Boreal Settings Research Articles

Accounting for albedo change to identify climate-positive tree cover restoration

Restoring tree cover changes albedo, which is the fraction of sunlight reflected from the Earth’s surface. In most locations, these changes in albedo offset or even negate the carbon removal benefits with the latter leading to global warming. Previous efforts to quantify the global climate mitigation benefit of restoring tree cover have not accounted robustly for albedo given a lack of spatially explicit data. Here we produce maps that show that carbon-only estimates may be up to 81% too high. While dryland and boreal settings have especially severe albedo offsets, it is possible to find places that provide net-positive climate mitigation benefits in all biomes. We further find that on-the-ground projects are concentrated in these more climate-positive locations, but that the majority still face at least a 20% albedo offset. Thus, strategically deploying restoration of tree cover for maximum climate benefit requires accounting for albedo change and we provide the tools to do so.

Seasonal patterns in nutritional condition of caribou (Rangifer tarandus) in the southern Northwest Territories and northeastern British Columbia, Canada

Evaluating nutritional condition provides insights of nutritional influences on wildlife populations. We sampled three measures of condition — body fat, body mass, and loin thickness — of adult female caribou (Rangifer tarandus (Linnaeus, 1758)) in boreal settings in the Northwest Territories (NT), Canada, in December and March, 2016–2018, and in mountain and boreal settings in British Columbia (BC), Canada, in December and February, 2014–2015. We evaluated the effect of calf-rearing on condition in December, compared influences of summer–autumn versus winter on condition over winter, and developed an annual profile of nutritional condition with estimates from caribou dying in summer. Mean December body fat was 8.4% in females with calves and 11.4% in females without calves, demonstrating the influence of lactation on condition. Over winter, nutritional condition did not decline in northeastern BC and it declined slightly in NT: body fat by 0.55 percentage points, mass by 2.8 kg, and loin thickness did not change. Body fat peaked in December, changed little over winter, but declined to a minimum by early summer, temporally coinciding with elevated rates of adult female mortality. Consistent with those of other ungulate studies worldwide, our findings suggest a need to focus on nutritional limitations operating in late spring through early autumn.

Nurturing Environmental Transformation and Scholastic Success in Northern Manitoba

Effective non-traditional approaches to environmental lesson delivery and enrollee evaluation remain ephemeral in northern Manitoba as indicated by negative local attitudes towards imported and metropolitanized instruction (Martin, 2014; Mercredi, 2009). Current pandemic aside, and as increased attrition and abysmal failure rates have not changed in decades, there is relevance in exploring the experiential context and local implications of an inductive student model intended to improve remote environmental understanding and scholastic performance. To help prevent perpetuating a dis-order in which Indigenous expressions are neither recognized nor developed, learning experiences of University College of the North (UCN) students concerning regional freshwater availability and the calculation of stream flow were documented. Using componential analysis and participatory video as a mediating technology, allied empirical test scores and codified normative elements of self and environmental ‘awareness’ in traditional classrooms versus boreal settings were examined. Three exploratory factor axes explained more than 50% of the variance from an integrated but diverse set of 27 chosen variables. Titled axes declining in order of importance were Environmental Engagement, Scholastic Scoring and Non-Conventional Lesson Delivery. Seventy percent of unsolicited adult student responses suggest moralization and unique meta-ethical quale were undeniably and academically important. Empirical-‘ized’ findings advocate UCN must now ask which aspects of curriculum design, lesson delivery and enrollee assessment might result in greater scholastic success when nurturing personalized transformations in the milieu of ongoing threats to both freshwater sustainability and Cree safeguarding paradigms in northern Manitoba.

Surface Energy Flux Estimation in Two Boreal Settings in Alaska Using a Thermal-Based Remote Sensing Model

Recent Arctic warming has led to changes in the hydrological cycle. Circum-Arctic and circumboreal ecosystems are showing evidence of “greening” and “browning” due to temperature warming leading to shrub encroachment, tree mortality and deciduousness. Increases in latent heat flux from increased evapotranspiration rates associated with deciduous-dominated ecosystems may be significant, because deciduous vegetation has extremely high-water use and water storage capacity compared to coniferous and herbaceous plant species. Thus, the impact of vegetation change in boreal ecosystems on regional surface energy balance is a significant knowledge gap that must be addressed to better understand observed trends in water use/availability and tree mortality. To this end, output from a two-source energy balance model (TSEB) with modifications for high latitude boreal ecosystems was evaluated using flux tower measurements and Terra/Aqua MODIS remote sensing data collected over the two largest boreal forest types in Alaska (birch and black spruce). Data under clear and overcast days and from leaf-out to senescence from 2012 to 2016 were used for validation. Using flux tower observations and local model inputs, modifications to the model formulation for soil heat flux, net radiation partitioning, and canopy transpiration were required for the boreal forest. These improvements resulted in a mean absolute percent difference of around 23% for turbulent daytime fluxes when surface temperature from the flux towers was used, similar to errors reported in other studies conducted in warmer climates. Results when surface temperature from Terra/Aqua MODIS estimates were used as model input suggested that these model improvements are pertinent for regional scale applications. Vegetation indices and LAI time-series from the Terra/Aqua MODIS products were confirmed to be appropriate for energy flux estimation in the boreal forest to describe vegetation properties (LAI and green fraction) when field observations are not available. Model improvements for boreal settings identified in this study will be implemented operationally over North America to map surface energy fluxes at regional scales using long time series of remote sensing estimates as part of NOAA’s GOES Evapotranspiration and Drought Information System.

The beaver facilitates species richness and abundance of terrestrial and semi-aquatic mammals

Beavers are ecosystem engineers which are capable to facilitate many groups of organisms. However, their facilitation of mammals has been little studied. We applied two methods, camera trapping and snow track survey to investigate the facilitation of a mammalian community by the ecosystem engineering of the American beaver (Castor canadensis) in a boreal setting. We found that both mammalian species richness (83% increase) and occurrence (12% increase) were significantly higher in beaver patches than in the controls. Of individual species, the moose (Alces alces) used beaver patches more during both the ice-free season and winter. The Eurasian otter (Lutra lutra), the pine marten (Martes martes) and the least weasel (Mustela nivalis) made more use of beaver sites during the winter. Our study highlights the role of ecosystem engineers in promoting species richness and abundance, especially in areas of relatively low productivity. Wetlands and their species have been in drastic decline during the past century, and promoting facilitative ecosystem engineering by beaver is feasible in habitat conservation or restoration. Beaver engineering may be especially valuable in landscapes artificially deficient in wetlands.

Sediment accumulation rates in subarctic lakes: Insights into age-depth modeling from 22 dated lake records from the Northwest Territories, Canada

Age-depth modeling using Bayesian statistics requires well-informed prior information about the behavior of sediment accumulation. Here we present average sediment accumulation rates (represented as deposition times, DT, in yr/cm) for lakes in an Arctic setting, and we examine the variability across space (intra- and inter-lake) and time (late Holocene). The dataset includes over 100 radiocarbon dates, primarily on bulk sediment, from 22 sediment cores obtained from 18 lakes spanning the boreal to tundra ecotone gradients in subarctic Canada. There are four to twenty-five radiocarbon dates per core, depending on the length and character of the sediment records. Deposition times were calculated at 100-year intervals from age-depth models constructed using the ‘classical’ age-depth modeling software Clam. Lakes in boreal settings have the most rapid accumulation (mean DT 20 ± 10 yr/cm), whereas lakes in tundra settings accumulate at moderate (mean DT 70 ± 10 yr/cm) to very slow rates, (>100 yr/cm). Many of the age-depth models demonstrate fluctuations in accumulation that coincide with lake evolution and post-glacial climate change. Ten of our sediment cores yielded sediments as old as c. 9000 cal BP (BP = years before AD 1950). From between c. 9000 cal BP and c. 6000 cal BP, sediment accumulation was relatively rapid (DT of 20–60 yr/cm). Accumulation slowed between c. 5500 and c. 4000 cal BP as vegetation expanded northward in response to warming. A short period of rapid accumulation occurred near 1200 cal BP at three lakes. Our research will help inform priors in Bayesian age modeling.

Assemblages of epigaeic beetles and understory vegetation differ between stands of an introduced pine and its native congener in boreal forest

There is growing interest in the use of introduced (i.e. non-native) tree species as part of intensified forestry. This study aimed to evaluate the local-scale effects of the use of introduced tree species on animal and plant assemblages in a boreal setting. Capitalizing on a large-scale experiment involving the plantation of the North American lodgepole pine (Pinus contorta) and native Scots pine (Pinus sylvestris) in Sweden, we compared assemblages of epigaeic (i.e. ground-dwelling) beetles (Coleoptera) and understory vegetation between middle-aged stands of the two pine species. Total abundance of epigaeic beetles in lodgepole pine stands was approximately one-half of that in Scots pine stands. Lodgepole pine stands had lower beetle species richness than Scots pine but only in the event of past thinning. Such negative effects were apparent for beetles linked to most substrate types, but there was more variation in the response of different beetle families. Multivariate analyses revealed differences in the structure of beetle assemblages and understory vegetation between stands of the two pines. Many common beetles, including the superabundant Zyras humeralis (Staphylinidae), had lower abundance under lodgepole pine compared to Scots pine, whereas few displayed an opposite pattern. Several abundant understory vascular plants had lower cover at the expense of mosses in lodgepole pine stands. Our results show that many native epigaeic beetle species and the most common understory plants do occur in middle-aged stands of the introduced lodgepole pine in Sweden. Yet, the observed differences suggest that – in spite of the phylogenetic relatedness of the two tree species – the use of lodgepole pine as an alternative to Scots pine in Fennoscandian forestry is likely to affect the structure of epigaeic beetle and understory vegetation assemblages within stands. Further research will be needed to quantify the effects of different landscape-scale proportions and configurations of forest dominated by lodgepole pine and other introduced tree species on boreal biodiversity.

Monitoring the broadleaf fraction and canopy cover of boreal forests using spectral invariants

A recent method based on the spectral invariants theory to retrieve physically-based information on forest properties from remotely sensed hyperspectral imagery was tested in a southern boreal setting in central Finland. An atmospherically corrected Hyperion image and ground measurements from 66 forest stands were used. First, the novel concept of transformed green leaf single scattering spectral albedos was tested against leaf (needle) albedo measurements on Scots pine, Norway spruce and Silver birch from the study area. We found the transformed Beaked hazel albedo applied in previous studies could be used as reference also for the boreal tree species. Second, we derived a newly suggested spectrally invariant variable, the directional area scattering factor (DASF), to estimate the broadleaf fraction of forest stands. Based on our results, DASF seems highly promising as a potential new hyperspectral satellite product for change monitoring of broadleaf fraction over different vegetation zones. Finally, we plotted our results in the spectral invariants space, and suggest a new interpretation for the reference-dependent structural parameter pR. We propose this parameter is an indicator of canopy cover and suffers less from saturation problems than vegetation indices.

Geochemical signature of Ordovician Mn-rich sedimentary rocks on the Avalonian shelf

Mn-rich (3.26–15.6 wt.% MnO) sedimentary layers (coticules, Strohschiefer) occur in Ordovician siliciclastic sedimentary rocks that were deposited on the Avalonian shelf and subsequently metamorphosed between 340 and 380 Ma. The Mn-rich layers formed during periods of restricted clastic input, when Mn concentrated by a redox-controlled dissolution–precipitation process near the sediment–water interface, comparable to recent Mn-crusts in the boreal settings of the Baltic Sea, the Barents Sea, and the Kara Sea. Enhanced clastic sedimentation brought the process to a halt and buried the Mn-rich layers. Formation of Mn-rich layers resumed upon renewed reduction in clastic input. Nd and Sr isotope data exclude a volcanic or hydrothermal derivation of Mn. Instead, Mn input occurred via rivers from the continental crust. The Nd isotopic composition and geochemical fingerprints of Mn-rich and hosting Mn-poor sedimentary rocks suggests that the clastic input was dominated by material derived from Gondwana rather than from Avalonia. The occurrence of coticules, however, seems to be restricted to the Avalonian shelf.

Modeling the Production, Decomposition, and Transport of Dissolved Organic Carbon in Boreal Soils

Abstract: The movement of dissolved organic carbon (DOC) throughboreal ecosystems has drawn increased attention because of its poten-tial impact on the feedback of OC stocks to global environmentalchange in this region. Few models of boreal DOC exist. Herewe presenta one-dimensional modelwith simultaneous production, decomposition,sorption/desorption, and transport of DOC to describe the behavior ofDOC in the OC layers above the mineral soils. The field-observed con-centration profiles of DOC in two moderately well-drained black spruceforest sites (one with permafrost and one without permafrost), coupledwith hourly measured soil temperature and moisture, were used to in-versely estimate the unknown parameters associated with the sorption/desorption kinetics using a global optimization strategy. The model,along with the estimated parameters, reasonably reproduces the con-centration profiles of DOC and highlights some important potentialcontrols over DOC production and cycling in boreal settings. Thevaluesof estimated parameters suggest that humic OC has a larger potentialproduction capacity for DOC than fine OC, and most of the DOCproduced from fine OC was associated with instantaneous sorption/desorption whereas most of the DOC produced from humic OC wasassociated with time-dependent sorption/desorption. The simulatedDOC efflux at the bottom of soil OC layers was highly dependent onthe component and structure of the OC layers. The DOC efflux wascontrolled by advection at the site with no humic OC and moist con-ditions and controlled by diffusion at the sitewith the presence of humicOC and dry conditions.Key words: Black spruce, boreal, carbon, advection, diffusion,inversion.(Soil Science 2010;175: 223Y232)

End-Permian mass extinction pattern in the northern peri-Gondwanan region

The Permian-Triassic extinction pattern in the peri-Gondwanan region is documented biostratigraphically, geochemically and sedimentologically based on three marine sequences deposited in southern Tibet and comparisons with the sections in the Salt Range, Pakistan and Kashmir. Results of biostratigraphical ranges for the marine faunas reveal an end-Permian event comparable in timing with that known at the Meishan section in low palaeolatitude as well as Spitsbergen and East Greenland in northern Boreal settings although biotic patterns earlier in the Permian vary. The previously interpreted delayed extinction (Late Griesbachian) at the Selong Xishan section is not supported by our analysis. The end-Permian event exhibits an abrupt marine faunal shift slightly beneath the Permian-Triassic boundary (PTB) from benthic taxa- to nektic taxa-dominated communities. The climate along the continental margin of Neo-Tethys was cold before the extinction event. However, a rapid climatic warming event as indicated by the southward invasion of abundant warm-water conodonts, warm-water brachiopods, calcareous sponges, and gastropods was associated with the extinction event. Stable isotopic values of δ 13C carb, δ 13C org and δ 18O show a sharp negative drop slightly before and during the extinction interval. Sedimentological and microstratigraphical analysis reveals a Late Permian regression, as marked by a Caliche Bed at the Selong Xishan section and the micaceous siltstone in the topmost part of the Qubuerga Formation at the Qubu and Tulong sections. The regression was immediately followed by a rapid transgression beneath the PTB. The basal Triassic rocks fine upward, and are dominated by dolomitic packstone/wackestone containing pyritic cubes, bioturbation and numerous tiny foraminifers, suggesting that the studied sections were deposited during the initial stage of the transgression and hence may not have been deeply affected by the anoxic event that is widely believed to characterise the zenith of the transgression.

Scaling relationships for woody tissue respiration in two tropical rain forests

AbstractThe relationship between gross primary productivity (GPP) and net primary productivity (NPP) is not fully understood. One of the uncertainties relevant to this issue is the magnitude of woody tissue respiration. Although some data exist for temperate and boreal zones, measurements of woody tissue respiration in tropical forests are sparse. We made in situ chamber measurements of woody tissue respiration in two tropical rain forests, one in the Brazilian Amazon (Reserva Jarú) and one in Central Cameroon (Mbalmayo Reserve). We made measurements on a wide range of species at each site and over a range of stem diameters from 0·02 to 1·4 m. The rate of efflux of carbon dioxide (CO2) from bark at 25 °C, Rt, varied from 0·1 to 5·2 µmol m−2 s−1 across the two sites, and the efflux was related to both volume and surface area components of the measured stem sections. The temperature response in Rt was slightly higher at Jarú than at Mbalmayo, with Q10 values of 1·8 (± 0·1 SE) and 1·6 (± 0·1 SE), respectively. A log–log regression showed that Rt was significantly related to stem diameter, D (P < 0·001; r2 = 0·58–0·62) and was significantly higher at Mbalmayo than at Jarú (P < 0·001), but that the rate of increase in Rt with stem diameter, D, was similar between sites. At the Mbalmayo site, tree growth measurements made over a 4 month period were used to make two estimates of the maintenance (Rm) and construction (Rc) components of respiration embedded in Rt. The two methods agreed closely, suggesting that Rm was approximately 80% of Rc at this site. Rm could be strongly related to D using a sigmoidal relationship that described both surface area and volume components as sources of respiratory CO2 (r2 = 0·71). This functional model was combined with inventory, growth and climate data for the Mbalmayo site to make a first estimate of annual above‐ground woody tissue respiration, RA, which was 257 (± 18 SE) g C m−2 year−1. This value corresponds to approximately 10% of GPP, slightly lower than that found for another tropical rain forest, but higher than for temperate forests. When combined with data from six other sites in tropical, temperate and boreal settings, a very strong relationship was found between RA and leaf area index (LAI), and between RA/GPP and LAI (P < 0·001, r2 = 0·98). This indicates that RA exerts an appreciable constraint on NPP and that this constraint varies closely with LAI across widely differing types of woody vegetation.

Is the akagare phenomenon important to iodine uptake by wild rice ( Zizania aquatica)?

Akagare reclamation disease of plants, reported in Japan, is the situation where naturally occurring stable iodine (I) is released from the soil to the extent that it is chemically toxic to rice plants. It occurs after a soil is reflooded for rice production. Any process such as this, where a change in the environment results in a release of I, is important for the safe management of 129I. Iodine-129 is the most critical radionuclide in the safe disposal of Canada's nuclear fuel waste. The present concept for disposal anticipates a boreal setting, where wild rice ( Zizania aquatica) grows naturally and is cultivated. This study investigated the effect of flooding on I uptake by wild rice, using 125I. We grew wild rice on flooded and drained soils, and observed that I in flooded soil was an order of magnitude more soluble than in drained soil. The soil solid/liquid partition coefficient K d , in flooded soil was about 0.6 l kg −1 and in drained soil was about 6 l kg −1. This effect did result in higher concentrations of I in the plants grown on the flooded soil. The plant/soil concentration ratio on a dry weight basis, CR, for the edible seed, prior to processing, was 0.25 for wild rice grown on flooded soil and 0.17 for wild rice grown on drained soil. This difference is small and the values are not higher than many other crops. Very high mean CR values, up to 69, were observed for the lower submerged and emergent leaves of flooded wild rice. These may indicate a need to investigate I entry into littoral food chains.

The distribution of selected soil properties in relation to landscape morphology in forested Gray Luvisol soils

Properties of Gray Luvisol soils were examined in relation to landscape position in a boreal setting in Saskatchewan. The thickness of the organic, Ae and Bt horizons, the pH of the Ae, depth to carbonates and the percent clay in the Bt horizon were determined on samples taken from 80 profiles on a 70 × 56-m grid. At each sample location the landform element was described as one of eight elements based on the gradient, profile curvature and plan curvature. The results show that the distribution of soil properties varied as a function of landscape morphology and moisture regime. In general, the pH of the Ae horizons was higher, and the thickness of Ae and organic horizons were greater in convergent areas. In lower footslope soils, a shallow carbonate-rich water table led to a moderately alkaline pH in the Ae horizons and restricted profile development, presumably due to restricted vertical leaching. The ratio of Ae to Bt horizon thickness was greatest on upper slopes, decreasing in lower footslope soils and in convergent areas. The Bt horizons of lower footslope soils contained more clay than Bt horizons of upper slope soils, possibly as the result of the lateral redistribution of soluble and suspended constituents from divergent to convergent areas of the landscape. Keywords: Geomorphology, Luvisol, horizon development, soil depth, soil pH, illuviation

Lead in boreal soils and food plants

The soils of the boreal zone, characterized by acidic, low-organic-matter sands in uplands and organic deposits in lowlands, represent unique environments for heavy metals. The mobility and plant uptake of Pb can be substantially different than in other soils. A survey of natural levels of Pb in northern Ontario revealed concentrations of 26 mg kg−1 dry soil and 1.3 mg kg−1 dry blueberry leaf, with an apparent plant/soil concentration ratio (CR) of 0.051. In outdoor lysimeters with an acidic sand profile (pH 4.9) and under a boreal climate, 67% of a pulse of Pb, applied as Pb(NO3)2, was essentially immobile over 4 yr. The 33% that leached may have been mobilized by soluble organic ligands or the N03− companion ion. The solid/liquid partition coefficient (Kd) for this soil, using either applied 210Pb or stable Pb, was very low: 20 L kg−1 The CR for 210Pb in the same soil was correspondingly high: 0.10 for blueberry and 0.059 over all crops studied. In two organic soils, the Kd values were 9 × 103 L kg−1 (Sphagnum, pH 4.8) and 3 × 104 L kg−1 (sedge, pH 5.5) with corresponding CR values of 8 × 10−4 and 0.0085 for blueberries (0.0027 overall in the latter soil). The CR was most closely related to soil cation exchange capacity, although organic matter content and pH were undoubtedly important related factors. In combination, the acidic sand and organic soils of boreal settings represent extremes for the mobility of Pb.

A field and literature survey, with interpretation, of elemental concentrations in blueberry (Vaccinium angustifolium)

Blueberry species are important for assessment of pollutant impacts in boreal settings because they are effective colonizers of disturbed sites, are tolerant of high levels of certain heavy metals, and are an attractive food for humans. To investigate patterns in its accumulation of elements and to provide background data, the concentrations of Al, B, Ba, Br, Ca, Ce, Cl, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Si, Sr, Ti, Zn, and Zr were measured in leaves of Vaccinium angustifolium Ait. collected at 64 sites across much of the species range in Canada. These included both cultivated and natural populations. Ranges for 24 other elements in Vaccinium species have been compiled from the literature. Measurements of site and soil characteristics were made for the 64 sites to investigate their effects on concentrations in leaves. The concentration data were right-skewed, and this has implications for both data analysis and environmental impact assessment. The concentrations of most elements were positively correlated, and this was related to soil organic matter content and other soil properties. Plant concentrations were only weakly related to soil concentrations. Plant height was positively correlated to soil pH and leaf Ca, opposite to the expected trend. Overall, about half of the variation in plant concentrations was related to site-to-site variation; with the exception of Ni and Mg levels around Sudbury, Ontario, there was little indication of spatial grouping. The data indicate a relatively homogeneous elemental composition of V. angustifolium across the range sampled and between cultivated and natural populations. Key words: metals, nutrient, background, impact, pollutant.