Picea glauca dynamics and spatial pattern of seedlings regeneration along a chronosequence in the mixedwood section of the boreal forest

We studied Picea glauca dynamics in the boreal forest of Saskatchewan, Canada, using 35 stands ranging from < 1 to > 200 y after fire. We determined the spatial pattern and the importance of seedbed conditions to the recruitment of P. glauca. Basal area increased along the chronosequence peaking at 110 y after fire (51.5 m²ha^-1). The ratio of softwood to hardwood increased from 0.03 (16 y) to 17.0 (172 y). Picea glauca tree density increased with stand age, highest densities were observed in a 172 y stand (1413 stems ha^-1). Picea glauca dominated the canopy between 93 and 172 y after fire. Picea glauca snags appeared about 66 y after fire, and remained relatively low in density until 160 y. Saplings were present at varying densities along the chronosequence. Seedlings established immediately after fire and exhibited bimodality with lowest densities observed between 110 and 125 y. Analysis with Ripley's K, showed that seedlings were mainly distributed at random in young stands but were clumped at a distances < 12 m in old stands. In young stands, the majority of seedlings regenerated on the organic layer (LFH 73%), while recruitment was almost exclusively on logs in old stands (94%). Picea glauca regeneration depended on propagule availability and seedbed characteristics at early stand age. Logs and the resultant canopy gaps formed, appear to be critical for P. glauca regeneration in mature and old stands.