Climate change is predicted to increase rates of fire activity in boreal forests. A shortened fire return interval may result in different outcomes of community structure in the northern boreal forest, since the age of a forest influences seed production and potential post-fire regeneration. With two closely timed fires, dominant boreal conifers such as black spruce (Picea mariana) may be vulnerable to regeneration failures after fire because of the long time required to reach reproductive maturity. I report on the relationship between stand age and seed productivity of black spruce in northern Yukon Territory and central Alaska. I used fire history maps to select sites of various stand ages, including stand ages that would occur in a short fire return interval (less than 80 years) versus longer fire intervals (up to 200 years). At each site, I measured stand density and basal area using the point-center-quarter method. Ten black spruce trees were randomly selected for cone surveys and age analysis. I also selected a subset of five trees for detailed analyses of cone and seed production within yearly cohorts. The results of this study illustrate the strong relationships between stand age and stand basal area with cone and seed production of northern black spruce. The resulting equations can be used to predict the seed capacity and regeneration potential of black spruce stands with known stand basal area or stand age. I estimate, along with the number of seeds required to produce a two year old black spruce seedling on high quality seedbeds, stands burned at an age less than 50 years will likely have reduced black spruce post-fire density. On low quality seedbeds, black spruce forests are more vulnerable to regeneration failures and fire cycles less than 150 years are likely to result in reduced recruitment. Under a shortened fire return interval these northern black spruce forests are likely to have reduced post-fire density.

Climate change is predicted to increase rates of fire activity in boreal forests. A shortened fire return interval may result in different outcomes of community structure in the northern boreal forest, since the age of a forest influences seed production and potential post-fire regeneration. With two closely timed fires, dominant boreal conifers such as black spruce (Picea mariana) may be vulnerable to regeneration failures after fire because of the long time required to reach reproductive maturity. I report on the relationship between stand age and seed productivity of black spruce in northern Yukon Territory and central Alaska. I used fire history maps to select sites of various stand ages, including stand ages that would occur in a short fire return interval (less than 80 years) versus longer fire intervals (up to 200 years). At each site, I measured stand density and basal area using the point-center-quarter method. Ten black spruce trees were randomly selected for cone surveys and age analysis. I also selected a subset of five trees for detailed analyses of cone and seed production within yearly cohorts. The results of this study illustrate the strong relationships between stand age and stand basal area with cone and seed production of northern black spruce. The resulting equations can be used to predict the seed capacity and regeneration potential of black spruce stands with known stand basal area or stand age. I estimate, along with the number of seeds required to produce a two year old black spruce seedling on high quality seedbeds, stands burned at an age less than 50 years will likely have reduced black spruce post-fire density. On low quality seedbeds, black spruce forests are more vulnerable to regeneration failures and fire cycles less than 150 years are likely to result in reduced recruitment. Under a shortened fire return interval these northern black spruce forests are likely to have reduced post-fire density.

Conserving structural and compositional diversity in Fescue Prairie requires reintroducing natural disturbances according to their historic regime. Fire is an important natural process that may be a source of spatial heterogeneity in Fescue Prairies. The effects of burning in all months of the year except January and February were evaluated in a Fescue Prairie in central Saskatchewan for 6 years following burning on 2 sites that had not been previously burned and 2 sites that had been burned 5 years earlier. Except for burning in March, burning reduced cover of litter (P<0.01) and <i>Festuca hallii </i> (Vasey) Piper (P=0.01) while increasing bare soil (P<0.01) for 1 to 5 years. Cover of <i>Elymus lanceolatus </i>(Scribn. & J.G. Sm.) Gould (P<0.01), graminoids (P=0.02), and species evenness (P=0.01) increased with burning frequency. Burning in late-summer reduced cover of graminoids (P=0.03), plants other than the dominant grasses (P=0.03), and total plant cover (P=0.02). Burning increased the spatial variance (s2) in litter cover (P<0.01) and bare soil (P<0.01) for 1 to 3 years. Aside from burning in early spring, burning reduced s2 in total standing crop (P=0.02) and <i>F. hallii</i> (P=0.01). Variability in the cover of <i>E. lanceolatus </i>(P<0.01) and graminoids (P=0.04) increased with burning frequency. Canonical correspondence analysis (CCA) indicated that pre-burn history had a dominant effect on plant community composition, explaining 13% of the variation (P<0.01). The cumulative effects of repeated burning, annual variability in weather, and exposure to temperature extremes may have caused a shift in the composition of the plant community. The first 4 ordination axes explained 22% of the variation in plant community composition after burning, indicating that many other environmental or site variables controlled community composition. A range of burning dates and frequencies should be reintroduced or maintained in Fescue Prairie to create a mosaic of plant communities in various stages of recovery after burning. A mosaic will increase the structural and compositional diversity in remnant Fescue Prairies.

Conserving structural and compositional diversity in Fescue Prairie requires reintroducing natural disturbances according to their historic regime. Fire is an important natural process that may be a source of spatial heterogeneity in Fescue Prairies. The effects of burning in all months of the year except January and February were evaluated in a Fescue Prairie in central Saskatchewan for 6 years following burning on 2 sites that had not been previously burned and 2 sites that had been burned 5 years earlier. Except for burning in March, burning reduced cover of litter (P<0.01) and <i>Festuca hallii </i> (Vasey) Piper (P=0.01) while increasing bare soil (P<0.01) for 1 to 5 years. Cover of <i>Elymus lanceolatus </i>(Scribn. & J.G. Sm.) Gould (P<0.01), graminoids (P=0.02), and species evenness (P=0.01) increased with burning frequency. Burning in late-summer reduced cover of graminoids (P=0.03), plants other than the dominant grasses (P=0.03), and total plant cover (P=0.02). Burning increased the spatial variance (s2) in litter cover (P<0.01) and bare soil (P<0.01) for 1 to 3 years. Aside from burning in early spring, burning reduced s2 in total standing crop (P=0.02) and <i>F. hallii</i> (P=0.01). Variability in the cover of <i>E. lanceolatus </i>(P<0.01) and graminoids (P=0.04) increased with burning frequency. Canonical correspondence analysis (CCA) indicated that pre-burn history had a dominant effect on plant community composition, explaining 13% of the variation (P<0.01). The cumulative effects of repeated burning, annual variability in weather, and exposure to temperature extremes may have caused a shift in the composition of the plant community. The first 4 ordination axes explained 22% of the variation in plant community composition after burning, indicating that many other environmental or site variables controlled community composition. A range of burning dates and frequencies should be reintroduced or maintained in Fescue Prairie to create a mosaic of plant communities in various stages of recovery after burning. A mosaic will increase the structural and compositional diversity in remnant Fescue Prairies.