Picea mariana (Mill.) B.S.P Plantation on Cutover Peatland in Alberta (Canada): Evaluating the Effect of Fertilization and Resulting Carbon Stocks

Horticultural peat extraction in Canada is mainly performed by vacuum-harvesting, leading to a residual peat soil limited in nutrients and seed bank, which does not allow adequate plant recovery once extraction ceases. Restoration techniques have been designed for the rehabilitation of open bog areas in eastern Canada, but in western Canada many undisturbed peatlands have high cover of forest and the reintroduction of trees should be part of restoration goals. This study is focused on Picea mariana (Mill.) B.S.P (black spruce) plantation. Previous studies have shown that fertilization is needed, but the adequate dose of fertilizer to create the preferred habitat structures remains unclear. Fertilizer dose could also affect the colonization of non-target species such as Betula papyrifera (March.) and consequently microclimate conditions and competition could affect the growth of P. mariana. Results showed that a low dose of fertilizer (8.9 g/ bag) allowed P. mariana to establish while controlling the B. papyrifera colonization. Higher rates of fertilization resulted in dense B. papyrifera communities having a direct effect on photosynthetically active radiation and relative humidity at ground level. Black spruce plantation on cutover peat will also affect the site's carbon (C) balance. The C balance was estimated using the C stock in biomass of the forest plantation and soil respiration measurement (CO2 and CH4). Although B. papyrifera fixed C though biomass, they also may influence the site hydrology by higher evapotranspiration. After seven years post-restoration, the study site was a source of C due to dry conditions and lack of understory, resulting in peat oxidation. These results can be used to assist in the choice of suitable treatments when the restoration goal is the recovery of ecological functions in cutover peatlands.