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.

RELATIONSHIPS BETWEEN ATTACK RATES AND SURVIVAL OF WESTERN SPRUCE BUDWORM, CHORISTONEURA OCCIDENTALIS FREEMAN (LEPIDOPTERA: TORTRICIDAE), AND BUD DEVELOPMENT OF DOUGLAS-FIR, PSEUDOTSUGA MENZIESII (MIRB.) FRANCO

1992 ◽  
Vol 124 (2) ◽  
pp. 347-358 ◽  
Author(s):  
Roy F. Shepherd
Keyword(s):  
Close Association ◽  
Spruce Budworm ◽  
Larval Survival ◽  
Douglas Fir ◽  
Choristoneura Occidentalis ◽  
Western Spruce Budworm ◽  
Bud Development ◽  
Feeding Sites ◽  
Vegetative Buds ◽  
Wide Range

AbstractIndividual larvae of western spruce budworm (Choristoneura occidentalis Freeman) were observed from overwintering emergence to pupation at six locations spread over a wide range of altitudes and thus climate. A weekly census of 100 lower-crown buds per plot indicated large differences in rates of bud development and larval survival among locations.Emerging second-instar larvae attempted to mine swelling buds of Douglas-fir. If the buds were hard and tight, larvae mined 1-year-old needles until penetrable buds were available. Larvae dispersed over the crowns with only one larva becoming established in each bud; thus, many early-emerging and surplus larvae could not find suitable feeding sites and disappeared. Within the protective bud, survival was high. After buds flushed and larvae became exposed, densities dropped, probably due to increased predation and decreased food quality. Correlations indicated a close association between larval survival for the exposed period between bud flush and pupation, and overall larval survival.Douglas-fir trees responded to initial bud removal, but not to needle removal, by inducing latent buds in the axils of needles to grow into active vegetative buds ready to develop and flush the next spring. The number of these new vegetative buds formed was greatest when the initial buds were removed early in the season before flush, and decreased thereafter. Trees with vigorous crowns had the greatest response to defoliation by inducing the largest number of latent buds into becoming active vegetative buds; these were found mainly on the 2- and 3-year-old internodes.

scholarly journals Controls on Streamflow Densities in Semiarid Rocky Mountain Catchments

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 521
Author(s):  
Caroline Martin ◽  
Stephanie K. Kampf ◽  
John C. Hammond ◽  
Codie Wilson ◽  
Suzanne P. Anderson
Keyword(s):  
Elevation Gradient ◽  
Rocky Mountain ◽  
Surface Flow ◽  
Colorado Front Range ◽  
Front Range ◽  
Channel Network ◽  
Stream Discharge ◽  
Geologic Maps ◽  
National Hydrography Dataset ◽  
Active Flow

Developing accurate stream maps requires both an improved understanding of the drivers of streamflow spatial patterns and field verification. This study examined streamflow locations in three semiarid catchments across an elevation gradient in the Colorado Front Range, USA. The locations of surface flow throughout each channel network were mapped in the field and used to compute active drainage densities. Field surveys of active flow were compared to National Hydrography Dataset High Resolution (NHD HR) flowlines, digital topographic data, and geologic maps. The length of active flow declined with stream discharge in each of the catchments, with the greatest decline in the driest catchment. Of the tributaries that did not dry completely, 60% had stable flow heads and the remaining tributaries had flow heads that moved downstream with drying. The flow heads were initiated at mean contributing areas of 0.1 km2 at the lowest elevation catchment and 0.5 km2 at the highest elevation catchment, leading to active drainage densities that declined with elevation and snow persistence. The field mapped drainage densities were less than half the drainage densities that were represented using NHD HR. Geologic structures influenced the flow locations, with multiple flow heads initiated along faults and some tributaries following either fault lines or lithologic contacts.

A field experiment informs expected patterns of conifer regeneration after disturbance under changing climate conditions

2015 ◽  
Vol 45 (11) ◽  
pp. 1607-1616 ◽  
Author(s):  
Monica T. Rother ◽  
Thomas T. Veblen ◽  
Luke G. Furman
Keyword(s):  
Field Experiment ◽  
Pinus Ponderosa ◽  
Ponderosa Pine ◽  
Douglas Fir ◽  
Tree Regeneration ◽  
Colorado Front Range ◽  
Front Range ◽  
Average Growth ◽  
Growth And Survival ◽  
Treatment Type

Climate change may inhibit tree regeneration following disturbances such as wildfire, altering post-disturbance vegetation trajectories. We implemented a field experiment to examine the effects of manipulations of temperature and water on ponderosa pine (Pinus ponderosa Douglas ex P. Lawson & C. Lawson) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings planted in a low-elevation, recently disturbed setting of the Colorado Front Range. We implemented four treatments: warmed only (Wm), watered only (Wt), warmed and watered (WmWt), and control (Co). We found that measures of growth and survival varied significantly by treatment type. Average growth and survival was highest in the Wt plots, followed by the Co, WmWt, and Wm plots, respectively. This general trend was observed for both conifer species, although average growth and survival was generally higher in ponderosa pine than in Douglas-fir. Our findings suggest that warming temperatures and associated drought are likely to inhibit post-disturbance regeneration of ponderosa pine and Douglas-fir in low-elevation forests of the Colorado Front Range and that future vegetation composition and structure may differ notably from historic patterns in some areas. Our findings are relevant to other forested ecosystems in which a warming climate may similarly inhibit regeneration by dominant tree species.

INFLUENCE OF FOLIAR NITROGEN LEVELS ON SURVIVAL, DEVELOPMENT, AND REPRODUCTION OF WESTERN SPRUCE BUDWORM, CHORISTONEURA OCCIDENTALS (LEPIDOPTERA: TORTRICIDAE)

1985 ◽  
Vol 117 (1) ◽  
pp. 23-32 ◽  
Author(s):  
J. Wayne Brewer ◽  
John L. Capinera ◽  
Robert E. Deshon ◽  
Mary L. Walmsley
Keyword(s):  
Larval Mortality ◽  
Spruce Budworm ◽  
Dry Weight ◽  
Douglas Fir ◽  
Nitrogen Level ◽  
Pupal Weight ◽  
Western Spruce Budworm ◽  
Foliar Nitrogen ◽  
Nitrogen Levels ◽  
White Fir

AbstractThe influence of nitrogen levels in foliage of white-fir, Abies concolor, and Douglas-fir, Pseudotsuga menziesii, seedlings on various biological characteristics of the western spruce budworm, Choristoneura occidentalis Freeman, was studied. Seedlings were grown under greenhouse conditions and provided with nutrient solutions to maintain five foliar nitrogen levels ranging from 1.29 to 4.42% dry weight for white fir and 1.43 to 3.94% for Douglas fir. Larvae confined to treated seedlings were monitored through the next generation. Larval mortality was higher, and development time longer, at both upper and lower extremes of foliar nitrogen than at mid-level. Mean pupal weight was significantly greater for larvae reared on white fir with the mid-range foliar-nitrogen level. Mean number, and weight, of eggs laid were highest when larvae fed on foliage from the mid-range nitrogen level. Total number of larvae produced was lowest at the high and low extremes of foliar nitrogen levels.

scholarly journals Douglas-Fir Tussock Moth- and Douglas-Fir Beetle-Caused Mortality in a Ponderosa Pine/Douglas-Fir Forest in the Colorado Front Range, USA

Forests ◽  
2014 ◽  
Vol 5 (12) ◽  
pp. 3131-3146 ◽  
Author(s):  
José Negrón ◽  
Ann Lynch ◽  
Willis Schaupp ◽  
Javier Mercado
Keyword(s):  
Ponderosa Pine ◽  
Douglas Fir ◽  
Colorado Front Range ◽  
Front Range ◽  
Tussock Moth

ESTIMATING NUMBER OF WESTERN SPRUCE BUDWORM EGGS FROM EGG MASS MEASUREMENTS IN BRITISH COLUMBIA

1982 ◽  
Vol 114 (7) ◽  
pp. 643-645 ◽  
Author(s):  
J. W. E. Harris ◽  
A. F. Dawson
Keyword(s):  
British Columbia ◽  
Extended Period ◽  
Spruce Budworm ◽  
Douglas Fir ◽  
Population Trends ◽  
Egg Mass ◽  
Western Spruce Budworm ◽  
Growth Loss ◽  
Insect Populations ◽  
The Relationship

Western spruce budworm, Choristoneura occidentalis Freeman, periodically attacks Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco) in British Columbia, causing mortality, deformity, and growth loss. Insect populations are assessed annually by the Canadian Forestry Service's Forest Insect and Disease Survey, by branch sampling for egg mass densities; predictions of population trends and damage are based on these assessments. Eggs, laid in rows in masses affixed to needles, are a preferred stage to sample because they are easily collected, remain fixed in numbers for an extended period, and precede damage by sufficient time to plan suppression or other programs. Numbers of masses alone, however, may not show population trends accurately as egg numbers per mass varies. Thus it is sometimes necessary to count eggs (Miller 1957), which is a formidable task. Fortunately egg numbers can be estimated from the dimensions of egg masses (Washburn and Brickell 1973). In this study, we determined the relationship between egg numbers and egg mass length and number of rows for samples from Douglas-fir stands frequently affected by spruce budworm throughout British Columbia. Data were collected over 3 years, 1977-79, during which time budworm populations were in a period of decline.

Balancing risks of disturbance from mountain pine beetle and western spruce budworm

2009 ◽  
Vol 39 (4) ◽  
pp. 839-848 ◽  
Author(s):  
V.G. Nealis ◽  
M.K. Noseworthy ◽  
R. Turnquist ◽  
V.R. Waring
Keyword(s):  
Pinus Contorta ◽  
Mountain Pine Beetle ◽  
Lodgepole Pine ◽  
Spruce Budworm ◽  
Douglas Fir ◽  
Closed Field ◽  
Western Spruce Budworm ◽  
Mountain Pine ◽  
Pine Beetle ◽  
Population Processes

The effect of removing lodgepole pine ( Pinus contorta Dougl. ex Loud.) and retaining Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) to reduce the risk of disturbance from mountain pine beetle ( Dendroctonus ponderosae Hopk.) in mixed conifer stands in southern British Columbia, Canada, on population processes influencing outbreaks of western spruce budworm ( Choristoneura occidentalis Free.) was evaluated in 10 paired (open vs. closed) field plots. Overall feeding damage to Douglas-fir was significantly, but only slightly, lower in open stands compared with closed stands. Although open plots tended to recruit more budworms, the losses resulting from the dispersal of spring-emerging budworms in search of feeding sites were significantly greater in open plots. The forest management benefits of these early season losses were mitigated, however, by more mortality of budworms from natural enemies, particularly diseases, in the closed plots during the budworm feeding period. These results are discussed in terms of compensating population processes and balancing objectives in forest pest management. In this case, selective harvesting of lodgepole pine as a mitigation strategy for the mountain pine beetle conserved the midterm timber supply potential represented by associated Douglas-fir even in the presence of an outbreak of the western spruce budworm.

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