Spatiotemporal patterns of large-scale defoliation caused by the spruce budworm in Ontario since 1941

Abstract

Survey records of spruce budworm (Choristneura fumiferana Clem.) defoliation in Ontario, taken annually since 1941, were analysed using geographic information systems (GIS), spatial statistics, and time-series methods. Cumulative frequency maps indicated that the 41 × 106 ha of Ontario that had been defoliated in at least one year since 1941 could be split into three zones of frequent defoliation separated by two approximately 100 km wide, longitudinally oriented corridors of lower frequency. Analysis of annual records of the total area defoliated showed that the fluctuations in this time series are the result of a basic oscillation of approximately 36 years, which is modified by secondary fluctuations and occasionally by sharp drops. The secondary fluctuations are at least partially due to asynchrony in otherwise remarkably similar long-wave oscillations in the eastern (25.5 × 106 ha) and western (9.6 × 106 ha) zones of frequent defoliation. Analysis of this asynchrony showed that outbreaks in the eastern zone occurred 5 or 6 years before outbreaks in the central (6.6 × 106 ha) and western zones, which were synchronous. These observations contradict previous reports of the large-scale spread of outbreaks from west to east.

Lagged cumulative spruce budworm defoliation affects the risk of fire ignition in Ontario, Canada

“…Mixed forest fire cycles are longer (63-210 yr) and fire intensity is variable (Van Sleeuwen 2006). In this region, spruce budworm outbreaks recur approximately every 31-34 yr and typically occur 6 yr after outbreaks in the Abitibi Plains (Candau et al 1998).…”

Small changes in species composition despite stand-replacing bark beetle outbreak in Picea abies mountain forests

“…Although storm damage is the most important disturbance in temperate forests (Fischer et al 2013a), fire (Angelstam 1998;Ryan 2002) and insects, mainly bark beetles (Kulakowski et al 2003;McCarthy 2001;Nealis and Peter 2008) but also spruce budworm (Candau et al 1998), and their interactions (Kulakowski et al 2003) are most important in forests of the boreal zone worldwide. For the European boreal forests, Shorohova et al (2009) mentions fire and storms as the most important disturbances, with insects and fungal and bacterial diseases playing only a subordinate role, but according to Kuuluvainen (2014), at least in Finland, most of the fires in the past centuries have been started by man.…”

Spruce Budworm (Choristoneura fumiferana Clem.) Defoliation Promotes Vertical Fuel Continuity in Ontario’s Boreal Mixedwood Forest

“…), periodically erupts into large-scale outbreaks during which its favoured host species, balsam fir (Abies balsamea), and to a lesser extent white spruce (Picea glauca) and black spruce (Picea mariana), are defoliated and killed [1]. This insect is a major biotic disturbance throughout the boreal forest in the province of Ontario, Canada.…”

“…This insect is a major biotic disturbance throughout the boreal forest in the province of Ontario, Canada. During its last major outbreak (1977)(1978)(1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987), the spruce budworm defoliated roughly 20 million hectares in Ontario [1] and depleted an average of 35 million cubic meters of host tree wood volume annually in Canada [2]. Research points to a large-scale outbreak cycle of variable length averaging about 35 years [3] and lasting between five and fifteen years [2].…”

“…Research points to a large-scale outbreak cycle of variable length averaging about 35 years [3] and lasting between five and fifteen years [2]. Historical records showed that in Ontario the last major outbreak's peak in defoliated area occurred around 1980 [1].…”