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What Works in Conservation 2018

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

6. Peatland conservation

6.8. Threat: Invasive and other problematic species

Texte intégral

1This section includes evidence for the effects of interventions on peatland vegetation overall. Studies that only report effects on the target problematic species are, or will be, summarized in separate chapters (like Chapter 10).

6.8.1 All problematic species

No evidence found (no assessment)

2We have captured no evidence for the following intervention:

3• Implement biosecurity measures to prevent introductions of problematic species.

6.8.2 Problematic plants

Trade-off between benefit and harms

● Use prescribed fire to control problematic plants

4 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.

5 Moss cover: One replicated, paired, controlled study in bogs in Germany found that burning increased moss/lichen/bare ground cover in the short term (2–7 months after burning). Three replicated, paired studies in one bog in the UK found that moss cover (including Sphagnum) was higher in plots burned more often.

6 Herb cover: Four replicated, paired studies (two also controlled) in bogs in Germany and the UK examined the effect of prescribed fire on cottongrass Eriophorum spp. cover. One found that burning had no effect on cottongrass cover after 2–7 months. One found that burning increased cottongrass cover after 8–18 years. Two reported that cottongrass cover was similar in plots burned every 10 or 20 years. The study in Germany also found that burning reduced cover of purple moor grass Molinia caerulea after 2–7 months but had mixed effects, amongst sites, on cover of other grass-like plants and forbs.

7 Tree/shrub cover: Four replicated, paired studies (two also controlled) in bogs in Germany and the UK found that burning, or burning more often, reduced heather Calluna vulgaris cover. Two replicated, controlled studies in the bogs in Germany and fens in the USA found that burning, sometimes along with other interventions, had no effect on cover of other woody plants.

8 Vegetation structure: One replicated, paired, controlled study in a bog in the UK found that plots burned more frequently contained more biomass of grass-like plants than plots burned less often, but contained less total vegetation, shrub and bryophyte biomass.

9 Overall plant richness/diversity: Two replicated, controlled studies in fens in the USA and a bog in the UK found that burning reduced or limited plant species richness. In the USA, burning was carried out along with other interventions.

10 Assessment: trade-off between benefit and harms (effectiveness 45%; certainty 40%; harms 20%). Based on evidence from: bogs (five studies); fens (one study).

11https://www.conservationevidence.com/​actions/​1774

Unknown effectiveness (limited evidence)

● Physically remove problematic plants

12 Characteristic plants: One replicated, randomized, controlled study in a fen in Ireland reported that cover of fen-characteristic plants increased after mossy vegetation was removed.

13 Herb cover: Three replicated, controlled studies in fens in the Netherlands and Ireland reported mixed effects of moss removal on herb cover after 2–5 years. Results varied between species or between sites, and sometimes depended on other treatments applied to plots.

14 Moss cover: One replicated, randomized, controlled study in a fen in Ireland reported that removing the moss carpet reduced total bryophyte and Sphagnum moss cover for three years. Two replicated, controlled, before-and-after studies in fens in the Netherlands reported that removing the moss carpet had no effect on moss cover 2–5 years later in wet plots, but reduced total moss and Sphagnum cover in drained plots.

15 Overall plant richness/diversity: One replicated, controlled, before-and-after study in a fen in the Netherlands reported that removing moss from a drained area increased plant species richness, but that there was no effect in a wetter area.

16 Assessment: unknown effectiveness – limited evidence (effectiveness 48%; certainty 35%; harms 12%). Based on evidence from: fens (three studies).

17https://www.conservationevidence.com/​actions/​1768

● Use cutting/mowing to control problematic herbaceous plants

18 Plant community composition: Two replicated, randomized, paired, controlled, before-and-after studies in rich fens in Sweden found that mowing typically did not affect plant community composition. One controlled study in a fen meadow in the UK reported that mown plots developed different communities to unmown plots.

19 Characteristic plants: One replicated, randomized, paired, controlled, before-and-after study in a fen in Sweden found that mown plots contained more fen-characteristic plant species than unmown plots, although their overall cover did not differ significantly between treatments.

20 Vegetation cover: Of two replicated, randomized, paired, controlled, before-and-after studies in rich fens in Sweden, one found that mowing had no effect on vascular plant or bryophyte cover over five years. The other study reported that mowing typically increased cover of Sphagnum moss and reduced cover of purple moor grass Molinia caerulea, but had mixed effects on cover of other plant species.

21 Growth: One replicated, controlled, before-and-after study in a bog in Estonia found that clipping competing vegetation did not affect Sphagnum moss growth.

22 Assessment: unknown effectiveness – limited evidence (effectiveness 40%; certainty 35%; harms 10%). Based on evidence from: fens (two studies); fen meadows (one study); bogs (one study).

23https://www.conservationevidence.com/​actions/​1770

● Change season/timing of cutting/mowing

24 Plant community composition: One replicated, randomized, paired, before-and after study in a fen meadow in the UK reported that changes in plant community composition over time were similar in spring-, summer- and autumn-mown plots. One study in a peatland in the Netherlands reported that summer-and winter-mown areas developed different plant community types.

25 Overall plant richness/diversity: One replicated, randomized, paired, before-and after study in a fen meadow in the UK found that plant species richness increased more, over two years, in summer-mown plots than spring-or autumn-mown plots.

26 Assessment: unknown effectiveness – limited evidence (effectiveness 50%; certainty 25%; harms 10%). Based on evidence from: fen meadows (one study); mixed peatlands (one study).

27https://www.conservationevidence.com/​actions/​1771

● Use cutting to control problematic large trees/shrubs

28 Plant community composition: Two studies (one replicated, controlled, before-and-after) in fens in the USA and Sweden reported that the plant community composition changed after removing trees/shrubs to less like unmanaged fens or more like undegraded, open fen.

29 Characteristic plants: One study in a fen in Sweden found that species richness and cover of fen-characteristic plants increased after trees/shrubs were removed.

30 Vegetation cover: One study in a fen in Sweden found that bryophyte and vascular plant cover increased after trees/shrubs were removed. One replicated, controlled, before-and-after study in fens in the USA found that removing shrubs, along with other interventions, could not prevent increases in total woody plant cover over time.

31 Overall plant richness/diversity: One study in a fen in Sweden found that moss and vascular plant species richness increased after trees/shrubs were removed. However, one replicated, controlled, before-and-after study in fens in the USA found that removing shrubs, along with other interventions, prevented increases in total plant species richness.

32 Assessment: unknown effectiveness – limited evidence (effectiveness 60%; certainty 30%; harms 15%). Based on evidence from: fens (two studies).

33https://www.conservationevidence.com/​actions/​1772

● Use herbicide to control problematic plants

34 Plant community composition: One replicated, controlled, before-and-after study in fens in the USA found that applying herbicide to shrubs, along with other interventions, changed the overall plant community composition.

35 Tree/shrub cover: The same study found that applying herbicide to shrubs, along with other interventions, could not prevent increases in total woody plant cover over time.

36 Overall plant richness/diversity: The same study found that applying herbicide to shrubs, along with other interventions, prevented increases in plant species richness.

37 Assessment: unknown effectiveness – limited evidence (effectiveness 20%; certainty 20%; harms 30%). Based on evidence from: fens (one study).

38https://www.conservationevidence.com/​actions/​1776

● Introduce an organism to control problematic plants

39 Plant community composition: One controlled, before-and-after study in a fen meadow in Belgium found that introducing a parasitic plant altered the plant community composition.

40 Vegetation cover: The same study found that introducing a parasitic plant reduced cover of the dominant sedge Carex acuta but increased moss cover.

41 Overall plant richness/diversity: The same study found that introducing a parasitic plant increased overall plant species richness.

42 Assessment: unknown effectiveness – limited evidence (effectiveness 40%; certainty 20%; harms 15%). Based on evidence from: fen meadows (one study).

43https://www.conservationevidence.com/​actions/​1777

No evidence found (no assessment)

44We have captured no evidence for the following interventions:

  • Physically damage problematic plants
  • Use grazing to control problematic plants
  • Use covers/barriers to control problematic plants.

6.8.3 Problematic animals

Unknown effectiveness (limited evidence)

● Exclude wild herbivores using physical barriers

45 Vegetation cover: One replicated, paired, controlled study in a fen meadow in Poland reported that the effect of boar-and deer exclusion on vascular plant and moss cover depended on other treatments applied to plots.

46 Vegetation structure: The same study reported that the effect of boar-and deer exclusion on total vegetation biomass depended on other treatments applied to plots.

47 Overall plant richness/diversity: The same study reported that the effect of boar-and deer exclusion on plant species richness depended on other treatments applied to plots.

48 Assessment: unknown effectiveness – limited evidence (effectiveness 30%; certainty 25%; harms 10%). Based on evidence from: fen meadows (one study).

49https://www.conservationevidence.com/​actions/​1860

No evidence found (no assessment)

50We have captured no evidence for the following intervention:

51• Control populations of wild herbivores.

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