Canadian Boreal Plain Research Articles

A map of global peatland extent created using machine learning (Peat-ML)

Abstract. Peatlands store large amounts of soil carbon and freshwater, constituting an important component of the global carbon and hydrologic cycles. Accurate information on the global extent and distribution of peatlands is presently lacking but is needed by Earth system models (ESMs) to simulate the effects of climate change on the global carbon and hydrologic balance. Here, we present Peat-ML, a spatially continuous global map of peatland fractional coverage generated using machine learning (ML) techniques suitable for use as a prescribed geophysical field in an ESM. Inputs to our statistical model follow drivers of peatland formation and include spatially distributed climate, geomorphological and soil data, and remotely sensed vegetation indices. Available maps of peatland fractional coverage for 14 relatively extensive regions were used along with mapped ecoregions of non-peatland areas to train the statistical model. In addition to qualitative comparisons to other maps in the literature, we estimated model error in two ways. The first estimate used the training data in a blocked leave-one-out cross-validation strategy designed to minimize the influence of spatial autocorrelation. That approach yielded an average r2 of 0.73 with a root-mean-square error and mean bias error of 9.11 % and −0.36 %, respectively. Our second error estimate was generated by comparing Peat-ML against a high-quality, extensively ground-truthed map generated by Ducks Unlimited Canada for the Canadian Boreal Plains region. This comparison suggests our map to be of comparable quality to mapping products generated through more traditional approaches, at least for boreal peatlands.

What controls fire spatial patterns? Predictability of fire characteristics in the Canadian boreal plains ecozone

AbstractMost regulatory and certification agencies in Canada now require forest management plans to include some level of historical fire pattern approximation. As a result, sustainable forest management and enhancements to existing fire management policies and practices require a thorough understanding of the spatial fire patterns created and maintained by fire as well as the environmental conditions when they occur. To date, however, no boreal fire pattern study has examined relationships between the spatial arrangement of fire patterns, including vegetation remnants, and its main environmental top‐down and bottom‐up controls, based on a large number of fire events across large areas of the Canadian boreal forest. In this study, we leverage a recent, comprehensive, Landsat‐derived fire pattern dataset that includes information on fire vegetation remnants for the Canadian boreal plains ecozone, covering 507 fires and 2.5 Mha, to characterize the predictability of six fire pattern metrics. We then compare these metrics to multiple top‐down (monthly climate) and bottom‐up (topography, fuels, natural barriers, and disturbance history) controls on fire behavior. To do so, we first reduced the fire pattern metrics to three principal components and used a random forest modeling approach to better understand the main environmental explanatory controls. Across this large number of fires, we identified three dimensions of fire patterns: compactness, or the complexity of the perimeter; patchiness, or the spatial heterogeneity in the burned patches; and residualness, or the amount of fire vegetation remnants within the burned patches. We found that patchiness was mostly conditioned by the land cover through variables characterizing the type and connectedness of the fuels; however, summer and spring drought were locally important. Compactness responded to a combination of the disturbance history, land cover, and summer drought. The presence of water resulted in less compact fires. Residualness was a function of the disturbance history, topography, and land cover. Fires in lower elevations presented the most variable patterns, in response to changes in the amount and types of fuel. This research offers an enhanced understanding of the hierarchical interactions between resulting fire patterns and environmental conditions that are critical to supporting management decisions.

Peatland Hydrological Dynamics as A Driver of Landscape Connectivity and Fire Activity in the Boreal Plain of Canada

Drought is usually the precursor to large wildfires in northwestern boreal Canada, a region with both large wildfire potential and extensive peatland cover. Fire is a contagious process, and given weather conducive to burning, wildfires may be naturally limited by the connectivity of fuels and the connectivity of landscapes such as peatlands. Boreal peatlands fragment landscapes when wet and connect them when dry. The aim of this paper is to construct a framework by which the hydrological dynamics of boreal peatlands can be incorporated into standard wildfire likelihood models, in this case the Canadian Burn-P3 model. We computed hydrologically dynamic vegetation cover for peatlands (37% of the study area) on a real landscape in the Canadian boreal plain, corresponding to varying water table levels representing wet, moderate, and severely dry fuel moisture and hydrological conditions. Despite constant atmospheric drivers of fire spread (air temperature, humidity, and wind speed) between drought scenarios, fire activity increased 6-fold in moderate drought relative to a low drought baseline; severe (1 in 40 years) drought scenarios drove fires into previously fire-restrictive environments. Fire size increased 5-fold during moderate drought conditions and a further 20%–25% during severe drought. Future climate change is projected to lead to an increase in the incidence of severe drought in boreal forests, leading to increases in burned area due to increasing fire frequency and size where peatlands are most abundant. Future climate change in regions where peatlands have historically acted as important barriers to fire spread may amplify ongoing increases in fire activity already observed in Western North American forests.

Moving beyond bioclimatic envelope models: integrating upland forest and peatland processes to predict ecosystem transitions under climate change in the western Canadian boreal plain

AbstractBy the end of this century, much of the climate space of western Canada's boreal forest is expected to shift northwards and be replaced by climates that are currently associated with aspen forest, parkland and grassland ecosystems. In this study, we review the various processes that will mediate ecological responses to these projected changes in climate. We conclude that ecological transitions are unlikely to involve a gradual wave‐like shift in ecotonal boundaries. Instead, we predict that ecological changes will lag substantially behind changes in climate and that individual ecosystem components will respond at different rates. In particular, if precipitation inputs are maintained as expected, then peatlands should exhibit considerable resilience to climate change and remain a dominant feature on the landscape in 2100. Because peatlands retain large amounts of water on the landscape their continued presence may in turn slow the rate of forest loss, especially the aspen component. Thus, ecological response to climate change in the western boreal region may involve a transition to a novel ecosystem that includes peatlands and aspen as dominant features – unlike anything that exists today. Moreover, this interim stage may remain in place well into the next century, potentially providing additional time for forest‐dependent species to adapt. Copyright © 2015 John Wiley & Sons, Ltd.

Comparison of Temperature-Index Snowmelt Models for Use within an Operational Water Quality Model.

The accurate prediction of snowmelt runoff is a critical component of integrated hydrological and water quality models in regions where snowfall constitutes a significant portion of the annual precipitation. In cold regions, the accumulation of a snowpack and the subsequent spring snowmelt generally constitutes a major proportion of the annual water yield. Furthermore, the snowmelt runoff transports significant quantities of sediment and nutrients to receiving streams and strongly influences downstream water quality. Temperature-index models are commonly used in operational hydrological and water quality models to predict snowmelt runoff. Due to their simplicity, computational efficiency, low data requirements, and ability to consistently achieve good results, numerous temperature-index models of varying complexity have been developed in the past few decades. The objective of this study was to determine how temperature-index models of varying complexity would affect the performance of the water quality model SWAT (a modified version of SWAT that was developed for watersheds dominated by boreal forest) for predicting runoff. Temperature-index models used by several operational hydrological models were incorporated into SWAT. Model performance was tested on five watersheds on the Canadian Boreal Plain whose hydrologic response is dominated by snowmelt runoff. The results of this study indicate that simpler temperature-index models can perform as well as more complex temperature-index models for predicting runoff from the study watersheds. The outcome of this study has important implications because the incorporation of simpler temperature-index snowmelt models into hydrological and water quality models can lead to a reduction in the number of parameters that need to be optimized without sacrificing predictive accuracy.

Relationship between Aboveground Biomass and Percent Cover of Ground Vegetation in Canadian Boreal Plain Riparian Forests

Vegetation biomass is the ideal variable to estimate vegetation abundance and productivity and is necessary for studies of community structure. However, biomass data are difficult and destructive to collect, unlike areal cover data. To date, equations to predict biomass from percent cover have been developed for upland ground flora; however, these equations are lacking for riparian forests. We quantified relationships between aboveground biomass and percent cover of eight ground floristic growth forms (short forbs, tall forbs, ferns, clubmosses, horsetails, graminoids, dwarf shrubs, and bryoids) in riparian forests of the Canadian Boreal Plain and tested whether relationships differ for ground plants growing in two different successful stages (early and late). Without exception, linear relationships were identified with percent cover (P 0.001) that explained 61-93% of the variation in biomass. Slopes of these lines depended on growth form but not on successional stage. When direct biomass measurements are not appropriate or possible, the relationships presented can be used to rapidly and nondestructively estimate biomass in the Boreal Plain riparian forests. FOR .S CI. 58(1):47-53.

Understanding Shifts in Wildfire Regimes as Emergent Threshold Phenomena

Ecosystems driven by wildfire regimes are characterized by fire size distributions resembling power laws. Existing models produce power laws, but their predicted exponents are too high and fail to capture the exponent's variation with geographic region. Here we present a minimal model of fire dynamics that describes fire spread as a stochastic birth-death process, analogous to stochastic population growth or disease spread and incorporating memory effects from previous fires. The model reproduces multiple regional patterns in fire regimes and allows us to classify different regions in terms of their proximity to a critical threshold. Transitions across this critical threshold imply abrupt and pronounced increases in average fire size. The model predicts that large regions in Canada are currently close to this transition and might be driven beyond the threshold in the future. We illustrate this point by analyzing the time series for large fires (>199 ha) from the Canadian Boreal Plains, found to have shifted from a subcritical regime to a critical regime in the recent past. By contrast to its predecessor, the model also suggests that a critical transition, and not self-organized criticality, underlies forest fire dynamics, with implications for other ecological systems exhibiting power-law-like patterns, in particular for their sensitivity to environmental change and control efforts.

Tradeoffs between forestry resource and conservation values under alternate policy regimes: A spatial analysis of the western Canadian boreal plains

An important element of resource management and conservation is an understanding of the tradeoffs between marketed products, such as timber, and measures of environmental quality, such as biodiversity. In this paper, we develop an integrated economic-ecological spatial optimization model that we then apply to evaluate alternate forest policies on a 560,000 km 2 study region of managed boreal forest in Alberta and British Columbia, Canada. The integrated model incorporates dynamic forest sector harvesting, current levels of oil and gas sector development, coarse-filter or habitat-based old forest indicators, a set of empirical forest bird abundance models, and statistical models of the natural and current fire regimes. Using our integrated model, economic tradeoff curves, or production possibility frontiers, are developed to illustrate the cost of achieving coarse-filter targets by a set time (50 years) within a 100-year time horizon. We found levels of ecological indicators and economic returns from the timber industry could both be increased if spatial constraints imposed by the current policy environment were relaxed; other factors being equal, this implies current policy should be revised. We explore the production possibility frontier's relationship to the range of natural variation of old forest habitat, and show how this range can be used to guide choices of preferred locations along the frontier. We also show that coarse-filter constraints on the abundance of certain habitat elements are sufficient to satisfy some fine-filter objectives, expressed as the predicted abundances of various species of songbirds.

Modeling configuration dynamics of harvested forest landscapes in the Canadian boreal plains

Habitat configuration has important implications for the persistence of faunal and floral populations at a variety of spatial scales. Forest harvesting alters habitat configurations. However, measuring and predicting such alterations remains challenging, in part because previously developed metrics of habitat configuration are often not statistically independent of habitat amount. Thus, their ability to measure independent effects of habitat configurations and habitat amount on ecosystem components such as wildlife populations has been limited. Here, we evaluate habitat configuration based on newly developed metrics that are independent of habitat amount but do not depend on regression residuals of abundance and configuration relationships on any population of landscapes. We use these new metrics to measure and predict changes in habitat configuration following forest harvesting in the boreal forest of Alberta, Canada. Our findings clearly demonstrate changes in habitat configuration resulting from forest harvesting can be predicted precisely with information about initial habitat patch structure and harvesting patterns. Because forest harvesting has significant implications for habitat configuration, accurately predicting these changes is critical for determining if forest harvesting strategies are sustainable for ecosystem components and processes. This study provides a set of novel, robust metrics for tracking landscape-scale changes in habitat configuration in harvested boreal forests.

Modification of SWAT for modelling streamflow from forested watersheds on the Canadian Boreal Plain

Several modifications were made to the Soil and Water Assessment Tool (SWAT) to better represent processes occurring within forested watersheds on the Boreal Plain in Canada. The modified model, called SWATBF, was applied to the Willow Creek watershed (15.1 km2) in north central Alberta. The performance of the model for the calibration period (2001–2003) was good with coefficients of efficiency of 0.89 and 0.81 being achieved for the prediction of monthly and daily runoff, respectively. However, it was found that SWATBF did not perform as well for the validation period (2004–2006) with the monthly and daily coefficients of efficiency being 0.44 and 0.27, respectively. Potential sources of error to explain the decline in model performance for the validation period are discussed. SWATBF has the potential to be used as a tool by forest managers for predicting the effects of land use change on the Boreal Plain provided that it can be satisfactorily validated.

Effect of watershed subdivision on water-phase phosphorus modelling: An artificial neural network modelling application

This study is an effort to incorporate low-cost time-variant remote sensing (RS) information in watershed-scale total phosphorus (TP) modelling. Four watershed subdivisions were delineated to assess the impact of watershed subdivision on the prediction accuracy of TP concentration in stream water. Four TP artificial neural network (ANN) models were designed to incorporate RS data into a semi-distributed approach. The remotely derived enhanced vegetation index and the normalized difference water index were successful in representing vegetation dynamics in the devised models. The models were applied to a 15.6 km2 watershed in the Canadian Boreal Plain. Eight measures of goodness-of-fit statistics were used for model evaluation. Although statistical model evaluation did favour the finest resolution in this case study, the differences in performance indicators among the four models were insignificant for any practical application. The encouraging results from this exercise demonstrate the applicability of the ANN semi-distributed modelling approach and the usefulness of RS data in simulating TP dynamics. Such models can potentially serve as valuable tools for watershed-scale forest management.

Runoff and inorganic nitrogen export from Boreal Plain watersheds six years after wildfire and one year after harvest

This investigation in the Swan Hills, Alberta, located on the Canadian Boreal Plain, examined May through October runoff before, during and six years after wildfire in a 4th order watershed, compared to a 3rd order reference watershed. It also examined runoff and inorganic nitrogen flow-weighted mean concentration and areal export for 1 year after winter harvest in four 1st order watersheds compared to five reference 1st and 2nd order watersheds. Runoff and areal exports were normalized to precipitation at each site. Runoff impact ratios (year 1 post-disturbance value divided by the pre-disturbance value) for burned and harvested watersheds were 60 and 70% higher, respectively, than reference watersheds (P = 0.06). Runoff from the burned watershed remained elevated 6 years after fire. A trend for higher nitrate and ammonium concentrations, combined with higher runoff yielded impact ratios for areal ammonium and nitrate exports that were 130 and 170% higher, respectively, in harvested than reference watersheds (P = 0.08 for both). The proportion of the watershed harvested was positively related to runoff (r2 = 0.94, P = 0.03) and ammonium impact ratios (r2 = 0.96, P = 0.02), but not nitrate impact ratios (P = 0.30). Areal nitrate export in snowmelt was low in harvested watersheds compared to their pre-harvest condition and to reference watersheds.

Joint production of timber, carbon, and wildlife habitat in the Canadian boreal plains

This study investigates the relationships and trade-offs between forest carbon management, sustained timber yield, and the production of wildlife habitat to provide a more complete picture of the costs and challenges faced by forest managers for a particular case study in Canada’s boreal mixedwood region. The work presented is an extension of a previously published model that analysed the joint production of timber supply and wildlife habitat using a natural disturbance model approach to ecosystem management. The primary contribution of the present study is the detailed incorporation of a carbon budget model into the framework developed previously. Using the Carbon Budget Model of the Canadian Forest Sector, dynamics specific to separate biomass and dead organic matter carbon pools are represented for individual forest cover types. Results indicate the potential for cost thresholds in the joint production of timber supply and carbon sequestration. These thresholds are linked to switch points in the decision between multiple use and specialized land management practices. Cobenefits in the production of carbon and wildlife habitat are shown to depend on ecological parameters, harvest flow regulations, and incentives for timber supply provided by the market.

Quaternary stratigraphy of the Prophet River, northeastern British ColumbiaThis article is one of a selection of papers published in this Special Issue on the theme Geology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.

Exposures in the Prophet River valley in northeast British Columbia provide a unique glimpse into the Quaternary history of the northwest Canadian Boreal Plains. The region shows evidence of Late Wisconsinan Laurentide glaciation in the form of widespread till, containing abundant erratic clasts derived from the Canadian Shield. Vertical sections along the Prophet River expose non-glacial and advance glacial sediments below this till. Pre-Late Wisconsinan non-glacial or interglacial floodplain sediments are interbedded with fluvial gravels at many sites. Macrofossils within horizontally laminated organic-rich black clay and silt indicate deposition on the floodplain of the paleo-Prophet River within an oxbow lake. The climate during deposition is interpreted to be similar to present, supporting a dominantly spruce forest. Wood obtained from eight sites provided non-finite radiocarbon ages, and one sample provided an age of 49 300 ± 2000 BP, which is also considered non-finite. Glaciolacustrine clays and silts, deposited during impoundment of eastward-flowing drainage by the advance of the Laurentide Ice Sheet (LIS) in the Late Wisconsinan, overlie the non-glacial sediments throughout the valley. A blanket of clast-poor, clay-rich till up to 20 m thick, and deposited by the LIS, drapes the glaciolacustrine sediments. Since deglaciation, the Prophet River has incised the valley and formed fluvial terraces at different levels above the modern river.

Artificial neural networks and time series modelling of TP concentration in boreal streams: a comparative approach

Increased nutrient concentrations in fresh waters may lead to depressed dissolved oxygen concentrations, increased cyanobacterial biomass, and potentially high levels of cyanobacterial toxin production. Phosphorus loading, during snow melt and storm events, is the main source of nutrient enrichment to water bodies on the Canadian Boreal Plain. This study compared two approaches for modelling total phosphorus (TP) concentration: autoregressive moving average with exogenous input (ARMAX) and artificial neural network (ANN) models. Derived models were applied to a small forested watershed on the Canadian Boreal Plain. Results showed that ANN outperformed ARMAX based on four measures of goodness-of-fit statistics. This study confirmed that the ANN modelling approach is superior to ARMAX in modelling time-correlated gapped data, provided step-by-step guidelines for modelling time-correlated variables, and presented a feasible alternative for modelling diffuse pollutants in small forested watersheds. Key words: watershed, snow melt, diffuse pollutants, phosphorus, artificial neural networks (ANN), time series (TS), multi-slab hidden layer, ARMAX, boreal forest.

Neural networks modelling of streamflow, phosphorus, and suspended solids: application to the Canadian Boreal forest

Sediment has long been identified as an important vector for the transport of nutrients and contaminants such as heavy metals and microorganisms. The respective nutrient loading to water bodies can potentially lead to dissolved oxygen depletion, cyanobacteria toxin production and ultimately eutrophication. This study proposed an artificial neural network (ANN) modelling algorithm that relies on low cost readily available meteorological data for simulating streamflow (Q), total suspended solids (TSS) concentration, and total phosphorus (TP) concentration. The models were applied to a 130-km2 watershed in the Canadian Boreal Plain. Our results demonstrated that through careful manipulation of time series analysis and rigorous optimization of ANN configuration, it is possible to simulate Q, TSS, and TP reasonably well. R2 values exceeding 0.89 were obtained for all modelled data cases. The proposed models can provide real time predictions of the modelled parameters, can answer questions related to the impact of climate change scenarios on water quantity and quality, and can be implemented in water resources management through Monte Carlo simulations.

Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain

Methyl mercury (MeHg) concentrations in macroinvertebrates and fish were compared among five lakes in burned catchments and five reference lakes on the western Canadian Boreal Plain to determine the influence of forest fire on MeHg bioaccumulation. Two years after fire, MeHg concentrations in five of six aquatic taxa were similar in burned and reference lakes. Among a larger set of 12 lakes, MeHg concentrations in biota were negatively correlated with lake water pH, trophic status, and hardness, reflecting a pre-existing gradient in water chemistry. Biomagnification of MeHg (as determined by regression of MeHg concentration on baseline-adjusted δ15N) was negatively correlated with lake water chlorophyll a concentration. A subsequent logging experiment interrupted by fire provided an opportunity to compare pre- and post-fire MeHg concentrations in aquatic biota. Three months after fire, biota MeHg concentrations had decreased by 32%–50%, and lake water ammonium concentrations had increased 11-fold relative to the previous year. In this nutrient-rich setting, fire may lower MeHg concentrations in aquatic biota over the short-term by inducing an increase in lake productivity that dilutes MeHg at the base of the food web.

Runoff and phosphorus export patterns in large forested watersheds on the western Canadian Boreal Plain before and for 4 years after wildfire

We examined water and phosphorus export patterns in four large (130 to 247 km2) Boreal Plain watersheds (two burned and two reference) before and for 4 years after wildfire and the influence of precipitation intensity and timing on these patterns. Time series analysis of the one burned and one reference watershed monitored before and after fire demonstrated that relative to changes in the reference watershed over the same time period, runoff and dissolved and particulate phosphorus exports were higher in the burned watershed during the four post-fire years than before the fire (P = 0.001). Comparison of post-fire means in all four watersheds monitored for the post-fire years demonstrated that mean water and particulate phosphorus exports were 1.6 (P = 0.01) and 3.7 (P = 0.03) times higher in burned than reference watersheds, respectively. A similar pattern existed for dissolved phosphorus exports, but differences were not significant (P = 0.13). Thus, the pre- vs. post-fire comparison was consistent with, and more powerful than, the post-fire treatment vs. reference comparison. As of year 4 post-fire, burned watersheds continued to export more water and particulate phosphorus per unit area than reference watersheds, particularly during peak flow periods. Key words: watershed disturbance, boreal forest, stream, water quality, fire, phosphorus, runoff.

Effects of nutrient enrichment on recruitment of age-0 fathead minnows (Pimephales promelas): potential impacts of environmental change on the Boreal Plains

Eutrophication in lakes on the Canadian Boreal Plains is predicted to increase because of climate and land-use changes. The resulting increase in lake productivity might then increase recruitment of young fish via increased food availability, growth, and survival. To assess this hypothesis, we manipulated nutrient concentrations in experimental ponds and examined mechanisms influencing production and survival of age-0 fathead minnows (Pimephales promelas). Nutrient enrichment increased phytoplankton biomass (chlorophyll a) sevenfold in treatment compared to reference systems. In response, fish laid more eggs and survival of age-0 fish was enhanced, both of which contributed to a more than fivefold increase in total number of age-0 fish that survived to the end of the growing season in treatment versus reference systems. A complementary enclosure experiment suggested that enhanced growth and decreased susceptibility to starvation contributes to the greater survival of age-0 fish when food resources are increased. Furthermore, overwinter mortality of age-0 fathead minnows in experimental ponds was strongly size-selective; no fish smaller than 20 mm survived winter. Because of these effects on egg production and growth and survival of age-0 fish, environmental changes predicted for the Boreal Plains could significantly alter the dynamics of fish populations.

Effect of pipeline installation on crop yield and some biological properties of boreal soils

Pipeline construction on the Grey soils of the Canadian boreal plains, which have a thin Ah horizon, could have considerable impact on their properties and productivity. This study was conducted because the effects of pipeline installation on crop yield and biological properties of these soils have not been well-documented. Soil was sampled from a Grey Luvisol and a Dark Grey Solod prior to pipeline construction in 1991, and in each of the following 3 yr. The right-of-way (RoW) was divided into three zones: a road (or work) area used for vehicular traffic; a trench where the pipeline was buried; and a pile (or spoil) area where soil was stockpiled during construction. The RoW was cropped to barley (Hordeum vulgare L.) in 1992 through 1994. Barley yield was low in 1992 (830–1120 kg ha−1), and near average (2050–3290 kg ha−1) in 1993 and 1994. Except for low shoot P concentration (1.1–1.3 mg g−1) in 1992, macronutrient concentrations (N, P and K) in barley tissues were within normal ranges. Soil organic carbon was reduced by 12–28% in all RoW areas in 1993 and 1994. Soil total N was reduced by 29–49% in all RoWs in 1992 and increased slightly from those levels in 1993 and 1994. Pipeline construction affected soil microbial biomass carbon (MBC) in the three RoW areas differently, and the effect was not consistent from year to year. However, the average level of MBC was not adversely impacted. In 1994, soil phosphatase activity in the RoW zones tended to be lower as compared to pre-pipeline installation, particularly in the pile area of the Dark Grey Solod. It is concluded that although some soil biological properties were degraded by pipeline construction, and barley yield was reduced in 1992, crop production in the following 2 yr was not significantly affected. Key words: Barley, carbon, microbial biomass, nitrogen, phosphatase, pipeline