Mixedwood Plains Research Articles

Vulnerability Assessment of Groundwater Influenced Ecosystems in the Northeastern United States

Groundwater-influenced ecosystems (GIEs) are increasingly vulnerable due to groundwater extraction, land-use practices, and climate change. These ecosystems receive groundwater inflow as a portion of their baseflow or water budget, which can maintain water levels, water temperature, and chemistry necessary to sustain the biodiversity that they support. In some systems (e.g., springs, seeps, fens), this connection with groundwater is central to the system’s integrity and persistence. Groundwater management decisions for human use often do not consider the ecological effects of those actions on GIEs. This disparity can be attributed, in part, to a lack of information regarding the physical relationships these systems have with the surrounding landscape and climate, which may influence the environmental conditions and associated biodiversity. We estimate the vulnerability of areas predicted to be highly suitable for the presence of GIEs based on watershed (U.S. Geological Survey Hydrologic Unit Code 12 watersheds: 24–100 km2) and pixel (30 m × 30 m pixels) resolution in the Atlantic Highlands and Mixed Wood Plains EPA Level II Ecoregions in the northeastern United States. We represent vulnerability with variables describing adaptive capacity (topographic wetness index, hydric soil, physiographic diversity), exposure (climatic niche), and sensitivity (aquatic barriers, proportion urbanized or agriculture). Vulnerability scores indicate that ~26% of GIEs were within 30 m of areas with moderate vulnerability. Within these GIEs, climate exposure is an important contributor to vulnerability of 40% of the areas, followed by land use (19%, agriculture or urbanized). There are few areas predicted to be suitable for GIEs that are also predicted to be highly vulnerable, and of those, climate exposure is the most important contributor to their vulnerability. Persistence of GIEs in the northeastern United States may be challenged as changes in the amount and timing of precipitation and increasing air temperatures attributed to climate change affect the groundwater that sustains these systems.

The changing agricultural landscape in Canada’s Mixedwood Plains Ecozone (2011–2022) and the implications for biodiversity

The changing agricultural landscape in Canada’s Mixedwood Plains Ecozone (2011–2022) and the implications for biodiversity

Predicting the Presence of Groundwater-Influenced Ecosystems in the Northeastern United States with Ensembled Models

Globally, groundwater-influenced ecosystems (GIEs) are increasingly vulnerable to groundwater extraction and land use practices. Groundwater supports these ecosystems by providing inflow, which can maintain water levels, water temperature, and the chemistry necessary to sustain the biodiversity that they support. Many aquatic systems receive groundwater as a portion of baseflow, and in some systems, the connection with groundwater is significant and important to the system’s integrity and persistence. There is a lack of information about where these systems are found and their relationships with environmental conditions in the surrounding landscape. Additionally, groundwater management for human use often does not address maintaining the ecological functions of GIEs. We used correlative distribution modeling methods (GLM, GAM, MaxEnt, Random Forest) to predict landscape-scale habitat suitability for GIEs in two ecologically distinct ecoregions (EPA Level II ecoregions: Atlantic Highlands and Mixed Wood Plains) in the northeastern United States. We evaluated and combined the predictions to create ensemble models for each ecoregion. The accuracy of the ensemble models was 75% in the Atlantic Highlands and 86% in the Mixed Wood Plains. In the Mixed Wood Plains, hydric soil, surface materials, and soil permeability were the best predictors of GIE presence, whereas hydric soil, topographic wetness index, and elevation were the best predictors of GIE presence in the Atlantic Highlands. Approximately 1% of the total land area in each ecoregion was predicted to be suitable for GIEs, highlighting that there likely is a small proportion of the landscape occupied by these systems.

Geochemical changes in Eastern Canadian lake sediment cores spanning the last ∼150 years highlight a relative shift towards increased metals and erosive materials

Since the start of the Industrial Revolution, the chemical cycling of numerous elements has been fundamentally altered. Using 210Pb-dated sediment cores from 37 Eastern Canadian lakes situated in 4 ecozones, we quantified the geochemical change experienced across this region since ca. 1850 CE using high-resolution computed X-ray Tomography and micro-X-ray fluorescence (µ-XRF) ITRAX scanners. Independent calibrations of µ-XRF ITRAX intensities using ICP-MS and -AES found strong correlations for numerous elements. Using relative abundance measures and absolute concentration estimates, we observed that most of our study lakes recorded temporal enrichments of metals, with several sites exceeding Canadian sediment quality guidelines. Using principal component analysis, we identified that parameters commonly associated with erosion (strontium and titanium), organic matter (molybdenum incoherence to coherence scattering ratio), and metals (zinc and lead) were key variables structuring within and among-lake variation since ca. 1850 CE. Calcium was identified as an additional variable, particularly for lakes in the Mixedwood Plains (MWP) ecozone, which may be linked to catchment activities including land-use changes. Temporally, many lakes shifted towards greater accumulation of inorganic sediment, coeval with higher Pb and Zn concentrations, reaching maxima ca. 1970 CE before decreasing rapidly. These results suggest that most lakes in the region were subjected to environmental pollution but that controls on key atmospheric pollutants in North America were effective across a large part of the country.

Below canopy evapotranspiration in four different variable retention harvesting treatments in a red pine plantation forest

AbstractVariable retention harvest (VRH) is a silvicultural approach that retains differing proportions and patterns of canopy trees across a harvested area to emulate natural disturbance effects on stand structure and enhance the resilience of the regenerating stand to abiotic and biotic stresses. Four VRH treatments were applied to an 83‐year‐old red pine (Pinus resinosa Ait.) plantation forest in the Mixedwood Plains Ecozone of Canada that included 55% aggregate retention (55A), 55% dispersed retention (55D), 33% aggregate retention (33A), 33% dispersed retention (33D) and an unharvested control (CN). In the sixth growing season after harvest, tree stem sap flow and eddy covariance flux measurements were used to examine the impacts of VRH on the dominant components of total stand evapotranspiration (ET), i.e., canopy transpiration (TC) and water flux from the understory vegetation and soil (ETU) as well as understory and canopy water use efficiency (WUE). A positive relationship was found between harvest intensity and the growth of understory vegetation and ETU. The contribution of ETU to ET was higher in the dispersed compared to the aggregate VRH treatments. Canopy transpiration contributed 83% of ET in the CN plot and 58%, 55%, 30% and 23% in the 55D, 55A, 33A and 33D treatments, respectively. Overall, VRH treatments resulted in increased canopy WUE but little comparative effect on understory WUE. Our results suggest that the dispersed retention pattern led to higher ET and productivity than the aggregate pattern of the same retention level. Where carbon sequestration and climate change mitigation is the primary management objective, higher retention levels such as 55D might be used to favour stand level carbon storage while accepting slower rates of understory development. Our findings on the effects of VRH on productivity and WUE of the canopy and understory will help forest managers to better employ VRH as an option to meet multiple objectives and adapt forests to a warmer, more variable climate.

Cyanobacterial blooms in Ontario, Canada: Continued increase in reports through the 21st century

Favot EJ, Holeton C, DeSellas AM, Paterson AM. 2023. Cyanobacterial blooms in Ontario, Canada: Continued increase in reports through the 21st century. Lake Reserv Manage. XX:XXXXXX. The Ontario Ministry of the Environment, Conservation and Parks samples algal composition in response to public reports of suspected algal blooms, which have been tracked since 1994. In a previous analysis, Winter et al. noted a significant increase in the number of reports of confirmed algal blooms dominated by cyanobacteria from 1994 to 2009. Here, we determined that this increasing trend in the yearly number of confirmed cyanobacterial bloom reports (CCBRs) has persisted in Ontario over the intervening decade, to 2019. More than half of CCBRs were from waterbodies on the Precambrian Shield, in the Georgian Bay (5E) ecoregion, known for cottaging and water-based tourism. Data from the Ontario Lake Partner Program (LPP) was used to investigate total phosphorus (TP) concentrations in waterbodies with CCBRs. Approximately 44% of the waterbodies with a CCBR (mean TP 12.99 µg/L, n = 135) had average spring TP concentrations less than 10 µg/L, compared to 64% for LPP waterbodies with no reported or confirmed cyanobacterial blooms (mean TP 9.79 µg/L, n = 918). The most common taxon of cyanobacteria dominating bloom samples in inland waterbodies was Dolichospermum, followed by Aphanizomenon in waterbodies on the Precambrian Shield, and Microcystis in the Mixedwood Plains ecozone in southern Ontario. While an increase in public awareness cannot be ruled out in contributing to the rise in CCBRs across Ontario, the high proportion of cyanobacterial blooms occurring in oligotrophic waterbodies suggests that there may be a link to climate warming, rendering conditions more favorable for these blooms to occur.

Climate change and nutrient enrichment altering sedimentary diatom assemblages since pre-industrial time: evidence from Canada’s most populated ecozone

Lakes worldwide are under threat by a myriad of environmental stressors that have been increasing in number and magnitude. These stressors can be regional such as climate change, or local such as nutrient-rich runoff, invasive species, and road salt contamination, to name but a few. To protect lake ecosystems from further deterioration, we need long-term data to define pre-disturbance baselines and to identify stressors that are causing the greatest ecological changes. Paleolimnology is an effective approach to reconstruct limnological history, providing an important window into past changes. Here, we applied paleolimnological tools to explore the pre-industrial and contemporary diatom assemblage changes of 27 lakes located in the most populated ecozone in Canada, the Mixedwood Plains. We also examined a full sediment core for Lac des Chicots (Southern Québec), aiming to disentangle the impacts of natural versus anthropogenic interactions and to assess their relative effects on the lake’s biotic structure. Our ordination analysis suggests that the Mixedwood Plains lakes have experienced varying lake-specific ecological changes over the past ~150 years, with two major trends across most study lakes: (1) a prevalent increase in planktic species, and (2) a rise in mesotrophic/eutrophic taxa in lakes receiving high human impacts. Our case study of Lac des Chicots identifies ecological impacts from both historical natural events and recent human activities, such as cultural eutrophication and climate warming. Overall, our study demonstrates that lakes in the Mixedwood Plains ecozone have experienced marked ecological changes that are mainly associated with human impacts.

Brook trout occupancy in rivers and streams of the Mixedwood Plains Ecozone, Ontario

AbstractBrook trout (Salvelinus fontinalis) are an iconic freshwater salmonid native to northeastern North America. They prefer cold, clean rivers and lakes, and have been culturally, socially and economically valued for decades. Overharvest and deforestation associated with European settlement in southern Ontario, Canada led to notable declines in brook trout abundance in rivers and streams by the late 1800s. Today, they are threatened by further habitat degradation, non‐native species, and climate change. In this study, we document brook trout occupancy in rivers and streams of the Mixedwood Plains Ecozone in southern Ontario, between 1970–1980 and 2000–2010. We used generalised linear models to determine occupancy variation between the two time periods at five spatial scales spanning multiple watershed levels. We detected a decline in occupancy between time periods for the tertiary (from 23% to 17%) and quaternary (from 35% to 22%) watershed scales. In the Credit River‐Sixteen Mile Creek watershed, mean occupancy decreased to a third of past estimate (from 31% to 10%). For a subset of 86 sites with overlapping sampling in both periods no temporal trend was detected, but a post‐hoc analysis indicated low statistical power (0.07), which suggested that more intensive sampling would be needed to better quantify brook trout occupancy changes at this scale. The occupancies quantified for the past period in our study may serve as benchmarks for brook trout restoration efforts.

Evaluating the 2019 IPCC refinement for estimating methane conversion factors in Canada

Methane emissions from liquid manure management in Canada are an important greenhouse gas source. A wide range of seasonal temperatures, distribution of livestock farms, and various management practices in Canada means that regional methane conversion factors (MCF) that account for spatially discrete climate and management should be used. This study explores the impacts of using the 2019 IPCC Refinement methodology on estimates of MCFs across Canada. MCFs were calculated for 3403 locations across Canada using historical weather data, with varying management parameters at each location (emptying efficiency, timing, and frequency of manure removal). Sensitivity to two model parameters was also evaluated (minimum manure temperature, damping factor). Results showed the influence of climate, as average MCF in each ecozone ranged from 0.27 in the Mixedwood Plains to 0.15 in the Taiga. Further climate variation within ecozones was evident. For example, the MCF range within Mixedwood Plains was 0.17 to 0.33. The MCF reduction by improving management was evident as the average MCF in Canada was 0.15 for triannual removal, 0.21 for biannual removal, 0.28 for one-time removal in spring, and 0.32 for one-time removal in fall. Emptying efficiency was found to be critical; for example, the average MCF for triannual removal with 100% efficiency was 0.14 but increased to 0.15 at 95%, 0.17 at 85%, and 0.30 at 50% efficiency. The damping factor had higher sensitivity in terms of model parameters because it influences peak manure temperature in summer before manure removal. Our results suggest that the average MCF in Canada will be similar to the 2006 IPCC value, but that using the 2019 IPCC Refinement provides a greater ability to represent the variations in climate and management regionally across the country. This will improve accuracy and enable inventory practitioners to reflect regional farm management changes in national methane emission estimates.

Projected changes in bird assemblages due to climate change in a Canadian system of protected areas.

National parks often serve as a cornerstone for a country’s species and ecosystem conservation efforts. However, despite the protection these sites afford, climate change is expected to drive a substantial change in their bird assemblages. We used species distribution models to predict the change in environmental suitability (i.e., how well environmental conditions explain the presence of a species) of 49 Canadian national parks during summer and winter for 434 bird species under a 2°C warming scenario, anticipated to occur in Canada around the mid-21st century. We compared these to existing species distributions in the 2010s, and classified suitability projections for each species at each park as potential extirpation, worsening, stable, improving, or potential colonisation. Across all parks, and both seasons, 70% of the projections indicate change, including a 25% turnover in summer assemblages and 30% turnover in winter assemblages. The majority of parks are projected to have increases in species richness and functional traits in winter, compared to a mix of increases and decreases in both in summer. However, some changes are expected to vary by region, such as Arctic region parks being likely to experience the most potential colonisation, while some of the Mixedwood Plains and Atlantic Maritime region parks may experience the greatest turnover and potential extirpation in summer if management actions are not taken to mitigate some of these losses. Although uncertainty exists around the precise rate and impacts of climate change, our results indicate that conservation practices that assume stationarity of environmental conditions will become untenable. We propose general guidance to help managers adapt their conservation actions to consider the potentially substantive changes in bird assemblages that are projected, including managing for persistence and change.

Importance of the traditional food systems for First Nations adults living on reserves in Canada

ObjectiveTo describe the traditional food (TF) systems of First Nations in Canada, including intake, barriers and promoters.MethodsThe First Nations Food, Nutrition and Environment Study is a cross-Canada participatory study of First Nations adults below the 60th parallel that obtained data for communities excluded from other national studies. A food frequency questionnaire was used to establish frequency of TF intake (number of days in a year) to allow comparisons across ecozones/regions in Canada. Grams of TF intake were also calculated using frequency multiplied by average portions from 24-h recalls. Closed- and open-ended questions attempted to identify some of the key barriers and concerns regarding TF access and use. Multivariable analyses were run to determine what factors are associated with increased TF consumption.ResultsAcross communities, there is a strong preference by adults to have TF in the diet more often. Consumption of land animals was most frequently reported in most ecozones except for the Pacific Maritime and Mixedwood Plains, where fish and plants, respectively, were more frequently consumed. First Nations identified structural and environmental challenges such as development, government regulations and climate change, along with household barriers such as insufficient capital for equipment and transportation, lack of time and absence of a hunter in the household. Multivariable analyses revealed that the highest intake of TF occurred in the Taiga Plains ecozone, and for older individuals and men.ConclusionIdentifying solutions that empower First Nations at all levels is required to overcome the multiple challenges to the inclusion of TF in the diet.

Multi-trophic level responses to environmental stressors over the past ~150 years: Insights from a lake-rich region of the world

Multiple stressors affect water quality and biodiversity in lakes worldwide. However, our understanding of which combinations of stressors are of greatest impact and how lakes have shifted from their pre-industrial baselines is fragmented. Questions remain regarding how multiple trophic groups are affected by global change stressors and whether region-specific differences need to be considered. Here, we apply multiple factor analyses together with latent variable modeling to quantify potential interactions within and among taxa that span multiple trophic levels (i.e. diatoms, cladocerans and chironomids) to improve our understanding of paleo-environmental dynamics from a suite of Canadian lakes spanning four ecozones: the Boreal Shield, the Mixedwood Plains, the Atlantic Highlands, and the Atlantic Maritimes. Across all ecozones, multi-trophic assemblages were distinguished in a multiple factor analysis along a land-use gradient, with mesotrophic/eutrophic diatoms and profundal chironomids tolerant of low bottom-water oxygen concentrations recorded in more disturbed sites. Functional units across three indicator groups formed distinct networks of co-responses to key environmental and land-use gradients, although cladocerans seemed to be driven by additional (i.e., residual) gradients. Applying a temporal beta-diversity approach between modern and pre-industrial assemblages, we detected significantly greater turnover of diatom functional groups in high versus low human impact sites (p = 0.03, n = 57), with similar but non-significant trends apparent with the chironomid and cladoceran groups. Ecozonal differences in temporal turnover were also evident in diatom (p = 0.003, n = 57) and chironomid functional groups (p = 0.04, n = 41). The ecozonal differences may be partially due to differential sensitivities of the pre-industrial assemblages and may also be driven by historical disturbances. Our work highlights how the magnitude and direction of ecological change vary across ecozones and can modify responses to human impacts, with a general trend of higher species turnover in sites with greater human disturbance.

The Hydradephaga (Coleoptera: Haliplidae, Gyrinidae, Dytiscidae) Fauna of Manitoulin Island, Ontario, Canada, the World's Largest Freshwater Island

The Haliplidae, Gyrinidae and Dytiscidae (Coleoptera: Adephaga), or Hydradephaga, of Manitoulin Island, Ontario, Canada were surveyed during the years 1998 to 2003. A total of 2,421 individuals from 86 species were collected from 79 different localities, among which 51 species are newly recorded from that region. This study brings to 88 the number of Hydradephaga recorded in Manitoulin Island. The Nearctic component of the fauna is made up of 76 species (86.4%), while the Holarctic component is made up of 12 species (13.6%). Most species have a transcontinental distribution, but 19 species (21.6%) are recognized as species with eastern affinities. Most of these species are typical of the Canadian Boreal, Mixedwood Plains and Maritimes Ecozones except Platambus semivittatus (LeConte), Matus o. ovatus Leech, Hydrovatus pustulatus Melsheimer, and Laccophilus proximus Say, which stand out as unique Mixedwood Plains Ecozone (roughly corresponding to the Eastern Temperate Forest ecoregion in the United States) species. In an examination of the island fauna, the presence of Hygrotus falli (Wallis), Laccophilus proximus, and Graphoderus occidentalis Horn is deemed notable since they are relatively uncommon in eastern Canada.

A multi-Criteria Wetland Suitability Index for Restoration across Ontario’s Mixedwood Plains

Significant wetland loss (~72%; 1.4 million hectares) in the Province of Ontario, Canada, has resulted in damage to important ecosystem services that mitigate the effects of global change. In response, major agencies have set goals to halt this loss and work to restore wetlands to varying degrees of function and area. To aid those agencies, this study was guided by four research questions: (i) Which physical and ecological landscape criteria represent high suitability for wetland reconstruction? (ii) Of common wetland suitability metrics, which are most important? (iii) Can a multi-criteria wetland suitability index (WSI) effectively locate high and low wetland suitability across the Ontario Mixedwood Plains Ecozone? (iv) How do best sites from the WSI compare and contrast to both inventories of presettlement wetlands and current existing wetlands? The WSI was created based on seven criteria, normalized from 0 (low suitability) to 10 (high suitability), and illustrated through a weighted composite raster. Using an Analytical Hierarchy Process (AHP) and importance determined from a scoping review of relevant literature, soil drainage had the greatest meaning and weight within the WSI (48.2%). The Getis-Ord Gi* index charted statistically significant “hot spots” and “cold spots” of wetland suitability. Last, the overlay analysis revealed greater similarity between high suitability sites and presettlement wetlands supporting the severity of historic wetland cannibalization. In sum, this transferable modeling approach to regional wetland restoration provides a prioritization tool for improving ecological connectivity, services, and resilience.

Spatially-integrated estimates of net ecosystem exchange and methane fluxes from Canadian peatlands

BackgroundPeatlands are an important component of Canada’s landscape, however there is little information on their national-scale net emissions of carbon dioxide [Net Ecosystem Exchange (NEE)] and methane (CH4). This study compiled results for peatland NEE and CH4 emissions from chamber and eddy covariance studies across Canada. The data were summarized by bog, poor fen and rich-intermediate fen categories for the seven major peatland containing terrestrial ecozones (Atlantic Maritime, Mixedwood Plains, Boreal Shield, Boreal Plains, Hudson Plains, Taiga Shield, Taiga Plains) that comprise > 96% of all peatlands nationally. Reports of multiple years of data from a single site were averaged and different microforms (e.g., hummock or hollow) within these peatland types were kept separate. A new peatlands map was created from forest composition and structure information that distinguishes bog from rich and poor fen. National Forest Inventory k-NN forest structure maps, bioclimatic variables (mean diurnal range and seasonality of temperatures) and ground surface slope were used to construct the new map. The Earth Observation for Sustainable Development map of wetlands was used to identify open peatlands with minor tree cover.ResultsThe new map was combined with averages of observed NEE and CH4 emissions to estimate a growing season integrated NEE (± SE) at − 108.8 (± 41.3) Mt CO2 season−1 and CH4 emission at 4.1 (± 1.5) Mt CH4 season−1 for the seven ecozones. Converting CH4 to CO2 equivalent (CO2e; Global Warming Potential of 25 over 100 years) resulted in a total net sink of − 7.0 (± 77.6) Mt CO2e season−1 for Canada. Boreal Plains peatlands contributed most to the NEE sink due to high CO2 uptake rates and large peatland areas, while Boreal Shield peatlands contributed most to CH4 emissions due to moderate emission rates and large peatland areas. Assuming a winter CO2 emission of 0.9 g CO2 m−2 day−1 creates an annual CO2 source (24.2 Mt CO2 year−1) and assuming a winter CH4 emission of 7 mg CH4 m−2 day−1 inflates the total net source to 151.8 Mt CO2e year−1.ConclusionsThis analysis improves upon previous basic, aspatial estimates and discusses the potential sources of the high uncertainty in spatially integrated fluxes, indicating a need for continued monitoring and refined maps of peatland distribution for national carbon and greenhouse gas flux estimation.

New model-based insights for strategic nitrogen recommendations adapted to given soil and climate

Managing nitrogen (N) fertilizer applied in agricultural fields is important for increasing crop productivity while limiting the environmental contamination caused by release of reactive N, especially for crops with high N demand (e.g., corn, Zea mays L.). However, for given soil properties, the optimum amount of N applied depends on climatic conditions. The central question to N management is then what should be the recommended N rate for given soil and climate that would minimize the release of reactive N while maintaining the crop productivity. To address this central challenge of N management, we used a recently developed model-based methodology (called “Identifying NEMO”), which was proved to be effective in identifying ecophysiological optimum N rate and optimum nitrogen use efficiency (NUEopt). We performed modeling for dominant soils and various agroclimatic conditions in five regions along the Mixedwood Plains ecozone, where more than 90% of Canadian corn production takes place. Here, we analyzed for the first time the effect of soil and climate on ecophysiological optimum N rate in an ecozone where there exists a significant agroclimatic gradient. Our results indicated that there were some commonalities among all soils and regions, which we could classify them into two groups with NUEopt ranging from 10 to 17 kg dry yield kg−1 N. For cases with low NUEopt, the recommended N for an expected dry yield of 8 t ha−1 varied from 115 to 199 kg ha−1, whereas they were much lower (79–154 kg ha−1) for cases with high NUEopt. These recommendations were 20–40 kg ha−1 lower than provincial recommendations. Moreover, we found that the different behavior of the two groups was due to soil textures and soils available water holding capacity. For most locations, soils with intermediate available water holding capacity (i.e., 12–15%v) had relatively higher expected yield and lower recommended N.

A model-based methodology to derive optimum nitrogen rates for rainfed crops – a case study for corn using STICS in Canada

While the application of nitrogen (N) fertilizer increases crop productivity, the amount of N not taken up by the crop is released as reactive N causing adverse environmental effects, which are associated with short-term climate variations and consist of nitrous oxide emissions, ammonia volatilization, and nitrate leaching. Finding the optimum rate of N application accounting for both economic and environmental aspects is challenging because it varies according to soil texture and climatic conditions. In this paper, a model-based methodology is developed to identify the ecophysiological optimum N rates at which the applied N leads to minimum N excess with little loss in maximum achievable yield. A slope-based method is proposed to identify the optimum nitrogen use efficiency (NUEopt) and to determine the corresponding optimum N rate (Nopt) for each growing season in given agroclimatic regions according to soil properties. It uses the yield predicted by a process-based crop model, long time series of climate data, and a newly proposed Mitscherlich Baule-plateau (MB-P) function. The NUEopt is identified by evaluating the linearity of the relationship between yield and Nopt, and the reduction in yield compared to maximum achievable yield for a given soil and various growing seasons. We illustrate the methodology and its performance by presenting corn yield response to N rate applications predicted by the STICS crop model for dominant soils with contrasting properties with 48–61 years of daily climate data from five major regions located along an agroclimatic gradient of the Mixedwood Plains ecozone in Canada (42.3°N 83°W - 46.8°N 71°W), which is the main grain corn production ecozone of Canada. Our case study in this ecozone indicates that a newly proposed yield MB-P function outperforms the two commonly used functions, i.e., linear-plateau, and MB functions. The proposed methodology provides valuable information such as the likelihood of achieving a yield in a given region, the recommended N rate for given expected yield, the consequent N excess or deficit, and the reduction in yield compared to maximum achievable yield. The proposed methodology can be used in any region where a crop model has been adapted, and soil properties and time series of climate data are available. This approach sets the stage for an in-depth environmental assessment on reactive N within an integrated decision support system.

Carbon dynamics on agricultural land reverting to woody land in Ontario, Canada

The 2015 Paris Agreement reinforces the importance of the land sector and its contribution to greenhouse gas (GHG) reductions. Thus, there is growing interest in improving estimates of the GHG balance in response to land-use changes (LUCs) involving agriculture and forestry, for national-scale reporting, and for carbon (C) offsets. Large agricultural areas in Europe, Russia and North America are reverting to forest, either naturally or through planting, after abandonment of agricultural land, and this trend may have a substantial impact on carbon budgets. We report results of a pilot project in the Mixedwood Plains ecozone of eastern Canada to analyze the change in the C budget on a landscape over 15 years on abandoned cropland where woody vegetation is regenerating. Thirty-six plots (2 km × 2 km) with paired aerial photographs taken circa 1994 and circa 2008 at a scale of 1:10,000 or larger were randomly selected from the 20 km × 20 km National Forest Inventory (NFI) grid. A spatially-explicit version of the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) was used to estimate impacts of LUC on C stocks and fluxes. Polygons identifying areas of LUC within each photo plot were delineated, classified, and evaluated to provide input data for the model. The rate of C accumulation in our study area was found to be relatively constant over the entire simulation period, at 1.07 Mg C/ha/yr. Abandoned agricultural land reverting to woody lands could play an important role in regional and national C sequestration in Canada, but more research is required to quantify the areal extent of this LUC.

Measuring and monitoring linear woody features in agricultural landscapes through earth observation data as an indicator of habitat availability

The loss of natural habitats and the loss of biological diversity is a global problem affecting all ecosystems including agricultural landscapes. Indicators of biodiversity can provide standardized measures that make it easier to compare and communicate changes to an ecosystem. In agricultural landscapes the amount and variety of available habitat is directly correlated with biodiversity levels. Linear woody features (LWF), including hedgerows, windbreaks, shelterbelts as well as woody shrubs along fields, roads and watercourses, play a vital role in supporting biodiversity as well as serving a wide variety of other purposes in the ecosystem. Earth observation can be used to quantify and monitor LWF across the landscape. While individual features can be manually mapped, this research focused on the development of methods using line intersect sampling (LIS) for estimating LWF as an indicator of habitat availability in agricultural landscapes. The methods are accurate, efficient, repeatable and provide robust results. Methods were tested over 9.5Mha of agricultural landscape in the Canadian Mixedwood Plains ecozone. Approximately 97,000km of LWF were estimated across this landscape with results useable both at a regional reporting scale, as well as mapped across space for use in wildlife habitat modelling or other landscape management research. The LIS approach developed here could be employed at a variety of scales in particular for large regions and could be adapted for use as a national scale indicator of habitat availability in heavily disturbed agricultural landscape.

Thresholds in forest bird richness in response to three types of forest cover in Ontario, Canada

Identification of threshold values in avian responses to habitat loss provides science-based guidelines on how to best manage anthropogenically altered landscapes for wildlife preservation. Our objectives were to test for thresholds in species richness of forest-breeding birds in relation to deciduous, coniferous, mixed, and total forest cover in two landscapes varying in the amount of forest present, and to determine whether thresholds for each forest type were coincident within and among landscapes, and across two spatial scales. We used Ontario Breeding Bird Atlas data to calculate species richness of forest-breeding birds. Percent deciduous, coniferous, mixed, and total forest cover were determined in 250 m radius circles around survey locations (local scale) and for 10 × 10 km squares (landscape scale) in the fragmented, sparsely forested Mixedwood Plains ecozone and in the more continuously forested Ontario Shield ecozone. Best-fit models explaining variation in species richness were selected from candidate sets of models that included 1–6 variables in addition to segmented or linear terms for forest cover. Threshold models had support at the local and landscape scales, and for all forest types. Thresholds ranged from 4 to 45 % cover, being slightly higher in the more continuously forested landscape, and for more prevalent forest types. Thresholds can provide useful targets for conservation efforts, but it is crucial to recognize that habitat levels should be maintained above threshold values to avoid ecological degradation, and to address the habitat requirements of species with occupancy thresholds above those of the assemblage.