Relations among stand structure, dispersal of second-instar western spruce budworm, defoliation, and height growth of young conifers

1988 ◽  
Vol 18 (6) ◽  
pp. 796-802
Author(s):  
Clinton E. Carlson ◽  
Ward W. McCaughey ◽  
Leon J. Theroux
Keyword(s):  
Ponderosa Pine ◽  
Stand Structure ◽  
Basal Area ◽  
Spruce Budworm ◽  
Height Growth ◽  
Western Montana ◽  
Western Spruce Budworm ◽  
Mature Trees ◽  
Subalpine Fir ◽  
Host Trees

Local stand structure had little influence on dispersal of second-instar western spruce budworm (Choristoneuraoccidentalis Freeman). Numbers of dispersing larvae caught on traps averaged 37 larvae/m2 in the cut stands, as high as were found in adjacent uncut stands, and were not related to basal area of overstory in harvested stands, distance to the adjacent uncut stands, or budworm populations in the uncut stands. Despite high numbers of dispersing larvae, defoliation of host regeneration in cut stands was low (87% of the nonlarch host incurred less than 25% defoliation) and was not predictable (p ≤ 0.05) from dispersing larvae. Defoliation of mature trees in the adjacent uncut stands averaged 20% and ranged to 45%. Three-year height growth of postharvest host conifers in the cut stands increased with smaller overstory basal area, greater initial height, and greater crown ratio, but was not affected by the small amount of budworm defoliation. Regression models of 3-year height growth were similar among host western larch (Larixoccidentalis Nutt.), grouped nonlarch hosts (Douglas-fir, Pseudotsugamenziesii var. glauca (Beissn.) Franco; grand fir, Abiesgrandis (Dougl.) Forbes; and subalpine fir, A. lasiocarpa (Hook.) Nutt.), and grouped nonhosts (ponderosa pine, Pinusponderosa Dougl.; and lodgepole pine, P. contorta var. latifolia). Larval dispersal may be influenced more by forestwide conditions and spring weather than by local stand factors. Larvae reaching target seedlings likely are removed by predators such as birds and ants. Vigorous small host trees appear to be poor habitat for budworms; the insect had little effect on height growth of 5- to 20-year-old seral conifer stands of western Montana.

scholarly journals Effects of a Western Spruce Budworm Outbreak on Private Lands in Eastern Oregon, 1980–1994

2008 ◽  
Vol 23 (1) ◽  
pp. 19-25
Author(s):  
David L. Azuma ◽  
David L. Overhulser
Keyword(s):  
Host Species ◽  
Forest Inventory ◽  
Stand Structure ◽  
Basal Area ◽  
Spruce Budworm ◽  
Analysis Data ◽  
Western Spruce Budworm ◽  
Private Lands ◽  
Forest Inventory And Analysis ◽  
Salvage Harvesting

Abstract Forest Inventory and Analysis data from three inventory periods were used to examine the effects of a western spruce budworm outbreak on private lands in eastern Oregon. Growth was negatively related to defoliation with differences between crown ratio and species. The mortality and salvage harvesting caused changes in stand structure on private lands. Although many stands showed a decrease in basal area, there was no detectable decrease in host species as a percentage of basal area. The combined effect of mortality, harvest, and loss in predicted growth may be as much as 30% of the initial standing volume.

Stand response to western spruce budworm and Douglas-fir bark beetle outbreaks, Colorado Front Range

1993 ◽  
Vol 23 (3) ◽  
pp. 479-491 ◽  
Author(s):  
Keith S. Hadley ◽  
Thomas T. Veblen
Keyword(s):  
Bark Beetle ◽  
Stand Structure ◽  
Fire Suppression ◽  
Rocky Mountain ◽  
Spruce Budworm ◽  
Douglas Fir ◽  
Colorado Front Range ◽  
Front Range ◽  
Western Spruce Budworm ◽  
Wide Range

The montane forests (i.e., below ca. 2900 m) of the Colorado Front Range have experienced repeated outbreaks of western spruce budworm (Choristoneuraoccidentalis Free.) and Douglas-fir bark beetle (Dendroctonuspseudotsugae Hopk.), both of which locally attack Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco). In this study we examine the effects of historically documented outbreaks of these insects on succession, stand structure, and radial growth of host and nonhost species in Rocky Mountain National Park. The most recent budworm (1974–1985) and bark beetle (1984–present) outbreaks resulted in the most severe and widespread disturbance of these forests since the late 1800s. Stand response to these outbreaks is primarily a function of stand structure and age characteristics of Douglas-fir prior to an outbreak. Young, vigorous postfire stands show minimal budworm defoliation, and in these stands only remnant trees from the prefire generation appear susceptible to beetle-caused mortality. Dense stands exhibit higher budworm-induced mortality, which hastens the natural thinning process and shifts dominance towards the nonhost species. The stands most severely disturbed by the combined insect agents are multistoried stands with high host densities and a wide range of stem sizes. The stand response to these disturbances include the growth release of shade-intolerant, seral species, and in some cases, a higher survivorship among midsized individuals of the host Douglas-fir. The net result of the combined insect outbreaks is the temporary slowing of the successional trend towards a steady-state Douglas-fir forest. Fire suppression, by increasing the density of suppressed Douglas-fir, has previously been shown to favor increased outbreak severity of western spruce budworm in the northern Rockies. However, in the Front Range, recent increases in outbreak severity and their synchroneity may also be the result of large areas of forest, burned during the late 19th century during European settlement, simultaneously entering structural stages susceptible to insect outbreak.

scholarly journals Ponderosa Pine and Lodgepole Pine Growth Response to One-Time Application of Herbicide During Seedling Establishment in Western Montana

2003 ◽  
Vol 18 (3) ◽  
pp. 149-154 ◽  
Author(s):  
Chad E. Keyser ◽  
Kelsey S. Milner
Keyword(s):  
Pinus Ponderosa ◽  
Ponderosa Pine ◽  
Seedling Establishment ◽  
Pinus Contorta ◽  
Lodgepole Pine ◽  
Tree Height ◽  
Height Growth ◽  
Western Montana ◽  
Growth Effect ◽  
Percent Cover

Abstract This study examined long-term diameter and height response of ponderosa pine (Pinus ponderosa) and lodgepole pine (Pinus contorta var. latifolia) to a one-time application of herbicide during seedling establishment in western Montana. Two herbicide trials initiated in 1981 and 1983 by Champion International Corporation were resurrected during the summer of 1997. Analysis of variance (ANOVA) F-tests along with Duncan's Multiple Range tests (DMR) were performed on mean tree dbh, tree height, and competing vegetation percent cover estimates. In addition, a graphical analysis of mean annual height growth over time was performed. Significant increases (alpha = 0.05) in ponderosa pine dbh (25 to 44%) and height (11 to 28%) were found after 16 yr of growth on Velpar L. (hexazinone) treated plots, while lodgepole pine had significant increases in dbh (70 to 118%) and height (41 to 82%) after 15 yr of growth on Velpar L. treated plots. Graphical analyses indicated a positive height growth effect for a period of 11 to 13 yr following treatment for ponderosa pine; however, total height gains had decreased in recent years. Positive increases in height growth for lodgepole pine were continuing after 15 yr of growth. These results indicate that a one-time application of herbicide applied during seedling establishment will promote faster tree growth in western Montana. We also note that proper density management will be necessary early in the life of the stand to maintain height gains. West. J. Appl. For. 18(3):149–154.

Western Spruce Budworm Damage Affects Form and Height Growth of Western Larch

1973 ◽  
Vol 3 (1) ◽  
pp. 17-26 ◽  
Author(s):  
Wyman C. Schmidt ◽  
David G. Fellin
Keyword(s):  
Feeding Behavior ◽  
Apical Dominance ◽  
Spruce Budworm ◽  
Height Growth ◽  
Western Spruce Budworm ◽  
Western Larch ◽  
Reduced Height ◽  
Lateral Shoots ◽  
Terminal Shoot ◽  
Usual Diet

An unusual feeding behavior of the western spruce budworm (Choristoneuraoccidentalis Freeman) reduced height growth and deformed young western larch (Larixoccidentalis Nutt.). On western larch, budworm larvae did not confine their feeding to foliage, their usual diet on other conifers; they also fed on and severed stems of current-year terminal and lateral shoots. A 5-year study in young larch stands showed that: (1) amount and severity of budworm damage increased annually, (2) all trees were damaged sometime during the study, (3) severance of the terminal shoot was the most serious type of budworm damage to larch, (4) severances reduced net height growth at least one-fourth and resulted in forked, bushy-topped trees, and (5) specific forks in the tree did not persist more than 5 years because of the strong apical dominance characteristic of larch.

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.

The influence of stand structure on ecophysiological leaf characteristics of Pinus ponderosa in western Montana

2001 ◽  
Vol 31 (12) ◽  
pp. 2173-2182 ◽  
Author(s):  
Linda M Nagel ◽  
Kevin L O'Hara
Keyword(s):  
Leaf Area ◽  
Pinus Ponderosa ◽  
Ponderosa Pine ◽  
Stand Structure ◽  
Structural Difference ◽  
Leaf Nitrogen ◽  
Western Montana ◽  
Light Extinction ◽  
Area Index ◽  
Canopy Depth

The effects of vertical arrangement of foliage in even-aged and multiaged stand structures of ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws.) on overall stand growth, light interception, and physiological leaf properties were tested on five plot pairs in western Montana. The primary structural difference between stand structures involves greater canopy depth and stratification of foliage in the multiaged stands. Both area- and mass-based maximum photosynthetic rates (Aarea and Amass) were relatively constant with canopy depth in both stand structures. Area- and mass-based leaf nitrogen (Narea and Nmass) decreased with increasing canopy depth in the even-aged stand structures but not in the multiaged. Specific leaf area (SLA) tended to increase with increasing canopy depth, although this relationship was only significant in the multiaged stand structures. The typical linear relationship observed for many species between photosynthetic rate and leaf nitrogen was not present in either stand structure; however, Narea was highly correlated to SLA in both even-aged and multiaged stand structures (R2 = 0.66 and R2 = 0.52, respectively). There were no differences in the light extinction coefficient (k), basal area growth or efficiency, or stand-level leaf area index between even-aged and multiaged plot pairs. Relative constancy in leaf physiology combined with similarities in site occupancy and growth rates help explain how different stand structures of ponderosa pine maintain similar rates of woody biomass productivity.

ANTS PREYING ON PUPAE OF THE WESTERN SPRUCE BUDWORM, CHORISTONEURA OCCIDENTALIS (LEPIDOPTERA: TORTRICIDAE), IN EASTERN OREGON AND WESTERN MONTANA

1984 ◽  
Vol 116 (12) ◽  
pp. 1665-1669 ◽  
Author(s):  
Lorna C. Youngs ◽  
Robert W. Campbell
Keyword(s):  
Spruce Budworm ◽  
Western Montana ◽  
Choristoneura Occidentalis ◽  
Western Spruce Budworm ◽  
Formica Obscuripes

AbstractIn 1981 and 1982, the following ant species and numbers were detected preying on pupae of the western spruce budworm, Choristoneura occidentalis Freeman, in eastern Oregon and western Montana: Formica obscuripes Forel, 174; Camponotus modoc Wheeler, 160; C. laevigatus Smith, 53; C. vicinus Mayr, 48; F. podzolica Francoeur, 43; F. accreta Francoeur, 32; F. neorufibarbis Emery, 12; F. lasioides Emery, 1; and Formica sp. (microgyna group). The Camponotus species and F. obscuripes were detected preying on budworm on one-third or more of the trees they foraged.

Pre-wildfire fuel treatments affect long-term ponderosa pine forest dynamics

2007 ◽  
Vol 16 (1) ◽  
pp. 128 ◽  
Author(s):  
Barbara A. Strom ◽  
Peter Z. Fulé
Keyword(s):  
Ponderosa Pine ◽  
Stand Structure ◽  
Fire Severity ◽  
Stable State ◽  
Basal Area ◽  
Fire Intensity ◽  
Fuel Treatments ◽  
Alternative Stable State ◽  
Pine Regeneration ◽  
Crown Base Height

The 2002 Rodeo–Chediski fire, the largest wildfire in south-western USA history, burned over treated stands and adjacent untreated stands in the Apache–Sitgreaves National Forest, setting the stage for a natural experiment testing the effectiveness of fuel reduction treatments under conditions of extraordinary fire severity. In seven pairs of treated–untreated study sites measured 2 years after the fire, thinning was strongly associated with reduced burn severity. Treated areas had more live trees, greater survival, and reduced fire intensity as indicated by crown base height and bole char. Ponderosa pine regeneration was patchy but more dense in treated areas. We assessed decade- to century-long effects of the pre-wildfire fuel treatments using the Forest Vegetation Simulator (FVS). Differences between treated and untreated areas were projected to persist for several decades after the fire in terms of stand structure characteristics and for at least 100 years in terms of species composition, with ponderosa pine making up ~60% of basal area in treated areas but only 35% in untreated areas. Future ecosystem development may take the trajectory of recovery to a ponderosa pine/Gambel oak forest or of a shift to an alternative stable state such as an oak-dominated shrubfield, with untreated areas more apt to undergo a shift to a shrubfield state. Current management decisions about fuel treatments have multi-century legacies.

Forest fire frequency and western spruce budworm outbreaks in western Montana

1987 ◽  
Vol 22 (3-4) ◽  
pp. 251-260 ◽  
Author(s):  
Leslie Anderson ◽  
Clinton E. Carlson ◽  
Ronald H. Wakimoto
Keyword(s):  
Forest Fire ◽  
Spruce Budworm ◽  
Fire Frequency ◽  
Western Montana ◽  
Western Spruce Budworm

Balsam fir mortality following the last spruce budworm outbreak in northwestern Quebec

1995 ◽  
Vol 25 (8) ◽  
pp. 1375-1384 ◽  
Author(s):  
Yves Bergeron ◽  
Alain Leduc ◽  
Claude Joyal ◽  
Hubert Morin
Keyword(s):  
Stand Structure ◽  
Management Strategies ◽  
Basal Area ◽  
Spruce Budworm ◽  
Balsam Fir ◽  
Forest Composition ◽  
Regression Analyses ◽  
Site Characteristics ◽  
Forest Mosaic ◽  
Independent Effects

Balsam fir (Abiesbalsamea (L.) Mill.) mortality caused by the last spruce budworm (Choristoneurafumiferana (Clem.)) outbreak (1970–1987) was studied in 624 sites belonging to a complex natural forest mosaic originating from different fires in northwestern Quebec. Multiple regression analyses were used to assess the respective effects of stand structure, species composition, site characteristics, and the forest composition surrounding the stand on observed stand mortality. Mortality was observed to increase in relation to diameter of the trees, basal area of balsam fir, and the number of stands dominated by conifers in the forest mosaic. All of these factors showed significant independent effects, but 60% of the variance remained unexplained. Site characteristics, however, did not show a significant relationship to stand mortality. The results suggest that forest composition at both the stand and the forest mosaic levels may be responsible for differing degrees of defoliation that result in differences in stand mortality. Forest management strategies that favor the presence of mixed compositions both at the stand level and at the mosaic level may contribute to decreased stand vulnerability.

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