Comprendre la mecanique du processus de recolonisation vegetale des tourbieres exploitees (French text)

The recolonization of abandoned milled bogs is poor. In an attempt to understand the underlying reasons, the recolonization process was considered as a series of environmental filters which selectively allows the survival of only those species with suitable autecological traits. Study species were the most common mosses and vascular plants in milled or abandoned milled bogs in Québec. A first study examined the relative immigration potential of study species to milled bogs. Study species differ markedly in terms of their populations in edges of milled bogs, maximum fecundity and dispersal potential by wind, water or animals. Overall, several species of mosses, ericaceous shrubs and trees have high potential to immigrate to milled bogs. A second study focussed on the stability of milled peat surfaces. Three aspects were examined: the wind erosion potential of peats as a function of their degree of decomposition, the surface roughness lengths of milled peatlands, and the stability of milled peat substrates in the field. Milled peats are highly prone to wind erosion when loose, especially the less decomposed peats. However, once a light crust is formed, they are all stable. Insignificant wind erosion was also observed in the field in spite of very low roughness lengths. However, milled surfaces are very unstable, apparently as a result of seasonal freeze-thaw action. A third study examined the germination and establishment potential of vascular plants, first by examining seedling emergence as a function of seed burial depth and second by measuring their seedling growth rates. Burial sensitivity and root performance were functions of seed mass while relative growth rate could be predicted by seedling specific leaf area. The final study brought elements of previous studies together to determine whether a trait-based approach could be used to predict and better understand natural recolonisation of milled peatlands. For all species and vascular plants alone, abundance of species in edges of milled bogs and edge bias relative to milled edges were independent causes of recolonisation. Propagule wing loading for all species and propagule fall time for vascular plants were also important. The restoration of abandoned milled peatlands should benefit from this better understanding of the recolonisation process.