White Spruce Forests Research Articles

The logging of a world heritage site: Wood Buffalo National Park, Canada

Logging of the riparian old-growth white spruce forests of Wood Buffalo National Park took place from 1951 to 1991. Operations were conducted in the Peace River valley in the Big Island block (Timber Berth (TB) 408) and the Peace Delta block, and in the Athabasca River valley. Approximately 70% of the pre-logging old-growth riparian forests have been lost to logging, leaving a remnant of ~100 km2 in the park, of which ~30 km2 are found in TB408. A minimum of 100 km2 has been logged from TB408. Natural regeneration has failed on 93% of these lands (9300 ha). The logging agreement, which expired in 1981, was renewed in 1983, the same year in which Wood Buffalo National Park was declared a UNESCO World Heritage Site. The history of logging in Wood Buffalo National Park is characterized by government mismanagement and industrial malpractice. There was never legal authority to log in Wood Buffalo National Park, as it contravened the National Parks Act (1930). The need for restoration is discussed. Key words: boreal, forestry, management, Peace River, riparian, white spruce, Wood Buffalo National Park

POPULATION GENETICS OF THE SPRUCE BUDWORM,CHORISTONEURA FUMIFERANA(CLEM.) FREEMAN (LEPIDOPTERA: TORTRICIDAE), IN RELATION TO GEOGRAPHICAL AND POPULATION DENSITY DIFFERENCES

AbstractCollections (68) of spruce budworm from 33 locations from Newfoundland to Alaska were analysed for isozyme frequencies using horizontal starch gels. Collections represented pre-, early-, mid-, late-, and post-outbreak stages of several populations in balsam fir, white spruce, and mixed host forests, as well as successive annual collections at several locations. Isozymes were measured at 11 loci in mature larvae and at six loci in pheromone-trapped males; frequencies were essentially the same in both stages, and from all host species. Three loci (IDH-2, LDH-1, and AAT-1) were found to be sex-linked, with no heterozygotes in females. Mean percentage heterozygosity ranged from 13.2 to 23.1; at individual locations it tended to decrease over successive years of outbreak and over successive collections in the same year. Contingency chi-square analysis indicated small differences related to location and outbreak history but all populations were generally homogeneous over the entire range. Nevertheless, one allozyme of AAT-1 exhibited a significant cline in frequency from the southeast to the northwest. Gene flow across the entire range appeared to be appreciable.

Old-growth white spruce and balsam poplar forests of the Peace River Lowlands, Wood Buffalo National Park, Canada: Development, structure, and diversity

Thirty-seven permanent plots were established and sampled during 1993 and 1994 in Timber Berth 408, Peace River Lowlands, of Wood Buffalo National Park. Sites were sampled for vegetation, bird, physical, and structural attributes. The transition from mature to old-growth conditions occurs at different times in balsam poplar and white spruce forests. In lowland balsam poplar forests, old-growth attributes begin to appear after a stand age of ≈ 80 years, and in lowland white spruce, after ≈ 160 years. Both forest types may persist in excess of 300 years. Attributes shared by, and unique to, both lowland balsam poplar and white spruce old-growth are described. The development of log attributes over time follows opposing trends in flood and fire-origin forests. The preferred rooting medium of white spruce shifts from mineral soil early in succession to decaying wood under pre-existing canopies. Log and snag structure, decay, and dynamics are discussed in relation to time, bryophyte and lichen communities. Canopy height and roughness, total tree cover, and snag and tree animal cavities are described; indicator communities of birds are identified. We conclude with a summary of attributes characteristic of boreal riverine old-growth forests.

Effects of Needle Architecture on Warbler Habitat Selection in a Coastal Spruce Forest

Habitat associations of mobile foragers are well documented, but causes behind such patterns are seldom as well defined. Black—throated Green Warblers (Dendroica virens) attain greater densities in red (Picea rubens) than in white spruce (P. glauca) forests in coastal Maine and use red spruce foliage significantly more than predicted on the basis of availability. These habitat associations may be explained best by small—scale differences in vegetation structure, which can influence foraging efficiency. Red spruce have shorter needles held at more acute angles to woody stems than do white spruce. I predicted that D. virens prefers red spruce because of ease of perching and foraging on needles with this structure. Moreover, red spruce preferences should be exaggerated in moist vegetation, since white spruce needle structure and arrangement may wet and reduce plumage insulation capabilities more quickly. Three aviary experiments were performed with D. virens to test the role of structural differences in vegetation on foraging—site and perching—site selection: wetting of vegetation, decreasing white spruce needle angle to resemble red spruce, and reduction of white spruce needle length to approximate red spruce. Moistening of red spruce branches did not affect the foraging or microhabitat use of experimental warblers. Needle angle reduction did not change perching—site preferences, but foraging significantly shifted in favor of white spruce. Needle length manipulations resulted in significantly greater use of white spruce than in controls, for both perching and foraging substrates. The relationships found in this study between individual habitat selection and fine—scale features of habitat structure are consistent with the larger—scale patterns of habitat occupancy seen in this system, and have important implications in understanding habitat requirements for declining forest passerine populations. _kw Dendroica virens

Throughfall nitrogen in a white spruce forest in southwest Alberta, Canada

Rates of transfer of nitrogen in throughfall were measured in a Piceaglauca (Moench) Voss forest in southwest Alberta, Canada. Total annual flux of N in throughfall was estimated to be 6.8 kg•ha−1•year−1. The highest rates of N deposition in throughfall occurred during the spring. The pattern of seasonal variation of N in throughfall suggested that different processes of N accumulation in and loss from the canopy may have been operating at different times of the year. Annual leaching of N from the canopy was estimated to be 4.09 kg•ha−1•year−1 and represented 24% of the total amount of N returned to the forest floor (leachates plus litter fall).

Effects of Clear‐Cut Harvesting on Boreal Ground‐Beetle Assemblages (Coleoptera: Carabidae) in Western Canada

We compared pitfall catches from four types of mature lodgepole pine—white spruce forest with those from five age classes of young forest regenerating subsequent to clear‐cutting. Ground beetles were most abundant in the youngest sites (1–2 years since cutting) and in the mature stands on moist soil. Species richness was higher in regenerating sites than in mature forest. Cluster analysis grouped the ground‐beetle fauna according to forest age and forest type, suggesting that there is a general pattern of recovery after logging. Responses of common species to forest cutting fell into three groups: (1) forest generalists (2 species) were not dramatically affected, (2) species of open habitat (27 species) appeared and/or increased in abundance, and (3) mature forest species (10 species) disappeared or decreased in abundance. Populations of many mature forest species appear to recover following logging, but several specialists did not recolonize even the oldest regenerating stands. Furthermore, fragmentation and creation of large areas of relatively homogeneous young forest stages through logging may have detrimental long‐term effects even on the more abundant forest generalists. We must better understand subtle variations in habitat in order to maintain invertebrate diversity while harvesting the boreal forest.

Nitrification and denitrification in a white spruce forest in southwest Alberta, Canada

Nitrification and denitrification were measured in a 120-year-old Piceaglauca (Moench) Voss forest in southwestern Alberta. Nitrifying activity could not be detected using short-term incubations of F–H and upper mineral soil horizons. Long-term incubations for nitrifying potential indicated that nitrifying organisms were present. The results suggest that the population of nitrifying organisms must have been small, their activity was limited, or the microhabitat necessary for their activity was not adequately simulated by the soil slurries in the short-term incubations. Low rates of denitrification were detected but probably did not represent a substantial loss of N from the soil–plant system. Low rates of denitrification may have been due to a lack of substrate (NO3−), reflecting the low rates of nitrification.

Aboveground biomass production and nutrient accumulation on postharvested white spruce sites in interior Alaska

Nutrient content and biomass of aboveground annual production, and nutrient content of total aboveground biomass, of 14-year-old assemblages of plants developing on harvested white spruce (Piceaglauca (Moench) Voss) sites were estimated by vegetation harvesting and compared with values previously measured in mature white spruce stands. The aboveground biomass production of 14-year-old regenerating trembling aspen (Populustremuloides Michx.) clumps was 3 times higher than the aboveground production of mature white spruce stands, while the aboveground production of other regenerating communities was lower or equivalent to the production of mature white spruce. However, the nutrient content of aboveground current biomass was greater in all regenerating communities than in mature white spruce stands, except on regenerating sites where the forest floor was absent. The amount of nutrient incorporated in current aboveground biomass was 5 times greater in trembling aspen clumps than in mature white spruce stands. Furthermore, the total N, P, and K content of aboveground vegetation corresponded, in 14-year-old trembling aspen clumps, to a value that ranged from 50 to 109% of the amount found in the aboveground biomass of mature white spruce forests, while this value ranged from 4 to 14% on other regeneration types. Trembling aspen and balsam poplar (Populusbalsamifera L.) both showed the greatest concentrations of N and P in foliar litter fall. These observations suggest that the development of a trembling aspen clump after clear-cutting contributes to the acceleration of nutrient cycling. On the other hand, the development of herbaceous communities during the same period after clear-cutting was accompanied by much lower nutrient cycling rates in the aboveground portion of the vegetation.

Nitrogen mineralization and nitrification in successional ecosystems on the Tanana River floodplain, interior Alaska

Nitrogen (N) mineralization and nitrification were compared among ecosystems representing a primary successional sequence on the Tanana River floodplain of interior Alaska. These processes displayed marked seasonality, were closely related to substrate chemistry, and reflected the impact of vegetation clearing. The highest rates of N mineralization were encountered in the June to July incubation periods, and rates generally declined during the remainder of the summer. The early season period (June to July) was the interval of most favorable litter and mineral soil temperature and most available energy supply for microbial mineralization of detrital materials. Minimal rates were encountered during the winter. Litter layer N mineralization rates were highest in the early-successional poplar–alder (Populusbalsamifera–Alnustenuifolia (Nutt.) stage and declined with advancing succession in poplar (Populusbalsamifera) and mature white spruce (Piceaglauca) (Moench) Voss) stands. The poplar–alder stage displayed the highest rate of nitrification. Nitrate constituted 98% of the mineralized N in early-successional poplar–alder forest floors but fell to 4 and 0% in poplar and white spruce forest floors, respectively. Nitrogen mineralization was closely related to significant increases in the lignin/N ratio across the sequence of vegetation types. The rate of surface mineral soil net N mineralization increased with succession in response to higher soil organic matter content. The range of average total seasonal net N mineralization (260–1600 mg N•m−2) for litter layer plus mineral soil among successional stages in this study was generally lower than the 1200–8400 mg N•m−2 reported by investigators for other studies in temperate latitudes. Vegetation clearing increased the magnitude of temporal fluxes as well as total annual mineral N production. The most consistent increases were encountered in the poplar–alder vegetation type. The average seasonal total net N mineralization for forest floor plus mineral soil in this vegetation type increased from 1500 to 3264 mg N•m−2 as a result of clearing. Soil temperature declined with advancing succession and generally increased as a consequence of clearing. However, these changes were not as closely correlated with N mineralization as were the changes in substrate chemistry encountered across this successional sequence.

Importance of leaf area index and forest type when estimating photosynthesis in boreal forests

Leaf area index (LAI) and vegetation type are two ecological variables that influence atmosphere-biosphere exchange of CO 2 and that can be estimated from remote sensing techniques. A forest ecosystem process model was used to examine the importance of LAI and species-dependent physiology when estimating photosynthesis in 21 black spruce, white spruce, quaking aspen, paper birch, and balsam poplar forests near Fairbanks, Alaska. Model sensitivity analyses for these 21 stands showed that uncertainty in LAI and species composition caused errors in net canopy assimilation of as much as 42–70% and 14–36%, respectively, depending on forest type. The sensitivity of net canopy assimilation to species-dependent physiology was greater between needleleaf coniferous and broadleaf deciduous life forms than among species within life forms. A simple regression model that recognized stand differences in LAI and life-form type (needleleaf coniferous, broadleaf deciduous) accounted for 94% of the variation in simulated net canopy assimilation for the 21 stands. Expanding the model to include species composition rather than life-form type only accounted for an additional 1% of the variation in simulated net canopy assimilation. The statistical model was applied to a synthetic aperture radar scene that discriminatted black spruce, white spruce, balsam poplar, and alder forests in a 76.8 km 2 region near Fairbanks. This analysis showed that regional net canopy assimilation was as sensitive to the area of each forest type as it was to the LAI of each forest type. The analyses reported in this article highlight the importance of recognizing physiological differences among needleleaf coniferous and broadleaf deciduous forest types when estimating regional net canopy assimilation in boreal forests.

Carbon and nitrogen cycling in North American boreal forests

A model of boreal forest dynamics was adapted to examine the factors controlling carbon and nitrogen cycling in the boreal forests of interior Alaska. Empirical relationships were used to simulate decomposition and nitrogen availability as a function of either substrate quality, the soil thermal regime, or their interactive effects. Test comparisons included black spruce forests growing on permafrost soils and black spruce, birch, and white spruce forests growing on permafrost-free soils. For each forest, simulated above-ground tree biomass, basal area, density, litterfall, moss biomass, and forest floor mass, turnover, thickness, and nitrogen concentration were compared to observed data. No one decay equation simulated forests entirely consistent with observed data, but over the range of upland forest types in interior Alaska, the equation that combined the effects of litter quality and the soil thermal regime simulated forests that were most consistent with observed data. For black spruce growing on permafrost soils, long-term simulated forest dynamics in the absence of fire resulted in unproductive forests with a thick forest floor and low nitrogen mineralization. Fires were an important means to interrupt this sequence and to restart forest succession.

The evolution and maintenance of white spruce woodlands on the Mackenzie Delta, N.W.T., Canada

White spruce forests on the most elevated surfaces of the Mackenzie Delta are dying out and are being replaced by open spruce/lichen‐heath or spruce/bog woodlands. Soil profiles indicate that these woodlands have not received flood‐deposited sediments for many years. The active layer is only 20 to 50 cm deep by mid‐summer, and the organic soils are colder and more acidic than soils under white spruce forests flooded during spring ice breakup in 1961, 1972, and 1982. Spruce regeneration is limited to those stands that are flooded periodically, have moderately‐closed canopies, and have a ground cover of herbs rather than feathermosses and lichens. It is proposed that a decrease in flood frequency is primarily responsible for the poor regeneration of white spruce on the most elevated delta surfaces. Spruce woodlands on the delta could succeed to tundra vegetation if present fluvial regimes continue.

Seasonal patterns of soil respiration and CO2 evolution following harvesting in the white spruce forests of interior Alaska

The effect of timber harvesting on soil respiration was investigated in a white spruce (Piceaglauca (Moench.) Voss) forest in interior Alaska. Clear-cutting increased respiration levels, especially in midsummer. Respiration estimates from an uncut, 133-year-old stand of white spruce averaged about 0.45 g•m−2•h−1 over two field seasons. In two adjacent cleared areas, the evolution of CO2 from the soil occasionally exceeded 0.6 g•m−2•h−1. Soil temperature and moisture regimes were increased after harvesting, presumably owing to increased insolation and reduced evapotranspiration. It was possible to relate the changes in these environmental parameters, by soil horizon, to respiration through previously developed nonlinear models and linear regression.

White spruce expansion at the tree line and recent climatic change

White spruce (Piceaglauca (Moench) Voss) populations at their northern limit of distribution, the tree line along the east coast of Hudson Bay, expanded significantly during the last 100 years in response to recent climatic warming. Expansion began around 1880 but was more important during the 20th century, especially between 1920 and 1965. Although no major change in the position of the forest limit and the latitudinal tree line occurred, local altitudinal tree lines rose a few tens of meters. The seed regeneration line increased to about 100 meters above the present altitudinal tree line during the same period. Tree density increased below the local tree lines at many sites. There, spruce expansion was stepwise, as indicated by widely distributed clustered cohorts belonging to the 10–29, 50–59, and 70–89 age-class groups. Although the expansion process was stimulated by nearby old seed bearers, long-distance seed dispersal did occur. The development of contagious dispersion during the formation of white spruce groves or forests caused important local ecological changes, particularly in snow patterns and tree growth. Fire selectively influenced tree regeneration during the past centuries. Black spruce krummholz were progressively decimated during the last 400 years before present, although the species was characterized by low postfire regeneration. Vigorous postfire white spruce regeneration was stimulated by favorable climatic conditions 100 years ago in the northernmost forest site. Conclusions from this study support the hypothesis that Holocene tree line displacements were of low magnitude in northern Québec, and that the primary influence of climatic change was on tree density.

Bioassay of forest floor phosphorus supply for plant growth

This paper considers the extent to which phosphorus (P) supply for plant use is controlled by the chemical quality of forest floor organic matter, independent of climate. Using plant bioassays, forest floor materials from representative examples of each of the major forest types in interior Alaska were examined for nutrient supplying power. The work supports conclusions reached in earlier studies which indicated that black spruce forest floors were highly nutrient limited compared with those of other interior Alaska forest types. In addition, floodplain white spruce forests may experience marked P deficiency because of dilution of the element by periodic siltation. Potential phosphorus supply for seedling growth was best described by P concentration of the rooting medium. The supply also was related to the concentrations of lignin and tannin which control forest floor decomposition and recycling of P within the microbial population.

Effects of extra food on Peromyscus and Clethrionomys populations in the southern Yukon.

If food supply limits density in rodent populations, the addition of supplemental food ought to increase population size. From May to September we added food on 2-hectare areas of white spruce forest in the southern Yukon. In 1977, we used oats with no measurable impact. In 1978 and 1979 we used sunflower seeds and doubled or tripled the population densities of Peromyscus maniculatus and Clethrionomys rutilus. Supplemental feeding with sunflower seeds increased juvenile production in both species, probably by increasing early juvenile survival. The breeding season ended at the same time on experimental and control areas, and the onset of maturity in juveniles was not affected by feeding. Survival of adult rodents was not improved by feeding. Immigration into sunflower seed areas was very high, and was the major factor producing the increase in population density. Body weight was not changed by feeding. Food supply is thus one factor limiting population density in these subarctic small mammals, but we do not know why supplemental food produces no more than a 2- to 3-fold effect on densities.

THE DISTRIBUTION OF AERIALLY-APPLIED SPRAY DEPOSITS IN SPRUCE TREES

AbstractA plot of 6 m tall white spruce trees was treated with an aerial application of an oil-base spray containing a non-toxic compound, Tris (2 ethyl hexyl) phosphate (referred to as TOF), which was amenable to gas-liquid chromatographic analysis The spray was formulated and applied at a rate to approximate the eastern Canadian operational spruce budworm control sprays. Meteorological measurements were made in the airspace from mid-crown height to the height of spray emission for the period of spray application and deposition. Spray deposit collection units (kromekote cards and glass plates) were used to record spray deposit at ground level.Foliage samples and complete branches were taken from each of three trees at a series of heights and each of the four compass quadrants and returned to the laboratory for chemical analysis. Spray deposit was determined in terms of ppm TOF on the foliage. The kromekote cards provided information from which the drop size characteristics of the spray cloud and the deposit in terms of drops/cmK were determined; a colorimetric analysis of spray deposit on the glass plates indicated the volume of spray deposited.Analysis of the spray deposits on the foliage indicated gradients in deposits with most on the upper, outer, upwind portions of the trees and least on the lower, inner, downwind portions. These differences were significant. These gradients can be attributed to two weather factors (a) the prevailing wind drifting the pesticide cloud through the forest canopy resulting in a filtering to produce a decreasing gradient from upwind to downwind side of the tree, and (b) air eddies around the tree tops resulting in an increased deposit and slight penetration of the spray cloud on the outer downwind portions of the tree.This study demonstrates that a finely atomized spray applied to a white spruce forest under suitable weather conditions will give a deposit on the outer portions of the tree with a variation of only about 50% in spray deposit but with significantly less deposit on the inner, lower portions of the tree.

Weight loss of litter and cellulose bags in a thinned white spruce forest in interior Alaska

Thinning in a white spruce, Piceaglanca (Moench) Voss, forest in interior Alaska stimulated organic matter decomposition in the forest floor as indicated by weight loss of litter and cellulose bags. The general higher weight loss in the most heavily thinned plot is attributed to observed higher average seasonal temperatures. Cellulose bags placed in the boundary between the fermentation–humus and the humus–mineral soil layers of the forest floor showed a significantly higher weight loss than those placed on top of the litter layer. This was attributed to more favorable moisture conditions and a more direct contact with the decomposing microbial populations in the fermentation–humus and humus–mineral soil layers.Regardless of thinning treatment, elements were grouped according to their rate of release from decomposing organic matter as follows: K > Mg > C ≈ P ≈ N ≈ Ca, where potassium is lease resistant. Since relatively small differences in weight loss of litter bags were observed between the treatments, similar studies should extend over a longer period in order to obtain a better understanding of the decomposition processes.

Effects of Clearcut Logging on Wild Ungulates in the Central Albertan Foothills

The effects on big game of clearcut logging a mature white spruce forest (Picea glauca) in strips 10-chains wide, with residual strips 5-chains wide to be logged 12 years later, were studied in a 6-square-mile area of the Rocky Mountain foothills near Hinton, Alberta. Use by deer, elk and moose decreased during the first 5 years following clearcut logging with the decrease most pronounced in scarified cut-overs. Five years after logging, browse production in the unscarified area exceeded the 529 lb./acre in the unlogged forest. In years 9 and 17 the logged unscarified area produced three and four times as much browse as the unlogged forest while production in the logged scarified area averaged 10% below the unscarified area. Changes in species composition and height affected both browse utilization and cover. These habitat changes were further evident in estimates of ungulate use. Observed numbers of big game 17 years after logging and scarification were much lower than expected from the forage carrying-capacity estimates. Forage carrying capacity potentials were one moose/7.7, one elk/3.6 and one deer/0.7 acres. However, in summer, observed populations were one moose/213.3, one elk/71.1 and one deer/40.0 acres respectively. Observed use of the area dropped drastically in winter, apparently due to the absence of adequate cover, to no moose or elk and only one deer/1280 acres.

Small Mammals and Regeneration of White Spruce Forests in Western Alberta

The fate of 7,800 pesticide—treated and radiotagged white spruce seeds (Picea glauca (Moench) Voss var. albertiana (S. Brown) Sarg.) was studied under field conditions near Hinton, Alberta, Canada, from 1962 to 1967. Approximately 50% of spring—placed seeds were destroyed by small mammals within 4 months, whereas only 19% or less of winter—placed seeds were lost within a year. From five to six times more seeds germinated following the winter seeding operations than after the first spring seeding test. Calcualted ground seed—eating small—mammal populations varied from 2.0 to 7.4 (average 4.5) animals per acre in spring and from 4.9 to 12.2 (average 8.1) in the fall. Percentages of seeds destroyed were more directly related to time of seeding than to the number of animals present.