Peatland Ecology Research Group (PERG)
Université Laval
 
Scope
 
Natural regeneration of mined peatlands 1994


Leader
Team
Description
Peatlands have been mined for several decades for the extraction of horticultural peat. Some sites are well revegetated, while others are devoid of vegetation many years after abandonment.

The peat extraction method has a marked influence on the degree of regeneration. Peatlands harvested by cutting (prior to 1970) are rapidly recolonized by typical peatland species, compared to vacuum-harvested sites. However, in both cases, sphagnum mosses are rare, a situation that can be explained by unfavourable hydrological conditions. In vacuum-harvested sites, poor revegetation can be explained by a combination of factors, including peat desiccation and oxidation, erosion, frost heaving, and problems associated with seed and spore dispersal.



Block-cutting of peat, Isle-Verte, Bas-Saint-Laurent  (from Risi et al. 1954).


 



Vacuum-mined bog with poor regeneration, Rivière-du-Loup, Bas-Saint-Laurent  (Photo: C. Lavoie).



The abandonment sequence also strongly influences the recolonization process. The abandonment of a plot surrounded by areas still under exploitation favours mass invasion by trees and prevents the reintroduction of Sphagnum mosses.


Cacouna peatland: maximum exploitation, 1963 (Photo: M. Girard).




Cacouna peatland: revegetation state in 1990. Block cut stopped around 1974 and vaccumed section abandoned in 1989 (Photo: M. Girard).



In sites where spontaneous regeneration occurs, there is indications that some functions of the ecosystem are coming back. Microbial activity re-establishes itself slowly and we measure, in the Sphagnum cover, some characteristics similar to those of the acrotelm of natural peatlands. On the other hand, bird species in vacuum-harvested sites that regenerate naturally differ from those present in non-exploited neighbouring plots, even after several years.

Invasive species in mined peatlands

Although most vacuum-harvested bogs are devoid of plant species, some sites are massively invaded by birches (Betula spp.) and cotton-grass (Eriophorum vaginatum). Invasion by birch appears to be a temporary phenomenon: tree decline is observed in most sites several years after establishment. Cotton-grass invasion could be perceived as beneficial as it stabilizes the peat surface and creates a more humid environment which should, in theory, help the establishment of other peatland plants. However, this plant also creates other problems, such as precipitation interception and greenhouse gas emissions. We are trying to determine which invasions are beneficial or detrimental to recently restored sites. We are monitoring on a yearly basis (since 1998) a peatland invaded by cotton-grass (St-Henri-de-Lévis, Québec) and since 2003 a restored bog massively invaded by birches (Maisonnette, New Brunswick).


Vacuum-mined bog invaded by birches, Cacouna, Bas-Saint-Laurent  (Photo: C. Lavoie).




Part of a restored peatlands dominated by cotton-grass (Eriophorum vaginatum), Bois-des-Bel, Bas-Saint-Laurent (Photo: J.M. Waddington).



For more information about works on bog natural regeneration, invasive species or conservation, see the Research Laboratory on Invasive Plants (LAREPE).

Reference:
Risi, J., C. E. Brunette and H. Girard. 1954. Étude chimiques des tourbes du Québec. VI-Tourbière Small Tea Field. VII-Tourbière Large Field. Province de Québec, Ministère des mines, Services des Laboratoires. Report No 301.


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