Conservation Evidence: Evidence Data

Collected Evidence: Collected Evidence: Directly plant non-woody plants: freshwater wetlands Twenty-four studies evaluated the effects, on vegetation, of directly planting emergent, non-woody plants in freshwater wetlands. Sixteen studies were in the USA. There was one study in each of Guam, the Netherlands, Israel, Ireland, the UK, Italy, Australia and China. Two pairs of studies in Minnesota and South Dakota took place in the same area but used different experimental set-ups. VEGETATION COMMUNITY Community composition (1 study): One replicated, site comparison study around fresh/brackish lakes in Australia reported that as planted rush stands aged, their near-shore plant community became more similar to that behind mature natural rush stands. Overall richness/diversity (9 studies): Two studies (including one replicated, randomized, controlled) in freshwater marshes in China and the USA reported that planting herbs increased plant species richness and/or diversity for up to five years. Two controlled studies in freshwater marshes in the USA reported that planted and unplanted sites had similar plant species richness after 2–3 years. Three studies in the USA, the UK and Australia compared plant species richness in marshes that had been planted with herbs (sometimes along with other interventions) and natural marshes, and reported that it was never higher in planted marshes. Three studies involving freshwater marshes in Guam, the USA and Italy simply quantified plant species richness for up to 13 years after planting herbs (along with other interventions). Characteristic plant richness/diversity (1 study): One replicated, paired, controlled study in freshwater wetlands in the USA found that plots planted with wetland-characteristic herbs had a similar richness of wetland-characteristic plant species, after three years, to unplanted plots. VEGETATION ABUNDANCE Overall abundance (4 studies): One before-and-after study of a freshwater marsh and wet meadow in China found that vegetation cover was greater five years after planting herbs than in the year before planting. One replicated, paired, controlled study in freshwater wetlands in the USA found that plots planted with herbs had similar overall vegetation cover, after three years, to unplanted plots. One replicated, site comparison study around fresh/brackish lakes in Australia found that as planted rush stands aged, the density of plants in adjacent near-shore vegetation became more similar to mature natural stands. One study in a freshwater marsh in the USA simply quantified vegetation cover and density over 1–9 years after planting herbs (along with other interventions). Characteristic plant abundance (1 study): One replicated, paired, controlled study in freshwater wetlands in the USA found that plots planted with wetland-characteristic herbs had greater cover of wetland-characteristic plants, after three years, than unplanted plots. Individual species abundance (13 studies): Thirteen studies quantified the effect of this action on the abundance of individual plant species. For example, one replicated, paired, controlled study in freshwater wetlands in the USA found that both planted herb species had greater cover in planted than unplanted plots, after three years. Three studies in the UK, the USA and Australia compared the abundance of herb species where they had been planted to their abundance in natural marshes: two found that the planted species was more dense in planted than natural areas after 5–14 years, and one found that planted rush stands became more dense (i.e. more like natural stands) as they aged. VEGETATION STRUCTURE Overall structure (1 study): One replicated, site comparison study around fresh/brackish lakes in Australia reported that as planted rush stands aged, their width increased – becoming more like mature natural stands. Height (4 studies): One replicated, site comparison study around fresh/brackish lakes in Australia reported that as planted rush stands aged, their maximum height increased – becoming more like mature natural stands. One before-and-after study of a freshwater marsh and wet meadow in China found that vegetation was taller five years after planting herbs than in the year before planting. One site comparison study of wet meadows in the USA reported that sedge tussocks in a restored meadow were shorter than sedge tussocks in natural meadows, 11–14 years after planting (along with other interventions). One replicated study in wet basins in the USA simply reported an increase in the average height of a herb species over three growing seasons after it was planted. Diameter/perimeter/area (1 study): One site comparison study of wet meadows in the USA reported that sedge tussocks in a restored meadow had a smaller perimeter than sedge tussocks in natural meadows, 11–14 years after planting (along with other interventions). Basal area (1 study): One site comparison study of wet meadows in the USA reported that the basal area of sedge tussocks was lower in a restored meadow than in natural meadows, 11–14 years after planting (along with other interventions). Individual plant size (2 studies): Two replicated studies in wet meadow restoration sites in the USA reported that the size of Carex stricta seedlings increased over two months or three growing seasons after planting. This was true for the average number of shoots/plant and biomass/plant. OTHER Survival (14 studies): Nine studies (eight replicated) in the USA and Israel quantified survival rates of individual herbs planted in freshwater wetlands. Survival rates ranged from 0% to 100% after 1–3 growing seasons. Eight studies (including five replicated and two before-and-after) in Guam, the USA, the Netherlands and Israel reported 0% survival or absence of planted (or sown) herb species, in at least some cases, after three months to seven years. Proposed factors affecting survival included elevation/water levels, herbivory, time of planting and plug type. Growth (2 studies): Two studies monitored true growth of individual herbs (rather than changes in average height of survivors). The two studies (one replicated) in Ireland and the USA reported that herbs grew over 1–2 growing seasons after planting. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3256https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3256Sat, 10 Apr 2021 13:26:49 +0100Collected Evidence: Collected Evidence: Directly plant non-woody plants: brackish/saline wetlands Thirty studies evaluated the effects, on vegetation, of directly planting emergent, non-woody plants in brackish/saline wetlands. Twenty-four studies were in the USA. There was one study in each of Canada, New Zealand, Spain, Italy and Australia. One study was a global systematic review. Four of the studies monitored different outcomes of one planting experiment in California. Two other studies used the same marsh as each other. Two studies shared some plots with each other. VEGETATION COMMUNITY Community composition (1 study): One replicated, site comparison study around fresh/brackish lakes in Australia reported that as planted rush stands aged, their near-shore plant community became more similar to that behind mature natural rush stands. Overall richness/diversity (3 studies): One controlled study on a brackish sandflat in the USA reported that an area planted with wetland herbs contained more plant species, after eight years, than an adjacent unplanted area. One replicated, site comparison study around fresh/brackish lakes in Australia found that the near-shore vegetation behind >8-year-old planted rush stands and mature natural stands contained a similar number of plant species. One study of a fresh/brackish/saline marsh in Italy simply quantified plant species richness for up to 13 years after planting herbs (along with other interventions). VEGETATION ABUNDANCE Overall abundance (4 studies): Two site comparison studies (one replicated) of brackish/saline marshes in the USA reported that areas planted with herbs (sometimes along with other interventions) contained less vegetation, after 2–3 growing seasons, than nearby natural marshes. This was true for biomass and cover. One replicated, site comparison study around fresh/brackish lakes in Australia found that the density of near-shore vegetation behind older planted rush stands was similar to that behind mature natural stands. One replicated, randomized, paired, controlled study in an estuary in the USA reported that plots planted with salt marsh vegetation contained more vegetation biomass than unplanted plots, after three growing seasons. Individual species abundance (18 studies): Eighteen studies quantified the effect of this action on the abundance of individual plant species. Four studies in the USA compared the abundance of plant species in planted and unplanted areas. Two replicated studies found that planted herb species were typically more abundant in planted than unplanted plots, after 2–4 growing seasons. One replicated, paired, controlled study reported that there were fewer common reed Phragmites australis stems in plots planted with other wetland herbs (and shrubs) than in unplanted plots, after 1–3 years. One replicated, randomized, controlled study reported species-specific effects of planted individuals on recruitment of conspecific seedlings. Nine studies in the USA and Australia compared the abundance of herb species where they had been planted to their abundance in natural brackish/saline marshes. Results varied between studies, species, metrics and time since planting. One before-and-after study of an intertidal site in the USA reported greater abundance of smooth cordgrass Spartina alterniflora over five years after planting (along with other interventions) than before. Seven studies (six replicated) in brackish/saline marshes in the USA and Canada simply quantified the abundance of individual species over 1–3 growing seasons after they were planted (sometimes along with other interventions). VEGETATION STRUCTURE Overall structure (2 studies): One replicated, randomized, paired, controlled, site comparison study in a salt marsh in the USA found that plots planted with herbs contained more canopy layers than unplanted plots after 2–4 growing seasons. One replicated, site comparison study around fresh/brackish lakes in Australia reported that as planted rush stands aged, their width increased – becoming more similar to mature natural stands. Height (11 studies): Three replicated studies in salt marshes in the USA found that vegetation in areas planted with herbs was at least as tall as vegetation in unplanted areas, 2–4 growing seasons after planting. Of six site comparison studies that compared vegetation height in planted and natural marshes (sometimes along with other interventions), three studies in the USA reported that vegetation was shorter in planted marshes after 2–5 growing seasons. Two studies in the USA and Australia found that vegetation was typically a similar height in planted and natural marshes after 2–11 years. One study in the USA found that vegetation was taller in planted marshes after three growing seasons. Four replicated studies in brackish/saline marshes in the USA simply quantified the height of herbs over 1–5 growing seasons after they were planted; in three of these studies, the average height increased over time. OTHER Survival (17 studies): Seventeen studies (including 13 replicated and one systematic review) in the USA, Canada, New Zealand, Spain and multiple countries quantified survival rates of individual herbs planted (or sown) in brackish/saline wetlands. Survival rates ranged from 0% to 100% after 20 days to 2 years. Four studies in the USA, New Zealand and multiple countries reported 0% survival or absence of planted herb species, in at least some cases, after nine months to eight years. Proposed factors affecting survival included elevation/water levels, age of planted individuals, treatment with root dip, planting date, soil pH, damage by waterbirds, salinity and sediment organic matter content. Growth (2 studies): Two studies monitored true growth of individual herbs (rather than changes in average height of survivors). One replicated study in a brackish marsh in the USA reported that in 8 of 10 cases, rushes/bulrushes grew in both height and circumference over the second year after planting. One replicated study in an estuary in Spain reported growth of planted small cordgrass Spartina maritima and glasswort Sarcocornia perennis over the year after planting. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3257https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3257Sat, 10 Apr 2021 13:27:23 +0100Collected Evidence: Collected Evidence: Directly plant trees/shrubs: freshwater wetlands Seventeen studies evaluated the effects, on vegetation, of directly planting trees/shrubs in freshwater wetlands. Fifteen studies were in the USA. Two were in Australia. Two of the studies took place in the same site, but used different experimental set-ups. VEGETATION COMMUNITY Community composition (2 studies): Two replicated studies of freshwater wetlands in the USA found that planting trees/shrubs (sometimes along with other interventions) had no significant effect on aspects of plant community composition, after 1–11 years. Specifically, planted and unplanted wetlands had a similar proportion of species in different plant groups and relative abundance of different plant groups. Overall richness/diversity (1 study): One replicated, randomized, controlled, before-and-after study in depressional wetlands in the USA found that wetlands sparsely planted with tree seedlings contained a similar number of plant species, after 1–4 years, to unplanted wetlands. VEGETATION ABUNDANCE Overall abundance (2 studies): Two replicated studies (one site comparison; one randomized, controlled, before-and-after) of freshwater wetlands in the USA found that planting trees/shrubs (sometimes along with other interventions) had no significant effect on overall vegetation cover (both ground and canopy, separately or combined) after 1–11 years. 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 planting trees/shrubs (after reprofiling) had less horizontal vegetation cover, after 7–11 years, than nearby swamps recovering naturally from logging. Height (6 studies): One replicated, site comparison study in the USA found that swamps created by planting trees/shrubs (after reprofiling) contained shorter woody vegetation, after 7–11 years, than nearby swamps recovering naturally from logging. Herbaceous vegetation, however, was of similar height. Five studies (four replicated) in freshwater wetlands in the USA simply quantified the height of trees and shrubs over 1–6 growing seasons after they were planted; in four of these studies, the average height typically increased over time. Diameter (1 study): One study in a freshwater wetland in the USA reported an increase in the diameter of surviving trees over the year after they were planted. Basal area (1 study): One replicated, site comparison study in the USA found that swamps created by planting trees/shrubs (after reprofiling) had a lower vegetation basal area, after 7–11 years, than nearby swamps recovering naturally from logging. OTHER Survival (15 studies): Fifteen studies (including eight replicated) in the USA and Australia quantified survival of individual trees/shrubs planted in freshwater wetlands. Survival rates ranged from 0% to 100% after 4–66 months. Seven of the studies (including six replicated) in the USA and Australia reported 0% survival of planted vegetation in at least some cases, after 1–6 growing seasons. Proposed factors affecting survival included elevation/water levels, the season of planting, protection from herbivores, root pruning, extreme weather, and if/how invasive vegetation was removed before planting. Growth (2 studies): Two studies monitored true growth of individual trees/shrubs (rather than changes in average height of survivors). The two studies, in freshwater wetlands in the USA, reported that planted trees grew in diameter and/or height over their first 1–2 growing seasons. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3258https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3258Sat, 10 Apr 2021 13:27:32 +0100Collected Evidence: Collected Evidence: Directly plant trees/shrubs: brackish/saline wetlands Forty-seven studies evaluated the effects, on vegetation, of directly planting trees/shrubs in brackish/saline wetlands. Forty-four studies involved planting mangroves or other coastal swamp trees: 20 in Asia, seven in Central America, six in Africa, four in North America, four in South America, two in Oceania and one globally. Three studies involved planting shrubs in the USA or Spain. There was overlap in the sites used in two studies. One systematic review included several of the other summarized studies. VEGETATION COMMUNITY Overall extent (3 studies): Two before-and-after studies in India and South Africa reported that the area of mangrove forest was greater 6–42 years after planting mangrove trees (sometimes along with other interventions) than in the years before. One study in Sri Lanka simply quantified the area of mangrove vegetation present 8–10 years after planting seedlings (and propagules). Tree/shrub richness/diversity (6 studies): Three site comparison studies in the USA, Mexico and Brazil reported that where mangrove forests developed after planting trees (sometimes along with other interventions), they contained a similar number of tree species to mature and/or naturally regenerating forests after 10–30 years. One site comparison study in Vietnam reported that after 14–34 years, a planted mangrove forest contained more tree species than a (slightly older) naturally regenerated forest. One replicated, paired, before-and-after, site comparison study in Kenya reported that planted mangrove forest contained fewer adult tree species than mature natural forest after five years, but more species of seedling. One study in a former shrimp pond in Thailand simply reported the number of unplanted tree species that had colonized six years after planting (along with other interventions). VEGETATION ABUNDANCE Tree/shrub abundance (9 studies): Three replicated, site comparison studies of coastal sites in the Philippines, the USA and Brazil reported that where mangrove forests developed after planting trees (sometimes along with other interventions), woody vegetation was typically more dense than in mature natural forests and/or naturally regenerating forests. Two site comparison studies in Kenya and Vietnam found that tree abundance (density and biomass) was similar in planted and natural mangroves after 5–34 years. One site comparison study in Mexico reported that a planted mangrove forest contained fewer trees than pristine natural forests after 12 years. Two site comparison studies in the Philippines reported mixed results according to time since planting and site. One study in Thailand simply quantified the abundance of mangrove trees six years after planting (along with other interventions). Algae/phytoplankton abundance (1 study): One site comparison study in Kenya found that mangrove forests restored by planting contained a similar algal biomass, after eight years, to mature natural forests. However, mangrove forests created by planting into bare sediment contained less algal biomass than mature natural forests. Individual species abundance (7 studies): Seven studies quantified the effect of this action on the abundance of individual plant species. Four of the studies compared the abundance of woody vegetation or algae in planted mangrove forests and mature natural forests – and sometimes naturally regenerating forests (see original papers for data). One replicated, paired, controlled study in a brackish wetland in the USA reported that there were fewer common reed Phragmites australis stems in plots planted with wetland shrubs (and herbs) than in unplanted plots, after 1–3 years. One before-and-after study of an intertidal site in the USA reported greater abundance of red mangrove Rhizophora mangle over five years after planting (along with other interventions) than before. VEGETATION STRUCTURE Overall structure (3 studies): Three replicated, site comparison studies of coastal sites in the Kenya, the USA and the Philippines reported that where mangrove forests developed after planting trees (sometimes along with other interventions), their overall structure differed from mature natural forests for up to 50 years. Height (18 studies): Four site comparison studies (three replicated, three paired) of coastal sites in Kenya, the USA, Brazil and the Philippines reported that where mangrove forests developed after planting trees (sometimes along with other interventions), the vegetation was shorter than in mature and naturally regenerating forests after 5–30 years. One site comparison study in Mexico reported that planted mangrove forests contained taller trees than pristine natural forests after 12 years. Fourteen studies (four replicated) in Asia, Central/South America, Africa and North America simply quantified the height of mangrove trees for up to six years after they were planted; in 13 of these studies, the average height increased over time. Diameter (7 studies): Two site comparison studies in Mexio and Vietnam reported that tree diameters were similar in planted and natural mangroves after 12–34 years. In contrast, two site comparison studies in Brazil and the Philippines reported that planted mangroves contained thinner tree stems than mature natural mangroves after 7–12 years. The study in Brazil also reported that stem diameters were thinner than in naturally regenerating areas. Three studies in India and Nigeria simply quantified the diameter of mangrove trees for up to three years after they were planted; in all three studies, the average stem diameter increased over time. Basal area (3 studies): Two site comparison studies (one also replicated, paired, before-and-after) in Kenya and Mexico reported that planted mangrove forests had a smaller basal area than mature natural forests after 5–12 years. One replicated, site comparison study in the USA reported that where mangrove forests developed after planting trees (along with other interventions), their basal area was similar to mature natural forests after 17–30 years. OTHER Survival (37 studies): Thirty-six studies (including one review and one systematic review) quantified survival rates of individual trees/shrubs planted in brackish/saline wetlands. Survival rates ranged from 0% to 100% after 15 days to 21 years. The studies were of mangroves in North America, Central/South America, Asia, Africa, Oceania or globally, and of shrubs in the USA or Spain. Six studies reported 100% survival in some cases. Eleven studies reported 0% survival or absence of planted species in some cases. In six studies, survival of planted seedlings was not distinguished from survival of seeds or propagules. Proposed factors affecting survival included elevation/water levels, exposure to wind/waves, soil properties, sediment deposition, oyster/barnacle colonization, salinity, use of guidance and post-planting care. Growth (9 studies): Nine studies monitored true growth of individual trees/shrubs (rather than changes in average height of survivors). The nine studies, in Colombia, the USA, the Philippines, Brazil and China, reported that planted trees/shrubs typically grew, over periods from 40 days to 50 years. One replicated study in the USA reported that planted seedlings grew less quickly than naturally colonizing seedlings. One replicated, site comparison study in the Philippines found that growth rates of trees in planted mangroves became more similar to those in mature natural mangroves over time. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3259https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3259Sat, 10 Apr 2021 13:27:43 +0100Collected Evidence: Collected Evidence: Introduce fragments of non-woody plants: freshwater wetlands Five studies evaluated the effects, on vegetation, of introducing fragments of emergent, non-woody plants to freshwater wetlands. Three studies were in the USA. Two studies were in one marsh in Australia, but used different experimental set-ups. VEGETATION COMMUNITY VEGETATION ABUNDANCE Overall abundance (2 studies): Two replicated, randomized, paired, controlled, before-and-after studies in a floodplain marsh in Australia found that plots planted with wick grass Hymenachne acutigluma had similar overall vegetation cover to unplanted plots after one year. One of the studies continued for longer, and found that planted plots had greater overall vegetation cover than unplanted plots after three years. Herb abundance (1 study): One replicated, randomized, paired, controlled, before-and-after study in a floodplain marsh in Australia found that plots planted with wick grass Hymenachne acutigluma had similar overall sedge/grass cover to unplanted plots after one year. Individual species abundance (4 studies): Four studies quantified the effect of this action on the abundance of individual plant species. For example, of two replicated, randomized, paired, controlled, before-and-after studies in a floodplain marsh in Australia, one found that wick grass Hymenachne acutigluma was more frequent and had greater cover, after 1–3 years, in plots where its runners had been planted than where they had not been planted. The other study reported that wick grass cover was present, with approximately 1% cover, in 5 of 10 plots where its runners had been planted. This study monitored vegetation one year after planting. VEGETATION STRUCTURE OTHER Germination/emergence (1 study): One replicated, randomized, paired, controlled study in a floodplain marsh in Australia found that planting wick grass Hymenachne acutigluma had no significant effect on the germination rate of invasive mimosa Mimosa pigra over three years. Survival (5 studies): Two replicated studies planted sedge Carex fragments into freshwater wetlands in the USA. One study reported 38–79% survival of planted tubers over one growing season, whilst the other study reported 0–73% survival of planted rhizomes after 1–9 months. One replicated study in a tidal freshwater marsh in the USA reported that 6–31% of planted California bulrush Schoenoplectus californicus rhizomes had produced shoots after three months. For two other species, all planted rhizomes died within three months. Two replicated, randomized, paired, controlled, before-and-after studies in a floodplain marsh in Australia reported absence of planted wick grass Hymenachne acutigluma from 17–50% of plots after one year. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3260https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3260Sat, 10 Apr 2021 13:28:02 +0100Collected Evidence: Collected Evidence: Introduce fragments of non-woody plants: brackish/saline wetlands Three studies evaluated the effects, on vegetation, of introducing fragments of emergent, non-woody plants to brackish/saline wetlands. Two studies were in one bog in Canada. One study was in China. VEGETATION COMMUNITY VEGETATION ABUNDANCE Overall abundance (2 studies): Two replicated, paired, controlled, before-and-after studies in salt-contaminated bogs in Canada found that plots planted with rhizomes or sown with fragments of salt marsh herbs had similar overall vegetation biomass, after one year, to plots that had not been planted or sown. Herb abundance (1 study): One replicated, paired, controlled, before-and-after studies in salt-contaminated bogs in Canada found that plots sown with fragments of salt marsh herbs had greater overall cover of the introduced species, after one year, to unsown plots. However, biomass of the introduced species did not significantly differ between sown and unsown plots. Individual species abundance (2 studies): Two replicated studies (one also before-and-after) in brackish/saline wetlands in Canada and China simply quantified the abundance of herb species, over one year or growing season after planting herb fragments. VEGETATION STRUCTURE OTHER Germination/emergence (1 study): One replicated study on a tidal flat in China reported that at least 25% of bulrush Scirpus mariqueter corms (bulb-like organs) produced shoots within the first growing season after planting. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3261https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3261Sat, 10 Apr 2021 13:28:14 +0100Collected Evidence: Collected Evidence: Introduce fragments of trees/shrubs: freshwater wetlands One study evaluated the effects, on vegetation, of introducing tree/shrub fragments to freshwater wetlands. The study was in the USA. VEGETATION COMMUNITY VEGETATION ABUNDANCE VEGETATION STRUCTURE OTHER Survival (1 study): One study in a floodplain swamp clearing in the USA reported 12% overall survival of planted unrooted tree cuttings over two years. For two of four species, no monitored seedlings survived. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3262https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3262Sat, 10 Apr 2021 13:28:25 +0100Collected Evidence: Collected Evidence: Introduce fragments of trees/shrubs: brackish/saline wetlandsWe found no studies that evaluated the effects, on vegetation, of introducing tree/shrub fragments to brackish/saline wetlands. ‘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%2Fconservationevidencejournal.com%2Factions%2F3263https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3263Sat, 10 Apr 2021 13:28:45 +0100Collected Evidence: Collected Evidence: Introduce seeds of non-woody plants: freshwater wetlands Thirteen studies evaluated the effects, on vegetation, of introducing seeds of emergent, non-woody plants to freshwater wetlands. Eleven studies were in the USA. Two studies were in Australia. Two of the studies were based on exactly the same set of pools. Two sets of studies in the USA and Australia used the same general sites, but different experimental set-ups. VEGETATION COMMUNITY Community composition (1 study): One replicated, site comparison study of created wetlands in the USA reported that wetlands sown with herb (and some shrub) seeds contained a different overall plant community to unsown wetlands, after 1–2 years. Overall richness/diversity (1 study): The same study reported that wetlands sown with herb (and some shrub) seeds had higher plant diversity than unsown wetlands, after 1–2 years. VEGETATION ABUNDANCE Overall abundance (4 studies): Three replicated studies (two also randomized, paired, controlled, before-and-after) in wetlands in the USA and Australia found that plots sown with herb seeds (and in one study, some shrub seeds) had similar overall vegetation cover to unsown plots, after 1–3 years. One replicated, before-and-after study in the USA reported that vegetation biomass developed over 15 months after sowing mixed herb seeds. Biomass included all the sown species. Characteristic plant abundance (3 studies): Two replicated, controlled studies of recently excavated ephemeral pools in the USA found that native, pool-characteristic species were more common, over seven years, in pools where they were sown than where they were not sown. One of the studies found that this was true when a mixture of characteristic species were densely sown, but not when a single species was sparsely sown. One replicated, before-and-after study in experimental wet basins in the USA quantified the overall density of target sedge meadow species, in the vegetation that developed over 16 weeks after sowing. Herb abundance (2 studies): Two replicated, randomized, paired, controlled, before-and-after studies in a floodplain marsh in Australia found that plots sown with herb seeds had similar overall sedge/grass cover to unsown plots, after 1–3 years. Individual species abundance (8 studies): Eight studies quantified the effect of this action on the abundance of individual plant species. For example, four replicated, before-and-after studies in Australia and the USA reported that sown herb species were absent from plots in some cases, after 1–3 years. The two studies in Australia reported low abundance (<20% frequency and <2% cover) of wick grass Hymenachne acutigluma 1–3 years after sowing its seeds – although in one of the studies this was greater than in unsown plots. VEGETATION STRUCTURE Height (1 study): One replicated study in the USA reported data on cordgrass height, for up to three growing seasons after sowing. OTHER Germination/emergence (4 studies): Two replicated studies in the USA reported ≤1–61% germination of grass-like plants and forbs, after their seeds were sown onto wetlands. Another replicated study in the USA reported that seeds of six wetland herb species did not germinate when sown into a floodplain where an invasive plant was present (but being controlled). One replicated, randomized, paired, controlled study in a floodplain marsh in Australia found that sowing herb seeds had no significant effect on the number of invasive mimosa Mimosa pigra seedlings germinating, for up to three years. Survival (6 studies): Six studies in freshwater wetlands in Australia and the USA reported absence of sown (or planted) herb species, in at least some cases, after one month to seven years. It is not always clear whether this reflects death of seedlings or failure of seeds to germinate. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3264https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3264Sat, 10 Apr 2021 15:34:48 +0100Collected Evidence: Collected Evidence: Introduce seeds of non-woody plants: brackish/saline wetlands Eight studies evaluated the effects, on vegetation, of introducing seeds of emergent, non-woody plants to brackish/saline wetlands. There were three studies in the USA, two in the Netherlands and two in China. The other study was a global systematic review. VEGETATION COMMUNITY VEGETATION ABUNDANCE Individual species abundance (4 studies): Four replicated studies quantified the effect of this action on the abundance of individual plant species. One study in an estuary in China also gave a before-and-after comparison, and reported higher density and biomass of seablite Suaeda salsa five months after sowing its seeds than on the bare sediment present before sowing. VEGETATION STRUCTURE Height (1 study): One replicated study on a mudflat in the Netherlands reported that the average height of surviving common cordgrass Spartina anglica plants increased, between one and six months after sowing cordgrass seeds. OTHER Germination/emergence (5 studies): Five replicated studies in the Netherlands, the USA and China quantified germination rates of seeds sown into intertidal areas. Some seeds germinated in all five studies, at a rate of <1% to 25%. Two studies reported that no seeds germinated for some species and/or in some environments. Survival (3 studies): One replicated study in a salt marsh in the Netherlands quantified survival rates of individual germinated seedlings: 0–83% over their first growing season, depending on species and site conditions. Another replicated study in a salt marsh in the Netherlands reported that after two growing seasons, common cordgrass Spartina anglica was absent from 90% of plots in which had been sown. One global systematic review reported variable survival of herbs sown (or planted) in salt marshes: 0% to ≥95% after 20 days to 13 years, depending on the study. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3265https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3265Sat, 10 Apr 2021 15:35:13 +0100Collected Evidence: Collected Evidence: Introduce tree/shrub seeds or propagules: freshwater wetlands Two studies evaluated the effects, on vegetation, of introducing seeds or propagules of trees/shrubs to freshwater wetlands. One study was in Australia and one study was in the USA. VEGETATION COMMUNITY VEGETATION ABUNDANCE Tree/shrub abundance (1 study): One study in a floodplain swamp clearing in the USA simply reported the number of tree seedlings present within three years of sowing tree seeds. There were no seedlings of two of the five sown species. VEGETATION STRUCTURE OTHER Germination/emergence (1 study): One replicated study in Australia reported 0–18% germination of tree/shrub seeds sown into a wet meadow, depending on the species and whether vegetation was cleared before sowing. Survival (1 study): The same study reported 0% survival, after 8 months, of seedlings that had germinated from sown tree/shrub seeds. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3266https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3266Sat, 10 Apr 2021 15:35:45 +0100Collected Evidence: Collected Evidence: Introduce tree/shrub seeds or propagules: brackish/saline wetlands Nineteen studies evaluated the effects, on vegetation, of introducing seeds or propagules of trees/shrubs to brackish/saline wetlands. All 19 studies involved planting mangrove propagules: seven in Asia, five in North America, three in Central America, two in Oceania, one in South America and one globally. Three studies in the USA shared some study sites. VEGETATION COMMUNITY Overall extent (2 studies): Two studies in the USA and Sri Lanka simply quantified the area of mangrove vegetation present 6–14 years after planting propagules (along with other interventions). Relative abundance (1 study): One replicated, paired, site comparison study in the USA reported that mangrove forests created by planting propagules (after reprofiling) supported a different relative abundance of tree species to natural forests, after 7–15 years. Tree/shrub richness/diversity (2 studies): Two replicated, site comparison studies in the USA reported that mangrove forests created by planting propagules (along with other interventions) contained a similar number of tree species to mature natural forests, after 7–30 years. VEGETATION ABUNDANCE Tree/shrub abundance (3 studies): Three replicated, site comparison studies of coastal sites in the USA and the Philippines reported that where mangrove forests developed after planting propagules (along with other interventions), trees were typically more dense than in mature natural forests. VEGETATION STRUCTURE Overall structure (1 study): One replicated, site comparison study in the USA reported that mangrove forests created by planting propagules (along with other interventions) had a different overall physical structure to mature natural forests, after 17–30 years. Height (4 studies): Four studies (three replicated) in Thailand, the USA, Mexico and the United Arab Emirates simply quantified the height of surviving mangrove trees for up to 16 years after sowing seeds or planting propagules; in all of these studies, the average height increased over time. Diameter/perimeter/area (3 studies): Two site comparison studies (one also replicated and paired) in the USA reported that mangrove forests created by planting propagules (after reprofiling) contained thinner trees, on average, than mature natural forests, after 7–18 years. One study in a coastal area planted with mangrove propagules in Thailand reported that the average diameter of surviving seedlings increased over time. Basal area (3 studies): Three site comparison studies (two also replicated, one also paired) in the USA compared mangrove forests created by planting propagules (along with other interventions) and mature natural forests. Two of the studies reported that planted forests had a smaller basal area than mature natural forests, after 7–18 years. The other study reported that planted forests had similar basal area to mature natural forests, after 17–30 years. OTHER Germination/emergence (2 studies): One replicated study in the United Arab Emirates reported 65–92% germination of sown grey mangrove Avicennia marina seeds, across five coastal sites. One replicated study in a brackish/saline estuary in China reported 38–100% germination of planted mangrove propagules, depending on the species and habitat. Survival (16 studies): Fifteen studies quantified survival of individual tree/shrub propagules planted in brackish/saline wetlands (or plants originating from them). All 15 studies were of mangroves: in Central/South America, Asia, North America, Oceania or gloablly. All reported survival in at least some cases, from 20 days to 30 years after planting. Five studies reported 100% survival in some cases. However, nine studies reported 0% survival or absence of planted species in some cases. In five studies, survival of seeds or propagules was not distinguished from survival of planted seedlings. Proposed factors affecting survival rates included elevation/water levels, substrate, invertebrate herbivory, use of tree shelters, mechanical stress, oyster colonization, use of guidance, post-planting care and repeated planting. Growth (5 studies): Five studies monitored true growth of individual trees/shrubs (rather than changes in average height of survivors). All five studies (three replicated) in Australia, the USA, Colombia and the Philippines reported that mangrove seedlings, originating from planted seeds or propagules, grew over time. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3267https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3267Sat, 10 Apr 2021 15:36:07 +0100Collected Evidence: Collected Evidence: Transplant or replace blocks of vegetation: freshwater marshes Four studies evaluated the effects, on vegetation, of transplanting or replacing blocks of freshwater marsh vegetation. Three studies were in the USA. One study was in the UK. VEGETATION COMMUNITY Community composition (1 study): One replicated, paired, controlled study in rewetted marshes in the USA found that plots of transplanted marsh vegetation contained a plant community characteristic of wetter conditions than plots without transplants after one growing season – but not after two. Overall richness/diversity (2 studies): One replicated, before-and-after study in the UK reported that plant species richness within transplanted freshwater marsh vegetation was similar before transplanting and six years later. There was a temporary increase in richness after one year. One replicated, paired, controlled study in rewetted freshwater marshes in the USA found that plots of transplanted marsh vegetation contained more wetland plant species than plots without transplants after one growing season – but that there was no significant difference after two. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, paired, controlled study in rewetted freshwater marshes in the USA found that plots of transplanted marsh vegetation had greater cover of wetland plants than plots without transplants, after 1–2 growing seasons. Individual species abundance (2 studies): One replicated, site comparison study in a wet prairie in the USA found that after three growing seasons, the density of prairie cordgrass Spartina pectinata stems was lower in transplanted sods than in pristine or source prairies. One before-and-after study of transplanted freshwater marsh vegetation in the UK reported changes in the frequency of individual plant species from before to six years after transplanting. VEGETATION STRUCTURE Height (1 study): One replicated, site comparison study in a wet prairie in the USA found that after three growing seasons, prairie cordgrass Spartina pectinata was shorter in transplanted sods than in pristine or source prairies. Diameter/perimeter/area (2 studies): Two studies (one replicated) in wet prairies in the USA found that the average area of small transplanted sods (≤0.28 m2 initial size) increased over 3–4 growing seasons. One of the studies transplanted larger sods (0.65 m2 initial size) and reported that their average area decreased over 3–4 growing seasons. OTHER Survival (2 studies): Two studies (one replicated) in wet prairies in the USA reported ≥90% survival of transplanted sods of wet prairie vegetation after 3–4 growing seasons. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3268https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3268Sat, 10 Apr 2021 15:36:31 +0100Collected Evidence: Collected Evidence: Transplant or replace blocks of vegetation: brackish/salt marshes One study evaluated the effects, on vegetation, of transplanting or replacing blocks of brackish/salt marsh vegetation. The study was in Australia. VEGETATION COMMUNITY Community composition (1 study): One replicated, controlled, site comparison study in an estuarine salt marsh in Australia found that areas where sods of saltwater couch Sporobolus virginicus were transplanted had a similar overall plant community composition to areas without transplants, after 3–4 years. The plant community in the transplanted areas was >70% similar to natural areas in only 4 of 12 comparisons. VEGETATION ABUNDANCE VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3269https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3269Sat, 10 Apr 2021 15:36:47 +0100Collected Evidence: Collected Evidence: Transplant or replace wetland soil: freshwater marshes Ten studies evaluated the effects, on vegetation, of transplanting wetland soil to restore or create freshwater marshes. Nine studies were in the USA. One study was in Guam. Two studies were in the same region but used different sites. VEGETATION COMMUNITY Community composition (3 studies): Two replicated, controlled studies in rewetted marshes in the USA found that areas amended with wetland soil contained a plant community characteristic of wetter conditions than unamended plots after one growing season – but not after two. One replicated, randomized, controlled study in a recently excavated marsh in the USA found that amended and unamended plots contained a plant community of similar overall wetness after both one and two growing seasons. Overall richness/diversity (10 studies): Eight studies (including four at least replicated and controlled) in freshwater marshes in the USA reported that areas amended with wetland soil had greater plant richness and/or diversity than unamended areas and/or nearby natural marshes. One replicated, paired, controlled study in rewetted freshwater marshes in the USA found that plots amended with sieved marsh soil contained a similar number of wetland plant species to unamended plots, after 1–2 growing seasons. One before-and-after study of freshwater pool in Guam simply quantified plant species richness one year after adding wetland soil (along with other interventions). Characteristic plant richness/diversity (1 study): One replicated, randomized, paired, controlled study in a freshwater marsh in the USA reported that plots amended with wetland soil developed a greater richness of wetland-characteristic plant species than unamended plots, at the end of the growing season. VEGETATION ABUNDANCE Overall abundance (6 studies): Six controlled studies in freshwater marshes in the USA reported that plots amended with wetland soil typically contained more vegetation overall than unamended plots, after 1–2 growing seasons. This was true for cover and biomass, but not stem density. Individual species abundance (7 studies): Seven studies (including one replicated, randomized, paired, controlled, site comparison) in freshwater marshes, meadows and pools in the USA and Guam quantified the effect of this action (sometimes along with others) on the abundance of individual plant species. Results were mixed and likely depended on the composition of the donor wetland. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3270https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3270Sat, 10 Apr 2021 15:48:02 +0100Collected Evidence: Collected Evidence: Transplant or replace wetland soil: brackish/salt marshesWe found no studies that evaluated the effects on vegetation, of transplanting wetland soil to restore or create 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%2Fconservationevidencejournal.com%2Factions%2F3271https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3271Sat, 10 Apr 2021 15:48:19 +0100Collected Evidence: Collected Evidence: Transplant or replace wetland soil: freshwater swampsWe found no studies that evaluated the effects on vegetation, of transplanting wetland soil 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%2Fconservationevidencejournal.com%2Factions%2F3272https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3272Sat, 10 Apr 2021 15:48:30 +0100Collected Evidence: Collected Evidence: Transplant or replace wetland soil: brackish/saline swampsWe found no studies that evaluated the effects on vegetation, of transplanting wetland soil 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%2Fconservationevidencejournal.com%2Factions%2F3273https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3273Sat, 10 Apr 2021 15:48:42 +0100