Principal components analysis, followed by K-means cluster analysis, was used to detect variation... more Principal components analysis, followed by K-means cluster analysis, was used to detect variations in the timing and magnitude of Pinus contorta Dougl. ex Loud. growth releases attributed to mountain pine beetle outbreaks in 31 stands of central British Columbia. Four major growth release patterns were identified from 1970 to 2000. Variations in the timing of growth releases among clustered stands corresponded well to aerial survey data indicating the timing of beetle outbreaks in the study area. Redundancy analysis was used to determine how variations in the timing and magnitude of growth releases attributed to beetle outbreaks changed with variations in climate or stand conditions over the study area. The first RDA axis, which accounted for 39% of the variations in growth patterns among stands, was significantly (P <0.05) correlated with gradients in the percentage of pine in stands killed by mountain pine beetle, summer aridity, variation in summer precipitation, distance from initial infestation site, average pine age, and maximum August temperatures. The second RDA axis explained 6% of the variations and was significantly correlated with gradients in the beetle climate suitability index, extreme cold month temperatures, and site index. Comparisons of growth release patterns with aerial survey data and redundancy analyses indicated that dendrochronological techniques are useful for identifying mountain pine beetle outbreaks in central British Columbia, particularly among stands that had a density high enough to produce a growth release signal. Provided future studies account for interannual weather fluctuations, identification of growth increases due to stand thinning caused by beetle outbreaks will be useful for reconstructing the history of beetle outbreaks over much longer time periods.
Canadian Journal of Forest Research-revue Canadienne De Recherche Forestiere, 2001
... Picea sitchensis (Bong.) Carrière) trees. The trees that had been selected as early or late f... more ... Picea sitchensis (Bong.) Carrière) trees. The trees that had been selected as early or late flushing were subjected to artificial wounding to simulate attack by the white pine weevil, Pissodes strobi (Peck). Samples were taken at ...
Canadian Journal of Forest Research-revue Canadienne De Recherche Forestiere, 1996
ABSTRACT The intensity of the traumatic resin response in white spruce, Picea glauca (Moench) Vos... more ABSTRACT The intensity of the traumatic resin response in white spruce, Picea glauca (Moench) Voss, to attack by the white pine weevil, Pissodes strobi Peck, was studied in trees with different severities of attack. The response level was highest in trees where the attacks failed, i.e., where eggs were laid but the brood was killed and no adults emerged. Successfully attacked trees had, on average, only 62% of the response intensity of trees with failed attacks. Response intensity in trees that had been subjected only to feeding was much lower, at 42% of the failed attack response. Healthy unattacked trees showed no or little traumatic resin response. Response intensity varied in a nonlinear fashion with the number of eggs laid, increasing rapidly from zero in healthy trees, being highest in trees having between 10 and 60 egg punctures, and progressively lower again in trees with higher numbers of egg punctures. For a given number of egg punctures, resistant white spruce trees had a consistently higher traumatic resin response than susceptible trees. The number of eggs laid on a leader was inversely related to the intensity of the traumatic resin response and to the timing of the attack. Fewer eggs were laid on leaders with high traumatic resin response or attacked late in the season than on leaders with lower resin response or attacked early in the season.
The historical pattern of outbreaks of the spruce budworm, Choristoneura fumiferana (Clem.), in w... more The historical pattern of outbreaks of the spruce budworm, Choristoneura fumiferana (Clem.), in white spruce stands in the Fort Nelson Forest District of northeastern British Columbia was reconstructed with the use of dendrochronology. Outbreaks occurred on an average every 26 years, with 5–6 outbreaks in the past century in the northern regions of the district, while southern regions experienced between 0 (the most southern sites) and 4 outbreaks. In the northern regions, outbreaks began about 10 years earlier and the period of defoliation was longer than in the southern regions of the district. The southern limit of the range of the spruce budworm in British Columbia is marked by the predominance of the Montane Boreal White and Black Spruce biogeoclimatic subzone that has cool and wet summers that may not favor budworm development. Therefore, outbreaks that begin in the more suitable northern habitat would move southward only when favorable environmental conditions develop. Along with the high number of outbreaks in the northern regions of the district, there has been no direct control of the budworm, and overmature stands are maintained through suppression of fire and lack of harvesting. Many of these stands are entering a state of general decline with protracted mortality, resulting from a complex of secondary insects and pathogens.
Phenology of budburst development of Sitka spruce, Picea sitchensis Bong. Carr., measured at two ... more Phenology of budburst development of Sitka spruce, Picea sitchensis Bong. Carr., measured at two sites on Vancouver Island, British Columbia, Canada, was under strong genetic control, with family heritability (h2f) ranging from 0.45 to 1.0, depending on phenology stage. On average, families with resistance to the white pine weevil, Pissodes strobi (Peck), initiated and maintained a faster rate of bud development than families from susceptible parents, requiring lower heat accumulation to reach particular stages of bud development. However, a large overlap occurred, with one resistant family having a budburst phenology not significantly different from the susceptible families and some susceptible families having phenology as early as that of resistant families. It is postulated that resistance is a multicomponent trait based on different resistance mechanisms, some of which may be correlated with phenology but not others. Close observation of weevil behaviour through the season indicated that resistant families experienced reduced weevil presence, copulation and oviposition rate with respect to susceptible families.
... The ANN method introduced in this article is sufficiently general to be applicable to many fo... more ... The ANN method introduced in this article is sufficiently general to be applicable to many forest ecological modeling applications. FOR. Sc. 46(2):229-239. Additional Key Words:Dendrochronology, dendroclimatology, Douglas-fir, forest growth, response function analysis. ...
Principal components analysis, followed by K-means cluster analysis, was used to detect variation... more Principal components analysis, followed by K-means cluster analysis, was used to detect variations in the timing and magnitude of Pinus contorta Dougl. ex Loud. growth releases attributed to mountain pine beetle outbreaks in 31 stands of central British Columbia. Four major growth release patterns were identified from 1970 to 2000. Variations in the timing of growth releases among clustered stands corresponded well to aerial survey data indicating the timing of beetle outbreaks in the study area. Redundancy analysis was used to determine how variations in the timing and magnitude of growth releases attributed to beetle outbreaks changed with variations in climate or stand conditions over the study area. The first RDA axis, which accounted for 39% of the variations in growth patterns among stands, was significantly (P <0.05) correlated with gradients in the percentage of pine in stands killed by mountain pine beetle, summer aridity, variation in summer precipitation, distance from initial infestation site, average pine age, and maximum August temperatures. The second RDA axis explained 6% of the variations and was significantly correlated with gradients in the beetle climate suitability index, extreme cold month temperatures, and site index. Comparisons of growth release patterns with aerial survey data and redundancy analyses indicated that dendrochronological techniques are useful for identifying mountain pine beetle outbreaks in central British Columbia, particularly among stands that had a density high enough to produce a growth release signal. Provided future studies account for interannual weather fluctuations, identification of growth increases due to stand thinning caused by beetle outbreaks will be useful for reconstructing the history of beetle outbreaks over much longer time periods.
Canadian Journal of Forest Research-revue Canadienne De Recherche Forestiere, 2001
... Picea sitchensis (Bong.) Carrière) trees. The trees that had been selected as early or late f... more ... Picea sitchensis (Bong.) Carrière) trees. The trees that had been selected as early or late flushing were subjected to artificial wounding to simulate attack by the white pine weevil, Pissodes strobi (Peck). Samples were taken at ...
Canadian Journal of Forest Research-revue Canadienne De Recherche Forestiere, 1996
ABSTRACT The intensity of the traumatic resin response in white spruce, Picea glauca (Moench) Vos... more ABSTRACT The intensity of the traumatic resin response in white spruce, Picea glauca (Moench) Voss, to attack by the white pine weevil, Pissodes strobi Peck, was studied in trees with different severities of attack. The response level was highest in trees where the attacks failed, i.e., where eggs were laid but the brood was killed and no adults emerged. Successfully attacked trees had, on average, only 62% of the response intensity of trees with failed attacks. Response intensity in trees that had been subjected only to feeding was much lower, at 42% of the failed attack response. Healthy unattacked trees showed no or little traumatic resin response. Response intensity varied in a nonlinear fashion with the number of eggs laid, increasing rapidly from zero in healthy trees, being highest in trees having between 10 and 60 egg punctures, and progressively lower again in trees with higher numbers of egg punctures. For a given number of egg punctures, resistant white spruce trees had a consistently higher traumatic resin response than susceptible trees. The number of eggs laid on a leader was inversely related to the intensity of the traumatic resin response and to the timing of the attack. Fewer eggs were laid on leaders with high traumatic resin response or attacked late in the season than on leaders with lower resin response or attacked early in the season.
The historical pattern of outbreaks of the spruce budworm, Choristoneura fumiferana (Clem.), in w... more The historical pattern of outbreaks of the spruce budworm, Choristoneura fumiferana (Clem.), in white spruce stands in the Fort Nelson Forest District of northeastern British Columbia was reconstructed with the use of dendrochronology. Outbreaks occurred on an average every 26 years, with 5–6 outbreaks in the past century in the northern regions of the district, while southern regions experienced between 0 (the most southern sites) and 4 outbreaks. In the northern regions, outbreaks began about 10 years earlier and the period of defoliation was longer than in the southern regions of the district. The southern limit of the range of the spruce budworm in British Columbia is marked by the predominance of the Montane Boreal White and Black Spruce biogeoclimatic subzone that has cool and wet summers that may not favor budworm development. Therefore, outbreaks that begin in the more suitable northern habitat would move southward only when favorable environmental conditions develop. Along with the high number of outbreaks in the northern regions of the district, there has been no direct control of the budworm, and overmature stands are maintained through suppression of fire and lack of harvesting. Many of these stands are entering a state of general decline with protracted mortality, resulting from a complex of secondary insects and pathogens.
Phenology of budburst development of Sitka spruce, Picea sitchensis Bong. Carr., measured at two ... more Phenology of budburst development of Sitka spruce, Picea sitchensis Bong. Carr., measured at two sites on Vancouver Island, British Columbia, Canada, was under strong genetic control, with family heritability (h2f) ranging from 0.45 to 1.0, depending on phenology stage. On average, families with resistance to the white pine weevil, Pissodes strobi (Peck), initiated and maintained a faster rate of bud development than families from susceptible parents, requiring lower heat accumulation to reach particular stages of bud development. However, a large overlap occurred, with one resistant family having a budburst phenology not significantly different from the susceptible families and some susceptible families having phenology as early as that of resistant families. It is postulated that resistance is a multicomponent trait based on different resistance mechanisms, some of which may be correlated with phenology but not others. Close observation of weevil behaviour through the season indicated that resistant families experienced reduced weevil presence, copulation and oviposition rate with respect to susceptible families.
... The ANN method introduced in this article is sufficiently general to be applicable to many fo... more ... The ANN method introduced in this article is sufficiently general to be applicable to many forest ecological modeling applications. FOR. Sc. 46(2):229-239. Additional Key Words:Dendrochronology, dendroclimatology, Douglas-fir, forest growth, response function analysis. ...
Uploads