated, site comparison study in the USA reported that excavated marshes had lower woody plant cover than natural marshes, after 12–13 years. Individual species abundance (10 studies): Ten studies quantified the effect of this action on the abundance of individual plant species. Two of these studies were replicated site comparisons in the USA, and reported mixed responses. For example, broadleaf cattail Typha latifolia typically had lower cover in excavated than natural marshes in one study, but greater cover in excavated than natural marshes in the other study. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3213https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3213Fri, 09 Apr 2021 09:10:10 +0100Collected Evidence: Collected Evidence: Reprofile/relandscape: brackish/salt marshes Nine studies evaluated the effects, on vegetation, of reprofiling/relandscaping to restore or create brackish/salt marshes. Seven studies were in the USA. One was in Belgium. One was in Italy. Two of the studies were based on the same marsh. VEGETATION COMMUNITY Overall extent (2 studies): One paired, site comparison study in an estuary in the USA reported that vegetation coverage on reprofiled sediment, after 2–3 years, did not clearly differ from natural marsh areas in two of three comparisons. One replicated, paired, site comparison study in the USA reported that reprofiled coastal areas, where submerged sediment had been pushed into ridges, contained a smaller proportion of salt marsh habitat than nearby natural areas. Overall richness/diversity (2 studies): Two studies in Belgium and Italy simply quantified plant species richness in marshy areas that had been reprofiled or excavated (sometimes along with other interventions), for up to 23 years after intervention began. Characteristic plant richness/diversity (1 study): One study in an estuary in the USA simply reported the number of salt marsh plant species that colonized an area of reprofiled sediment over seven years. VEGETATION ABUNDANCE Overall abundance (2 studies): One site comparison study of salt marshes in the USA reported that a marsh created by reprofiling sediment (along with other interventions, including planting) had lower overall vegetation cover than a nearby natural marsh, after three growing seasons. One study in an estuary in Belgium simply quantified the cover of vegetation that colonized an area of reprofiled sediment over five years. Individual species abundance (6 studies): Six studies quantified the effect of this action on the abundance of individual plant species. Of four site comparison studies in the USA, three reported that the dominant herb species was typically less abundant – in terms of cover or biomass – in marshes that had been reprofiled (sometimes along with other interventions) than in natural areas, after 2–5 years. The other study reported that density of the dominant herb species in a reprofiled (and planted) marsh was within the range of nearby natural marshes, after five years. Two studies in the USA and Belgium simply quantified cover of individual plant species over five years after reprofiling (sometimes along with other interventions). VEGETATION STRUCTURE Overall structure (1 study): One replicated, paired, site comparison study in the USA found that the layout of salt marsh habitat (e.g. patch size and complexity) differed between reprofiled coastal areas, where submerged sediment had been pushed into ridges, and nearby natural areas. Height (1 study): One site comparison study in the USA reported that California cordgrass Spartina foliosa was shorter in a 5-year-old reprofiled marsh (also planted with cordgrass) than in nearby natural marshes. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3214https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3214Fri, 09 Apr 2021 09:10:21 +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: Reprofile/relandscape: brackish/saline swamps Five studies evaluated the effects, on vegetation, of reprofiling/relandscaping to restore or create brackish/saline swamps. Three studies were in the USA. Two of these shared a study site. There was one study in Singapore and one in Thailand. VEGETATION COMMUNITY Overall extent (1 study): One study of a coastal site in the USA reported that the area of mangrove vegetation increased between 6 and 14 years after reprofiling (and planting propagules). Relative abundance (2 studies): Two site comparison studies in the USA and Singapore reported that areas of reprofiled coastal land (sometimes also planted with propagules) supported a different relative abundance of tree species to natural forests, after roughly 3–15 years. Overall richness/diversity (1 study): One site comparison study in Singapore reported that an area of reprofiled coastal land colonized by mangrove vegetation had higher plant species richness, after three and a half years, than an adjacent mature mangrove patch. Tree/shrub richness/diversity (3 studies): Two replicated, site comparison studies in the USA, reported that where mangrove forests developed on reprofiled (and planted) sites, they contained a similar number of tree species to nearby mature forests after 7–30 years. One study in a former shrimp pond in Thailand simply reported the number of mangrove tree species that spontaneously colonized in the six years after reprofiling (along with other interventions). VEGETATION ABUNDANCE Overall abundance (1 study): One site comparison study in Singapore reported that an area of reprofiled coastal land colonized by mangrove vegetation had a higher density of individual plants, after three and a half years, than an adjacent mature mangrove patch. Tree/shrub abundance (3 studies): Two replicated, site comparison studies in the USA, reported that where mangrove forests developed on reprofiled (and planted) sites, they contained a greater density of trees than nearby mature forests after 17–30 years. One study in a former shrimp pond in Thailand simply reported the number of mangrove trees that spontaneously colonized in the six years after reprofiling (along with other interventions). 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 reprofiling (along with other interventions). VEGETATION STRUCTURE Overall structure (1 study): One replicated, site comparison study in the USA reported that where mangrove forests developed on reprofiled (and planted) sites, they had a different overall structure to nearby mature forests after 17–30 years. Height (2 studies): One replicated, site comparison study in the USA, reported that where mangrove forests developed on reprofiled (and planted) sites, they had a shorter canopy than nearby mature forests after 17–30 years. One site comparison study in Singapore reported that in an area of reprofiled coastal land colonized by mangrove vegetation, most plants were in a similar height category to those in an adjacent mature mangrove patch, but that the maximum plant height was lower. Vegetation was surveyed three and a half years after reprofiling. Diameter/perimeter/area (2 studies): Two site comparison studies in the USA reported that mangrove forests that developed on reprofiled (and planted) coastal areas contained thinner trees, on average, than mature natural forests, after 7–18 years. Basal area (3 studies): Three site comparison studies in the USA compared mangrove forests that developed on reprofiled (and planted) coastal areas to mature natural forests. Two of the studies reported that restored forests had a smaller basal area than mature natural forests, after 7–18 years. The other study reported that restored forests had a similar basal area to mature natural forests, after 17–30 years. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3216https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3216Fri, 09 Apr 2021 09:10:45 +0100Collected Evidence: Collected Evidence: Remove surface soil/sediment: freshwater marshes Six studies evaluated the effects, on vegetation, of removing surface soil/sediment to restore or create freshwater marshes. Four studies were in the USA. One study was in the Netherlands. One study was in Japan. VEGETATION COMMUNITY Community composition (3 studies): Two replicated, site comparison studies in the USA reported that freshwater marshes being restored by removing excess soil/sediment (along with other interventions) typically contained a different overall plant community, after 1–12 years, to both degraded and natural marshes nearby. One replicated study of dune slacks in the Netherlands simply reported changes in the overall plant community composition over four years after stripping topsoil (along with other interventions). Overall richness/diversity (4 studies): One replicated, site comparison study of dune slacks in the Netherlands reported that overall plant species richness was greater in restored slacks (topsoil stripped five years previously, along with other interventions) than in mature unmanaged slacks. One replicated, site comparison study in the USA reported that freshwater marshes being restored by removing topsoil (along with other interventions) contained fewer wetland plant species, after 1–12 years, than nearby natural marshes. Two studies (including one site comparison) in freshwater marshes in the USA and Japan reported that the effect of removing topsoil on overall plant species richness depended on the amount removed. Characteristic plant richness/diversity (2 studies): One replicated, site comparison study of a floodplain marsh in Japan found that where stripped plots were colonized by plants within two growing seasons, they contained more wetland-characteristic species than an adjacent unstripped area. One replicated study of dune slacks in the Netherlands simply reported the number of characteristic plant species present over five years after stripping topsoil (along with other interventions). VEGETATION ABUNDANCE Overall abundance (3 studies): Three studies (two replicated) in the Netherlands, the USA and Japan simply quantified the overall abundance of vegetation that colonized – within five years – freshwater wetlands stripped of topsoil (sometimes along with other interventions). Characteristic plant abundance (2 studies): Two studies (one replicated) in freshwater marshes in the USA and Japan simply quantified the abundance of wetland-characteristic plant species that colonized – within five years – areas stripped of topsoil. Individual species abundance (5 studies): Five studies quantified the effect of this action on the abundance of individual plant species. For example, one replicated, site comparison study in the USA found that pothole wetlands restored by removing excess sediment (sometimes along with planting herbs) had lower hybrid cattail Typha x glauca cover than unrestored wetlands after 2–7 years, and similar hybrid cattail cover to nearby natural wetlands. One replicated study of dune slacks in the Netherlands simply quantified the cover of individual species present over five years after stripping topsoil (along with other interventions). Only two species had >1% cover in any slack. VEGETATION STRUCTURE Overall structure (1 study): One study in a freshwater marsh in the USA reported that the effect of removing topsoil on the abundance of tall vegetation depended on the amount removed. Visual obstruction (1 study): One replicated, site comparison study of pothole wetlands in the USA found that the effect of removing excess sediment (sometimes along with planting herbs) on horizontal vegetation cover, 2–7 years later, depended on the elevation/vegetation zone. Height (1 study): One site comparison study in the USA reported that sedge tussocks were shorter in a wet meadow restored by removing excess sediment (along with other interventions, including planting sedges) than in nearby natural meadows, after 11–14 years. Diameter/perimeter/area (1 study): One site comparison study in the USA reported that sedge tussocks had a smaller perimeter in a wet meadow restored by removing excess sediment (along with other interventions, including planting sedges) than in natural meadows, after 11–14 years. Basal area (1 study): One site comparison study in the USA reported that the basal area of sedge tussocks was smaller in a wet meadow restored by removing excess sediment (along with other interventions, including planting sedges) than in nearby natural meadows, after 11–14 years. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3221https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3221Fri, 09 Apr 2021 13:07:41 +0100Collected Evidence: Collected Evidence: Remove surface soil/sediment: brackish/salt marshes One study evaluated the effects, on vegetation, of removing surface soil/sediment to restore or create brackish/salt marshes. The study was in the Netherlands. VEGETATION COMMUNITY Overall richness/diversity (1 study): One study in the Netherlands reported that 23 plant species colonized over two years after stripping topsoil from coastal farmland. VEGETATION ABUNDANCE Individual species abundance (1 study): One study in the Netherlands reported the frequency of plant species that colonized over two years after stripping topsoil from coastal farmland. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3222https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3222Fri, 09 Apr 2021 13:08:28 +0100Collected Evidence: Collected Evidence: Remove surface soil/sediment: freshwater swampsWe found no studies that evaluated the effects, on vegetation, of removing surface soil/sediment to restore or create 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%2F3223https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3223Fri, 09 Apr 2021 13:08:44 +0100Collected Evidence: Collected Evidence: Remove surface soil/sediment: brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of removing surface soil/sediment to restore or create 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%2F3224https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3224Fri, 09 Apr 2021 13:08:54 +0100