Interaction between forest tent caterpillar and forest composition: role of predation in outbreak dynamics and effects on litter, soils and tree regeneration.
– Concordia University and Université du Québec en Abitibi-Témiscamingue (UQAT)
The forest tent caterpillar (FTC) is a frequent and significant defoliator of hardwood forests throughout Canada. Outbreaks are currently on the rise in Quebec, Ontario, Saskatchewan, Manitoba & Alberta, and cities including Rouyn-Noranda, Winnipeg and Regina are engaged in control programs. Historically, infestations usually collapsed after one or two years of defoliation, but recently longer and more severe outbreaks have been observed. These events have led to tree mortality in some regions, and in others FTC have been implicated as a factor leading to the decline of hardwood stands (e.g., quaking aspen). One side effect of a changing climate is that outbreaks of FTC may become more severe which could result in more significant mortality from a pest that previously was of little economic concern.
Outbreaking population dynamics imply dramatic variations in mortality rates. Research often focuses on the increase of mortality that terminates outbreaks, but factors involved in keeping endemic populations low have rarely been considered. Recent research suggests that while parasitoids and disease play a key role in outbreak collapses, generalist predators could be important in keeping endemic populations low. The current upsurge provides a good opportunity to build on this work by comparing predation rates in endemic (low density) and increasing populations. The hypothesis is that predation rates will be higher in endemic populations, high enough to keep the population down, but that they will be lower in high density populations due to predator saturation, removing this check from continued increase.
The objective of this project is to understand ecosystem processes in FTC outbreaks. Specifically, the role of predators in keeping down and ending outbreaks (upstream) and the effects of FTC population surges on soil processes, specifically arthropod communities and tree regeneration (downstream). This will be accomplished via monitoring during outbreaks presently occurring in two main FTC foci: Abitibi and Outaouais. Incorporating this information will improve the quality of modelling of forest tent caterpillar population dynamics.
Stay tuned for results