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Articles containing the keyword 'Choristoneura fumiferana'

Category : Article

article id 5595, category Article
R.A. Fleming. (1996). A mechanistic perspective of possible influences of climate change on defoliating insects in North America's boreal forests. Silva Fennica vol. 30 no. 2–3 article id 5595. https://doi.org/10.14214/sf.a9240
Keywords: climate change; disturbance regimes; boreal forest dynamics; Abies balsamea; natural selection; North America; Choristoneura fumiferana; insect outbreaks; phenological relationships; plant quality; extreme weather; thresholds
Abstract | View details | Full text in PDF | Author Info

There is no doubt that tree survival, growth, and reproduction in North America's boreal forests would be directly influenced by the projected changes in climate if they occur. The indirect effects of climate change may be of even greater importance, however, because of their potential for altering the intensity, frequency, and perhaps even the very nature of the disturbance regimes which drive boreal forest dynamics. Insect defoliator populations are one of the dominating disturbance factors in North America's boreal forests and during outbreaks trees are often killed over vast forest areas. If the predicted shifts in climate occur, the damage patterns caused by insects may be considerably changed, particularly those of insects whose temporal and spatial distributions are singularly dependent on climatic factors. The ensuing uncertainties directly affect depletion forecasts, pest hazard rating procedures, and long-term planning for pest control requirements. Because the potential for wildfire often increases in stands after insect attack, uncertainties in future insect damage patterns also lead to uncertainties in fire regimes. In addition, because the rates of processes key to biogeochemical and nutrient recycling are influenced by insect damage, potential changes in damage patterns can indirectly affect ecosystem resilience and the sustainability of the multiple uses of the forest resource.

In this paper, a mechanistic perspective is developed based on available information describing how defoliating forest insects might respond to climate warming. Because of its prevalence and long history of study, the spruce budworm, Choristoneura fumiferana Clem. (Lepidoptera: Tortricidae), is used for illustrative purposes in developing this perspective. The scenarios that follow outline the potential importance of threshold behaviour, historical conditions, phenological relationships, infrequent but extreme weather, complex feedbacks, and natural selection. The urgency of such considerations is emphasized by reference to research suggesting that climate warming may already be influencing some insect lifecycles.

  • Fleming, E-mail: rf@mm.unknown (email)

Category : Research article

article id 382, category Research article
Steen Magnussen, René I. Alfaro, Paul Boudewyn. (2005). Survival-time analysis of white spruce during spruce budworm defoliation. Silva Fennica vol. 39 no. 2 article id 382. https://doi.org/10.14214/sf.382
Keywords: mortality; hazard rates; defoliation stress index; Cox proportional hazard regression; Choristoneura fumiferana
Abstract | View details | Full text in PDF | Author Info
Mortality and defoliation (DF%) in 987 white spruce (Picea glauca (Moench) Voss) trees were followed from 1992 to 2003 during an outbreak of the spruce budworm Choristoneura fumiferana (Clem.) in 15 white-spruce-dominated uneven-aged stands in the Fort Nelson Forest District near Prince George, British Columbia. Four stands were aerially sprayed with Bacillus thuringiensis (Bt). Defoliation and mortality levels were elevated in non-sprayed stands. The relationship between defoliation and survival-times was captured in a Cox proportional hazard model with a defoliation stress index (DSI), diameter (DBH), crown class (CCL), a random stand effect, Bt-treatment, and number of years of exposure to stand-level defoliation (DYEAR) as predictors. The DSI, optimized for discrimination between survivors and non-survivors, is the discounted sum of five lagged DF% values. Survival probabilities were predicted with a maximum error of 0.02. Hazard rates increased by 0.06 for every one point increase in DSI. CCL and random stand effects were highly significant. Bt-treatment effects were fully captured by DSI, CCL, and DYEAR.
  • Magnussen, Canadian Forest Service, Victoria, BC, Canada. V8Z 1M5 E-mail: smagnussen@pfc.forestry.ca (email)
  • Alfaro, Canadian Forest Service, Victoria, BC, Canada. V8Z 1M5 E-mail: ria@nn.ca
  • Boudewyn, Canadian Forest Service, Victoria, BC, Canada. V8Z 1M5 E-mail: pb@nn.ca

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