The natural revegetation of a harvested peatland in southern Quebec: A spatial and dendroecological analysis

In North America peat has been harvested for horticultural use since the beginning of the 20th century. Many peatlands are now abandoned after decades of mining, and natural revegetation of pear occurs. To document the revegetation patterns of these bare organic surfaces, we studied the Cacouna-Station bog which is representative of abandoned peatlands in Quebec (Canada). The Cacouna-Station bog is characterized by mined trenches (block-cut) alternating with raised balks, and by sections which were bulldozed for harvesting with modem methods i.e. vacuum. Three sections within the peatland were selected to study the spatial distribution of plants, according to the vegetation structure and harvesting method. Trees were sampled to describe establishment patterns in each section. Twenty years after abandonment, the block-cut trenches were well-revegetated (> 50% plant cover) by typical peatland species. However, Sphagnum species are much more common in natural conditions than at Cacouna-Station, where they are restricted to a small portion of the peatland. Moisture deficit in the upper pear layer likely explains this situation. Additional drainage contributed to lower the water table in the bulldozed section where Betula populifolia proliferated. Tree species were unable to establish during harvesting activities. In the trenches, however, there was a sharp rise in the number of Larix laricina seedlings, two years after mining was abandoned. This 2-year lag is possibly related to the occurrence of a good year for seed production. Height and diameter data from tamarack and birch growing in the trenches suggest that seedlings were suppressed under the dense ericaceous shrub cover. The scarcity of Sphagnum and mosses in the majority of trenches along with the absence of a new acrotelm indicate that the Cacouna-Station bog is not returning to a functional peatland ecosystem.