Ecological Modifications Caused by the Removal of Tree and Shrub Canopies in the Mackenzie Delta

Résumé

Environmental and floristic evidence is presented to show that after removal of the white spruce (Picea glauca) and willow-alder (Salix spp.-Alnus crispa) canopies from exposed sites in the Mackenzie River Delta, Northwest Territories, environmental degradation is such that secondary succession of low-arctic tundra heath, moss and lichen species takes place. The extreme exposure of cleared sites enables a hardy group of tundra plants to compete with the local flora and invade the previously forested location. Site degeneration is further evidenced by turf hummocks and a characteristic "hummock-type" active layer configuration that developed within only 20 years after clear-cutting.