Pure Black Spruce Research Articles

An indicator species highlights continuous deadwood supply is a key ecological attribute of boreal old‐growth forests

AbstractOld‐growth forests are optimal habitats for many woodpeckers, which are often themselves excellent indicators of deadwood‐associated biodiversity. Old‐growth forests are, however, heterogeneous ecosystems in terms of structure, composition, and deadwood characteristics, thus implying a varied use of these forests by woodpeckers. In boreal landscapes, old‐growth stands are threatened by forest harvesting; however, there is little information in regard to the consequences for biodiversity with the loss of specific types of old‐growth forests. This study aimed to assess how the black‐backed woodpecker (Picoides arcticus), a biodiversity indicator species associated with old‐growth forest attributes, uses different types of old‐growth forests for its foraging needs. We identified woodpecker foraging marks in 24 boreal old‐growth forest stands in eastern Canada that were dominated by black spruce (Picea mariana), located within the home range of eight black‐backed woodpeckers. We identified the various old‐growth forest types using a typology based on the structural attributes of old‐growth stands. We classified the sampled stands into four old‐growth forest types, corresponding to different successional stages (recent or old, relative to the onset of the old‐growth stage), composition (pure black spruce or mixed black spruce–balsam fir [Abies balsamea]), and productivity (ongoing paludification or not). The black‐backed woodpecker foraged in all types of old‐growth forests, but favored dense old‐growth forests that were not paludified and that showed a high temporal continuity (i.e., old‐growth dynamics probably started more than a century ago). The temporal continuity of the old‐growth state allows for the continuous supply of large, slightly decayed snags, the preferred foraging substrates of the black‐backed woodpecker. The old‐growth forest type most favored by this woodpecker is, however, also the forest type most often targeted first by logging operations. Protecting the biodiversity associated with recent deadwood in managed areas thus requires maintaining a sufficient area and density of dense, old‐growth black spruce‐dominated forests in managed areas.

Does the type of silvicultural practice influence spruce budworm defoliation of seedlings?

AbstractSpruce budworm (Choristoneura fumiferana (Clem)) is the main defoliator in the boreal forest of North America, and its outbreaks have major ecological and economic consequences and represent a challenge for forest management. Numerous studies have addressed the effects of this defoliator on mature trees, whereas the effects of spruce budworm on regeneration remain elusive. Furthermore, intensive exploitation practices during the last decades have left a large area of the Canadian boreal forest in an early development stage. In this context, it becomes vital to understand those factors affecting the severity of spruce budworm‐related defoliation on regeneration. Here, we determine the defoliation severity of black spruce and balsam fir seedlings in both mature pure black spruce and black spruce–balsam fir stands subjected to two different silvicultural treatments (clear‐cutting and partial cutting). Defoliation intensity varied between stand types, silvicultural treatments, species, and height classes. Seedlings in black spruce–balsam fir stands experienced twice the defoliation of those in pure black spruce stands (black spruce seedlings 10% vs. 23%; balsam fir seedlings 29% vs. 47%, respectively). Harvesting methods also influenced seedling defoliation. Under clear‐cutting, black spruce seedlings (24%) were three times as defoliated as black spruce seedlings in partial cutting stands (8%), whereas balsam fir seedlings in clear‐cutting plots experienced twice the defoliation (42%) of balsam fir seedlings in partial cutting plots (20%). The level of defoliation also increased with seedling height. This study will help silvicultural strategies adapt to the effects of natural disturbance regimes. As the intensity and severity of defoliator outbreaks are expected to increase under climate change, these results will help guide forest management strategies to select harvesting methods that will limit the effects of defoliation on conifer regeneration.

Early Regeneration Dynamics of Pure Black Spruce and Aspen Forests after Wildfire in Boreal Alberta, Canada

Research Highlights: Black spruce (Picea mariana Mill.) and trembling aspen (Populus tremuloides Michx.) both regenerated vigorously after wildfire. However, pure semi-upland black spruce stands are at increasing risk of changing successional trajectories, due to greater aspen recruitment. Background and Objectives: Black spruce and aspen are found across the boreal forest with black spruce dominating lowlands and aspen being common in uplands. Both species are well adapted to wildfire with black spruce holding an aerial seedbank while aspen reproduce rapidly via root suckering. In the summer of 2016, the Horse River wildfire burned 589,617 hectares of northern Alberta’s boreal forest. Methods: We assessed early regeneration dynamics of both pure aspen and pure black spruce forests. For black spruce, 12 plots were established in both bog and semi-upland habitats to assess seedling regeneration and seedbed availability. For aspen, 12 plots were established in each of the low, moderate, and high burn severities, as well as 5 unburned plots. Results: Post-fire black spruce regeneration densities did not differ between bog and semi-upland habitats, but were positively correlated with forb cover and charred organic matter seedbeds. Aspen regeneration within pure black sprue stands was substantial, particularly in semi-upland habitats, indicating a potential shift in successional trajectory. Fire severity did not significantly affect aspen regeneration in pure aspen stands, but regeneration density in all severity types was >90,000 stems ha−1. Aspen regeneration densities were negatively related to post-fire forb and shrub cover, likely due to competition and cooler soil temperature.

Ecogeographic variation in black spruce wood properties across Quebec’s boreal forest

Ecogeographic variation in black spruce clear wood properties was investigated for the two main vegetation types of the managed boreal forest of the province of Quebec, Canada. In total, 409 co-dominant and dominant trees from 82 mature stands were sampled. Basic wood density, modulus of elasticity and microfibril angle were measured using SilviScan. Mature fiber length was determined using a high-resolution Fiber Quality Analyzer. Wood growing in pure black spruce stands had longer mature fibers, a significantly denser wood with better mechanical characteristics than the wood growing in mixed stands with balsam fir. All wood properties were clearly influenced by radial growth and species composition.Given the limited number of sample plots for mapping purposes, a two-stage modeling approach was assessed to predict stand-level estimates of black spruce clear wood properties. This scaling-up method, based on field measurements and ring data from 3350 inventory plots, has improved the performance of all models. Stand-level models explained 47%, 57%, 63% and 63% of variance in wood density, modulus of elasticity, microfibril angle and mature fiber length respectively with estimated root mean square errors of 8.9kg/m3, 0.52GPa, 0.60° and 0.06mm.An east-west gradient in black spruce clear wood properties was revealed as possibly the by-product of the change in relative proportions of both studied vegetation types across the study area. The results indicate that the black spruce wood from western regions of the managed boreal forest has a better potential for producing pulp and paper, lumber or engineered products due to its longer mature fibers and higher mechanical properties.

Daily burned area and carbon emissions from boreal fires in Alaska

Abstract. Boreal fires burn into carbon-rich organic soils, thereby releasing large quantities of trace gases and aerosols that influence atmospheric composition and climate. To better understand the factors regulating boreal fire emissions, we developed a statistical model of carbon consumption by fire for Alaska with a spatial resolution of 450 m and a temporal resolution of 1 day. We used the model to estimate variability in carbon emissions between 2001 and 2012. Daily burned area was mapped using imagery from the Moderate Resolution Imaging Spectroradiometer combined with perimeters from the Alaska Large Fire Database. Carbon consumption was calibrated using available field measurements from black spruce forests in Alaska. We built two nonlinear multiplicative models to separately predict above- and belowground carbon consumption by fire in response to environmental variables including elevation, day of burning within the fire season, pre-fire tree cover and the differenced normalized burn ratio (dNBR). Higher belowground carbon consumption occurred later in the season and for mid-elevation forests. Topographic slope and aspect did not improve performance of the belowground carbon consumption model. Aboveground and belowground carbon consumption also increased as a function of tree cover and the dNBR, suggesting a causal link between the processes regulating these two components of carbon consumption. Between 2001 and 2012, the median carbon consumption was 2.54 kg C m-2. Burning in land-cover types other than black spruce was considerable and was associated with lower levels of carbon consumption than for pure black spruce stands. Carbon consumption originated primarily from the belowground fraction (median = 2.32 kg C m-2 for all cover types and 2.67 kg C m-2 for pure black spruce stands). Total carbon emissions varied considerably from year to year, with the highest emissions occurring during 2004 (69 Tg C), 2005 (46 Tg C), 2009 (26 Tg C), and 2002 (17 Tg C) and a mean of 15 Tg C year-1 between 2001 and 2012. Mean uncertainty of carbon consumption for the domain, expressed as 1 standard deviation (SD), was 0.50 kg C m-2. Uncertainties in the multiplicative regression model used to estimate belowground consumption in black spruce stands and the land-cover classification were primary contributors to uncertainty estimates. Our analysis highlights the importance of accounting for the spatial heterogeneity of fuels and combustion when extrapolating emissions in space and time, and the need for of additional field campaigns to increase the density of observations as a function of tree cover and other environmental variables influencing consumption. The daily emissions time series from the Alaskan Fire Emissions Database (AKFED) presented here creates new opportunities to study environmental controls on daily fire dynamics, optimize boreal fire emissions in biogeochemical models, and quantify potential feedbacks from changing fire regimes.

A Height Growth Model and Associated Growth Intercept Models for Estimating Site Index in Black Spruce (Picea mariana Mill. B.S.P.) Plantations in Northern Ontario, Canada

Abstract Site quality is a key component of growth and yield models because height growth rates are known to be influenced by available site resources. Accurate prediction of future growth and yield requires site quality information for both plantations and natural stands. The forest industry in northern Ontario relies on high-quality wood and fiber from black spruce (Picea mariana Mill. B.S.P.); therefore, these tools are essential to ensure sustainable forest management. Although there are site index (SI) models for natural-origin black spruce stands in northern Ontario, models for estimating site quality of young black spruce plantations have not been developed. We used stem analysis data collected from 62 plantations (>40 years of age) of pure black spruce across northern Ontario to develop height growth, SI, and variable growth intercept models. The distinct height growth patterns we observed may be attributed to early silvicultural treatments (site preparation and herbicide) in plantations allowing black spruce trees to attain breast height (1.3 m) faster than in fire-origin stands in northern Ontario. Our models can be used to estimate site quality of black spruce plantations, a key consideration for silviculture and forest management planning. We also compare our managed stand SI model to one we developed from a comparable subset of data from black spruce growing in unmanaged stands and propose a method to assign an SI with a common base age to pure upland black spruce stands regardless of origin.

Clonal and nonclonal genetic structure of subarctic black spruce (Picea mariana) populations in Yukon territory

Black spruce (Picea mariana) reproduces sexually from seeds and asexually by layering. There is a prevalent concept that clonal reproduction maintains populations of this species in the subarctic and arctic regions. We used microsatellite DNA markers of the nuclear genome to investigate the genetic structure of montane and subalpine black spruce populations from the Western Yukon Plateau in relation to this concept. Sixty individual trees at a minimum distance of 4 m from each other were sampled from each of four populations and individual trees were genotyped for eight microsatellite loci. Each of the 60 individuals from three montane pure black spruce populations growing on flat terrain at relatively low elevations had unique multilocus genotypes, indicating an absence of clonal structure in those populations. However, in an anthropologically undisturbed climax white spruce-dominated subalpine black spruce population on a northwest slope near Mount Nansen, the majority of the sampled individuals belonged to eight genetically distinct clones (genets). Clone size differed by altitude, the dominant genet being nearest the timberline–tundra ecotone. The results indicate that black spruce reproduction is variable and adaptive, being primarily sexual in flat-terrain montane populations previously subjected to fire disturbance, but mixed vegetative–sexual in the anthropogenically undisturbed subalpine population. This study is the first to employ molecular markers a priori to examine the mode of reproduction in natural black spruce populations.

Genetic variation and control of chloroplast pigment concentrations and related needle-level traits in Picea rubens, Picea mariana, and their hybrids: moisture and light environmental effects

Chlorophyll pigment concentrations and proportions, nitrogen (N), and needle morphology traits, are important components of growth and were examined in five hybrid index categories from controlled crosses of various crosstypes, ranging from pure black spruce (BS) [Picea mariana (Mill.) B.S.P.] to pure red spruce (RS) (Picea rubens Sarg.) grown under controlled light and water environments. Black spruce had on average 10% greater total chlorophyll concentration (CHL) than RS. Red spruce had proportionately less chlorophyll a:b and CHL:CAR (carotenoid) ratios than BS. Nitrogen (N) concentrations were 1.75 and 1.60% for BS and RS, respectively. Black spruce had the lowest carbon (C):N ratio (29.7) and RS had among the highest (32.3). Interestingly, there was no difference in specific needle area among hybrid indices. Most of the chlorophyll pigment, C and N traits followed an additive inheritance model, evidenced by a near-linear relationship from BS to RS across hybrid indices. However, for CHL, CAR, and CHL:CAR ratio, parental analysis showed significant male effects and non-significant female and male × female interaction effects. Black spruce males had 15.1 and 9.6% higher CHL and CAR, respectively, than hybrid or RS males, thus showing an underlying paternally inherited genetic control. Controlling for N differences, analysis of covariance (ANCOVA) showed that sun-grown seedlings had 22.2% or 300 μg g−1 lower CHL than shade-grown seedlings. Controlling for N, ANCOVA showed that the drought-grown seedlings actually had 6.7% or 100 μg g−1 greater CHL than the irrigated seedlings. Sun plus drought conditions gave the lowest CHL, N, and CHL:CAR ratio of all treatments, showing an additive multi-stress effect. There was a significant hybrid index × light effect as a result of rank changes. Sun-grown RS had the lowest CHL and N values, whereas shade-grown RS had among the highest CHL and N values. Red spruce are at a competitive disadvantage compared with BS and most hybrid spruce in high light, high drought, and high light plus drought conditions. Red spruce will be strongly limited in its distribution by successional opportunities resulting from prevalent harvesting practices such as clearcutting. Silvicultural modifications and genetic restoration will be required to maintain RS on the landscape of northeastern North America.

Simulating carbon exchange of Canadian boreal forests: II. Comparing the carbon budgets of a boreal mixedwood stand to a black spruce forest stand

The boreal forest, earth's second largest terrestrial biome, is currently thought to be an important net carbon sink for the atmosphere. In this study, a newly developed carbon exchange model of TRIPLEX-Flux (with half-hourly time step) is used to simulate the ecosystem carbon exchange of a 75-year-old boreal mixedwood forest stand in northeast Ontario and a 110-year-old pure black spruce stand in southern Saskatchewan, Canada. Results of net ecosystem exchange (NEE) simulated by TRIPLEX-Flux for 2004 are compared with those measured by eddy-flux towers and suggest overall agreement between model simulation and observations. The mean coefficient of determination ( R 2) is approximately 0.77 for boreal mixedwood and 0.62 for old black spruce. Differences between model simulation and observation may be attributed to uncertainties not only in model input parameters and calibration, but also in eddy-flux measurements caused by systematic and random errors. The model is able to capture the diurnal variations of NEE for the growing season (from May to August) of 2004 for both sites. Both boreal mixedwood and old black spruce were acting as carbon sinks for the atmosphere during the growing season of 2004. However, the boreal mixedwood stand shows higher ecosystem productivity, carbon sequestration, and carbon use efficiency than the old black spruce stand.

The Response of Conifer and Broad-Leaved Trees and Shrubs to Wildfire and Clearcut Logging in the Boreal Forests of Central Labrador

Abstract To assess the differences between forest management and natural disturbance, we retrospectively compared crown cover of woody plant species between burned and clearcut sites after 5, 14, and 27 years of succession. All 16 sites had been dominated by black spruce (Picea mariana) before disturbance. We found no difference in species richness between disturbance types, but richness was lowest on 5-year-old sites for both disturbances. Burned and clearcut sites differed in the cover of woody plant species, differences increasing slightly with time since disturbance. Both balsam fir (Abies balsamea) and black spruce were more abundant on 14- and 27-year-old clearcut plots than burned plots. Black spruce cover was always greater than fir, but the spruce:fir ratio on clearcut plots was lower than on burned plots. Our data suggest that fire and clearcut logging affect postdisturbance succession differently. Contrary to other studies, logging resulted in more commercially valuable black spruce than fire, and broad-leaved woody plants were not in greater abundance on logged sites. However, the persistence of fir through logging suggests that the resulting forest would be of lower commercial value than a pure black spruce forest. North. J. Appl. For. 22(1):35–41.

Développement d’un outil de classification de la structure des peuplements et comparaison de deux territoires de la pessière à mousses du Québec

Forest stand structure is an important element for biodiversity and, from a sustainable forest management perspective, uneven-sized stands should be managed in order to maintain the structural diversity over the landscape. The first objective of this study is to develop a statistical tool to characterize stand structure that can be used in forest management planning. The second objective is to classify the stand structure of two regions to illustrate a possible use for the tool. The statistical tool for characterizing stand structure has been developed from forest inventory data gathered by the ministère des Ressources naturelles du Québec, using discriminant analysis. The analysis makes it possible to classify the stands into three types of structure, even-sized, uneven-sized and inverse J-shaped, with an error rate estimated at only 7%. Proportions of different structure types in Quebec’s eastern black spruce forest region have been compared with those found in the western black spruce forest region. Nearly 90% of the western black spruce forest region is composed of pure black spruce stands, contrary to the eastern black spruce region, where there are more pure fir and mixed spruce-fir stands. Most of the western black spruce forest stands are even-sized (62%), while almost 70% of the eastern black spruce forest stands are uneven-sized or inverse J-shaped. Pure black spruce stands are more even-sized than pure fir stands, but regional differences are also found within pure black spruce stands. Our results show that it is possible to develop a robust tool that makes it possible to classify thousands of stands rapidly. Such tools are required if we want to consider stand structure for appropriate management prescriptions in the boreal forest. Key words: Even- and uneven-sized structure, fire regime, Picea mariana, Abies balsamea, boreal forest, structural diversity

Tree-ring patterns in stems and root systems of black spruce (Picea mariana) caused by spruce budworms

Radial growth along the stems and root systems of black spruce trees (Picea mariana (Mill.) BSP) was examined to determine the effects of spruce budworm defoliation. A mixed conifer and pure black spruce stand located in the boreal zone of Quebec, Canada were sampled. Following defoliation, dendrochronological analyses revealed the percent growth reduction in the ring width at different stem heights and throughout the root system. Ring widths of black spruce were found to be reduced during the last three spruce budworm outbreaks. The reduction of the tree-ring width after spruce budworm outbreaks started first in the crown region and was followed by reduction at the stem base. For the whole root system, the ring-width index exhibited a decrease. The root system showed a high sensitivity to defoliation by spruce budworm. Inside the root system, the growth reduction after a spruce budworm outbreak was variable in each root branch. The growth decrease of the pure black spruce stand was less intensive than in the mixed stand.

Negative heterosis not apparent in 22-year-old hybrids of Picea mariana and Picea rubens

Work from the 1970s indicated that, relative to either parent species, crosses between red spruce (Picea rubens Sarg.) and black spruce (Picea mariana (Mill.) B.S.P.) were inferior with respect to both growth and photosynthesis. We re-examined the hypothesis that there is negative heterosis in hybrids of red and black spruce using 22-year-old trees in a common garden study planted on two sites. The trees were the product of controlled crossings and represent a continuum from hybrid class 0 (pure black spruce) to hybrid class 1 (pure red spruce). Progeny of all controlled crosses were measured for height and diameter. A subset of families were measured for gas exchange and were assessed using a hybrid index based on needle color, needle configuration, twig ridges, twig bark color, vegetative bud color, and cone scale morphology. Tree growth rate linearly declined with the increasing proportion of red spruce germplasm (increasing hybrid index). In 1994, intermediate hybrid index classes did not differ in gas exchange from either pure black spruce (hybrid index class 0) or pure red spruce (hybrid index class 1), and in 1996, hybrids displayed slightly higher rates of gas exchange. Thus, negative heterosis was not apparent in 22-year-old trees. Individual tree hybrid index generally agreed with expectation based on midparent means, although the relationship was stronger on the higher productivity site (r2 = 0.91) than the poorer productivity site (r2 = 0.54).Key words: black spruce, heterosis, hybrid, photosynthesis, red spruce.

Base-Age Invariant Polymorphic Site Index Curves for Black Spruce and Balsam Fir Within Central Newfoundland

Abstract Increasing management intensity within Newfoundland requires that regional site index equations be species-specific and base-age invariant. Accordingly, base-age invariant polymorphic site index curves for black spruce and balsam fir were developed for use on upland mineral sites within central insular Newfoundland. Specifically, employing mean dominant height and breast-height age data derived from 129, 0.081 ha permanent sample plots situated in pure black spruce (n = 71) and mixed black spruce/balsam fir (n = 58) stands, site index equations were calibrated by species and stand type. In addition, given the approximate numeric equivalence of the resultant parameter estimates, data for both species and stand types were combined and a pooled equation calibrated. The equations were evaluated on their bias and predictive ability over 10-, 20-, and 30-year projection periods. Results indicated that the predictions were positively biased averaging +1.29 m, +2.36 m, and +3.15 m for 10-, 20-, and 30-year projection periods, respectively. Corresponding 95% prediction error intervals for these periods were -0.56 to +3.14 m, -0.88 to +5.44 m, and -1.27 to +6.56 m. These biases and prediction errors are within acceptable limits for site-class designations; however, explicit use of the site-index equations with growth and yield models would depend on error tolerances specified by individual users. North. J. Appl. For. 9(1):18-22

Ten-year growth response to fertilizers by semimature black spruce and spruce-poplar mixedwoods near Kapuskasing, Ontario

Five- and 10-year mean DBH, BA and volume growth responses to N, P and K fertilizer combinations are reported for three field trials in semimature black spruce and spruce-poplar mixedwoods in the clay belt of northern Ontario. Responses, though present, were generally nonsignificant. Modest responses to N, improved somewhat by the addition of K, but not P, were noted in a pure black spruce stand on an upland site. On a lowland site, however, no response by pure black spruce to either N or K, and only a small, nonsignificant response to P, were noted. In an upland mixedwood stand containing mainly black spruce and balsam poplar, responses were variable. In comparison with jack pine in northern Ontario, black spruce has responded poorly to mineral fertilizers. Results are discussed in relation to foliar nutrient concentrations and are compared with results from other fertilizer trials in the eastern boreal forest.

Cytophotometric Differentiation Of HIGH Elevation Spruces: Physiological and Ecological Implications

Red and black spruce and their hybrids can be determined by morphological indices; however, the criteria are somewhat subjective and increasingly difficult to use at higher elevations. Although the chromosome number is identical (2n = 24), red spruce has twice as much nuclear DNA (48 pg) than black spruce (24 pg) and thus the species and their hybrids can also be separated by cytophotometry. This is relevant to spruce decline studies because black spruce is much more resistant to high elevation environmental stresses, both natural and anthropogenic. It also has implications for the effect of climatic changes on the composition of high elevation spruce-fir forests because red spruce can outcompete black spruce under more mesic conditions. Four elevation transects sampling spruce on the east and west sides of Mount Washington (New Hampshire) and Camels Hump (Vermont) and a single transect on the southwest side of Whiteface Mountain (New York) were made to investigate the degree of hybridization and introgression between these two species. A positive correlation was found between increased elevation and increased black spruce genes on Mount Washington and Camels Hump. Pure black spruce was found on Mount Washington from 1356 m to 1582 m. No pure black or red spruce was found on Camels Hump although the proportion of red spruce alleles was significantly greater on Camels Hump. All trees sampled at all elevations on Whiteface Mountain were pure red spruce. Thus the proportion of black spruce alleles in high elevation spruce populations decreases from east to west. This closely parallels the increase in spruce decline which increases from east to west.

A NEW APPROACH TO THE NORTHERN SPRUCE REGENERATION PROBLEM

Lack of reproduction of black spruce, Picea mariana, in pure black spruce stands in old cut-over areas, has always been a great subject of discussion and one for intensive work among foresters. Many reasons such as the absence of an adequate seed supply stored on top of humus, or adverse germination conditions are said to be partly responsible.This study on the humus of this unregenerated cut-over area, indicates clear cutting of this stand will influence the normal concentration of definite micro-nutrients such as manganese and magnesium.The augmentation of manganese in the soil has a detrimental effect on the growth of plants when, its concentration is too high. The diminution of magnesium, which is an element necessary to stimulate the growth, must create abnormal nutritive conditions of the habitat. This visible lack of equilibrium might be the cause of the absence of seedlings of Picea mariana on certain parts of this cut-over area.