Canadian Forest Service Publications
Decline of an ecotone forest: 50 years of demography in the southern boreal forest. Birch, J. D., Lutz, J. A., Hogg, E. H., Simard, S. W., Pelletier, R., LaRoi, G. H., & Karst, J. (2019). Ecosphere, 10(4), e02698.
Issued by: Northern Forestry Centre
Catalog ID: 40416
Availability: PDF (download)
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Variation in tree recruitment, mortality, and growth can alter forest community composition and structure. Because tree recruitment and mortality events are generally infrequent, long-time scales are needed to confirm trends in forests. We performed a 50-yr demographic census of a forest plot located on the southern edge of the Canadian boreal forest, a region currently experiencing forest die-back in response to direct and indirect effects of recent severe droughts. Here, we show that over the last 30 yr biomass, basal area, growth, and recruitment have decreased along with a precipitous rise in mortality across the dominant tree species. The stand experienced periods of drought in combination with multiple outbreaks of forest tent caterpillar (Malacosoma disstria) and bark beetles. These insect disturbances interacted to increase mortality rates within the stand and decrease stand density. The interaction of endogenous and exogenous factors may shift forests in this region onto novel successional trajectories with the possibility of changes in regional vegetation type.
Plain Language Summary
Forest community composition and structure can be affected by factors such as variation in tree recruitment, mortality and growth. Long-time scales are used to confirm trends in forests because tree recruitment and mortality events are infrequent. We performed a 50-yr analysis of a forest plot located on the southern edge of the Canadian boreal forest. Over the last 30 years, biomass, area, growth and recruitment have decreased along with an increase in mortality across the main tree species. Disturbances such as periods of drought and insect outbreaks interacted to increase mortality rates and decrease density in this stand. We present evidence suggesting that in response to recent drought and warming, a different successional pathway has developed in some tree stands along the southern edge of the western Canadian boreal forest. Continued monitoring of long-term plots will help identify change and trends within the Canadian boreal forest.