Version classiqueVersion mobile

What Works in Conservation 2018

 | 
William J. Sutherland
, 
Lynn V. Dicks
, 
Nancy Ockendon
, 
et al.

6. Peatland conservation

6.7. Threat: Natural system modifications

Texte intégral

6.7.1 Modified water management

Beneficial

● Rewet peatland (raise water table)

1 Plant community composition: Ten of thirteen studies reported that rewetting affected the overall plant community composition. Six before-and-after studies (four also replicated) in peatlands in Finland, Hungary, Sweden, Poland and Germany reported development of wetland-or peatland-characteristic communities following rewetting. One replicated, paired, controlled study in the Czech Republic found differences between rewetted and drained parts of a bog. Three site comparison studies in Finland and Canada reported differences between rewetted and natural peatlands. In contrast, three replicated studies in peatlands in the UK and fens in Germany reported that rewetting typically had no effect, or insignificant effects, on the plant community.

2 Characteristic plants: Five studies (including one replicated site comparison) in peatlands in Canada, the UK, China and Poland reported that rewetting, sometimes along with other interventions, increased the abundance of wetland-or peatland-characteristic plants. Two replicated site comparison studies, in fens and fen meadows in Europe, found that rewetting reduced the number of fen-characteristic plant species. Two studies (one replicated, paired, controlled, before-and-after) in fens in Sweden reported that rewetting had no effect on cover of fen-characteristic plants.

3 Moss cover: Twelve studies (two replicated, paired, controlled) in peatlands in Europe and Canada reported that rewetting, sometimes along with other interventions, increased Sphagnum moss cover or abundance. However two replicated studies, in bogs in Latvia and forested fens in Finland, reported that rewetting did not affect Sphagnum cover. Five studies (one paired, controlled, before-and-after) in bogs and fens in Finland, Sweden and Canada reported that rewetting did not affect cover of non-Sphagnum mosses/lichens. However two controlled studies, in bogs in Ireland and the UK, reported that rewetting reduced cover of non-Sphagnum bryophytes. One study in Finland reported similar moss cover in rewetted and natural peatlands, but one study in Canada reported that a rewetted bog had lower moss cover than target peatlands.

4 Herb cover: Twenty-one studies (four replicated, paired, controlled) reported that rewetting, sometimes along with other interventions, increased cover of at least one group of herbs: reeds/rushes in five of seven studies, cottongrasses Eriophorum spp. in eight of nine studies, and other/total sedges in 13 of 15 studies. The studies were in bogs, fens or other peatlands in Europe, North America and China. Of four before-and-after studies in peatlands in the UK and Sweden, three reported that rewetting reduced cover of purple moor grass Molinia caerulea but one reported no effect. One replicated site comparison study, in forested fens in Finland, reported that rewetting had no effect on total herb cover. Two site comparison studies in Europe reported that rewetted peatlands had greater herb cover (total or sedges/rushes) than natural peatlands.

5 Tree/shrub cover: Ten studies (two paired and controlled) in peatlands in Finland, the UK, Germany, Latvia and Canada reported that rewetting typically reduced or had no effect on tree and/or shrub cover. Two before-and-after studies in fens in Sweden and Germany reported that tree/shrub cover increased following rewetting. One before-and-after study in a bog in the UK reported mixed effects of rewetting on different tree/shrub species.

6 Overall vegetation cover: Of four before-and-after studies (including three controlled), two in bogs in Ireland and Sweden reported that rewetting increased overall vegetation cover. One study in a fen in New Zealand reported that rewetting reduced vegetation cover. One study in a peatland in Finland reported no effect.

7 Overall plant richness/diversity: Six studies (including one replicated, paired, controlled, before-and-after) in Sweden, Germany and the UK reported that rewetting increased total plant species richness or diversity in peatlands. However, five studies found no effect: in bogs in the Czech Republic and Latvia, fens in Sweden and Germany, and forested fens in Finland. One study in fen meadows in the Netherlands found scale-dependent effects. One paired, controlled, before-andafter study in a peatland in Finland reported that rewetting reduced plant diversity. Of four studies that compared rewetted and natural peatlands, two in Finland and Germany reported lower species richness in rewetted peatlands, one in Sweden found higher species richness in rewetted fens, and one in Europe found similar richness in rewetted and natural fens.

8 Growth: One replicated site comparison study, in forested fens in Finland, found that rewetting increased Sphagnum moss growth to natural levels.

9 Assessment: beneficial (effectiveness 80%; certainty 80%; harms 10%). Based on evidence from: bogs (fifteen studies); fens (fourteen studies); fen meadows (one study); mixed or unspecified peatlands (six studies).

10https://www.conservationevidence.com/​actions/​1756

Unknown effectiveness (limited evidence)

● Irrigate peatland

11 Vegetation cover: One replicated, paired, controlled, before-and-after study in a bog in Canada found that irrigation increased the number of Sphagnum moss shoots present after one growing season, but had no effect after two. One before-and-after study in Germany reported that an irrigated fen was colonized by wetland-and fen-characteristic herbs, whilst cover of dryland grasses decreased.

12 Assessment: unknown effectiveness – limited evidence (effectiveness 55%; certainty 30%; harms 1%). Based on evidence from: bogs (one study); fens (one study).

13https://www.conservationevidence.com/​actions/​1859

No evidence found (no assessment)

14We have captured no evidence for the following interventions:

  • Reduce water level of flooded peatlands
  • Restore natural water level fluctuations.

6.7.2 Modified vegetation management

Likely to be beneficial

● Cut/mow herbaceous plants to maintain or restore disturbance

15 Plant community composition: Six replicated studies in fens and fen meadows in the UK, Belgium, Germany and the Czech Republic reported that mowing altered the overall plant community composition (vs no mowing, before mowing or grazing). One site comparison study in Poland reported that mowing a degraded fen, along with other interventions, made the plant community more similar to target fen meadow vegetation.

16 Characteristic plants: Four studies (including one replicated, paired, controlled, before-and-after) in fens and fen meadows in Switzerland, Germany, the Czech Republic and Poland found that cutting/mowing increased cover of fen meadow- or wet meadow-characteristic plants. One replicated before-and-after study, in fens in the UK, found that a single mow typically did not affect cover of fen-characteristic plants. In Poland and the UK, the effect of mowing was not separated from the effects of other interventions.

17 Moss cover: Four replicated, paired studies (three also controlled) in fens and fen meadows in Belgium, Switzerland and the Czech Republic found that mowing increased total moss or bryophyte cover. Two replicated studies (one also controlled) in fens in Poland and the UK found that a single mow typically had no effect on bryophyte cover (total or hollow-adapted mosses).

18 Herb cover: Six replicated studies (three also randomized and controlled) in fens and fen meadows in Belgium, Germany, Poland and the UK found that mowing reduced cover or abundance of at least one group of herbs (including bindweed Calystegia sepium, purple moor grass Molinia caerulea, reeds, sedges, and grass-like plants overall). One before-and-after study in a fen in Poland found that mowing, along with other interventions, increased sedge cover. One replicated, randomized, paired, controlled study in fen meadows in Switzerland found that mowing had no effect on overall herb cover.

19 Tree/shrub cover: Of three replicated studies in fens, two in the UK found that a single mow, sometimes along with other interventions, reduced overall shrub cover. The other study, in Poland, found that a single mow had no effect on overall shrub cover.

20 Vegetation structure: In the following studies, vegetation structure was measured 6–12 months after the most recent cut/mow. Three replicated studies in fens in Poland and the UK reported that a single mow, sometimes along with other interventions, had no (or no consistent) effect on vegetation height. One replicated, paired, site comparison study in fen meadows in Switzerland found that mowing reduced vegetation height. Three studies in fen meadows in Switzerland, Poland and Italy found mixed effects of mowing on vegetation biomass (total, moss, sedge/rush, or common reed Phragmites australis). One replicated, paired, site comparison study in Germany reported that vegetation structure was similar in mown and grazed fen meadows.

21 Overall plant richness/diversity: Eight studies in fens and fen meadows in the UK, Belgium, Switzerland, Germany, the Czech Republic and Poland found that mowing/cutting increased plant species richness (vs no mowing, before mowing or grazing). Three studies (two replicated, randomized, paired, controlled) in fens in Poland and the UK found that a single mow, sometimes along with other interventions, typically did not affect plant richness/diversity.

22 Assessment: likely to be beneficial (effectiveness 70%; certainty 60%; harms 10%). Based on evidence from: fens (seven studies); fen meadows (seven studies).

23https://www.conservationevidence.com/​actions/​1759

● Cut large trees/shrubs to maintain or restore disturbance

24 Plant community composition: One study in a fen in Poland found that where shrubs were removed, along with other interventions, the plant community became more like a target fen meadow over time.

25 Characteristic plants: One study in a fen in Poland found that where shrubs were removed, along with other interventions, the abundance of fen meadow plant species increased over time.

26 Vegetation cover: One replicated, paired, controlled study in a forested fen in the USA found that cutting and removing trees increased herb cover, but did not affect shrub cover.

27 Vegetation structure: One replicated, paired, controlled study in a forested fen in the USA found that cutting and removing trees increased herb biomass and height.

28 Assessment: likely to be beneficial (effectiveness 60%; certainty 45%; harms 5%). Based on evidence from: fens (two studies).

29https://www.conservationevidence.com/​actions/​1761

Trade-off between benefit and harms

● Use grazing to maintain or restore disturbance

30 Plant community composition: One replicated, paired, site comparison study in Germany found that the overall plant community composition differed between grazed and mown fen meadows.

31 Characteristic plants: One replicated, paired, controlled study in Germany reported that the abundance of bog/fen-characteristic plants was similar in grazed and ungrazed fen meadows. One replicated before-and-after study, in a fen in the UK, reported that cover of fen-characteristic mosses did not change after grazers were introduced. One replicated, paired, site comparison study in Germany found that grazed fen meadows contained fewer fen-characteristic plant species than mown meadows.

32 Herb cover: Two before-and-after studies in fens in the UK reported that grazing increased cover of some herb species/groups (common cottongrass Eriophorum angustifolium, carnation sedge Carex panicea or grass-like plants overall). One of the studies found that grazing reduced cover of purple moor grass Molinia caerulea, but the other found that grazing typically had no effect on this species.

33 Moss cover: One replicated before-and-after study, in a fen in the UK, reported that cover of fen-characteristic mosses did not change after grazers were introduced. One controlled, before-and-after study in a fen in the UK found that grazing reduced Sphagnum moss cover.

34 Tree/shrub cover: Of two before-and-after studies in fens in the UK, one found that grazing reduced overall shrub cover but the other found that grazing typically had no effect on overall shrub cover.

35 Overall plant richness/diversity: Of two before-and-after studies in fens in the UK, one (also controlled) reported that grazing increased plant species richness but the other (also replicated) found that grazing had no effect. One replicated, paired, site comparison study in Germany found that grazed fen meadows contained fewer plant species than mown meadows.

36 Assessment: trade-off between benefit and harms (effectiveness 40%; certainty 40%; harms 25%). Based on evidence from: fens (two studies); fen meadows (two studies).

37https://www.conservationevidence.com/​actions/​1762

Unknown effectiveness (limited evidence)

● Remove plant litter to maintain or restore disturbance

38 Plant community composition: Two studies (including one replicated, paired, controlled, before-and-after) in a fen meadow in Germany and a fen in Czech Republic found that removing plant litter did not affect plant community composition.

39 Vegetation cover: One replicated, paired, controlled, before-and-after study in a fen in the Czech Republic found that removing plant litter did not affect cover of bryophytes or tall moor grass Molinia arundinacea.

40 Overall plant richness/diversity: Of two replicated, controlled studies, one (also randomized) in a fen meadow in Germany reported that removing plant litter increased plant species richness and diversity. The other study (also paired and before-and-after) in a fen in the Czech Republic found that removing litter did not affect vascular plant diversity.

41 Assessment: unknown effectiveness – limited evidence (effectiveness 35%; certainty 38%; harms 7%). Based on evidence from: fens (one study); fen meadows (one study).

42https://www.conservationevidence.com/​actions/​1760

● Use prescribed fire to maintain or restore disturbance

43 Characteristic plants: One replicated before-and-after study in a fen in the UK reported that burning, along with other interventions, did not affect cover of fen-characteristic mosses or herbs.

44 Herb cover: One replicated, controlled study in a fen in the USA reported that burning reduced forb cover and increased sedge/rush cover, but had no effect on grass cover. One replicated before-and-after study in a fen in the UK reported that burning, along with other interventions, reduced grass/sedge/rush cover.

45 Tree/shrub cover: Two replicated studies in fens in the USA and the UK reported that burning, sometimes along with other interventions, reduced overall tree/shrub cover.

46 Overall plant richness/diversity: Two replicated, controlled studies in a fen in the USA and a bog in New Zealand found that burning increased plant species richness or diversity. However, one replicated before-and-after study in a fen in the UK reported that burning, along with other interventions, typically had no effect on plant species richness and diversity.

47 Assessment: unknown effectiveness – limited evidence (effectiveness 40%; certainty 35%; harms 20%). Based on evidence from: fens (two studies); bogs (one study).

48https://www.conservationevidence.com/​actions/​1763

6.7.3 Modified wild fire regime

No evidence found (no assessment)

49We have captured no evidence for the following interventions:

  • Thin vegetation to prevent wild fires
  • Rewet peat to prevent wild fires
  • Build fire breaks
  • Adopt zero burning policies near peatlands.

Lire

Open access

Acheter

Rechercher dans OpenEdition Search

Vous allez être redirigé vers OpenEdition Search