scholarly journals THE VULNERABILITY OF BALSAM FIR TO SPRUCE BUDWORM ATTACK IN NORTHWESTERN ONTARIO, WITH SPECIAL REFERENCE TO THE PHYSIOLOGICAL AGE OF THE TREE

1958 ◽  
Vol 34 (4) ◽  
pp. 405-422 ◽  
Author(s):  
J. R. Blais
Keyword(s):  
Special Reference ◽  
Tree Mortality ◽  
Spruce Budworm ◽  
Balsam Fir ◽  
Site Quality ◽  
Physiological Age ◽  
Northwestern Ontario ◽  
Relationship Of ◽  
The Relationship ◽  
Relative Vulnerability

The annual defoliation by spruce budworm and the progressive mortality of balsam fir trees were recorded in nine study plots in northwestern Ontario over a period of 11 years. In addition to general observations on the relationship of tree mortality to defoliation, some information was obtained on the relative vulnerability of the trees with respect to size, physiological age (flowering condition), and vigor (site quality).

THE RELATIONSHIP OF THE SPRUCE BUDWORM (CHORISTONEURA FUMIFERANA, CLEM.) TO THE FLOWERING CONDITION OF BALSAM FIR (ABIES BALSAMEA (L.) MILL.)

1952 ◽  
Vol 30 (1) ◽  
pp. 1-29 ◽  
Author(s):  
J. R. Blais
Keyword(s):  
Direct Effect ◽  
Choristoneura Fumiferana ◽  
Abies Balsamea ◽  
Spruce Budworm ◽  
Balsam Fir ◽  
Larval Stages ◽  
Competition For Food ◽  
Relationship Of ◽  
The Relationship

Populations of the spruce budworm were studied on flowering and nonflowering balsam fir trees. Generally more eggs were found on the flowering trees. The flowering balsam fir trees were found to harbor higher populations in the early larval stages owing to the presence on these trees of staminate flowers and flower cups. The behavior of the larvae in relation to staminate flowers and flower cups was studied in both the field and the laboratory. Larvae that fed partially on pollen developed more rapidly than larvae that fed exclusively on foliage. Pollen as a food did not appear to have any direct effect on survival or fecundity. Other experiments showed that mortality was higher, development retarded, and fecundity reduced in insects forced to feed on old foliage in contrast with those fed on the current year's growth. Defoliation was more severe on flowering trees in the earlier stages of the infestation. However, as populations increased, wandering increased owing to competition for food. This resulted in an overflow of larvae from flowering to nonflowering trees.

Effects of Spruce Budworm Outbreaks on the Productivity and Stability of Balsam Fir Forests

1984 ◽  
Vol 60 (5) ◽  
pp. 273-279 ◽  
Author(s):  
David A. MacLean
Keyword(s):  
Tree Mortality ◽  
Choristoneura Fumiferana ◽  
Spruce Budworm ◽  
Balsam Fir ◽  
Wood Production ◽  
Ecological Stability ◽  
Short Term ◽  
Eastern Canada ◽  
Feasible Method ◽  
Human Usage

Effects of spruce budworm (Choristoneura fumiferana (Clem.)) outbreaks on the productivity and stability of forests in eastern Canada are reviewed and discussed. Defoliation results in reduced growth of trees, widespread tree mortality, and loss of wood production, and thereby causes major forest management problems. At present, the only feasible method for limiting damage and losses from budworm outbreaks over large areas is to apply chemical or biological insecticides periodically to kill larvae and protect the forest from defoliation and tree mortality. Although budworm outbreaks definitely disrupt the wood-producing capacity of forests (or the short-term "stability of forests for human usage"), in terms of overall ecological stability, outbreaks apparently act as a cycling mechanism that allows advance fir-spruce regeneration to succeed the fir-spruce overstory.

The Regenerative Cycle: An Efficiency Basis having Special Reference to the Number of Feed Water Heating Stages

1941 ◽  
Vol 146 (1) ◽  
pp. 5-19 ◽  
Author(s):  
H. S. Horsman
Keyword(s):  
Special Reference ◽  
Feed Water ◽  
Final States ◽  
Boiler Plant ◽  
Worked Example ◽  
The Difference ◽  
Relationship Of ◽  
The Relationship ◽  
Regenerative Cycle ◽  
The Ideal

The efficiency of the regenerative cycle may be defined as the ratio of the heat converted into work (in British Thermal Units per pound of steam) to the heat supplied to 1 lb. of steam in the boiler plant. Where feed heating is employed, however, the heat converted into work is less than the adiabatic heat drop as calculated from the initial and final states of expansion. The difference between these quantities is termed “unavailable heat” in the paper, and the efficiency is therefore given as the ratio of the adiabatic heat drop less the unavailable heat, to the heat supplied to 1 lb. of steam in the boiler plant. The object of the paper is to illustrate the advantage derived from working in terms of unavailable heat. Values of this quantity are given, and the author provides a worked example showing their use. Appendixes I and II deal with investigations of the case in which the number of feed heating stages is infinitely great, i.e. the conditions for the ideal efficiency. The relationship of the ideal efficiency to other efficiencies corresponding to various finite numbers of feed heating stages is indicated.

Tree mortality and radial growth losses caused by the western spruce budworm in a Douglas-fir stand in British Columbia

1982 ◽  
Vol 12 (4) ◽  
pp. 780-787 ◽  
Author(s):  
R. I. Alfaro ◽  
G. A. Van Sickle ◽  
A. J. Thomson ◽  
E. Wegwitz
Keyword(s):  
Radial Growth ◽  
Tree Mortality ◽  
Small Diameter ◽  
Basal Area ◽  
Spruce Budworm ◽  
Douglas Fir ◽  
Radial Increment ◽  
Western Spruce Budworm ◽  
Number Of Stems ◽  
The Relationship

The effects of defoliation by western spruce budworm (Choristoneuraoccidentalis (Freeman)), on Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) radial growth at breast height and tree mortality are given. Four hundred and twenty trees were marked in an 81-year-old stand, and their defoliation levels were recorded annually from 1970 to 1980 in an outbreak that lasted from 1970 to 1974, inclusive. Forty-one trees were felled and dissected in 1977, 3 years after recovery began. The number of stems per hectare was reduced by 39.3% and basal area by 11.6% through mortality, most occurring among the small diameter, suppressed, and intermediate trees. Relationships were established between mortality and defoliation. Radial increments were examined, and the presence of four outbreaks during the life of the stand was detected. The combined effect of these infestations amounted to a loss of about 12% of the estimated potential diameter had not the insects been active. The most recent outbreak (1970–1974) caused a total of 10 years of subnormal growth, including 5 years due to defoliation and 5 years of recovery. The relationship between radial increment losses and defoliation intensity and duration is studied and quantified.

A TECHNIQUE FOR ESTIMATING THE FECUNDITY OF NATURAL POPULATIONS OF THE SPRUCE BUDWORM

1957 ◽  
Vol 35 (1) ◽  
pp. 1-13 ◽  
Author(s):  
C. A. Miller
Keyword(s):  
Natural Populations ◽  
Spruce Budworm ◽  
Regression Equations ◽  
Green River ◽  
Actual Increase ◽  
Late Instar ◽  
The Mean ◽  
Adult Dispersal ◽  
Relationship Of ◽  
The Relationship

In a severe infestation late-instar spruce budworm larvae that normally feed on current foliage may be forced to complete development on old foliage. This results in a reduction in fecundity. The precise causes of this reduction are not known, but factors that may be involved are the amount and the age of the old foliage consumed. The relationship of pupal case size and fecundity is used as a basis for estimating the expected fecundity in a natural population under these conditions of partial larval starvation. Three regression equations applicable to conditions on the Green River area, New Brunswick, are presented. An index of the actual increase of a population is obtained from an E/F ratio. Ratios may be compared in order to indicate some aspects of oviposition. Actual and expected egg populations can also be compared, subject to certain limitations, to indicate some aspects of adult dispersal. The mean number of eggs per mass in relation to degree of infestation and a simplified method of counting eggs per mass are also discussed.

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