Canadian Forest Service Publications
Ponderosa pine forest dynamics at the northern extent of the species range. 2011. Arsenault, A.; Vyse, A.; Barton, K. Abstract. Page 298 in Anonymous. Proceedings of Plant Canada 2011: Plant Adaptation to Environmental Change. Joint meeting of the Canadian Society of Agronomy, Canadian Society of Horticultural Science, Canadian Society of Plant Physiologists, Canadian Botanical Association, Canadian Phytopathological Society, and Canadian Wee Science Society. 17-21 July 2011, Halifax, NS.
Available from: Atlantic Forestry Centre
Catalog ID: 33339
Ponderosa pine forests reach their northern limit in British Columbia where they are considered at risk due to the cumulative effects of anthropogenic disturbances, urban encroachment and agriculture. Surprisingly, very little research has been done on the dynamics of this unique Canadian ecosystem. The drought of 2003 and a subsequent severe bark beetle outbreak are rapidly changing the Ponderosa pine forests of southern British Columbia. We studied the effect of the beetle outbreak and the historical dynamics of Ponderosa pine forests using age distributions in 12 one kilometre transects in the Thompson valley west of Kamloops. Mountain pine beetle mortality was severe with over 95% of ponderosa pine larger than 30 cm in diameter killed on all transects over a three year period. Two distinct age structures were discernible. Most of the areas that were easily accessible by roads or trails had a cohort of trees that regenerated between 1880 and 1910 suggesting there was widespread severe disturbance. This is supported by historical records which indicate that there was logging throughout the range of ponderosa pine in the province at that time. However the stands that were in more remote locations exhibited an all-age distribution. Stands with little regeneration will likely shift to a grassland phase, while adjacent patches of grasslands with Ponderosa pine trees encroaching on them will likely be the future Ponderosa pine forest. We propose that Ponderosa pine forests and adjacent grasslands may form a shifting ecotone mosaic, alternating in dominance through space and time as a result of complex responses to variation in climate and disturbance history.