Populus tremuloides Michx. postfire stand dynamics in the northern boreal-cordilleran ecoclimatic region of central Yukon Territory, Canada

Postfire vegetation development among 8–185-year-old stand was assessed based on 100 relevés from the northern boreal-cordilleran ecoclimatic region (61–63°N) in the central Yukon Territory, Canada. Vegetation sampling included only stands thought to have originated from postfire Populus tremuloides Michx. regeneration that occurred on well drained and low gradient sites. Seven vegetation types were recognized based on cluster analysis and Kruskal–Wallis testing. Relevé ordination using Detrended Correspondence Analysis (70% explained variance) indicated six of the vegetation types represented a secondary successional chronosequence, based on their juxtaposition and a strong correlation of the primary axis with stand age ( r = 0.89, P < 0.001). No correlation ( P > 0.05) occurred between stand location and age. The youngest vegetation (8–11 years) had a moderate cover of P. tremuloides and Salix spp. up to 5 m tall, with a ground cover of Ceratodon purpureus (Hedw.) Brid. and Bryum caespiticium Hedw. This vegetation was expected to result in P. tremuloides, mixed P. tremuloides and Picea glauca (Moench) Voss, and P. glauca/Hylocomium splendens forest stands with increasing age, respectively. P. tremuloides// Calamagrostis purpurascens— Arctostaphylos uva-ursi stands formed the mid-seral vegetation. Along the chronosequence, total tree, P. tremuloides, shrub, and herb cover peaked 50–70 years after stand initiation; P. glauca cover, total and nonvascular species richness, and dominance concentration gradually increased ( P < 0.001); vascular plant richness decreased; bryophytes had a U-shaped abundance pattern; and total plant cover was constant through time (∼125%). Richness totalled 113 species with averages of 13–18 per relevé. Coarse woody debris was most abundant (maxima 100–223 m 3/ha) during the first 20 years of stand development then declined to