Prairie Landscape Research Articles

Fall diet in sharp-tailed grouse (Tympanuchus phasianellus jamesi) and consumption of the grasshopper Melanoplus dawsoni in Alberta, Canada

Sharp-tailed grouse (Tympanuchus phasianellus) are an important component of northern grassland food webs, a reliable indicator species, and considered to be valuable to the preservation of biodiversity. Ecological stressors imposed on this species include habitat alteration, fragmentation, encroachment from agricultural development, insecticides, and the effects of climate change on prairie landscapes, all of which have the potential to alter food availability and trophic dynamics. Insects and spiders are an important food source for many grassland birds. The ecological roles of many arthropod species as prey and as contributors of other important ecosystem services remain relatively unexplored. This study examined esophageal crop contents from 164 plains sharp-tailed grouse (T. phasianellus jamesi) that were collected in 2017 and 2018 from three sites in southern and central Alberta, Canada. The remains of grasshoppers (Orthoptera: Acrididae, 18 species) were detected in 80% of esophageal crops collected in September, and 31% in October. Of the grasshopper samples, 91% and 63% respectively, were a single species identified as Dawson's grasshopper (Melanoplus dawsoni). Juvenile grouse consumed more grasshoppers than adult grouse in all cases. Studies on other gallinaceous game birds have also identified frequent consumption of single arthropod species, likely due to the range, catchability, and abundance of these species at certain times of year. This non-pest grasshopper species appears to form a significant part of the food supply for sharp-tailed grouse in the fall. Species-level arthropod ecology can contribute to a better understanding of ecosystem stability, optimal land management practices, and previously unexplored food web connections.

Mechanisms of Cold Region Hydrologic Change to Recent Wetting in a Northern Glaciated Landscape

AbstractThe Northern Great Plains (NGP) experienced a transition from a long drought cycle to a deluge cycle in the late 1900s. Embedded within this long‐term transition were shorter‐term decadal‐scale dry and wet periods. A recent NGP drought (1999–2004) was followed in 2005 by a wet period that continues to present day. However, how surface hydrology in a northern glaciated landscape responds to increased precipitation is poorly understood and a physically based modeling framework is needed to clarify the underlying processes. This study utilizes a physically based hydrologic model to investigate the impacts of increased precipitation on the water budget by examining its partition into intermediate processes from 2004–2017 in the Mauvais Coulee Basin (MCB). The MCB model evaluations against snow observations (2016–2017) and outlet streamflow observations (2004–2017) imply strong model performance. Simulated snow exhibits high spatiotemporal variation due to variability in precipitation, snow redistribution from stubble fields to wooded areas, and snow accumulation in small depressions. Our modeling results identify two major phases (before and after 2011) exhibiting different hydrologic responses. The period before 2011 is dominated by streamflow and evapotranspiration (ET), while extreme ET dominance is observed after 2011. This switch is due to climatic conditions involving changes in the vapor density difference and depressional and subsurface storage by intermediate processes. A clear contrast in the prewinter soil moisture‐streamflow relationship between before and after 2011 is reported. Our findings help illuminate the important influences of increased precipitation upon the intermediate processes in controlling streamflow in a northern glaciated prairie landscape.

Comparing stability in random forest models to map Northern Great Plains plant communities in pastures occupied by prairie dogs using Pleiades imagery

Abstract. Black-tailed prairie dogs (Cynomys ludovicianus) have been described as a keystone species and are important for grassland conservation, yet many concerns exist over the impact of prairie dogs on plant biomass production and consequently livestock production. The ability to map plant communities in pastures colonized by prairie dogs can provide land managers with an opportunity to optimize rangeland production while balancing conservation goals. The aim of this study was to test the ability of random forest (RF) models to classify five plant communities located on and off prairie dog towns in mixed-grass prairie landscapes of north central South Dakota, assess the stability of RF models among different years, and determine the utility of utilizing remote sensing techniques to identify prairie dog colony extent. During 2015 and 2016, Pleiades satellites were tasked to image the study site for a total of five monthly collections each summer (June–October). Training polygons were mapped in 2016 for the five plant communities and used to train RF models. Both the 2015 and 2016 RF models had low (1 %) out-of-bag error rates. However, comparisons between the predicted plant community maps using the 2015 imagery and one created with the 2016 imagery indicate over 32.9 % of pixels changed plant community class between 2015 and 2016. The results show that while RF models may predict with a high degree of accuracy, overlap of plant communities and interannual differences in rainfall may cause instability in fitted models. A final RF model combining both 2015 and 2016 data yielded the lowest error rates and was also highly accurate in determining prairie dog colony boundaries.

Stocking rate impacts on tallgrass prairie landscape carbon fluxes

AbstractCarbon sequestration in ecosystems reduces atmospheric CO2, a major forcing factor in global warming. We aimed to determine the ecosystem C balance under heavy and moderate stocking rates or ungrazed (UG) pastures during the first 2 yr of a 3‐yr period and to determine if changing to moderate stocking on a previously heavily stocked pasture would result in compensatory ecosystem C retention. During 2003 and 2004, net ecosystem C exchange (NEEc) was measured with eddy correlation towers on pastures that were UG, stocked at 2 acres per steer until the middle of the grazing season [intensive early stocking (IES)], and season‐long stocking at the high rate of 2 acres per steer (SLS‐H). In 2005, the SLS‐H pasture changed to a season‐long moderate stocking rate of 4 acres per steer (SLS‐H‐M). Net ecosystem C exchange was summed over an entire year from the burn date to the burn date the following year minus the C lost from burning and livestock export to estimate C balance. During the growing season, SLS‐H reduced ecosystem C retention compared with UG and IES in 2003 and 2004 (+223, +212, and –669 lb acre–1 for UG, IES and SLS‐H). In 2005, when the stocking rate on the SLS‐H pasture was changed to SLS‐H‐M, C retention was greater than under UG and IES (+107, +89, and +205 lb acre–1 for UG, IES and SLS‐H‐M). We conclude that following stocking at an abusive rate, there is compensatory C retention resulting from greater nutrient and water availability.

Rapid assessment of juniper distribution in prairie landscapes of the northern Great Plains

Woody plant species including eastern redcedar (Juniperus virginiana) and Rocky Mountain juniper (Juniperus scopulorum) are expanding throughout the prairie ecosystems of the Great Plains because of fire suppression, land management practices, and climate change. Juniper encroachment threatens native grasslands by altering soil characteristics, limiting herbaceous biomass, hindering native plant regeneration, and reducing rangeland productivity. Existing land cover products do not effectively characterize the distribution of juniper over a range of densities, making it difficult to assess the scale of the problem. We evaluated a method for rapid classification and mapping of juniper using matched filtering with Landsat 8 snow-covered and snow-free winter imagery (January-March), and snow-free spring imagery (April–June) for 2015–2016. We used data from two path/rows (29/30 and 30/30) in southeastern South Dakota and northeastern Nebraska (approximately 23,000 km2). In both path/rows, we found that snow-covered winter images increased contrast between juniper and the image background and resulted in the highest overall classification accuracies of 94.5% and 88.9% for juniper densities above 15%, compared to 91.4% and 85.7% for snow-free winter imagery and 57.8% and 74.1% for growing season imagery. Using winter imagery, we successfully captured pixels containing juniper density above 50% with ≥90% detection probability. However, the true positive rate dropped to less than 50% once juniper density fell below 20%. We identified 84 791 ha within the study area occupied by juniper (3.6% of the total area), including 27 504 ha in deciduous forests (33% of deciduous forest area) and 38 738 ha in grasslands (6% of grassland area).

Management regime and habitat response influence abundance of regal fritillary (Speyeria idalia) in tallgrass prairie

AbstractThe >2,570,000‐ha Flint Hills ecoregion of Kansas, USA, harbors the largest remaining contiguous tract of tallgrass prairie in North America, a unique system, as the remainder of North America's tallgrass prairie has succumbed to development and conversion. Consequently, the loss and degradation of tallgrass prairie has reduced populations of many North American prairie‐obligate species including the regal fritillary (Speyeria idalia) butterfly. Population abundance and occupied range of regal fritillary have declined >99%, restricting many populations to isolated, remnant patches of tallgrass prairie. Such extensive decline has resulted in consideration of the regal fritillary for protection under the Endangered Species Act. Although it is widely accepted that management practices such as fire, grazing, and haying are necessary to maintain prairie ecosystems, reported responses by regal fritillary to these management regimes have been ambiguous. We tested effects of prescribed fire across short, moderate, and long fire‐return intervals as well as grazing and haying management treatments on regal fritillary density. We also tested the relative influence of habitat characteristics created by these management regimes by measuring density of an obligate host plant (Viola spp.) and canopy cover of woody vegetation, grasses, forbs/ferns, bare ground, and litter. We found density was at least 1.6 times greater in sites burned with a moderate fire‐return interval vs. sites burned with short and long fire‐return intervals. Overall management regardless of fire‐return interval did not have an effect on density. Percent cover of grass had the strongest positive association, while percent cover of woody vegetation had the greatest negative effect on density. Our results indicate that patch‐burning is a viable and perhaps even ideal management strategy for regal fritillary in tallgrass prairie landscapes. Additionally, these results elucidate the importance of fire, particularly when applied at moderate‐return intervals to regal fritillary, and corroborate a growing suite of studies that suggest fire is perhaps not as detrimental to populations of regal fritillary as previously believed.

Wildlife value orientation of landowners from five states in the upper midwest, USA

ABSTRACTFive Upper Midwest states (Montana, North Dakota, South Dakota, Minnesota, Iowa) participated in a Plains and Prairie Landscape Conservation Cooperative (PPP-LCC) funded survey of landowners. All five surveys included a 13-item wildlife value orientation (WVO) scale to provide insight into how landowners in this region make land use decisions that affect wildlife habitat. Most landowners were utilitarian (59%), 11% were identified as mutualists, and pluralists and distanced landowners were 15% each. Pluralist and mutualist landowners placed more importance on wildlife considerations when making land use decisions compared to utilitarian and distanced landowners. However, landowners’ WVO was not related to their participation in United States Department of Agriculture (USDA) Farm Bill conservation programs. The proportion of WVO types among landowners varied considerably by age cohort. The proportion of utilitarians was highest for landowners born during the 1970s age cohorts and has since declined.

Landscape genetic evaluation of a tallgrass prairie corridor using the Greater Prairie-chicken (Tympanuchus cupido)

We studied current functional connectivity along a developing grassland corridor in the Midwestern U.S. and focused on connectivity for Greater Prairie-chickens (Tympanuchus cupido). Greater Prairie-chickens are an area-sensitive species that rely on grasslands and are an indicator species for the tallgrass prairie ecosystem in North America. The coordinated multi-agency Prairie Landscape Conservation Plan is one of the largest planned and implemented conservation corridors in the U.S., making this system ideal to examine factors associated with corridor functionality. We examined landscape functional connectivity and factors that impact genetic structure and gene flow of Greater Prairie-chickens to identify gaps in a planned prairie corridor that is currently being implemented. We collected feathers from 81 leks and obtained 31 hunter-harvested wings. We used a landscape genetic approach to evaluate eight hypotheses to explain functional connectivity and examine impacts of land cover and land use on isolation and genetic structure. Two populations were most supported based on 294 unique genotypes. Functional connectivity was influenced by land use, land cover, and anthropogenic development. Good connectivity exists within the Greater Prairie-chicken range, but improvements along the corridor in the northern portion of the extant range would be beneficial. We produced geographically specific recommendations as to where land management can potentially achieve the greatest impact. Our results help prioritize areas for ongoing conservation efforts, like prairie acquisition, restoration, and enhancement. Furthermore, identification of factors influencing connectivity in our study can be applied to improve conservation planning elsewhere in the tallgrass prairie ecosystem.

Evaluating the Impacts of Continuous and Rotational Grazing on Tallgrass Prairie Landscape Using High-Spatial-Resolution Imagery

This study evaluated the impacts of different grazing treatments (continuous (C) and rotational (R) grazing) on tallgrass prairie landscape, using high-spatial-resolution aerial imagery (1-m at RGB and near-infrared bands) of experimental C and R pastures within two replicates (Rep A and Rep B) in the southern Great Plains (SGP) of the United States. The imagery was acquired by the National Agriculture Imagery Program (NAIP) during the agricultural growing season of selected years (2010, 2013, 2015, and 2017) in the continental United States. Land cover maps were generated by combining visual interpolation, a support vector machine, and a decision tree classifier. Landscape metrics (class area, patch number, percentage of landscape, and fragmentation indices) were calculated from the FRAGSTATS (a computer software program designed to compute a wide variety of landscape metrics for categorical map patterns) based on land cover results. Both the metrics and land cover results were used to analyze landscape dynamics in the experiment pastures. Results showed that both grass and shrubs of different pastures differed largely in the same year and had significant annual dynamics controlled by climate. High stocking intensity delayed grass growth. A large proportion of bare soil occurred in sub-paddocks of rotational grazing that were just grazed or under grazing. Rep A experienced rapid shrub encroachment, with a large proportion of shrub at the beginning of the experiment. Shrub may occupy 41% of C and 15% of R in Rep A by 2030, as revealed by the linear regression analysis of shrub encroachment. In contrast, shrub encroachment was not significant in Rep B, which only had a small number of shrub patches at the beginning of the experiment. This result indicates that the shrub encroachment is mainly controlled by the initial status of the pastures instead of grazing management. However, the low temporal resolution of the NAIP imagery (one snapshot in two or three years) limits our comparison of the continuous and rotational grazing at the annual scale. Future studies need to combine NAIP imagery with other higher temporal resolution imagery (e.g., WorldView), in order to better evaluate the interannual variabilities of grass productivity and shrub encroachment.

Resource Availability and the Potential for Bison Introduction in a Landscape Mosaic

The tallgrass prairie ecosystem was historically maintained through the interaction of climate, fire, and grazing by large ungulates. Efforts are being made to return large ungulates (bison) back into prairie landscapes, but successful introductions can be constrained by suitable habitat as determined by resource availability (plant biomass, forage quality of the plant biomass, and soil carbon and nitrogen), particularly given some of these tracts are former arable land that has been restored to tallgrass prairie. The objective of this study was to quantify whether plant biomass (available forage) differs between prairie types, if forage quality varies across native prairie remnants and restored prairies, and if these differences are related to carbon and nitrogen storage in soil. We sampled native prairie remnants, low seeded-diversity older restored prairies, and high seeded-diversity younger restored prairies at Nachusa Grasslands, Illinois during July 2014. Total plant biomass differed between the three prairie types, with the high seeded-diversity younger-restored prairies having almost twice that of the low seeded-diversity older-restored prairies and more than twice that of the remnant prairies. In regard to forage quality, the percentage of crude protein in dry matter was greater in the remnant prairies compared to both of the restored prairie types. The high seeded-diversity younger restored prairies had the highest lignin concentration in the forage. The fat content of forage was highest in the high seeded-diversity younger restored prairies. Total soil carbon and nitrogen did not differ between the three prairie types at either the 0–10 cm or 10–20 cm depth. The preliminary findings of this study suggest bison grazing within the introduction unit at Nachusa Grasslands will be more intensive within restored prairies as compared to remnants.

Evaluating cropland in the Canadian prairies as an ecological trap for the endangered Burrowing Owl Athene cunicularia

Anthropogenic development may influence the choices animals make and their resulting reproductive success and survival. If such choices are maladaptive, the impact of anthropogenic change can be catastrophic to small or declining populations. Over the past century, Canada's prairie landscapes have been altered dramatically, with over two‐thirds of its native grasslands now having been converted to cropland. The decline of the endangered Burrowing Owl Athene cunicularia population is assumed to have resulted from this landscape change, yet no causal link has been demonstrated. One hypothesis to explain this population decline is that owls get caught in an ecological trap, whereby they prefer to establish nests at the start of each breeding season in landscapes that later confer lower reproductive success. Agricultural landscapes represent a plausible potential ecological trap because the short and sparse vegetation in annual crops (seeded each spring) is predicted to be attractive nesting/foraging habitat for Burrowing Owls when they arrive from northward migration, yet crops become substantially taller and denser over the growing season so prey are predicted to become less accessible by the time broods have hatched. We tested this ecological trap hypothesis in a 3‐year study, involving 379 Burrowing Owl pairs, across the agricultural landscapes of southern Alberta and Saskatchewan. In support of the hypothesis, Burrowing Owls did prefer to settle in breeding home‐ranges that contained a higher proportion of cropland, and their prey‐delivery rates during brood‐rearing were lower at nests with a higher proportion of cropland growing in the surrounding landscape. However, in contradiction to a key prediction, the number of fledglings produced (range = 0–9) was higher, not lower, for pairs with more actively growing cropland in their landscapes. Therefore, the decline of the Burrowing Owl in Canada does not appear to result from cropland forming an ecological trap during the breeding season. We also found a significant positive relationship between the amount of summer fallow within Burrowing Owl home‐ranges and the quantity of vertebrate prey delivered to the nest and the number of juveniles fledged, highlighting the importance of this declining land use in raptor conservation.

Correlates of Habitat Fragmentation and Northern Bobwhite Abundance in the Gulf Prairie Landscape Conservation Cooperative

AbstractThe northern bobwhite Colinus virginianus has experienced range-wide declines over the past several decades, primarily due to habitat loss and habitat fragmentation. As northern bobwhite populations continue to decline, there is a need for studies that address the impact of habitat changes on population persistence at multiple spatial scales. Our goal was to assess changes in habitat and land use related to northern bobwhite declines across multiple spatial scales in Texas, Oklahoma, and Louisiana. We determined northern bobwhite trends for 1972–2012 using Breeding Bird Survey data. At the regional scale, we compared northern bobwhite population trends with road density (2000, 2012), human population (1970–2010), and land use (1974–2012). At the county and local scales, we compared class-level landscape metrics between counties with stable and declining northern bobwhite abundances using Student's t-tests. Northern bobwhite populations decreased from 45.95 ± 1.01 birds/route in 1970 to 11.55 ± 0.64 birds/route in 2012. Road density and human population increased by 3,331.32 ± 66.28 m/km2 and 42,873 ± 8,687 people/county, respectively. Percent pasture and rangeland was relatively stable, as was percent woodland. Alternatively, the percentage of other land (houses, roads, wasteland) increased. At the county scale, Texas and Oklahoma counties with declining northern bobwhite populations had higher road densities, larger patches of pasture, smaller patches of woodland, and larger patches of cropland compared with stable populations. At the local scale, Texas and Oklahoma counties with declining northern bobwhite populations had less woody cover in smaller patches, and fewer but larger patches of herbaceous and bare ground, compared with populations with stable abundance. Therefore, managers can provide woody cover and reduce cropland effects at the local scale to support stable quail populations; however, the large-scale drivers of northern bobwhite decline, which are human population growth and resulting habitat loss, will be an important aspect of northern bobwhite conservation and management in the future.

Agricultural land cover does not affect the diet of Tree Swallows in wetland-dominated habitats

Agricultural practices have intensified during the past 50 yr, increasing crop production and altering the Canadian prairie landscape by removing or degrading uncropped habitats, including wetlands. We predicted that agricultural practices would alter invertebrate communities and the diets of consumers such as insectivorous birds. Using stable isotope analysis (δ13C and δ15N), we tested for differences in the assimilated diets and isotopic niche widths of adult and nestling Tree Swallows (Tachycineta bicolor) in grassland and cropland sites with similar wetland densities in Saskatchewan, Canada. We also assessed relationships between swallow diet and body size, mass, and condition. Dietary composition and niche width differed between years and age classes but were not consistently related to agricultural land cover. Aquatic insect prey (Diptera and Odonata) made up 75% of all swallow diets, but nestlings consumed a larger proportion of terrestrial Diptera, resulting in broader isotopic niche widths compared with adults. Age-specific dietary differences could have been related to temporal shifts in the insect community or distinct foraging by adults when feeding nestlings. The body mass and condition of adult and nestling swallows were unrelated to diet, but were higher on average in grassland than cropland habitat. Overall, Tree Swallows specialized in feeding on aquatic insects, regardless of agricultural land cover, at least in wetland-dominated habitats. Food resources originating from wetlands may play a critical role in supporting insectivorous bird populations in agricultural landscapes.

How to Detect Scale Effect of Ecosystem Services Supply? A Comprehensive Insight from Xilinhot in Inner Mongolia, China

Spatial scale plays a crucial role in the assessment and management of ecosystem services (ES), yet explicit information for identifying and understanding the scale effect on ES supply remains limited. In an attempt to detect scale effect on ES supply from a comprehensive perspective, this study developed a framework for integrating scale effect in three aspects, including individual ES patterns, pairwise ES interactions, and ecosystem service bundles (ESB). The framework was tested in Xilinhot, a prairie landscape city of Inner Mongolia, at four different levels of spatial scale. The results indicated that, most ES showed a decreasing clustering at coarser scales in terms of spatial pattern. At the same time, coarser scales resulted in fewer trade-offs and stronger synergies between pairwise ES. The identification of ESB varied greatly with scale, and this change reflected in the composition of ES variables and spatial distribution of bundles. We attributed the scale effect of the above three aspects to differences in social-ecological factors and their driving mechanisms at different scales. This comprehensive framework could support local managers to coordinate the management of multiple ES at different scales.

Generalized Additive Models of Climatic and Metabolic Controls of Subannual Variation in pCO2 in Productive Hardwater Lakes

AbstractSpatiotemporal variation in climate and weather, allochthonous carbon loads, and autochthonous factors such as lake metabolism (photosynthesis and respiration) interacts to regulate atmospheric CO2 exchange of lakes. Understanding this interplay in diverse basin types at different timescales is required to adequately place lakes into the global carbon cycle and predict CO2 flux through space and time. We analyzed 18 years of data from seven moderately hard lakes in an agricultural prairie landscape in central Canada. We applied generalized additive models and sensitivity analyses to evaluate the roles of metabolic and climatic drivers in regulating CO2 flux at the intra‐annual scale. At mean conditions with respect to other predictors, metabolic controls resulted in uptake of atmospheric CO2 when surface waters exhibited moderate primary production but released CO2 only when primary production was very low (<8 μg/L or when dissolved nitrogen was elevated (>2,000 μg/L), implying that respiratory controls offset photosynthetic CO2 uptake under these conditions. Climatically, dry conditions increased the likelihood of in‐gassing, likely due to evaporative concentration of base cations and/or reduced allochthonous carbon loads. While more research is required to establish the relative importance of climate and metabolism at other timescales (diel, autumn/winter), we conclude that these hard fresh waters characteristic of continental interiors are mainly affected by metabolic drivers of pCO2 at daily‐monthly timescales, are climatically controlled at interannual intervals, and are more likely to in‐gas CO2 for a given level of algal abundance than are soft water, boreal ecosystems.

Moderate patchiness optimizes heterogeneity, stability, and beta diversity in mesic grassland.

Heterogeneous disturbance patterns are fundamental to rangeland conservation and management because heterogeneity creates patchy vegetation, broadens niche availability, increases compositional dissimilarity, and enhances temporal stability of aboveground biomass production. Pyrodiversity is a popular concept for how variability in fire as an ecological disturbance can enhance heterogeneity, but mechanistic understanding of factors that drive heterogeneity is lacking. Mesic grasslands are examples of ecosystems in which pyrodiversity is linked strongly to broad ecological processes such as trophic interactions because grazers are attracted to recently burned areas, creating a unique ecological disturbance referred to as the fire–grazing interaction, or pyric herbivory. But several questions about the application of pyric herbivory remain: What proportion of a grazed landscape must burn, or how many patches are required, to create sufficient spatial heterogeneity and reduce temporal variability? How frequently should patches burn? Does season of fire matter? To bring theory into applied practice, we studied a gradient of grazed tallgrass prairie landscapes created by different sizes, seasons, and frequencies of fire, and used analyses sensitive to nonlinear trends. The greatest spatial heterogeneity and lowest temporal variability in aboveground plant biomass, and greatest plant functional group beta diversity, occurred in landscapes with three to four patches (25%–33% of area burned) and three‐ to four‐year fire return intervals. Beta diversity had a positive association with spatial heterogeneity and negative relationship with temporal variability. Rather than prescribing that these results constitute best management practices, we emphasize the flexibility offered by interactions between patch number and fire frequency for matching rangeland productivity and offtake to specific management goals. As we observed no differences across season of fire, we recommend future research focus on fire frequency within a moderate proportion of the landscape burned, and consider a wider seasonal burn window.

Effects of Land Use Change, Cultivation, and Landscape Position on Prairie Soil Organic Carbon Stocks

Temperate grassland soils are typically a sink for carbon. However, it is estimated that up to 99% of tallgrass prairies in North America have been converted to another land use. These conversions can lead to increased soil erosion and soil organic carbon (SOC) mineralization rates, turning a large carbon sink into a source. The purpose of this study was to compare by land use the retention of SOC, TSN, and fly ash on sloping landscapes with an emphasis on measuring the subsoil in addition to the surface soil. Eight paired plots were established on adjacent, sloping landscape profiles in western Iowa; one site a cropland and the other a remnant tallgrass prairie. The prairie landscape had a baseline SOC stock of 232 Mg-C ha-1. After roughly 150 years of agriculture the cropland had 52% less SOC, 39% less TSN, and 22% less fly ash which equates to annual losses of 0.55 Mg-C ha-1 yr-1, 0.04 Mg-N ha-1 yr-1, and 0.0002 Mg-fly ash ha-1 yr-1.

A Coupled Soil Water Balance Model for Simulating Depression‐Focused Groundwater Recharge

Core Ideas Ephemeral ponds in depressions are the foci of groundwater recharge in the Canadian Prairies. Freeze–thaw processes influence snowmelt runoff and depression‐focused recharge. A new water balance model was developed to represent these processes. The water balance model successfully simulated the observed soil processes. This model will provide a tool to estimate recharge in the prairie landscape. In arid and semiarid environments, focused infiltration of rain and snowmelt water under topographic depressions is an important mechanism of groundwater recharge. Quantifying the aggregated recharge from numerous small depressions is a major challenge in water resource management. Building on field‐based investigations into the surface water–groundwater interaction of individual depressions and their catchments (i.e., uplands) in the Canadian Prairies, we have developed a simple water balance model to simulate groundwater recharge considering the hydrological coupling of a depression–upland system. The model is based on the Versatile Soil Moisture Budget (VSMB), which has been widely used in the Canadian Prairies to simulate soil moisture conditions. We evaluated the new model, VSMB Depression‐Upland System (VSMB‐DUS), using field data consisting of an artificial flooding experiment and long‐term monitoring of a depression in Alberta, Canada. The model captured surface water level, soil moisture, and groundwater responses to the artificial flooding with reasonable accuracy and represented the interannual variability of recharge fluxes during a 5‐yr period (2007–2011), including dry and wet years. Simulated annual recharge varied between 12 and 45 mm, and annual precipitation varied between 453 and 597 mm during the 5‐yr period. The VSMB‐DUS tends to over‐ or underestimate snowmelt runoff in individual years; however, simulated recharge was only slightly affected by the errors in snowmelt runoff estimation. Due to its computational efficiency and robust algorithms, the VSMB‐DUS will provide a useful tool for estimating aggregated recharge in a large‐scale model grid cell containing hundreds of depression‐upland systems.

Environmentality on the Canadian Prairies: Settler‐Farmer Subjectivities and Agri‐Environmental Objects

AbstractState and institutional actors have been shaping settler‐farmer subjectivities in order to transform the landscape and thus the history and geography of the Canadian Prairies. This paper expands the application of environmentality from its origins in colonial forestry to interrogate agriculture on prairie landscapes. The Canadian state used the technologies of environmentality to influence “common sense” attitudes and behaviours, which acted to deterritorialize Indigenous communities and then manipulated their subjectivities to guarantee settler‐farmer access to land. Later, institutions and states moulded settler‐farmer subjectivities of correct farming behaviour in an effort to convert soil, water, and seeds into economic resources. These environmental objects, in turn, acted upon settler‐farmer subjects by setting biophysical and genetic limits such as soil fertility, water quality and quantity, and plant hardiness and disease resistance. Resisting environmentality requires understanding processes of subjugation while also creating counter‐narratives of “good” farming behaviour and Indigenous‐settler relations.

Inferring soil water movement and streamflow response in Canadian Prairie riparian areas using hydrologic state variables

AbstractFlat terrain and soils with variable permeability make it difficult to assess the relative importance of surface and subsurface runoff in the Canadian Prairies, especially in riparian areas that are critical for water transmission and solute transport. The main objective of this study is therefore to determine whether patterns of hydrologic state variables, namely, near‐surface soil moisture (SM), soil electrical conductivity (SEC), and soil temperature (ST), can help infer riparian‐to‐stream soil water movement in Prairie landscapes. Focus is on the near‐level Catfish Creek Watershed (south‐eastern Manitoba, Canada) where 3 riparian sites were monitored: a naturally vegetated grassland site, a headwater forested site, and a highly impacted grassed site adjacent to an engineered drainage dyke and a man‐made drainage channel. Data from 9 to 12 SM, SEC, and ST surveys completed at each site in 2015 using a 75‐point grid are matched with riparian water table data, surface water level data from adjacent drainage channels, and indicators of antecedent moisture conditions. Pattern characteristics, in the form of descriptive statistics and variogram parameters, are estimated for each state variable and then correlated to indicators of antecedent moisture conditions, stream, and subsurface water level data to infer soil water movement. Results show that potential evapotranspiration, depth to water table, and antecedent precipitation have a significant yet variable impact on SM, SEC, and ST patterns. A switching behaviour, between dry and wet conditions, is present in riparian areas characterized by grassland vegetation and well‐drained soils. The occurrence of shallow subsurface flow is inferred during the wettest conditions. Although riparian SM conditions are useful for predicting streamflow response in adjacent channels, such is not the case for riparian SEC and ST. Further investigations are however necessary to confirm the usefulness of SM spatial patterns for predicting streamflow response in other landscapes across the Canadian Prairies.