PARENT SESSION
Contributed Oral Session 130: Forest Infestations and Mortality
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 514 A, Level 5, Palais des congrès de Montréal
Elevated mortality of residual trees following single-tree felling in northern hardwood forests.
Caspersen, John*,1, 1 Faculty of Forestry, University of Toronto, Toronto, Ontario, Canada
ABSTRACT- It is widely recognized that residual trees in partially harvested stands are subject to damage caused by logging, and also to stress caused by sudden changes in light, temperature, humidity, soil moisture, and wind exposure. However, few studies have examined the long-term, population-level consequences of harvesting on residual trees. In this paper, I examine tree mortality in northern hardwood forests subject to single-tree felling. My analysis is designed to quantify three separate sources of mortality, including mortality caused by 1) natural processes, 2) intentional felling of trees, and 3) stress and/or felling damage to residual trees (post-cut mortality). Taken as an average across all merchantable tree sizes (> 9.1 cm DBH), the long-term rate of mortality due to natural causes was 1.5% per year. The intentional felling of trees increased the annual average rate of mortality to 3.1%, and post-cut mortality of residual trees increased the average an additional 0.2% to 3.3%. Thus, from a population-level perspective, the increased mortality caused by stress and/or felling damage to residual trees was small compared to both natural mortality and tree felling. However, the long-term population average obscures more dramatic transient effects of felling on small residual trees ( < 10 cm DBH), for which mortality risk increased by as much as 5% immediately after felling. This increase is several times greater than the natural mortality rate for small trees, and may therefore have a substantial impact on stand structure and community dynamics. Thus, any assessment of the adverse impacts of selection silviculture must account for the unintended effects of tree felling on small residual trees.
Key words: Tree mortality, selection silviculture, logging damage, post-harvest mortality