FERTILIZING AND MULCHING INFLUENCE ON THE PERFORMANCE OF 4 NATIVE WOODY SPECIES SUITABLE FOR REVEGETATION IN SUB-ARCTIC QUEBEC

Two plantations were established in the village of Whapmagoostui-Kuujjuaraapik to determine the effects of two types of fertilizer (fast or slow release) and two types of mulch (plastic or organic) on native woody species growth and survival in subarctic Quebec. In the first plantation, the species tested were Salix planifolia Pursh, Alnus crispa (Ait.) Pursh, Picea glauca (Moench) Voss, and Pinus banksiana Lamb. Four growing seasons after planting, cuttings of S. planifolia had the highest survival of all four species (96% in control plots) and a very good growth (4.8 mm and 5.7 cm growth in diameter and height, respectively). The performance of A. crispa was also very good (77% survival in control plots; 5.1 mm and 7.5 cm growth in diameter and height, respectively), while Picea glauca (17% survival in control plots; 0.6 mm and -9.0 cm growth in diameter and height, respectively) and Pinus banksiana (31% survival in control plots; 2.4 mm and 5.7 cm growth in diameter and height, respectively) performance was poor. The application of a slow-release fertilizer enhanced plant growth of all four species, but reduced the survival of A. crispa, particularly when a plastic mulch was used. Otherwise, mulching had no significant effect on either growth or survival of any of the other species. In the second plantation, established on a more exposed site, the survival of S. planifolia was lower (77% in control plots) than in the first plantation, and the application of a fast-release fertilizer there had a negative effect on plant growth. These latter results appear to be related to freezing injuries and winter killing of vegetative buds. Organic mulching did not influence plant growth on this second site, but the utilization of Alnus wood chips increased the survival of S. planifolia cuttings. We recommend the use of S. planifolia and also of A. crispa for revegetation purposes in subarctic Quebec. Application of a slow-release fertilizer can increase plant growth, but should not be combined with the use of plastic mulches, as plant survival is then negatively affected.