Restore or create traditional water meadows
Overall effectiveness category Likely to be beneficial
Number of studies: 22
Background information and definitions
This intervention involves restoring or creating traditional water meadows, also known as wet meadows. Water meadows are areas of grazing land or hay meadow that have carefully controlled water levels to keep the soil damp. In Europe they provide valuable breeding habitats for wading birds and other biodiversity.
Techniques used to restore or create plant communities associated with wet meadows may include topsoil removal, which rapidly reduces nutrient levels in nutrient-enriched soils and increases flooding frequency by lowering the ground surface (Hölzel & Otte 2003). In areas where target plant species are not present in the seed bank or plant species have limited dispersal, it may also be important to introduce plant species through sowing, planting or spreading hay from existing wet meadows (Hölzel & Otte 2003).
See also ‘Raise water levels in ditches or grassland’ for studies looking at the effects of raising water levels on grassland.
Hölzel N. & Otte A. (2003) Restoration of a species-rich flood meadow by topsoil removal and diaspore transfer with plant material. Applied Vegetation Science, 6, 131-140.
Supporting evidence from individual studies
A trial from 1985 to 1990 on what was once a species-rich wet meadow at the Veenkampen, near Wageningen, the Netherlands (Berendse et al. 1992) found that topsoil removal increased the number of plant species on plots managed as hay meadows, and allowed rare sedge (Cyperaceae) species to establish. Three 15 x 25 m plots had topsoil removed to 5 cm depth. Each had a different water level, so they were not replicated. The number of plant species in these plots remained relatively stable or increased between 1987 and 1990 regardless of water level (dry plots increased from 21 to 28 species). The number of plant species was greater than in plots without soil removal. From 1988, carnation sedge Carex panicea and three other sedge species usually restricted to nature reserves in the region were found. Plots that were mown once or twice each year without soil removal (five replicates of four different mowing and hay removal treatments on 10 x 15 m plots) lost plant species. They had 18-20 species in 1987 and 14-17 in 1990. No fertilizer was applied during the experiment.
A replicated, controlled, randomized study of two wet meadows over four years in Switzerland (Buttler 1992) found that overall winter and summer (August) cuts had positive effects on plant species densities in terms of individuals, leaves, shoots and flowers. However individual species were affected differently by cutting regime. For example, an annual winter cut caused an increase in the number of flowers for common reed Phragmites communis (now P. australis), whilst a summer cut reduced them. Some drier vegetation communities were damaged when cut in summer, whereas wetter communities were more resilient to summer mowing. In general, annual winter cuts tended to improve the vitality of vascular plants (in terms of increased number of individuals, flowering and biomass). Plant vitality was lowest in uncut plots and intermediate with an annual summer cut and winter cut every three years. Vegetation structure differed with treatments (hay removed) and uncut controls. The meadows had been abandoned for many years and treatments were applied in three blocks with three replicates. Vegetation was sampled in July-August within 11 x 11 m and 13 x 13 m permanent plots from 1983 to 1986.Study and other actions tested
A before-and-after study over one year on agricultural land that had been intensively managed in Oxfordshire, UK (McDonald 1993) found that sowing seeds from a nearby species-rich flood meadow aided restoration of the flood meadow. The existing seed bank contained 38 species (66% perennial and 34% annual species), of which only 55% were grassland species, including nine species of wet grassland. Following seed sowing in 1986, 43 species were recorded at the site, of which 61% were perennial and 39% annual species. Of the 53 species that did not germinate, 77% were grassland species, of which six were wet grassland species. To determine the existing seed bank, 12 stratified random soil samples (5000 cm³) were taken from the top 10 cm of recently ploughed soil in April 1986. Twenty-five subsamples (200 cm³) were taken from each and seeds were germinated and identified. Following harvest, seeds that had been harvested from a nearby species-rich flood meadow (Oxey Mead SSSI) in July were sown in October 1986. Plant species presence/absence was recorded in twelve 5 x 5 m quadrats in June 1987.Study and other actions tested
A 1994 review of methods to restore grasslands in the Netherlands (Bakker 1994) reports one experiment in which the plant community on a wet peaty grassland changed away from the desired plant community over 14 years, after cessation of fertilizer input and the introduction of grazing. Characteristic species, such as marsh marigold Caltha palustris, were replaced by tall plants, such as lesser pond sedge Carex acutiformis and reed sweetgrass Glyceria maxima. The restoration was considered unsuccessful. The authors argue that continued agricultural drainage on surrounding areas is responsible for the failure of the restoration, because the water table is not high enough to restore the plant community. Fertilizer applications were stopped in 1971. Plants were monitored from 1978 to 1992. Site location and details were not given.Study and other actions tested
A study of a degraded wet meadow in eastern Netherlands (Jansen & Roelofs 1996) found that a wet meadow plant community (Cirsio-Molinietum community) established within five years after topsoil removal (5-15 cm topsoil layer removed) on former agricultural land and alder carr. Almost all of the highly productive plant species had disappeared in that time. In contrast, species of the same wet meadow plant community remained rare or absent in the adjacent nutrient-rich (eutrophicated) wet meadow, in areas with and without topsoil removal. This may have been due to prolonged inundation resulting from the topsoil removal. Topsoil removal was undertaken in three areas of Lemselermaten nature reserve: a section of the nutrient-rich wet meadow (1991; ‘old reserve’) and the adjacent former agricultural grassland and alder carr (1989; ‘new reserve’). Vegetation was then mown annually in these areas and in the remainder of the nutrient-rich wet meadow. Three transects were established, one in the new reserve and two in the old reserve (with and without sod cutting). Vegetation cover and abundance was surveyed in several plots (4 m²) along each transect annually (July-August 1992-1994).Study and other actions tested
A controlled, randomized study of a former improved pasture in the Netherlands (Oomes et al. 1996) found that raising the water level resulted in a more rapid establishment of species typical of wet conditions, than vegetation management (cutting and removing hay; cutting, mulching and leaving hay; topsoil removal to 5 cm followed by cutting and removing hay). Hay removal plots had more new species than the mulched plots in the wet field (7 vs 2 species; 3 in dry field). Two years after topsoil removal, there were 37 species established in the wet field and 49 in the dry field, five years later there were 13 new species on wet fields and 22 on dry fields. In 1985, the water level was raised to its former level in one area (1.5-2 ha), the other area was left dry. The three management practices were implemented in each area: sod cutting (to remove topsoil) in one plot (375 m²) and hay removal and mulching each in five replicate plots (100 m²). Plant species composition was recorded annually (20-50 samples/plot).Study and other actions tested
A 1998 review of case studies in France, gathered from published and unpublished literature (Muller et al. 1998) reported one French study showing an increase in plant species richness (from 5 to 10-25 species over four years) on a wet grassland in Brittany following introduction of grazing by Camargue horses (Rozé 1993).
Rozé F. (1993) Successions végétales après pâturage extensif par des chevaux dans une roselière [Successional patterns after extensive grazing by horses in a Phragmites australis plant community]. Bulletin d’Ecologie, 24, 203-209.Study and other actions tested
A replicated before-and-after study of 15 restored wet meadows in agricultural landscapes in southern Sweden (Hellström & Berg 2001) found that the density of seven bird species increased and two decreased significantly following restoration. Three species showed a non-significant tendency to decrease and 11 showed no significant difference following restoration. A population was more likely to increase if it was present at the site pre-restoration. No single management regime (mowing, grazing, mowing/grazing, unmanaged) was favoured by a large number of species (but by just 2-4 species). Seven species were associated with site/meadow size (five negatively) and seven with surrounding habitat. Breeding bird survey data was obtained (following requests to relevant groups) using three survey methods: territory mapping, counts of duck broods and at two sites thorough field counts. The majority of meadows were located along lakeshores or rivers.Study and other actions tested
A controlled study in 1992-1997 of wet fen meadows in southern Germany (Patzelt et al. 2001) found that topsoil removal and the introduction of target species aided meadow restoration. The removal of the nutrient-rich topsoil (to depths of 20 cm, 40 cm or 60 cm) and introduction of target species in hay cut from four fen meadows (layer 5-10 cm thick) resulted in successful establishment of 57 fen meadow plant species over six years, including 13 regional Red List species. The total cover of hay species from the donor areas reached up to 70% on plots where 20 cm of topsoil was removed, 30% when 40 cm was removed and 5% on the 60 cm removal plots. Plots without hay were established for each level of topsoil removal as controls for comparison. Monitoring of vegetation was carried out several times each year on permanent 4 m² plots.Study and other actions tested
A replicated, controlled, randomized study of a species-poor agriculturally improved pasture in the UK (Tallowin & Smith 2001) found that topsoil removal and planting of seedlings, rather than seeds, resulted in establishment of species typical of a fen meadow plant community (Cirsio-Molinietum: purple moor grass Molinia caerulea-meadow thistle Cirsium dissectum community) over four years. When seedlings were planted, combined cover by Cirsio-Molinietum species was highest in treatments with topsoil removal (up to 75% in year four). Where topsoil was not removed, vegetation was dominated by a few competitive species such as common knapweed Centaurea nigra (up to 60% cover). Two years after sowing seeds from a Cirsio-Molinietum meadow, only three of the 17 species had established at more than trace amounts (combined cover of 8%). Treatments to reduce site fertility included cutting and removal of vegetation, cultivation, fallowing and topsoil removal (10-20 cm) and addition of straw and/or lignitic clay. Randomized block experiments were established with treatments applied to plots of 9 x 2 m where seeds were sown (1989-1992) and 2 x 2 m where seedlings of 14 species were planted (1994-1999). Plant composition of plots was sampled in June 1992 and 1997-1999.Study and other actions tested
A replicated site comparison study of former arable and pasture fields in the Netherlands (Verhagen et al. 2001) found that topsoil removal aided wet meadow restoration. Topsoil removal resulted in increasing similarity (up to 29%) to five target communities: small sedge Caricion nigrae community, Ericion tetralicis heathland and three nutrient-poor grassland communities (Junco-Molinion, Nardo-Galion saxatilis and Thero-Airio). Nutrient poor fen communities and a heathland community (Calluno-Genistion pilosae) did not establish. Target species increased steadily over time, but 50-100% were still missing from target communities after nine years. Environmental conditions were suitable or within the range for establishment for all communities, apart from two grassland communities; Thero-Airion and Junco-Molinion grasslands (only one site suitable for each). Local species pools were good for all but nutrient-poor fen communities. Topsoil was removed (to depths up to 50 cm in 1989-1995) from eight sites. Vegetation was monitored (July-August) annually at 3-12 plots (2 x 2 m) at each site from 1993 to 1995 until 1998. Vegetation and environmental conditions were compared to five reference plots for each community.Study and other actions tested
A before-and-after study in 1984-1994 in Västmanland, Sweden (Berg et al. 2002) found no increase in northern lapwing Vanellus vanellus population in the study area despite an increase in the area of managed wet meadows from 163 ha to 530 ha over the study period (approximately 220 pairs in 1985 vs 200 in 1994, range of 152-297 pairs). Both managed and unmanaged meadows were used less for nesting than expected based on their availability. However, average hatching success was significantly higher in meadows (78-90% for 54 nests in meadows), compared to spring-sown crops (29-50% of 1,236 nests). There were no differences between meadows and autumn-sown crops or cultivated grassland (approximately 85% and 75% success respectively). Before 1984, the majority of meadows in the area were overgrown and abandoned. The meadows and arable fields became flooded from mid-April to mid-May in years with high spring flooding.
A replicated, controlled study of a flood meadow (a former arable field) in Germany between 1998-2001 (Hölzel & Otte 2003) found that the removal of nutrient-rich topsoil and introduction of meadow seeds aided meadow restoration. Topsoil removal (to depths of 30 and 50 cm) and introduction of plant material from nearby species-rich flood meadows (alluvial Molinion and Cnidion meadows) resulted in a decline of arable weeds and ruderal species and an increase in resident grassland species and transferred species. After four years, 64% of all species found in established vegetation were from transferred plant material and 82% of the entire species pool at donor sites was transferred (including 31 species in the national and regional Red Data Book). Transfer rates ranged from 64 to 72%/strip for the flooded strips and 53 to 56% for the dry strips. Following soil removal in 1997, six strips (20 x 50 m) were covered with freshly mown plant material (5-10 cm thick) from nearby flood-meadows and two were left as controls. Plants were recorded annually in ten 10 x 10 m quadrats/strip and in six quadrats/donor meadow. Twenty soil cores (10 x 3 cm diameter) were taken from six plots with and two without soil removal and germinated seedlings were identified. Two samples (each six quadrats: 32 x 32 cm) of plant material (at the surface and 2 cm of the topsoil) were taken from four strips (February 1998 and 1999) to analyse transferred seeds.Study and other actions tested
A replicated, controlled, site-comparison study of 26 restored semi-natural grasslands in south-eastern Sweden (Lindborg & Eriksson 2004) found that continuously grazed control sites had higher plant species diversity and a higher proportion of typical grassland species in the community than restored grasslands. Plant species diversity at restored sites was 16-20 species/m² compared to 24-30 species/m² at continuously grazed control sites. Total species richness was positively associated with time since restoration (1-7 years) and the abundance of trees and shrubs. Overall species composition differed between restored and control sites, with control sites having a higher proportion of typical grassland species than restored sites. However within grassland types (dry, dry to damp (mesic) or damp to wet), species composition was similar between each pair of restored and control sites. Restored damp to wet grassland was dissimilar in species composition to all other plots. Abundance of 10 grazing-indicator species tended to be lower at restored sites. Restored site area (3-35 ha), time between abandonment and restoration, time since restoration and abundance of trees and shrubs were not related to species composition among restored sites or the 10 grazing-indicator species. Restored sites were grazed before abandonment and after restoration, control sites had been grazed continuously. The six control sites were compared to restored sites in the same region. Plants were sampled within 10 randomly distributed plots (1 m²) in July-August 2001. Trees and shrubs were counted within a 40 m diameter circle at each site.Study and other actions tested
A study in 84 ha of arable land adjoining Berney Marshes RSPB Reserve, Norfolk, England, describes their restoration to grazing marsh (Lyons & Ausden 2005). The fields were acquired in 1998, water levels were raised, foot drains were added, and grazing by sheep (and then cattle) was introduced. By 2003, plant communities had shifted towards those characteristic of lowland wet grassland. Breeding wading bird numbers increased, with 15-20 pairs of northern lapwing Vanellus vanellus and 5-10 pairs of common redshank Tringa totanus (depending on year). The fields are regularly used for foraging by a large proportion of the estimated 100,000 wintering waterfowl (e.g. Eurasian wigeon Anas penelope) now using the reserve.Study and other actions tested
A replicated, controlled study of 15 abandoned fen meadows in Switzerland (Billeter et al. 2007) found that mowing resulted in an increase in plant biodiversity. Mowing resulted in an increase in plant species richness (control: 28 species/2 m², mown: 33), number of indicator species (control: 16, mown: 18), broadleaved plants (control: 18/plot, mown: 21/plot), woody species (control: 1/plot, mown: 2/plot), mosses/liverworts (bryophyte) biomass (control: 55 g/m², mown: 85 g/m²), seedling density of Davall's sedge Carex davalliana (control: 0.40/m², mown 1.49/m²) and Devil's bit scabious Succisa pratensis (control: 1.04/m², mown: 0.53/m²) and a decrease in total biomass (control: 225 g/m², mown: 193 g/m²). Two indicator species increased substantially with mowing: bog-star Parnassia palustris (+10 plots) and heath spotted-orchid Dactylorhiza maculata/majalis (+13 plots). Two control and two mown (mid-September) plots (2 m²) were randomly established in each meadow (4-35 years since abandonment). Plant species richness (1998) and cover (2000) were recorded in late July-early August. Plant biomass (dry weight) was sampled in subplots (20 x 20 cm) in early August 2000 and separated into vascular plant, litter and moss/liverwort biomass. Life history traits were investigated for two abundant plant species: Davall’s sedge and Devil’s bit scabious (three/plot) and seedlings of the species were counted in five subplots/plot (10 x 10 cm) in May-June 2000.Study and other actions tested
A 2007 review of data from 36 wet meadows, in the Netherlands (majority), Germany and the UK (Klimkowska et al. 2007) found that restoration attempts have largely had limited success. On average, projects have resulted in an average increase in species richness below 10% of the target community. The more species-rich the meadow was at the start, the closer it was to the target community after restoration, however, there was a corresponding smaller increase in the number of target species. A combination of topsoil removal (deeper than 20 cm) and introducing seedlings (e.g. see (Patzelt et al. 2001, Verhagen et al. 2001, Hölzel & Otte 2003)) and a combination of these with rewetting, appeared most effective (an increase in ‘saturation index’ of up to 16%; this index reflects the completeness of restored communities in comparison to target communities). Rewetting alone appeared an ineffective restoration method. Data were obtained from professional networks, experts, peer-reviewed published sources and project records.Study and other actions tested
A replicated, controlled study in a grazed fen area in northern Germany (Rasran et al. 2007) found that wet meadow species increased and agricultural grassland species decreased following topsoil removal and hay transfer. Target species reached their maximum in the second year of the experiment where topsoil had been removed and hay transferred. Where topsoil had been removed but no hay introduced, the species increased slowly over four years. Most species transferred with the hay were only present in areas with removed topsoil, not on intact soil. Grazing had minimal effects, but did result in a significant increase of cumulative frequency of wet meadow species. Four blocks (12 x 24 m) were established that each combined three treatments: moderate grazing (yes/no), topsoil removal (yes/no; to a depth of 30 cm) and hay transfer from a species-rich fen meadow (yes/no; layer of 1-3 cm). Plant cover and species dominance was sampled in 16 permanent squares (1 m²) within each subplot in each combination of treatments in 2002-2005. Ten soil seed bank samples were taken from each plot in 2002.Study and other actions tested
A long-term replicated trial in 1987-2007 on seven semi-natural wet meadow sites in Münsterland, Germany (Poptcheva et al. 2009) found that mowing twice a year (in June/July and September) without fertilizer was the most effective regime for restoring target wet meadow plant communities and resulted in highest species richness. However, successional changes were still happening 20 years after the start of the trial, probably due to slow immigration of new species. Management regime had a stronger effect on the pattern of succession than other environmental or historic factors. Treatments were carried out from 1987 to 2007 in 200-250 m2 fields and plants were surveyed in four 2 x 2 m plots/field at least every second year. Above ground biomass was measured in 1989, 1993, 1998 and 2007 by harvesting eight 0.5 x 0.5 m plots/field.Study and other actions tested
A replicated controlled trial near Riedstadt, southwest Germany (Schmiede et al. 2009), found that five or six years after restoration of flood meadows by hay spreading the seed bank was still dominated by weedy species of the former arable land use. However the seed bank in control areas without hay spreading had significantly lower numbers of transferred flood meadow species. Five meadows were restored in 2000 and 2001. Plants present above ground and in the seed bank were sampled in 2006, in both restored areas and control areas that had been left to naturally regenerate.Study and other actions tested
A 2010 review of studies of scientific knowledge about how to re-establish plant communities in grasslands by reintroduction (Hedberg & Kotowski 2010) found that hay transfer has been shown to be an effective method in wet meadows. The review found 38 studies, 28 of which provided enough information to evaluate the outcome, 21 of these from European countries, six on wet meadows or fens. Studies were graded as: successful, of limited success, failed introductions, or without the necessary information to evaluate the outcome. All four studies on hay spreading in wet meadows or fens were successful (Patzelt et al. 2001, Hölzel & Otte 2003, Rasran et al. 2007, Klimkowska et al. 2010). Plug planting had limited success in one UK study (Tallowin & Smith 2001). Only one study looked at the effects of direct seeding on wet meadows and found the technique was not successful (Tallowin & Smith 2001).
Rasran L., Vogt K. & Jensen K. (2007) Effects of topsoil removal, seed transfer with plant material and moderate grazing on restoration of riparian fen grasslands. Applied Vegetation Science, 10, 451-460.Study and other actions tested
A replicated, controlled study in 2004-2007 of a degraded species-poor meadow in central Poland (Klimkowska et al. 2010) found that deep topsoil removal (40 cm), hay transfer from a species-rich meadow and exclusion of livestock resulted in a community most similar to the target vegetation. Shallow soil removal (20 cm) with hay transfer resulted in a community more similar to the degraded meadows. Hay transfer appeared to speed up the establishment of the target vegetation. Two plots (35 x 35 m) were subdivided to test combinations of the following treatments: topsoil removal (to 20 or 40 cm), hay transfer from a nearby meadow (collected mid-July 2004-2005, partly dried, stored for 1.5 months, spread in 5-7 cm layer) and livestock exclusion. Data were obtained from plots on plant species distribution and abundance (2004-2007) and biomass (2006-2007), species composition of degraded meadows and donor meadow were also collected (2004, 2006, 2007). The soil seed bank (top 5 cm) at the two topsoil removal depths and seed content of hay were also sampled in 2004.Study and other actions tested