Action: Introduce seeds of peatland herbs
- Ten studies evaluated the effects, on peatland vegetation, of introducing seeds of herbaceous peatland plants. Seven studies were in fens or fen meadows, two in bogs and one in unspecified peatland.
- Germination (2 studies): Two replicated studies reported that some planted herb seeds germinated. In a bog in Germany three of four species germinated, but in a fen in the USA only one of seven species germinated.
- Characteristic plants (3 studies): Three studies (two controlled) in fen meadows in Germany and a peatland in China reported that wetland-characteristic or peatland-characteristic plants colonized plots where herb seeds were sown (sometimes along with other interventions).
- Herb cover (4 studies): Three before-and-after studies (one also replicated, randomized, paired, controlled) in a bog in New Zealand, fen meadows in Switzerland and a peatland in China reported that plots sown with herb seeds developed cover of the sown herbs (and in New Zealand, greater cover than unsown plots). In China, the effect of sowing was not separated from the effects of other interventions. One replicated, randomized, paired, controlled study in a fen in the USA found that plots sown with herb (and shrub) seeds developed similar herb cover to plots that were not sown.
- Overall vegetation cover (3 studies): Of three replicated, controlled studies, one in a fen in the USA found that sowing herb (and shrub) seeds increased total vegetation cover. One study in a bog in New Zealand found that sowing herb seeds had no effect on total vegetation cover. One study in a fen meadow in Poland found that the effect of adding seed-rich hay depended on other treatments applied to plots.
- Overall plant richness/diversity (4 studies): Two replicated, controlled studies in fens in the USA and Poland found that sowing herb seeds had no effect on plant species richness (total or vascular). Two replicated, controlled, before-and-after studies in a bog in New Zealand and a fen meadow in Poland each reported inconsistent effects of herb sowing on total plant species richness.
This section considers introducing seeds of peatland herbs: directly sowing seeds, spreading vegetation fragments on the peatland that will not themselves grow but contain seeds (e.g. hay harvested from fens), or adding peat/soil that contains seeds of peatland plants. Adding vegetation fragments may have the additional benefit of protecting the peat surface, controlling moisture levels and providing shade. Note that this section does not include studies that only introduce, or report responses of, nurse plants (e.g. Caporn et al. 2007).
Direct introduction of peatland vegetation might be necessary in severely degraded or bare peatlands. Natural revegetation (from remnant plants, seed banks or dispersal) might not happen, might be very slow or might not produce the desired mix of species.
Caution: Collecting seeds from natural peatlands may damage the source site.
Key peatland types where this action may be appropriate: bogs, fens/fen meadows, tropical peat swamps.
Related actions: directly plant whole plants into peatland (mosses, herbs or shrubs/trees); spread vegetation onto peatland surface (mosses or mixed vegetation); restoration using more than three interventions, sometimes including planting; supporting interventions from this section used without introducing vegetation (e.g. mulching or fertilizing); experimental tests of interventions to complement planting (e.g. mulching or fertilizing).
Caporn S., Sen R., Field C., Jones E., Carroll J. & Dise N. (2007) Consequences of Lime and Fertilizer Application for Moorland Restoration and Carbon Balance. Moors for the Future Research Report.
Supporting evidence from individual studies
A replicated, controlled, before-and-after study in 1993–1995 in a historically mined raised bog in Germany (Sliva & Pfadenhauer 1999) reported that planted seeds germinated for three of four herb species, and that seedlings survived over two years. After two years, seedling densities (seedlings/400 cm2) were 8–45 for purple moor grass Molinia caerulea, 4–10 for sheathed cottongrass Eriophorum vaginatum, 0–1 for common cottongrass Eriophorum angustifolium and 0 for beaked sedge Carex rostrata (i.e. it did not germinate). In unsown plots, there were 0–3 seedlings/400 cm2. Plots covered with mulch, fleece or fibre mats after sowing contained more moor grass and sheathed cottongrass seedlings (14–45 seedlings/400 cm2) than uncovered plots (0–8 seedlings/400 cm2). In autumn 1993, seeds of the four species were spread onto 1 m2 plots of bare rewetted peat (20 plots/species; 40–48 seeds/400 cm2). Five plots/species were covered with mulch, five with synthetic fleece and five with jute fibre mat, whilst five were not covered. Fifteen additional plots were not seeded (but some were covered). Seedlings were counted in summer 1994 (two plots/treatment) and 1995 (three plots/treatment).
A replicated study in 1992 in a historically mined fen in Colorado, USA (Cooper & MacDonald 2000) reported that planted seeds germinated for one of seven herb species. Arrowgrass Triglochin maritima germinated in 15 of 25 plots (but not the very wettest or very driest). No seeds germinated for three Carex sedge species, common cottongrass Eriophorum angustifolium, elk sedge Kobresia simpliciuscula or Rocky Mountain iris Iris missouriensis. In June 1992, each species was planted into 25 separate 0.5 x 0.5 m plots (20 seeds/plot). Plots contained shallow surface peat (a “few” centimetres), had variable water levels and had been cleared of existing vegetation. Seeds were collected from the wild in 1991 and kept cold over winter. Seeds were watered after planting. Germination and seedling survival were recorded weekly until the end of August 1992.
A controlled, before-and-after study in 1991–1997 in a degraded fen meadow in Germany (Patzelt et al. 2001) reported that adding seed-rich hay, after removing topsoil, ensured that plots developed wetland-characteristic plant communities. Over six years, plots with hay added after removal of 20–40 cm of topsoil developed cover of fen-characteristic herbs, including sedge Carex spp. and purple moor grass Molinia caerulea. Plots with hay added after removal of 60 cm of topsoil developed cover of wetland-characteristic herbs (particularly rushes) in addition to fen-characteristic species. Plant communities in plots without added hay showed similar changes to those with hay when 40–60 cm of topsoil was removed, but developed cover of species from drier grasslands when 20 cm of topsoil was removed. All data were reported as a graphical analysis. The results were not tested for statistical significance. In February 1991, six 4,500 m2 plots in a historically farmed fen meadow were stripped of topsoil (to 20, 40 or 60 cm depth). Hay was cut from nearby fens and spread onto three of the plots (one stripped to each depth). From 1992 to 1997, vegetation cover was recorded annually in five 4 m2 quadrats/plot.
A replicated, randomized, paired, controlled, before-and-after study in 1998–2000 in a historically mined raised bog in New Zealand (Schipper et al. 2002) reported that plots seeded with bamboo rush Sporadanthus ferrugineus typically developed greater rush cover than unseeded plots, but that seeding had no consistent effect on total vegetation cover or species richness. Most of these results are not based on tests of statistical significance. After 810 days, seeded plots had greater bamboo rush cover in 8 of 12 comparisons (for which seeded: 2–32%; unseeded: 0–8% cover) and lower bamboo rush cover in only three comparisons (seeded: 0–3%; unseeded: 4–27%). Total vegetation cover increased similarly in seeded and unseeded plots, with no significant difference after 810 days (seeded: 38%; unseeded: 40%). Seeded plots contained fewer plant species than unseeded plots in 5 of 12 comparisons but more in 4 of 12, with no difference in the other three. In March 1998, forty-eight plots (25 m2) were established, in six blocks of eight, on bare rewetted peat. Hundreds of bamboo rush seeds (1 g) were spread on twenty-four plots (four random plots/block). Twenty-four control plots were not sown. Some plots were fertilized. Canopy cover of every plant species was estimated every 1–3 months until June 2000.
A replicated before-and-after study in 2004–2005 in two degraded fen meadows in Switzerland (Suter et al. 2006) reported that plots sown with fen plant seeds (some also ploughed or mulched) developed cover of fen-characteristic plants. Before sowing, plots were bare peat. After 2–10 months, cover of the sown fen plants was 10–45%. There were 50–160 individual plants/m2 (except in one site, where plots mulched with straw after sowing contained only 2 plants/m2). Vegetation cover and plant density did not significantly differ between plots sown in autumn and spring (see original paper). Forty-eight 2 x 2 m plots were established across two fen meadows (historically cultivated, but stripped of topsoil before the study began). Seeds were sown (10 different species; 200–800 seeds/species/plot) in October 2004 (8 plots), April 2005 (16 plots) or June 2005 (24 plots). Some random plots were ploughed before sowing or mulched afterwards. In August 2005, individual plants were counted and total vegetation cover estimated in the central 1.5 x 1.5 m of each plot.
A replicated, paired, controlled study in 2001–2005 in a degraded fen meadow in Germany (Rasran et al. 2007) found that in plots spread with hay from nearby fens, peatland-characteristic plants were more abundant than in plots without added hay. Over five years following hay addition, peatland-characteristic plants occurred in up to 28% of quadrats with up to 12% cover in each plot. In plots without added hay, peatland-characteristic plants occurred in <5% of quadrats with negligible cover. Amongst plots with added hay, abundance and cover were higher in those that had their topsoil removed prior to hay addition, but grazing had no additional effect (reported as a statistical model result). In 2001, thirty-two 6 x 6 m plots (in four blocks of eight) were established in a drained, abandoned, nutrient-enriched fen meadow. Freshly cut, seed-rich hay from an adjacent fen was added to 16 of the 32 plots. Additionally, four plots with hay and four plots without received each of the following treatments: topsoil stripping (30 cm depth) before hay addition, grazing (open to cattle) after hay addition, topsoil stripping plus grazing, or neither topsoil stripping nor grazing. Annually between 2002 and 2005, cover of every plant species was estimated in each plot, in 16 permanent 1 m2 quadrats.
A replicated, controlled, before-and-after, site comparison study in 2004–2007 in a degraded fen meadow in Poland (Klimkowska et al. 2010) found that the effect of adding hay on the meadow vegetation depended on other treatments applied to the plots: topsoil stripping and fencing. Overall, plots with and without added hay developed different plant communities over three years. However, only plots where hay was added after deep soil stripping developed a plant community similar to a target fen meadow (data reported as a graphical analysis; similarity not tested for statistical significance). The effect of hay addition on plant species richness, vascular plant cover, moss cover and vegetation biomass also depended on the other treatments (reported as statistical model results). For example, hay addition increased plant species richness in fenced plots (hay added: 23 species; no hay added: 18 species/4 m2 after three years) but had no effect in unfenced plots (data not reported). In 2004 and 2005, fen meadow hay was spread (5–7 cm thick) onto 4 m2 plots (number not clear). Some additional plots did not receive hay. All plots were historically drained, but were stripped of topsoil (20 cm or 40 cm depth) before adding hay. Half of the plots were fenced to exclude boar and deer. Vegetation cover and plant species were recorded annually between 2004 (before adding hay but after stripping soil) and 2007. Total vegetation biomass was measured from clippings taken in August 2006–2007.
A before-and-after study in historically mined peatland in China (Zhang et al. 2012) reported that an area sown with seeds (also rewetted and fenced to exclude livestock) developed cover of grasses and wetland-characteristic herbs. No statistical tests were carried out. Before restoration, the peatland was largely bare peat with some sedges Carex spp. and herbs characteristic of drier soils (precise cover not reported). After restoration, new wetland-characteristic species had colonized, including rush Blysmus sinocompressus (30% cover) and marsh marigold Caltha scaposa (2% cover). Also abundant were tussock grass Deschampsia cespitosa (20% cover) and couch grass Elymus nutans (10% cover). Forty-two hectares of Hongyuan peatland were sown with seeds of five plant species (50 kg; mainly couch grass, other species not reported). The peatland was historically mined, drained and grazed. The study does not distinguish between the effects of these interventions. Vegetation cover was visually estimated (precise methods and dates not reported).
A replicated, randomized, paired, controlled study in 2009–2011 in a fen in Michigan, USA (Bess et al. 2014) found that plots sown with herb (and shrub) seeds developed more vegetation cover overall than unsown plots, but similar cover of all monitored plant groups and similar species richness. After two years, sown plots had greater total vegetation cover (214%) than unsown plots (165%). Cover of individual plant groups did not differ significantly between sown and unsown plots (although it tended to be higher in the former): sedges (120 vs 81%), grasses (27 vs 15%), forbs (28 vs 33%), mosses (33 vs 29%), shrubs (4 vs 4%). The same was true for plant species richness (45 vs 43 species across all quadrats). Patterns were similar, but cover lower, one year after intervention. In 2009, twenty pairs of 9 m2 plots were established, in a ditch recently refilled with seed-rich fen spoil. Twenty plots (one random plot/pair) were sown with a mixture of herb (grasses, rushes, sedges, forbs) and shrub seeds. The other 20 plots were not sown. The study does not distinguish between the effects of sowing herbs and shrubs. In 2010 and 2011, vegetation cover was recorded in one 1 m2 quadrat/plot.
A replicated, controlled, before-and-after study in 2008–2011 in a degraded fen in Poland (Hedberg et al. 2014) found that adding seed-rich hay to plots did not affect vascular plant community composition or species richness. Ten drained plots were initially dominated by dryland plants. The overall composition of the plant community did not change over two years, whether hay was added or not. Two other, wetter plots were initially dominated by fen-characteristic herbs. In these plots, rushes and reeds became more abundant over two years, whether hay was added or not (all community data reported as a graphical analysis; results not tested for statistical significance). After two years, the number of vascular plant species was not significantly different in plots with or without added hay (data not reported). In autumn 2009, twelve plots were established in a drained, degraded fen. Ten plots remained fully drained. Hay from a nearby natural fen was spread onto five of these plots. Two plots were wetter, having been been stripped of 60 cm of topsoil 6–8 months before the initial vegetation sampling. Hay was spread onto half of each of these plots. In summer 2009 (before hay addition), 2010 and 2011, cover of every vascular plant species was estimated in each plot (details not clear).
- Sliva J. & Pfadenhauer J. (1999) Restoration of cut-over raised bogs in southern Germany – a comparison of methods. Applied Vegetation Science, 2, 137-148
- Cooper D.J. & MacDonald L.H. (2000) Restoring the vegetation of mined peatlands in the southern Rocky Mountains of Colorado, USA. Restoration Ecology, 8, 103-111
- Patzelt A., Wild U. & Pfadenhauer J. (2001) Restoration of wet fen meadows by topsoil removal: vegetation development and germination biology of fen species. Restoration Ecology, 9, 127-136
- Schipper L.A., Clarkson B.R., Vojvodic-Cukovic M. & Webster R. (2002) Restoring cut-over restiad peat bogs: a factorial experiment of nutrients, seed and cultivation. Ecological Engineering, 19, 29-40
- Suter M., Prohaska C. & Ramseier D. (2006) Covering bare ground suppresses unwanted willows and aids a fen meadow restoration in Switzerland. Ecological Restoration, 24, 250-255
- 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
- Klimkowska A., Kotowski W., Van Diggelen R., Dzierża P. & Brzezińska K. (2010) Vegetation re-development after fen meadow restoration by topsoil removal and hay transfer. Restoration Ecology, 18, 924-933
- Zhang X., Hongyu L., Baker C. & Graham S. (2012) Restoration approaches used for degraded peatlands in Ruoergai (Zoige), Tibetan Plateau, China, for sustainable land management. Ecological Engineering, 38, 86-92
- Bess J.A., Chimner R.A. & Kangas L.C. (2014) Ditch restoration in a large Northern Michigan fen: vegetation response and basic porewater chemistry. Ecological Restoration, 32, 260-274
- Hedberg P., Kozub Ł. & Kotowski W. (2014) Functional diversity analysis helps to identify filters affecting community assembly after fen restoration by top-soil removal and hay transfer. Journal for Nature Conservation, 22, 50-58