Collected Evidence: Collected Evidence: Install boardwalks/paths to prevent tramplingWe found no studies that evaluated the effects, on vegetation, of installing boardwalks or paths to prevent trampling in marshes or 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%2F3024https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3024Wed, 31 Mar 2021 14:43:45 +0100Collected Evidence: Collected Evidence: Adopt ecotourism principles/create an ecotourism siteWe found no studies that evaluated the effects, on marsh/swamp vegetation, of adopting ecotourism principles or creating an ecotourism site.   ‘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%2F3025https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3025Wed, 31 Mar 2021 14:46:14 +0100Collected Evidence: Collected Evidence: Raise water level to restore degraded freshwater marshes Five studies evaluated the effects, on vegetation, of raising the water level to restore degraded freshwater marshes. There were three studies in the USA and one in each of the Netherlands and Japan. VEGETATION COMMUNITY Overall extent (1 study): One before-and-after study of a floodplain in Japan reported that the area covered by marsh vegetation was higher five years after dechannelizing a river than 10 years before. Community types (1 study): One before-and-after study of a floodplain in Japan reported changes in the area covered by different marsh plant communities over five years after dechannelizing a river compared to 10 years before. Community composition (1 study): One replicated study of dune slacks in the Netherlands reported changes in the overall plant community composition after stopping groundwater extraction (along with other interventions). Overall richness/diversity (2 studies): One replicated, site comparison study of dune slacks in the Netherlands reported that overall plant species richness was greater in restored slacks (groundwater extraction stopped five years previously, along with other interventions) than in mature unmanaged slacks. One replicated, before-and-after study of floodplain marshes in the USA reported that total plant species richness tended to be lower over nine years after raising the water table than before, but that there was no significant difference for diversity. Characteristic plant richness/diversity (1 study): One replicated study of dune slacks in the Netherlands simply quantified the richness of characteristic plant species – typical of dune slacks or nutrient-rich marshes – over five years after stopping groundwater extraction (along with other interventions). VEGETATION ABUNDANCE Overall abundance (3 studies): One replicated, before-and-after study of floodplain marshes in the USA reported that total vegetation cover tended to be lower over nine years after raising the water table than before. One replicated, randomized, paired, controlled, before-and-after study of freshwater marshes in the USA found that damming to raise the water table prevented increases in understory vegetation cover over the following year. One replicated study of dune slacks in the Netherlands simply quantified total vegetation over five years after stopping groundwater extraction (along with other interventions). Cover never exceeded 50%. Herb abundance (1 study): One replicated, randomized, paired, controlled, before-and-after study of freshwater marshes in the USA found that damming to raise the water table had no significant effect on cover of sedges Carex There were similar increases in dammed and undammed marshes over one year. Characteristic plant abundance (1 study): One replicated, before-and-after study of floodplain marshes in the USA reported changes in the cover of wetland- and habitat-characteristic plant species over nine years after raising the water table. Individual species abundance (3 studies): Three studies quantified the effect of this intervention on the abundance of individual plant species. For example, one replicated, before-and-after study in the USA reported that rewetted floodplain marshes became dominated by a non-native wetland shrub, approximately 4–9 years after raising the water table. One replicated study of a freshwater wetland in the USA reported that the effects of reflooding on the density of emergent plant species depended on the species and water level. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3026https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3026Wed, 31 Mar 2021 14:47:11 +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: Raise water level to restore degraded freshwater swampsWe found no studies that evaluated the effects, on vegetation, of raising the water level to restore degraded 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%2F3028https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3028Wed, 31 Mar 2021 14:47:37 +0100Collected Evidence: Collected Evidence: Raise water level to restore degraded brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of raising the water level to restore degraded 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%2F3029https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3029Wed, 31 Mar 2021 14:47:55 +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: Lower water level to restore degraded brackish/salt marshesWe found no studies that evaluated the effects, on vegetation, of lowering the water level to restore degraded brackish/salt marshes.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3031https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3031Wed, 31 Mar 2021 15:20:22 +0100Collected Evidence: Collected Evidence: Lower water level to restore degraded freshwater swampsWe found no studies that evaluated the effects, on vegetation, of lowering the water level to restore degraded 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%2F3032https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3032Wed, 31 Mar 2021 15:20:38 +0100Collected Evidence: Collected Evidence: Lower water level to restore degraded brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of lowering the water level to restore degraded 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%2F3033https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3033Wed, 31 Mar 2021 15:20:55 +0100Collected Evidence: Collected Evidence: Facilitate tidal exchange to restore degraded freshwater marshesWe found no studies that evaluated the effects, on vegetation, of facilitating tidal exchange to restore degraded freshwater marshes.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3034https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3034Wed, 31 Mar 2021 19:33:44 +0100Collected Evidence: Collected Evidence: Facilitate tidal exchange to restore degraded brackish/salt marshes Seven studies evaluated the effects, on vegetation, of facilitating tidal exchange to restore degraded brackish/salt marshes. Six studies were in the USA. One study included sites in both the USA and Canada. VEGETATION COMMUNITY Overall extent (1 study): One before-and-after study in the USA reported that over 10 years after improving tidal exchange in a degraded marsh, the area of salt marsh vegetation increased – but not quite to historical, pre-degradation levels. Community types (1 study): One before-and-after study in the USA reported that 3–10 years after improving tidal exchange in a degraded marsh, the area of salt marsh community types differed from historical, pre-degradation levels. Community composition (3 studies): Three before-and-after studies in the USA found that in the four years after improving tidal exchange in degraded brackish/salt marshes, the overall plant community composition significantly differed to that present before intervention. However, in one of the studies this was only true in one of two marshes (the most degraded before intervention). One of the studies also reported that the overall plant community composition became more similar to adjacent natural brackish/salt marshes over two growing seasons after intervention. Overall richness/diversity (1 study): One replicated, before-and-after, site comparison study in the USA/Canada found that overall plant species richness was similar in ≥3-year-old tidally restored salt marshes and nearby natural salt marshes. However, there was also no significant difference between degraded marshes (before tidal restoration) and the natural marshes. Characteristic plant richness/diversity (1 study): One study of a coastal marsh in the USA reported that over three years after restoring tidal exchange (along with a prescribed burn), the number of salt-tolerant plant species increased, whilst the number of freshwater plant species decreased. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, site comparison study of salt marshes in the USA found that tidally restored areas had a lower overall plant stem density, after 13–54 years, than natural salt marshes. Characteristic plant abundance (2 studies): Two before-and-after studies of coastal marshes in North America reported that within three years of restoring tidal exchange (sometimes along with other interventions), total cover of fresh/brackish plant species decreased. In one study the total cover of salt-tolerant plant species increased, but in the other study it did not. One of the studies also found that tidally restored marshes had lower cover of salt-tolerant plants than nearby natural marshes. Individual species abundance (5 studies): Five studies quantified the effect of this action on the abundance of individual plant species. All five studies were in brackish/salt marshes in the USA. Three before-and-after studies reported increases in cover or frequency of smooth cordgrass Spartina alterniflora in the four years after improving tidal exchange. One replicated, site comparison study found that smooth cordgrass cover was lower in tidally restored areas than in natural salt marshes, 13–54 years after tidal restoration. Two before-and-after studies reported no clear change in frequency or cover of saltmeadow cordgrass Spartina patens in the four years after improving tidal exchange, but one before-and-after study reported an increase in saltmeadow cordgrass cover over two growing seasons after improving tidal exchange. Four studies reported declines in cover or frequency of less salt-tolerant species such as common reed Phragmites australis and cattails Typha spp. in the four years after improving tidal exchange (sometimes along with other interventions). One replicated, site comparison study found that common reed cover was similarly low (<1%) in tidally restored areas and natural salt marshes, 13–54 years after tidal restoration. VEGETATION STRUCTURE Vegetation height (3 studies): Two before-and-after studies of brackish/salt marshes in the USA found that common reed was shorter 1–4 years after improving tidal exchange than before. One replicated, site comparison study in the USA found that the maximum vegetation height was similar in tidally restored salt marshes and natural salt marshes, 13–54 years after tidal restoration. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3035https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3035Wed, 31 Mar 2021 19:34:00 +0100Collected Evidence: Collected Evidence: Facilitate tidal exchange to restore degraded freshwater swampsWe found no studies that evaluated the effects, on vegetation, of facilitating tidal exchange to restore degraded 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%2F3036https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3036Wed, 31 Mar 2021 19:34:19 +0100Collected Evidence: Collected Evidence: Facilitate tidal exchange to restore degraded brackish/saline swamps Four studies evaluated the effects, on vegetation, of facilitating tidal exchange to restore degraded brackish/saline swamps. Three studies were in Mexico and one was in India. VEGETATION COMMUNITY Overall extent (2 studies): Two before-and-after studies on the coasts of India and Mexico reported that the area of mangrove forest in each site was greater 5–6 years after restoring tidal exchange (sometimes along with planting mangrove seedlings) than in the years before. Community composition (1 study): One before-and-after study of a mangrove forest in Mexico reported that the tree community composition was identical before and five years after restoring tidal exchange: the same three tree species were present at both times. Community types (1 study): One before-and-after study of a mangrove forest in Mexico reported that the relative coverage of stands dominated by each of three tree species was similar before and five years after restoring tidal exchange. Tree/shrub richness/diversity (2 studies): One site comparison study in Mexico reported that a tidally restored mangrove forest contained a similar number of tree species to nearby natural mangroves, after 10–11 years. One before-and-after study in Mexico reported identical tree species richness in a mangrove forest before and five years after restoring tidal exchange. VEGETATION ABUNDANCE Tree/shrub abundance (2 studies): Two site comparison studies in Mexico reported that tidally restored mangrove forests contained a lower density of trees or seedlings than nearby natural mangroves. Individual species abundance (1 study): One site comparison study in Mexico compared the abundance of three mangrove tree species in a tidally restored area and nearby natural forests (see original paper for data). VEGETATION STRUCTURE Height (2 studies): One site comparison study in Mexico reported that trees in a tidally restored mangrove forest were a similar height to trees in nearby natural mangroves, after 10–11 years. Another replicated, site comparison study in Mexico reported that seedlings in a tidally restored mangrove forest were taller than seedlings in a nearby natural mangrove. Diameter (1 study): One site comparison study in Mexico reported that trees in a tidally restored mangrove forest had a similar diameter to trees in nearby natural mangroves, after 10–11 years. Basal area (1 study): One site comparison study in Mexico reported that trees in a tidally restored mangrove forest had a smaller basal area than trees in natural mangroves, after 10–11 years. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3037https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3037Wed, 31 Mar 2021 19:34:43 +0100Collected Evidence: Collected Evidence: Actively manage water level: freshwater marshes Ten studies evaluated the effects, on vegetation, of active water level management in freshwater marshes. Eight studies were in the USA. One study was in Cameroon and one study was in the Netherlands. VEGETATION COMMUNITY Community composition (1 study): One before-and-after study in the USA found that directly pumping water into drained marshes and wet meadows generated plant communities characteristic of wetter conditions. This change was reversed in some plots when the pump output was moved further away from the focal wetlands. Relative abundance (2 studies): One replicated, randomized, controlled study of freshwater marshes in the USA reported that irrigated and non-irrigated marshes supported a similar relative abundance of the most common plant species. One before-and-after study on a floodplain in Cameroon found that the relative abundance of some key plant species changed over four years after restoring wet-season flooding. There was also an increase in the cover of perennial relative to annual herbs. Overall richness/diversity (4 studies): One before-and-after study of a marsh/swamp in the USA found that overall plant diversity was higher in the autumn following a managed flood/drawdown than in the autumn before. Two before-and-after studies of marshes and wet meadows in the USA reported that plant species richness and/or diversity declined over 5–6 years of water level management (fluctuation or water addition). One study in the USA simply reported the number of plant species that colonized a floodplain, over three weeks after lowering the river level. VEGETATION ABUNDANCE Overall abundance (3 studies): One study of riparian moist/wet meadows in the USA reported that vascular plant biomass increased in two of three meadow types, over the second year of artificially augmented streamflow. Meanwhile, vascular plant cover declined in two of three meadow types. Two studies in the Netherlands and the USA simply quantified overall vegetation abundance after 1–9 growing seasons of active water level management (sometimes along with other interventions). Characteristic plant abundance (2 studies): Two before-and-after studies of marshes and wet meadows in the USA reported increases in abundance of some individual wetland- or habitat-characteristic species over 5–6 years of water level management (fluctuation or water addition). Moss abundance (1 study): One study of riparian moist/wet meadows in the USA reported that moss cover did not significantly change in two of three meadow types, over the second year of artificially augmented streamflow. It declined in the other meadow type. Individual species abundance (7 studies): Seven studies quantified the effect of this action on the abundance of individual plant species. For example, one before-and-after study of a marsh/swamp in the USA reported mixed effects of a managed flood/drawdown on species cover, including increased cover of Pacific willow Salix lucida and reduced cover of reed canarygrass Phalaris arundinacea. One controlled study of freshwater marshes in the USA found that irrigated marshes developed a greater biomass of pink smartweed Polygonum pensylvanicum, after one growing season, than marshes that were left dry. VEGETATION STRUCTURE Vegetation height (1 study): One replicated, randomized, controlled study of freshwater marshes in the USA reported that four common plant species were taller in irrigated than non-irrigated marshes. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3038https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3038Thu, 01 Apr 2021 10:02:54 +0100Collected Evidence: Collected Evidence: Actively manage water level: brackish/salt marshes Ten studies evaluated the effects, on vegetation, of active water level management in brackish/salt marshes. Six studies were in the USA. There was overlap in the sites used in two of these studies. Two studies were in Canada and based on the same experimental set-up. One study was in France and one was in Tunisia. VEGETATION COMMUNITY Community types (1 study): One before-and-after study of a lakeshore brackish/salt marsh in Tunisia reported an increase in coverage of bulrush-dominated vegetation over nine years of freshwater releases into the lake (to increase its level and restore winter flooding of the marsh). Community composition (3 studies): One replicated, paired, controlled, before-and-after study of brackish marshes in France reported that artificially flooded marshes developed different plant communities, over five years, to fields with unmanaged flooding. One before-and-after, site comparison study of brackish/salt marshes in the USA reported that the overall plant community composition changed more, over four years, in a marsh directly irrigated with treated wastewater than in downstream marshes. One replicated, paired, site comparison study of brackish/salt marshes in the USA reported that that marshes in which water levels were drawn down each spring/autumn (along with disking soils) shared only 24–34% of plant species with marshes that were not drawn down (or disked). Overall richness/diversity (5 studies): Two replicated, site comparison studies of brackish/salt marshes in the USA found that marshes in which water levels were managed (sometimes along with other interventions) had similar plant species richness and/or diversity to marshes without water level management. One replicated, site comparison study of brackish and salt marshes in the USA reported that marshes in which water levels were managed had similar or higher plant species richness, in winter, than marshes without water level management. One before-and-after, site comparison study of brackish/salt marshes in the USA reported that plant species richness increased, over four years, in marshes directly irrigated with treated wastewater – but only to similar levels as in downstream marshes. One replicated, paired, controlled, before-and-after study of brackish marshes in France reported that the effects of artificial flooding on plant species richness depended on whether the marshes were grazed. VEGETATION ABUNDANCE Overall abundance (2 studies): Two replicated, site comparison studies of brackish and salt marshes in the USA reported that marshes in which water levels were managed typically had similar overall vegetation cover to marshes without water level management. One of the studies also reported that cover of standing dead vegetation was higher in the managed marshes than in the unmanaged marshes. Individual species abundance (6 studies): Six studies quantified the effect of this action on the abundance of individual plant species. For example, four replicated, site comparison studies of brackish and salt marshes in the USA reported mixed effects of water level management on the abundance of saltmeadow cordgrass Spartina patens. One replicated, paired, controlled, before-and-after study of brackish marshes in France reported that the effects of artificial flooding on the cover of individual plant species depended on the flooding (and grazing) regime. VEGETATION STRUCTURE   OTHER Germination/emergence (2 studies): Two replicated studies of brackish marshes in Canada reported that seedlings of wetland plants germinated in the spring/summer following drawdowns, after a period of deep flooding. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3039https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3039Thu, 01 Apr 2021 10:03:10 +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: Actively manage water level: brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of active water level management in brackish/saline swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3041https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3041Thu, 01 Apr 2021 10:03:56 +0100Collected Evidence: Collected Evidence: Divert/block/stop saltwater inputsWe found no studies that evaluated the effects, on vegetation, of diverting/blocking/stopping saltwater inputs to marshes or 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%2F3042https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3042Thu, 01 Apr 2021 15:15:59 +0100Collected Evidence: Collected Evidence: Divert/block/stop freshwater inputsWe found no studies that evaluated the effects, on vegetation, of diverting/blocking/stopping excessive freshwater inputs to marshes or 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%2F3043https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3043Thu, 01 Apr 2021 15:18:12 +0100Collected Evidence: Collected Evidence: Cut/mow herbaceous plants to maintain or restore disturbance: freshwater marshes Twenty studies evaluated the effects, on vegetation, of cutting/mowing to maintain or restore disturbance in freshwater marshes. There were four studies in Belgium, three of which took place in one wetland area so probably shared some experimental plots. There were two studies in each of the UK, the USA and Estonia. There was one study in each of seven other European countries, Japan, Mexico and Brazil. In 15 of the studies vegetation was measured at least six months after the last cut. VEGETATION COMMUNITY Community composition (6 studies): Four replicated, paired, controlled studies (two also randomized and before-and-after) of freshwater marshes and wet meadows in Belgium, Switzerland, Mexico and Estonia reported that the overall plant community composition differed between cut and uncut sites after 1–5 years, or typically diverged in cut and uncut areas over 3–10 years. One before-and-after study in a freshwater marsh in Belgium reported that the overall plant community composition changed over seven years after resuming annual mowing. One replicated, paired, controlled, before-and-after study in wet grasslands in Germany reported that over 20 years, mowing increased the average moisture preference of the vegetation. Overall richness/diversity (11 studies): Seven studies (including two replicated, paired, controlled) in freshwater marshes in Belgium, the UK, Mexico and Estonia reported that cut marshes had higher plant species richness than uncut marshes. Two of these studies reported the same result for diversity. One before-and-after study in a freshwater marsh in Belgium reported that plant species richness increased over seven years after resuming annual mowing. Three replicated, paired, controlled studies in reedbeds in the UK and wet meadows in Germany and Estonia reported that cutting typically had no clear or significant effect on plant species richness, after 3–5 months or over 5–20 years. The two studies in the UK and Estonia found the same result for diversity. Characteristic plant richness/diversity (1 study): One replicated, paired, controlled, before-and-after study in a temporary marsh in France reported that two years of annual autumn cutting increased the number of habitat-characteristic plant species present. VEGETATION ABUNDANCE Overall abundance (3 studies): Two replicated, controlled studies (one also randomized, paired, before-and-after) in freshwater marshes in the USA found that cutting had no significant effect on overall vegetation cover over 72 days or three years. One replicated, paired, controlled study in wet grasslands in Belgium reported that plots mown annually for two years contained less above-ground biomass, just before mowing, than unmown plots. Herb abundance (1 study): One replicated, paired, controlled, before-and-after study in wet grasslands in Germany reported that mowing increased sedge cover over 20 years, but had no clear effect on cover of rushes, forbs, ferns, grasses and legumes. Tree/shrub abundance (1 study): One replicated, randomized, paired, controlled, before-and-after study in a wet prairie in the USA found that cutting had no significant effect on woody plant cover: there were similar increases, over three years, in cut and uncut plots. Bryophyte abundance (1 study): One replicated study in a freshwater marsh in Belgium reported that total moss cover increased over five years after resuming annual mowing. Individual species abundance (15 studies): Fifteen studies quantified the effect of this action on the abundance of individual plant species. For example, five studies (including one replicated, randomized, paired, controlled) in freshwater marshes in Belgium, the UK and the Czech Republic reported that common reed Phragmites australis was more abundant in cut than uncut areas. Two studies (one site comparison, one before-and-after) in fresh/brackish marshes in Belgium and Denmark reported that cutting reduced common reed cover or density. The two studies in Belgium reported that cutting had no clear effect on common reed frequency. Four studies (including one replicated, randomized, paired, before-and-after) in freshwater marshes in the Netherlands, Switzerland, Japan and Italy found that the effect of cutting on common reed abundance depended on factors such as the year, plant community type, cutting season, cutting intensity and time since mowing. VEGETATION STRUCTURE Overall structure (1 study): One replicated, randomized, paired, controlled study in wet meadows in Switzerland reported that mown plots experienced a shift in vegetation cover towards lower vegetation layers, over 3–4 years, compared to a shift to upper layers in unmown plots. Visual obstruction (1 study): One replicated, controlled study in a freshwater marsh in Belgium reported that summer-cut plots had lower horizontal vegetation cover than uncut plots (or winter-cut plots) over six years after resuming annual mowing. Height (6 studies): Three replicated, controlled studies (one also randomized and paired) in freshwater marshes in Belgium, the UK and the USA reported that cut marshes had shorter vegetation than uncut marshes. This was true for vegetation overall, vegetation other than common reed Phragmites australis, and for common reed cut in winter or spring (but not summer). Two replicated, paired, controlled, before-and-after studies in a marsh in Mexico and wet grasslands in Germany reported that cutting/mowing had no significant or clear effect on vegetation height, after 12 months or over 20 years. One site comparison study in the Czech Republic found that common reed was taller, when measured in the summer, in a winter-mown reedbed than in an unmown reedbed. Diameter/perimeter/area (5 studies): Two studies (one site comparison, one before-and-after) in fresh/brackish marshes in Belgium and Denmark reported that cutting, or time since last cutting, had no significant or clear effect on the stem diameter of common reed Phragmites australis. Two studies (including one replicated, randomized, paired, controlled) of reedbeds in the UK and the Czech Republic found that cut areas contained thicker reed stems than uncut areas, after one growing season. One replicated, randomized, paired, controlled, before-and-after study in wet meadows in Switzerland found that the effect of cutting on common reed shoot diameter depended on the plant community type and season of mowing. Basal area (1 study): One site comparison study in a fresh/brackish marsh in Denmark found that the basal area of common reed Phragmites australis stems was smaller in a reedbed cut two years previously than in a reedbed cut seven years previously. Only “tall” stems were sampled. OTHER Survival (1 study): One replicated, randomized, paired, controlled study in a wet prairie in the USA found that mowing had no significant effect on woody plant survival over the following year. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3044https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3044Thu, 01 Apr 2021 15:18:37 +0100Collected Evidence: Collected Evidence: Cut/mow herbaceous plants to maintain or restore disturbance: brackish/salt marshes Six studies evaluated the effects, on vegetation, of cutting/mowing to maintain or restore disturbance in brackish/salt marshes. Two studies were in France. There was one study in each of the USA, Denmark, South Africa and Estonia. VEGETATION COMMUNITY Community composition (1 study): One replicated, randomized, controlled, before-and-after study in brackish wet grasslands in Estonia found that annual cutting affected overall plant community composition, with significant differences between cut and uncut plots after four years. Overall richness/diversity (3 studies): Two replicated, site comparison studies in France found that cut and uncut reedbeds had similar overall plant species richness. One replicated, randomized, controlled, before-and-after study in brackish wet grasslands in Estonia found that cut and uncut plots typically had similar plant species richness and diversity over four years. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, site comparison study in France found that cut and uncut reedbeds had similar cover of plants other than common reed Phragmites australis. Individual species abundance (5 studies): Five studies quantified the effect of this action on the abundance of individual plant species. For example, two replicated, randomized, controlled, before-and-after studies in brackish marshes or grasslands in South Africa and Estonia found that cutting had mixed effects on the abundance of common reed Phragmites australis after 1–4 years, depending on the water level of the plots. One site comparison study in Denmark found that a fresh/brackish reedbed cut two years previously contained fewer “tall” common reed stems than a reedbed cut seven years previously. Two replicated, site comparison studies in France found that cut reedbeds contained a similar number (and, in one study, biomass) of live reed stems than uncut reedbeds, but far fewer dead stems. VEGETATION STRUCTURE Height (4 studies): Two controlled studies (one also replicated, randomized, before-and-after) in brackish marshes in the USA and South Africa reported that rushes or reeds were shorter in cut plots than in uncut plots, for up to one year after cutting. Two replicated, site comparison studies in France found that live reed stems were a similar height in cut and uncut reedbeds. Diameter/perimeter/area (3 studies): Two site comparison studies (one replicated) in fresh/brackish reedbeds in Denmark and France found that common reed Phragmites australis stems were a similar diameter in cut and uncut reedbeds. One replicated, randomized, controlled, before-and-after study in a brackish marsh in South Africa found that cutting reduced the diameter of common reed stems present one year later. Basal area (1 study): One site comparison study in a fresh/brackish marsh in Denmark found that the basal area of common reed Phragmites australis stems was smaller in a reedbed cut two years previously than in a reedbed cut seven years previously. Only “tall” stems were sampled. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3045https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3045Thu, 01 Apr 2021 15:21:23 +0100Collected Evidence: Collected Evidence: Cut large trees/shrubs to maintain or restore disturbance: freshwater marshes Four studies evaluated the effects, on vegetation, of cutting large trees/shrubs to maintain or restore disturbance in freshwater marshes. Three studies were in the USA. One was in Germany. VEGETATION COMMUNITY Community types (1 study): One study of a riparian wet meadow in Germany reported changes in the area of plant community types over four years after cutting trees/shrubs (along with grazing). Community composition (1 study): One replicated, randomized, controlled, before-and-after study aiming to restore freshwater marshes in the USA found that cutting trees (along with other interventions) significantly affected the overall plant community composition over the following five years. Overall richness/diversity (1 study): One study of a riparian wet meadow in Germany reported that plant species richness increased over four years after cutting trees/shrubs (along with grazing). VEGETATION ABUNDANCE Overall abundance (2 studies): Of two replicated, randomized, paired, controlled, before-and-after studies in the USA, one found that cutting and removing woody plants from a degraded wet prairie had no significant effect on overall vegetation cover three years later. The other study was in wet patches of a pine forest and found that understory vegetation cover increased more, over one year, where trees were thinned than where they were not thinned. Characteristic plant abundance (1 study): One replicated, randomized, controlled, before-and-after study of overgrown freshwater marshes in the USA reported that of 26 plant taxa that became more frequent after cutting trees (along with other interventions), 16 were obligate wetland taxa. Herb abundance (1 study): One replicated, randomized, paired, controlled, before-and-after study in wet patches of a pine forest in the USA found that cover of sedges Carex increased more, over one year, where trees were thinned than where they were not thinned. Tree/shrub abundance (2 studies): One replicated, randomized, paired, controlled, before-and-after study of a wet prairie in the USA found that woody plant cover declined, over three years, in plots where trees/shrubs were cut – but increased in plots where trees/shrubs were not cut. One study of a riparian wet meadow in Germany simply reported that some trees/shrubs regrew over four years after cutting trees/shrubs (along with grazing). Individual species abundance (1 study): One study quantified the effect of this action on the abundance of individual plant species. The replicated, randomized, paired, controlled, before-and-after study of a wet prairie in the USA found, for example, that cutting trees and shrubs had no significant effect on cover of the dominant herbaceous plant, tussock grass Deschampsia cespitosa, three years later. VEGETATION STRUCTURE Height (1 study): One site comparison study of a riparian wet meadow in Germany reported that an area in which trees/shrubs were cut back (along with reinstating cattle grazing) contained shorter vegetation than an adjacent unmanaged area. OTHER Survival (2 studies): One replicated, randomized, paired, controlled study in a wet prairie in the USA found that cutting woody plants did not significantly affect their survival in the following year. One study of a riparian wet meadow in Germany simply reported that 20% of black alder Alder glutinosa trees were still alive after being cut back and grazed for four years. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3046https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3046Thu, 01 Apr 2021 19:06:56 +0100Collected Evidence: Collected Evidence: Cut large trees/shrubs to maintain or restore disturbance: brackish/salt marshesWe found no studies that evaluated the effects, on vegetation, of cutting large trees/shrubs to maintain or restore disturbance in brackish/salt marshes.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3047https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3047Thu, 01 Apr 2021 19:10:37 +0100Collected Evidence: Collected Evidence: Cut large trees/shrubs to maintain or restore disturbance: freshwater swamps One study evaluated the effects, on vegetation, of cutting large trees/shrubs to maintain or restore disturbance in freshwater swamps. The study was in the USA. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Herb abundance (1 study): One replicated, randomized, controlled, before-and-after, site comparison study of freshwater swamps in the USA found that cutting woody vegetation (and applying herbicide) had no significant effect on herbaceous ground cover one year later: there were similar changes in treated and untreated swamps. VEGETATION STRUCTURE Basal area (1 study): One replicated, randomized, controlled, before-and-after, site comparison study of freshwater swamps in the USA found that cutting woody vegetation (and applying herbicide) had no significant effect on the basal area of woody vegetation one year later: there were similar changes in treated and untreated swamps. Canopy cover (1 study): The same study found that cutting woody vegetation (and applying herbicide) reduced canopy cover – to similar levels as in high-quality swamps after one year. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3048https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3048Thu, 01 Apr 2021 19:10:54 +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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