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Much of our understanding on temporary headwater streams is from arid and sub‐humid environments. We know less about zero‐flow periods in humid headwater catchments that experience seasonal snow cover. Our study characterised the temporal and spatial patterns of zero‐flow periods for forested headwater streams in a snow‐dominated landscape. We used 36 years of streamflow data from 13 headwater catchments within the Turkey Lakes Watershed located on the Canadian Shield in Ontario, Canada, near the eastern shores of Lake Superior. These headwater catchments differ substantially in their number of May–November zero‐flow days (0–166 days per year) despite being clustered in a small geographical area with similar geology, physiography and vegetation cover. The catchments also experience similar continental climatic conditions with relatively even precipitation inputs throughout the year (mean annual precipitation of 1210 mm/year). Inter‐annual variability in the number of zero‐flow days was primarily associated with May–November precipitation and evapotranspiration. Despite the large seasonal snowpacks that form in this region, the amount of snow did not appear to influence the extent of zero‐flow periods. We found that between‐catchment variability in zero‐flow occurrences was related to differences in catchment area and catchment properties typically associated with greater groundwater influence. Our study suggests that occurrences of zero‐flows in headwater streams can be highly variable even over small geographical regions and that flow permanence may be more sensitive to spring to fall weather conditions than the influence of snow due partly to the shallow soils typically found on the Canadian Shield. [ABSTRACT FROM AUTHOR]

Forests are critical source regions of high-quality drinking water but forest disturbances such as harvesting can alter stream dissolved organic carbon (DOC) concentrations and influence source water treatability. Most stream DOC-centric forest harvesting impact studies report on effects <10 years post-harvest; less is known about the legacy effects of forest harvesting on stream DOC. Here, inter- and intra-catchment variability in stream DOC concentration and export were evaluated in two northern hardwood-dominated headwater catchments (unharvested reference and 24 years post-clearcut). The relationship between stream DOC and the concentration, spatial distribution, and hydrologic connectivity of hillslope solute pool DOC was investigated. Stream DOC concentrations in the legacy clearcut catchment exceeded those in the reference catchment for all flow conditions. Inter-catchment differences in DOC export were inconsistent. Hillslope solute pool DOC concentrations decreased with soil depth but were not significantly different between catchments. Concentration–discharge regression analysis indicated that DOC was primarily transport-limited (flushing) in both catchments. Aqueous potassium silica molar ratio data indicate the influence of groundwater on stream chemistry and streamflow was similar in both catchments. Results suggest that while clearcut harvesting can have detectable decadal-scale effects on stream DOC concentrations in northern hardwood-dominated headwater catchments, the effects are limited and likely do not pose a reasonable threat to downstream drinking water treatment operations. [ABSTRACT FROM AUTHOR]

Accurate soil information is critically important for forest management planning and operations but is challenging to map. Digital soil mapping (DSM) improves upon the limitations of conventional soil mapping by explicitly linking a variety of environmental data layers to spatial soil point data sets to continuously predict soil variability across a landscape. Thus far, much DSM research has focussed on the development of ultrafine-resolution soil maps within agricultural systems; however, increasing availability of light detection and ranging (LiDAR) data presents new opportunities to apply DSM to support forest resource applications at multiple scales. This project describes a DSM workflow using LiDAR-derived elevation data and machine learning models (MLMs) to predict key forest soil attributes. A case study in the Hearst Forest in northeastern Ontario, Canada, is used to illustrate the workflow. We applied multiple MLMs to the Hearst Forest to predict soil moisture regime and textural class. Both qualitative and quantitative assessment pointed to the random forest MLM producing the best maps (63% accuracy for moisture regime and 66% accuracy for textural class). Where error occurred, soils were typically misclassified to neighbouring classes. This standardized, flexible workflow is a valuable tool for practitioners that want to undertake DSM as part of forest resource management and planning. Key words: digital soil mapping, machine learning, forest management. Des informations precises sur les sols sont absolument essentielles pour la planification et les operations d'amenagement forestier mais elles sont difficiles a cartographies La cartographie numerique des sols (CNS) constitue un progres par rapport aux limites de la cartographie conventionnelle des sols en reliant une variete de couches de donnees environnementales a des ensembles de donnees spatiales ponctuelles des sols pour predire la variabilite a travers un paysage de facon continue. Jusqu'a maintenant, beaucoup de travaux de recherche sur la CNS ont mis l'accent sur le developpement de cartes des sols a tres haute resolution pour des systemes agricoles. Cependant, la disponibilite croissante de donnees lidar offre de nouvelles opportunites d'appliquer la CNS en support a des applications qui concernent les ressources forestieres a de multiples echelles. Ce projet decrit un flux de travail de CNS qui utilise des donnees altimetriques derivees du lidar et des modeles d'apprentissage automatique (MAA) pour predire des attributs importants des sols. Une etude de cas dans la foret de Hearst, dans le nord-est de l'Ontario, au Canada, est utilisee pour illustrer le flux de travail. Nous avons applique plusieurs MAA a la foret de Hearst pour predire le regime d'humidite et la classe de texture. Une evaluation tant qualitative que quantitative indiquait que le MAA de foret aleatoire produisait les meilleures cartes (precision de 63 % pour le regime d'humidite et de 66 % pour la classe de texture). Lorsqu'il y avait des erreurs, les sols mal classes etaient typiquement places dans les classes voisines. Ce flux de travail standardise et flexible est un outil precieux pour les praticiens qui veulent entreprendre la CNS en tant que composante de la planification et de la gestion des ressources forestieres. [Traduit par la Redaction] Mots-cles: cartographie numerique des sols, apprentissage automatique, amenagement forestier., 1. Introduction Soils are a critical element of forest ecosystems in that soil mineralogy, nutrient supply, moisture retention, texture, structure, and porosity collectively influence forest composition and productivity (Leniham 1993; [...]

The adverse impacts of excessive soil nutrients on water quality and carbon sequestration have been recognized in tropical and temperate regions, with already widespread industrial farming and urbanization, but rarely in subarctic regions. However, recent studies have shown significant increases in porewater nitrogen (N) and phosphorus (P) concentrations in burned subarctic peatlands and downstream waters, which is a growing concern as climate change leads to increasing wildfires, permafrost thaws, and waterlogged peatlands. In this study, we present the results of a short-term incubation experiment conducted on soils from subarctic bogs and fens, aimed at evaluating the effects of high levels of nutrients on carbon gas production rates. We divided aliquots of the peatland soil samples into separate containers and added artificial porewater to each, enriching them with dissolved inorganic nitrogen (N), phosphorus (P), both, or none for controls. Overall, the fen samples showed higher carbon dioxide (CO2) and methane (CH4) production rates at 1, 5, 15, and 25 °C compared to the bog samples, which we attributed to differences in soil properties and initial microbial biomass. The bog sample with added N produced more CO2 compared to its control, while the fen sample with added P produced more CO2 compared to its control. It was unexpected that the addition of both N and P reduced CO2 but increased CH4 production in both soils compared to their controls. After a month, the pore water C, N, and P stochiometric ratios approached the initial soil microbial biomass ratios, suggesting microbial nutrient recycling in an inherently nutrient-poor soil environment. These preliminary results imply a complex response of carbon turnover in peatland soils to nutrient enrichment. [ABSTRACT FROM AUTHOR]

Industrial development within Canada's boreal zone has increased in recent decades. Forest management activities, pulp and paper operations, electric power generation, mining, conventional oil and gas extraction, nonconventional oil sand development, and peat mining occur throughout the boreal zone with varying impacts on water resources. We review impacts of these industries on surface water, groundwater, and wetlands recognizing that heterogeneity in the dominance of different hydrologic processes (i.e., precipitation, evapotranspiration, groundwater recharge, and runoff generation) across the boreal zone influences the degree of impacts on water resources. Through the application of best management practices, forest certification programs, and science-based guidelines, timber, pulp and paper, and peat industries have reduced their impacts on water resources, although uncertainties remain about long-term recovery following disturbance. Hydroelectric power developments have moved toward reducing reservoir size and creating more natural flow regimes, although impacts of aging infrastructure and dam decommissioning is largely unknown. Mineral and metal mining industries have improved regulation and practices, but the legacy of abandoned mines across the boreal zone still presents an ongoing risk to water resources. Oil and gas industries, including non-conventional resources such as oil sands, is one of the largest industrial users of water and, while significant progress has been made in reducing water use, more work is needed to ensure the protection of water resources. All industries contribute to atmospheric deposition of pollutants that may eventually be released to downstream waters. Although most industrial sectors strive to improve their environmental performance with regards to water resources, disruptions to natural flow regimes and risks of degraded water quality exist at local to regional scales in the boreal zone. Addressing the emerging challenge of managing the expanding, intensifying, and cumulative effects of industries in conjunction with other stressors, such as climate change and atmospheric pollution, across the landscape will aid in preserving Canada's rich endowment of water resources. Key words: natural resources, development, hydrology, biogeochemistry, cumulative effects, water quality, water quantity. Resume : Le developpement industriel dans la zone boreale canadienne s'est accru au cours des recentes decades. Les activites en amenagement forestier, les operations dans les pates et papiers, la generation de pouvoir electrique, les mines, l'extraction de l'huile et du gaz conventionnel, le developpement non conventionnel des sables bitumineux ainsi que le prelevement de la tourbe s'effectuent sur l'ensemble de la zone boreale avec divers impacts sur les ressources hydriques. Les auteurs passent en revue les impacts de ces industries sur l'eau de surface, l'eau souterraine et les terrains humides, tout en reconnaissant que l'heterogeneite de la dominance des differents processus hydrologiques (i.e., precipitation, evapotranspiration, recharge de la nappe phreatique et generation d'ecoulement de surface) sur l'ensemble de la zone boreale influence le degre des impacts sur les ressources hydriques. Grace a l'application de meilleurs pratiques d'amenagement, des programmes de certification forestiere et de guides scientifiquement etayes, les industries du sciage, des pates et papiers et de la tourbe ont reduit leurs impacts sur les ressources hydriques, bien que certaines incertitudes demeurant sur la recuperation a long terme suite aux perturbations. Le developpement de pouvoir hydroelectrique s'est oriente vers une reduction de la dimension des reservoirs creant ainsi des regimes de flux plus naturels, bien que les impacts des infrastructures vieillissantes et le demantelement des barrages demeurent inconnus. Les industries des mines et metaux ont ameliore leurs regles et pratiques, mais l'heritage des mines abandonnees sur l'ensemble de la zone boreale constitue toujours un risque pour les ressources aquatiques. Les industries de l'huile et du gaz, incluant les ressources non conventionnelles telles que les sables bitumineux sont les plus grands utilisateurs d'eau et, bien qu'on ait apporte des progres recents en reduisant l'utilisation de l'eau, il faudra encore plus de travail pour assurer la protection des ressources hydriques. Toutes les industries contribuent a la deposition de polluants eventuellement susceptibles de se retrouver dans les eaux en aval. Bien que la plupart des secteurs industriels s'activent pour ameliorer leurs performances environnementales en ce qui a trait aux ressources hydriques, les perturbations des regimes naturels de flux et les risques de degradation de la qualite de l'eau existent toujours aux echelles locales et regionales de la foret boreale. La preoccupation du defi emergent de l'amenagement des effets industriels, gagnant en expansion, en intensification et en accumulation, en conjonction avec d'autres agents stressants, comme les changements climatiques et la pollution atmospherique sur l'ensemble du paysage nous aideront a preserver la riche dotation du Canada en ressources hydriques. [Traduit par la Redaction] Mots-cles : ressources naturelles, developpement, hydrologie, biogeochimie, effets cumulatifs qualite de l'eau, quantite d'eau., 1. Introduction 1.1. Water as a defining feature Canada is a water rich nation, hosting ~5.4% (2.9 [km.sup.3]/year) of the global renewable water supply (5.4 x [10.sup.4] [km.sup.3]/year, FAO 2013). [...]

Peatlands cover approximately 12% of the Canadian landscape and play an important role in the carbon cycle through their centennial‐ to millennial‐scale storage of carbon under waterlogged and anoxic conditions. In recognizing the potential of these ecosystems as natural climate solutions and therefore the need to include them in national greenhouse gas inventories, the Canadian Model for Peatlands module (CaMP v. 2.0) was developed by the Canadian Forest Service. Model parameterization included compiling peat profiles across Canada to calibrate peat decomposition rates from different peatland types, to define typical bulk density profiles, and to describe the hydrological (i.e., water table) response of peatlands to climatic changes. A total of 1217 sites were included in the dataset from published and unpublished sources. The CORESITES table contains site location and summary data for each profile, as well as an estimate of total carbon mass per unit area (in megagrams of C per hectare). Total carbon mass per unit area at each location was calculated using bulk density and carbon content through each profile. The PROFILES table contains data for depth (in centimeters), bulk density (in grams per cubic meter), ash and carbon content (in percentage), and material descriptions for contiguous samples through each peat profile. Data gaps for bulk density and C content were filled using interpolation, regression trees, and assigned values based on material description and/or soil classification to allow for the estimation of total carbon mass per unit area. A subset of the sites (N = 374) also have pH and pore water trace‐elemental geochemistry data and are found in the WATER table. The REFERENCES table contains the full citation of each source of the data and is linked to each core location through the SOURCEDATA table. The LOOKUP table defines codes in the database that required more space that what was sufficient in the metadata tables. The data can be accessed on Open Government Canada and will be useful for future work on carbon stock mapping and ecosystem modeling. All metadata and data are provided © Her Majesty the Queen in Right of Canada, 2023 and information contained in this publication may be reproduced for personal or public noncommercial purposes with attribution, whereas commercial reproduction and distribution are prohibited except with written permission from NRCan; complete details are noted in the Supporting Information file Metadata S1 (see Class III.B.3: Copyright restrictions). [ABSTRACT FROM AUTHOR]

Boreal fens are minerotrophic peatlands that act as important control points for dissolved C between upland and aquatic ecosystems. Fens occupy a minerotrophic continuum from 'rich' having high water tables and large nutrient contributions from upland sources, to 'poor,' having low water tables and small nutrient contributions. Dissolved C within these fens will be influenced by the degree of minerotrophy, which in turn impacts peat pore water acidity and alkalinity and downstream productivity. To examine how dissolved C concentrations change along the minerotrophic gradient and to explore possible mechanisms controlling their concentration, pore water chemistry was analyzed from piezometers at 25-, 50-, and 100-cm depths in rich, intermediate, and poor fens during the snow-free periods of 2005, 2006 (dissolved organic C [DOC] only), 2007, and 2008. We found that dissolved inorganic C (DIC) concentrations increased with higher water tables (poor < intermediate < rich) and wetter years (2005 < 2007 ~ 2008). In contrast, DOC concentrations decreased with higher water tables (rich < intermediate < poor), but the effect differed among years. Wetter conditions resulted in high DOC concentrations in the intermediate fen, low concentration in the poor fen, and no change in the rich fen. Correlation analyses suggest that DIC concentrations may be linked to groundwater contribution of carbonate materials and DOC to ionic strength and mechanisms of productivity and decomposition. Although further experimentation is required to verify these mechanisms, the evidence points to the importance of minerotrophic status when considering the role of peatlands in watershed C balances and their response to changing climate. Abbreviations: DIC, dissolved inorganic carbon; DOC, dissolved organic carbon; FSR, forward stepwise regression; HIX, humification index; TN, total nitrogen; TR, tree regression. doi: 10.2136/sssaj2009.0111

Long‐term ecosystem studies are valuable for understanding integrated ecosystem response to global changes in atmospheric deposition and climate. We examined trends for a 35‐year period (1982/83–2017/18) in concentrations of a range of solutes in precipitation and stream water from nine headwater catchments spanning elevation and surficial geology gradients at the Turkey Lakes watershed (TLW) in northeastern Ontario, Canada. Average annual water year (WY, October to September) concentrations in precipitation significantly declined over the period for sulphate (SO42−), nitrate (NO3−) and chloride (Cl−), while calcium (Ca2+) and potassium (K+) concentrations increased, resulting in a significant pH increase from 4.2 to 5.7. Trends in stream chemistry through time are generally consistent with expectations associated with acidification recovery. Concentration of many stream water solutes (SO42−, Cl−, calcium [Ca2+], magnesium [Mg2+] and NH4+ generally decreased, while others (silica [SiO2] and dissolved organic carbon [DOC]) generally increased. Increases were also observed for alkalinity (six of nine catchments), acid neutralizing capacity ([ANC]; six of nine catchments) and pH (eight of nine catchments), while conductivity declined (six of nine catchments). Variability in trends among catchments are associated with differences in surficial geology and wetland cover. While absolute solute concentrations were generally lower at bedrock dominated high‐elevation catchments compared to till dominated lower elevation catchments, the rate of change of concentration was often greater for high elevation catchments. This study confirms continued, but non‐linear stream chemistry recovery from acidification, particularly at the less buffered high and moderate elevation sites. The heterogeneity of responses among catchments highlights our incomplete understanding of the relative importance of different mechanisms influencing stream chemistry and the consequences for downstream ecosystems. [ABSTRACT FROM AUTHOR]

Forest harvesting often increases catchment quickflow (QF, water delivered rapidly to the stream channel), a metric of high‐flow events controlling a catchment's solute and sediment export. Nevertheless, our understanding of QF responses to various silvicultural strategies (e.g., clearcutting, selection harvest, and shelterwood harvest) is incomplete. We present a 31‐year examination of QF delivery from treatment (clearcut, selection harvest, and shelterwood harvest) and control catchments in a deciduous forest landscape in central Ontario, Canada. Growing season root‐zone storage capacity was estimated using a water balance approach to evaluate temporal changes in QF response to precipitation (P) for pretreatment and posttreatment periods. Threshold relationships between QF and P were assessed for control and treatment catchments for pretreatment and posttreatment periods using piecewise regression. Root‐zone storage capacity demarcated shifts in the hydrologic regime arising from forest harvesting and subsequent regeneration. This was particularly pronounced for clearcutting where postharvest decline in root‐zone storage capacity was followed by a rise to preharvest values. Similar pretreatment threshold relationships between QF and P, and near‐identical P thresholds for producing significant QF, reflected similar soil and overburden depths in the catchments. Harvesting effects were indicated by increases in QF/P ratios for relative small P and the number of P events that generated QF, thus changing treatment QF vs. P threshold relationships. Prior to harvesting there was no significant increase in QF with P below a threshold P of 35–45 mm; however, there was a significant QF vs. P relationship below this threshold for all treatments postharvest. Clearcutting increased the number of QF events for the entire postharvest period and the first 9‐year postharvest compared to the other treatments; nevertheless, evidence for intertreatment differences in total QF depth delivered from the catchments during the growing season was inconclusive. Our work suggests that changes in threshold relationships between QF and P, coupled with knowledge of the physical processes underlying them, are useful when evaluating hydrologic responses to forest harvesting. [ABSTRACT FROM AUTHOR]

Industrial development within Canada's boreal zone has increased in recent decades. Forest management activities, pulp and paper operations, electric power generation, mining, conventional oil and gas extraction, nonconventional oil sand development, and peat mining occur throughout the boreal zone with varying impacts on water resources. We review impacts of these industries on surface water, groundwater, and wetlands recognizing that heterogeneity in the dominance of different hydrologic processes (i.e., precipitation, evapotranspiration, groundwater recharge, and runoff generation) across the boreal zone influences the degree of impacts on water resources. Through the application of best management practices, forest certification programs, and science-based guidelines, timber, pulp and paper, and peat industries have reduced their impacts on water resources, although uncertainties remain about long-term recovery following disturbance. Hydroelectric power developments have moved toward reducing reservoir size and creating more natural flow regimes, although impacts of aging infrastructure and dam decommissioning is largely unknown. Mineral and metal mining industries have improved regulation and practices, but the legacy of abandoned mines across the boreal zone still presents an ongoing risk to water resources. Oil and gas industries, including non-conventional resources such as oil sands, is one of the largest industrial users of water and, while significant progress has been made in reducing water use, more work is needed to ensure the protection of water resources. All industries contribute to atmospheric deposition of pollutants that may eventually be released to downstream waters. Although most industrial sectors strive to improve their environmental performance with regards to water resources, disruptions to natural flow regimes and risks of degraded water quality exist at local to regional scales in the boreal zone. Addressing the emerging challenge of managing the expanding, intensifying, and cumulative effects of industries in conjunction with other stressors, such as climate change and atmospheric pollution, across the landscape will aid in preserving Canada's rich endowment of water resources. [ABSTRACT FROM AUTHOR]

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Topography influences hydrological processes that in turn affect biogeochemical export to surface water on forested landscapes. The differences in long-term average annual dissolved organic carbon (DOC), organic and inorganic nitrogen [NO3−-N, dissolved organic nitrogen (DON)], and phosphorus (total dissolved phosphorus, TDP) export from catchments in the Algoma Highlands of Ontario, Canada, with similar climate, geology, forest and soil were established. Topographic indicators were designed to represent topographically regulated hydrological processes that influence nutrient export, including (1) hydrological storage potential (i.e. effects of topographic flats/depressions on water storage) and (2) hydrological flushing potential (i.e. effects of topographic slopes on potential for variable source area to expand and tap into previously untapped areas). Variations in NO3−-N export among catchments could be explained by indicators representing both hydrological flushing potential (91%, p < 0.001) and hydrological storage potential (65%, p < 0.001), suggesting the importance of hydrological flushing in regulating NO3−-N export as well as surface saturated areas in intercepting NO3−-N-loaded runoff. In contrast, hydrological storage potential explained the majority of variations among catchments in DON (69%, p < 0.001), DOC (94%, p < 0.001) and TDP (82%, p < 0.001) export. The lower explanatory power of DON (about 15% less) compared with that of DOC and TDP suggests another mechanism influencing N export, such as controls related to alternative fates of nitrogen (e.g. as gas). This study shows that simple topographic indicators can be used to track nutrient sources, sinks and their transport and export to surface water from catchments on forest landscapes. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

[Display omitted] • Significant increasing trends were recorded in annual DOC concentrations for most headwater streams and several lakes and lake outflows at the Turkey Lakes Watershed in the past 32 years. • Annual DOC variations in headwater streams were mainly influenced by precipitation chemistry, while air temperature was the most influential factor for lake and lake outflows. • The rate of DOC changes in headwater streams was positively related to the percentage of wetland cover in the catchments. Dissolved organic carbon (DOC) concentrations have increased over the past few decades in surface waters across Europe and North America. This has drawn a lot of attention, given the key role of DOC in the global carbon cycle and in surface water biogeochemistry and ecology. While many reports have focused on DOC response to environmental changes in headwater streams and lakes taken separately, there is a lack of studies that combines streams and lakes with varying catchment characteristics in a network-scale perspective. Here, long-term (1987–2018) trends were analyzed and environmental drivers of year-to-year variations in DOC concentrations were examined in headwater streams, lakes and lake outflows at the Turkey Lakes Watershed (TLW) in Ontario, Canada. Results indicated significant increasing of DOC trends in ten out of 12 headwater streams and in four out of 12 lakes and lake outflows over the study period. In addition, piecewise regression analysis detected breakpoints in the 2000 s for DOC time series data in some stations. Multivariate analysis showed that variations in hydro-climatic conditions and the chemistry of atmospheric precipitations explained 13 % to 99 % of year-to-year variations in DOC concentrations. Air temperature emerged as the most influential factor for lakes and lake outflows while precipitation chemistry was the main driver of inter-annual DOC variation in headwater streams. For the latter, the rate of DOC increase and the proportion of explained variance were mainly dependent on catchment characteristics, notably wetland cover which was related to mean catchment slope and total relief. In the context of global change, further research is needed to better understand how changes in climate and atmospheric deposition may be modulated by catchment attributes and ecosystem types for determining future DOC fate and behaviour in surface waters. [ABSTRACT FROM AUTHOR]