Action: Excavate pools (without planting)
Key messagesRead our guidance on Key messages before continuing
- Two studies evaluated the effects of excavating pools (without planting) on peatland vegetation. Both studies were based on the same experimental set-up in bogs in Canada.
- Plant community composition (1 study): One replicated, before-and-after, site comparison study in bogs in Canada reported that excavated pools were colonized by peatland vegetation over 4–6 years, but contained different plant communities to natural pools. In particular, cattail was more common in created pools.
- Vegetation cover (1 study): One replicated, before-and-after, site comparison study in bogs in Canada reported that after four years, created pools had less cover than natural pools of Sphagnum moss, herbs and shrubs.
- Overall plant richness/diversity (1 study): One replicated, before-and-after, site comparison study in bogs in Canada reported that after six years, created pools contained a similar number of plant species to natural pools.
Peatlands may contain permanent pools which contribute to habitat diversity. However, these pools can be lost following drainage, peat harvesting or drought (Beadle et al. 2015). Pools may also be filled in naturally as vegetation develops and peat accumulates, so they may need to be re-excavated to maintain certain communities (van Diggelen et al. 1996). This section considers excavating pools in peatlands, then leaving vegetation to naturally recolonize.
Key peatland types where this action may be appropriate: bogs, fens/fen meadows, tropical peat swamps.
Related actions: rewetting, which may need to be done to fill created pools; introduce peatland vegetation, including introductions into created pools i.e. planting mosses, planting herbs, spreading moss fragments or spreading mixed vegetation fragments.
Beadle J.M., Brown L.E. & Holden J. (2015) Biodiversity and ecosystem functioning in natural bog pools and those created by rewetting schemes. WIREs Water, 2, 65–84.
van Diggelen R., Molenaar W.J. & Kooijman A.M. (1996) Vegetation succession in a floating mire in relation to management and hydrology. Journal of Vegetation Science, 7, 809–820.
Supporting evidence from individual studies
A replicated, before-and-after, site comparison study in 1999–2003 in four bogs in eastern Canada (Mazerolle et al. 2006) found that created pools developed vegetation cover within four years, but reported that this remained lower than cover in and around natural pools. Initially, the created pools contained no vegetation. After four years, Sphagnum moss cover had increased to 9% (vs 80% in natural pools), herb cover had increased to 5% (natural: 10%) and shrub cover had increased to 5% (natural: 27%). Comparisons with natural pools were not tested for statistical significance. In 1999, four 6 x 8.5 m pools were created in one historically mined bog by excavating and rewetting (blocking drainage ditches and building embankments). No vegetation was introduced to these, although the surrounding site was sown with bog vegetation fragments. In 2003, vegetation cover was recorded in 36 quadrats/pool, each 30 x 30 cm, along six bank-to-bank transects. Vegetation cover of 70 natural pools, in unmined parts of nearby bogs, was recorded in 1999 and 2000. This study was based on the same experimental set-up as (2).
A replicated, before-and-after, site comparison study in 1999–2005 in seven bogs in Quebec, Canada (Fontaine et al. 2007) reported that created pools developed a different plant community to natural pools, but with similar species richness. After six years, the overall composition of the plant community differed between created and natural pools (data reported as a turnover index and graphical analysis). In particular, cattail Typha latifolia was more frequent in created pools (occurring in 69% of quadrats) than natural pools (0% of quadrats). Sphagnum mosses, Eriophorum cottongrasses and Carex sedges were sometimes more abundant in restored pools and sometimes less abundant, depending on the species (see original paper). Created and natural pools both contained 24 plant species/0.5 m2. In 1999, four 6 x 12 m pools were created in a historically mined bog by excavating and rewetting (blocking drainage ditches and building embankments). In 2005, cover of every plant species was estimated in 0.5 m2 quadrats situated on pool margins: 12 quadrats around the created pools and 30 around pools in each of six natural, unmined bogs. This study was based on the same experimental set-up as (1).
- Mazerolle M.J., Poulin M., Lavoie C., Rochefort L., Desrochers A. & Drolet B. (2006) Animal and vegetation patterns in natural and man-made bog pools: implications for restoration. Freshwater Biology, 51, 333-350
- Fontaine N., Poulin M. & Rochefort L. (2007) Plant diversity associated with pools in natural and restored peatlands. Mires and Peat, 2, Article-6