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Wetland decline under post-European settlement and land use change across western Canada has led to mitigation strategies, including wetland creation. Created wetlands can trigger environmental change, including woody species encroachment, in turn altering vegetation and soil. We quantify changes in shrub abundance from prior to wetland creation (1949) until 60 years later (2012) within a Mixedgrass ecosystem of the Verger watershed in Alberta, Canada. In addition, we compare remaining grassland with areas colonized by shrubland on similar ecosites for differences in (1) plant composition, including native and introduced flora, (2) herbage yield and forage accessibility for livestock, and (3) soil properties (surface organic depth, bulk density, mineral nitrogen (N), and carbon (C) concentration). Repeat photos show Shepherdia argentea shrublands increased from 0 to 88 ha (to 1.15% of study area) following wetland creation, with the greatest increase in the last 20 years. Relative to grasslands, shrublands had lower total plant diversity but greater presence of introduced plant species. Shrub patches were 94% lower in herbaceous production, with 77% of shrublands non-utilized by cattle, collectively leading to reduced grazing capacity. Relative to grasslands, shrublands had a thicker soil surface mulch layer, and where cattle were present, had increased mineral soil N and C. Overall, shrub encroachment following wetland creation has markedly altered vegetation and soils in this once grassland landscape, with negative impacts on native plant diversity, herbage production and forage accessibility, and has implications for the management of shrub encroachment.

Grassland management aimed at enhancing carbon (C) in soil is an important tool in mitigation of rising atmospheric CO₂, yet little is known of how grassland soil C changes with livestock stocking rate (SR). We relate soil organic and inorganic C mass (t ha⁻¹ to 60 cm depth) with cattle stocking over periods of 7–27 year for 32 paddocks distributed across nine community pastures in the mixed‐grass prairie of Saskatchewan, Canada. Initial analysis comparing Akaike information criterion models showed that cattle SR explained a greater proportion of variance in soil C, particularly soil organic C, than rainfall. Soil organic C mass increased with cattle SR (R² = .293; p = .001), even when the latter was normalized to account for differences in vegetation composition and growing conditions among pastures. Normalized SR varied from 0.49 to 2.30 times recommended levels, over which SOC increased from 24.7 to 57.4 t ha⁻¹. Increases in soil organic C under greater stocking coincided with increased abundance of introduced vegetation, particularly the rhizomatous grass Poa pratensis. Inorganic soil C accounted for 34.6% of total soil C, being particularly large below 30 cm soil depth, but did not vary with stocking rate. These findings indicate that both organic and inorganic C are important pools of C in northern temperate grassland soils, with soil organic C positively associated with long‐term cattle SR. Further studies are recommended to understand more fully the mechanisms regulating grazing impacts on soil C mass in northern temperate grasslands.

While northern temperate grasslands are important for supporting beef production, it remains unclear how grassland above- and belowground biomass responds to long-term cattle grazing. Here, we use a comprehensive dataset from 73 grasslands distributed across a broad agro-climatic gradient to quantify grassland shoot, litter, and shallow (top 30 cm) root biomass in areas with and without grazing. Additionally, we relate biomass to soil carbon (C) concentrations. Forb biomass was greater (p −1 for grazed vs. 2210 kg ha−1 for non-grazed; p > 0.05). Forb crude protein concentrations were lower (p −1) and without (7130 kg ha−1) grazing (p > 0.05). Surface mineral soil C concentrations were positively related to peak grassland biomass, particularly total (above + belowground) biomass, and with increasing forb biomass in grazed areas. Finally, total aboveground shoot biomass and soil C concentrations in the top 15 cm of soil were both positively related to the proportion of introduced plant diversity in grazed and non-grazed grasslands. Overall, cattle grazing at moderate stocking rates had minimal impact on peak grassland biomass, including above- and belowground, and a positive contribution exists from introduced plant species to maintaining herbage productivity and soil C.

Studies examining the influence of disturbance and management history on pasture soils across a large sampling area are uncommon. We report on the soil properties found in 102 northern temperate pastures sampled in central Alberta, Canada, and relate these attributes to ongoing pasture management practices compiled from producer surveys and aboveground measures of rangeland health (RH). Tame pastures, typically seeded to introduced forages, were associated with higher soil fertility (total carbon, nitrogen, and organic matter) than semi-native grasslands, which were associated with coarse-textured soils. Soil properties remained independent of most grazing and pasture management practices, including the grazing systems, class of livestock, fertilization, and stocking rate. However, manure application, often combined with harrowing, was associated with improved soil fertility and increased electrical conductivity (salinity). Soils with a fire history reported by land managers, largely in the Boreal natural region, were characterized by a greater soil C:N ratio. Soil surface properties (litter cover, litter depth, and bare soil) were responsive to grazing management, with growing season and year-round grazing associated with a thinner litter layer having less cover, and bare ground twice as high under continuous grazing compared with pastures rotationally grazed. Further, variation in soil surface cover was associated with contrasting RH classes (healthy, healthy with problems, and unhealthy), whereas soil attributes remained unrelated to RH. This study demonstrates that soils within these northern temperate grasslands are relatively insensitive to many pasture management practices, and highlights that existing RH assessments may provide limited insight into differences in mineral soil properties.

The spatial effects of vegetation control on early tree growth were investigated in central Alberta, Canada, for four years after the establishment of hybrid poplar plantations including the two cl...

Adaptive multi-paddock (AMP) grazing is a form of rotational grazing in which small paddocks are grazed with high densities of livestock for short periods, with long recovery periods prior to regrazing. We compared the fluxes of greenhouse gases (GHGs), including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), from soils of AMP-grazed grasslands to paired neighboring non-AMP-grazed grasslands across a climatic gradient in Alberta, Canada. We further tested GHG responses to changes in temperature (5 &deg, C vs. 25 &deg, C) and moisture levels (permanent wilting point (PWP), 40% of field capacity (0.4FC), or field capacity (FC)) in a 102-day laboratory incubation experiment. Extracellular enzyme activities (EEA), microbial biomass C (MBC) and N (MBN), and available-N were also measured on days 1, 13, and 102 of the incubation to evaluate biological associations with GHGs. The 102-day cumulative fluxes of CO2, N2O, and CH4 were affected by both temperature and moisture content (p &lt, 0.001). While cumulative fluxes of N2O were independent of the grazing system, CH4 uptake was 1.5 times greater in soils from AMP-grazed than non-AMP-grazed grasslands (p &lt, 0.001). There was an interaction of the grazing system by temperature (p &lt, 0.05) on CO2 flux, with AMP soils emitting 17% more CO2 than non-AMP soils at 5 &deg, C, but 18% less at 25 &deg, C. The temperature sensitivity (Q10) of CO2 fluxes increased with soil moisture level (i.e., PWP &lt, 0.4FC &le, FC). Structural equation modelling indicated that the grazing system had no direct effect on CO2 or N2O fluxes, but had an effect on CH4 fluxes on days 1 and 13, indicating that CH4 uptake increased in association with AMP grazing. Increasing soil moisture level increased fluxes of GHGs&mdash, directly and indirectly&mdash, by influencing EEAs. Irrespective of the grazing system, the MBC was an indirect driver of CO2 emissions and CH4 uptake through its effects on soil EEAs. The relationships of N-acetyl-&beta, glucosaminidase and &beta, glucosidase to N2O fluxes were subtle on day 1, and independent thereafter. AMP grazing indirectly affected N2O fluxes by influencing N-acetyl-&beta, glucosaminidase on day 13. We conclude that AMP grazing has the potential to mitigate the impact of a warmer soil on GHG emissions by consuming more CH4 compared to non-AMP grazing in northern temperate grasslands, presumably by altering biogeochemical properties and processes.

Creation and use of multi-use trails are increasing throughout grasslands of North America. While the direct and indirect ecological impacts of multi-use trails are generally understood, their specific impacts on adjacent grassland conservation require further assessment. Traditional scientific methods of quantifying trail impacts are often prohibitively costly in terms of required time, expertise, and equipment. Here, we evaluate the utility of a rapid assessment methodology—combining rangeland health protocols for grasslands with publicly available Google Earth mapping technologies—for capturing trail impacts as a function of distance from trail in a multi-use natural area in southwestern Alberta, Canada. Our methodology successfully detected a positive relationship between rangeland health scores and increasing distance from trail, indicating its viability as a rapid assessment tool. Second, this methodology was sensitive enough to allow the development of a more generalized statistical model demonstrating that rangeland health was best explained by a combination of slope, aspect, plant community type, and distance from trail. Combined, we suggest the limited costs of this method, combined with its ability to detect indirect impacts of trails on the health of adjacent grasslands, indicate this tool has potential utility for land managers where resources are limited. More specifically, we suggest this grassland health protocol can be highly effective as a first “rapid assessment,” prior to investing in more traditional ecological methodologies.Jessica Grenke, James F. Cahill, and Edward W. Bork. 2018. “Quantification of Multi-Use Trail Effects Using a Rangeland Health Monitoring Approach and Google Earth.” Natural Areas Journal 38(5):370-379.

Applying organic amendments to soil can increase soil organic carbon (SOC) storage and reduce greenhouse gas (GHG) emissions generated by agriculture, helping to mitigate climate change. However, it is necessary to determine which type of amendment produces the most desirable results. We conducted a 3-y field study comparing one-time addition of manure compost and its biochar derivative to a control to assess their effects on SOC and GHG emissions at ten annually cropped sites in central Alberta, Canada. Manure compost and biochar were applied at equivalent carbon rates (7 Mg ha−1) and tilled into the surface 10 cm of soil. Two years post-treatment, biochar addition increased surface (0–10 cm) SOC by 12 and 10 Mg ha−1 relative to the control and manure addition, respectively. Therefore, biochar addition led to the sequestration of SOC at a rate of 2.5 Mg ha−1 y−1 relative to the control. No treatment effect on deeper (10–100 cm) or cumulative SOC was found. In 2018 and 2019, manure addition increased cumulative GHG (sum of CO2, CH4, and N2O) emissions by 33%, on average, due to greater CO2 emissions relative to both the control and biochar addition. In contrast, in 2020, biochar addition reduced cumulative GHG emissions by an average of 21% due to lower CO2 emissions relative to both the control and manure addition. Our study shows that the application of biochar, rather than its manure compost feedstock, increased surface SOC sequestration and had either no effect on (first two years) or reduced GHG emissions (year three) relative to the control. We recommend that policy and carbon sequestration initiatives focus on optimizing biochar production-application systems to fully realize the potential of biochar application as a viable climate change mitigation practice in agriculture.

Our understanding of the effect of agroforestry systems on soil organic carbon (SOC) is largely limited to the upper layer of the mineral soil, while LFH (litter, partially decomposed litter and humus) and deeper soil layers are poorly studied. In this study, the effects of three different agroforestry systems (hedgerow, shelterbelt, and silvopasture) and their component land-cover types (treed area and adjacent herbland) on SOC stock in LFH and mineral soil layers (0–75 cm) were investigated across 36 sites in central Alberta, Canada. The SOC stock of mineral soil (0–75 cm) was not affected by agroforestry systems but by land-cover type. The treed area had greater (p

Adaptive multi-paddock (AMP) grazing, a grazing system in which individual paddocks are grazed for a short duration at a high stock density and followed by a long rest period, is claimed to be an effective tool to sustainably manage and improve grasslands and enhance their ecosystem services. However, whether AMP grazing is superior to conventional grazing (n-AMP) in reducing soil greenhouse gas (GHG) emissions is unclear. Here, we measured CO2, CH4, and N2O fluxes between August 2017 and August 2019 in 12 pairs of AMP vs. n-AMP ranches distributed across an agro-climatic gradient in Alberta, Canada. We found that field GHG fluxes did not differ between AMP and n-AMP grazing systems, but instead were regulated by specific management attributes, environmental conditions, and soil properties, including cattle stocking rate, cultivation history, soil moisture content, and soil bulk density. Specifically, we found that seasonal mean CO2 emissions increased with increasing cattle stocking rates, while CH4 uptake was lower in grasslands with a history of cultivation. Seasonal mean CO2 emissions increased while CH4 uptake decreased with increasing soil moisture content. In addition, CH4 uptake decreased with increasing soil bulk density. Observed N2O emissions were poorly predicted by the management, environmental conditions, and soil properties investigated in our study. We conclude that AMP grazing does not have an advantage over n-AMP grazing in reducing GHG fluxes from grasslands. Future efforts to develop optimal management strategies (e.g., the use of sustainable stocking rates and avoided cultivation) that reduce GHG emissions should also consider the environmental conditions and soil properties unique to every grassland ecosystem.

The maintenance of hydrologic function on grazing lands is an important management objective to sustain forage production during low moisture supply, safeguard other ecosystem goods and services and build resilience to a warming climate. Hydrologic function can be influenced by grazing patterns, as represented by variation in the timing, intensity and frequency of livestock use. While rotational, adaptive grazing (a short-duration, multi-paddock grazing system that emphasises plant recovery between grazing events) is growing in popularity and has the potential to influence grassland hydrological processes such as water infiltration, few studies have comprehensively examined infiltration in relation to on-ranch grazing practices. We examined water infiltration in grasslands on 52 ranches (set up as matched pairs) to examine whether adaptive grazing alters water infiltration in the Great Plains of western Canada, as compared to conventional grazing management employed on neighbouring ranches. We also used producer survey information to test for the influence of ongoing nuanced grazing practices on water infiltration rates, over and above the biophysical effects of soil texture, soil bulk density and plant litter, as well as cultivation history and climate. Overall, adaptive grazing, and specifically the use of higher rest-to-grazing ratios early in the growing season (prior to August 1), led to increased water infiltration in grassland soils. Water infiltration was positively associated with increased litter mass under adaptive grazing, whereas higher bulk density (and sandier) soils were associated with decreased infiltration rates. This study highlights the potential of specialised rotational grazing systems using cattle to improve soil hydrologic function in grazed grasslands.

How land-use and soil depth affect soil organic carbon (SOC) quality and stability, properties that are key to the long-term storage of C, is poorly understood in agroforestry systems. We examined the effects of land-use (forest vs. annual cropland) and soil depth (0–10 vs. 10–30 cm) on the quality (availability of C for decomposition), structural stability (composition of C functional groups), and thermal stability (energy yield and temperature characteristics during thermal oxidation) of SOC in a hedgerow system in central Alberta, using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and thermal analysis methods. The SOC quality (proportion of O-alkyl C) was higher, while the proportion of H- and C-substituted aromatic C and structural stability (hydrophobicity index (HB/HI), aromaticity index (ARM), and alkyl index (A/OA)) were all lower in the forest than in the cropland. The SOC also had lower thermal stability (higher energy density and lower temperature at which 50% of the mass was lost (TG-T50)) in the forest than in the cropland. Between the two soil depths, SOC quality (proportion of N-alkyl C, O-alkyl C and di-O-alkyl C) was higher, but the proportion of H- and C-substituted aromatic C and structural and thermal stabilities were lower, within the surficial 0–10 cm layer than in the 10–30 cm soil. We conclude that while the forest land-use within the hedgerow system had a higher SOC quality, it had lower SOC structural and thermal stabilities, suggesting that SOC under the forest land-use may be more susceptible to decline under climate change or other forms of anthropogenic disturbance.

Livestock grazing affects plant community composition, diversity, and carbon (C) and nutrient cycling in grasslands. Grazing leads to plant communities that have higher relative abundance of grazing-tolerant species, which in turn may alter the chemical composition of biomass and subsequent litter decomposition rates. To better understand the effects of long-term grazing and associated vegetation shifts on biogeochemical cycling in northern temperate grasslands of western Canada, we studied litter decomposition over 18 months at 15 locations, stratified across the Mixed-grass Prairie, Central Parkland, and Foothills Fescue natural subregions. At each location, we examined decomposition in an area exposed to grazing and an area where cattle were excluded. We used litterbags containing leaf litter from seven major grass species representing different grazing tolerances and included a local source of community litter from each study site and cellulose paper as standards. Decomposition was affected by litter types, with litter from grazing-tolerant species such as Poa pratensis and Bouteloua gracilis having faster decomposition rates compared to grazing-intolerant species, supporting the hypothesis that changes in vegetation composition due to grazing influences biogeochemical cycling by modifying litter decomposition in grasslands. Litter decomposition was also overall most rapid in the cool–wet Foothills Fescue, followed by the temperate mesic Central Parkland, and slowest in the warmer–drier Mixed-grass Prairie. Combined with known grazing-induced changes in grassland composition, these findings indicate that livestock grazing may accelerate litter decomposition rates in the more mesic Foothills Fescue and parkland regions, but not the more arid Mixed-grass Prairie. Overall, this study elucidates the role of livestock grazing and its associated effects on litter decomposition and ecosystem processes in northern grassland ecosystems.

Grasslands cover more than 40% of the terrestrial surface of Earth and provide a range of ecological goods and services, including serving as one of the largest reservoirs for terrestrial carbon. An understanding of how livestock grazing, influences grassland soil organic carbon (SOC), including its concentration, vertical distribution and association among soil-particle sizes is unclear. We quantified SOC concentrations in the upper 30 cm of mineral soil, together with SOC particle-size association, within 108 pairs of long-term grazed and non-grazed grassland study sites spanning six distinct climate subregions across a 5.7 M ha area of Alberta, Canada. Moderate grazing enhanced SOC concentration by 12% in the upper 15 cm of soil. Moreover, SOC concentrations in mineral layers were associated with regional climate, such that SOC increased from dry to mesic subregions. Our results also indicate that C concentrations in each of 2000–250, 250–53

Canadian agriculture is a source of greenhouse gases (GHG) and agroforestry has the potential to sequester carbon (C), and mitigate agricultural GHG emissions. Agroforestry systems are common features in Canada’s agricultural landscape; however, there are limited empirical data to support implementation of agroforestry practices for GHG mitigation. This shortfall of data may be a contributing factor to the lack of policy that supports the use of agroforestry for GHG mitigation in the Canadian agricultural landscape. We reviewed published studies that compared C stocks in vegetation and soils, and/or GHG emissions in agroforestry systems to traditional agriculture across Canada, with the aims of assessing the benefit of adopting agroforestry for GHG reduction. We then identified data gaps and obstacles that could direct future research. We found that most studies reported increases in vegetation and soil organic C storage in areas with woody species compared to herbaceous crops. Agroforestry systems also reduced the emission of CH4 and N2O, and increased CO2 respiration from soil, but few studies have examined these gases. The small set of studies we reviewed demonstrated the potential of agroforestry to store terrestrial C and mitigate GHG emissions. However, additional research is required to verify this pattern across geographic regions, determine the regional potential for development of agroforestry systems, and assess the potential atmospheric GHG reduction at regional and national scales.

Conversion of native grassland to other agricultural land uses can alter soil properties such as organic matter, but little is known about how this impacts soil physical quality indicators in the mixedgrass and aspen parkland natural subregions of the Canadian prairies. This study evaluated soil physical properties in three land use systems (native grasslands, introduced pastures and annual croplands) at seven sites across south-central Alberta, Canada. Hydraulic conductivity (K), pore size fractions and S-index were derived from moisture retention curves measured using a HYPROP system. Fractal aggregation was determined from the mass-diameter relationship of soil aggregates (0.25–8 cm diameter) using 3D laser scanning. All our results, except for K, showed a consistent trend of soil quality differences in the following ranking: native grassland > introduced pasture > annual cropland. Relative to croplands, introduced pastures led to an increase from 9 to 12% in medium-size pores (as median volume fraction of 9–50 μm diameter), whereas this pore fraction in native grassland was 19% (Ps

The sustainability of grazing lands lies in the nexus of human consumption behavior, livestock productivity, and environmental footprint. Due to fast growing global food demands, many grazing lands have suffered from overgrazing, leading to soil degradation, air and water pollution, and biodiversity losses. Multidisciplinary efforts are required to understand how these lands can be better assessed and managed to attain predictable outcomes of optimal benefit to society. This paper synthesizes our understanding based on previous work done on modelling the influences of grazing of soil carbon (SC) and greenhouse gas emissions to identify current knowledge gaps and research priorities. We revisit three widely-used process-based models: DeNitrification DeComposition (DNDC), DayCent, and the Pasture Simulation model (PaSim) and two watershed models: The Soil & Water Assessment Tool (SWAT) and Variable Infiltration Capacity Model (VIC), which are widely used to simulate C, nutrient and water cycles. We review their structures and ability as process-based models in representing key feedbacks among grazing management, SOM decomposition and hydrological processes in grazing lands. Then we review some significant advances in the use of models combining biogeochemical and hydrological processes. Finally, we examine challenges of incorporating spatial heterogeneity and temporal variability into modelling C and nutrient cycling in grazing lands and discuss their weakness and strengths. We also highlight key research direction for improving the knowledge base and code structure in modelling C and nutrient cycling in grazing lands, which are essential to conserve grazing lands and maintain their ecosystem goods and services.

Substantial interest exists in understanding the role of low-disturbance construction methods in mitigating industrial impacts to native grassland soils and vegetation. We assessed soil and vegetation responses to conventional high-disturbance sod-stripping and revegetation on sandy soils, and the alternative practice of low-disturbance access matting to provide a temporary work surface on sandy and loamy soils. Treatments were associated with high-voltage transmission tower construction during 2014 within the Mixedgrass Prairie. High-disturbance sites were hydroseeded in May of 2015, while low-disturbance sites recovered naturally. We assessed soil physical (bulk density, water infiltration) and chemical properties (organic matter, pH, and electrical conductivity) after construction and herbage biomass for three growing seasons. Sod-stripping led to 53% greater soil bulk density and 51% less organic matter than nondisturbed controls, while water infiltration increased by 32% in these high-sand (>80%) soils. In contrast, access matting led to minimal soil property changes regardless of the texture. While total herbage biomass was unaffected by all construction treatments, sod-stripping reduced grass biomass by 80% during the first growing season, which coincided with a 119% increase in forb mass. Root biomass (0–15 cm) also declined 77% with sod-stripping. Vegetation biomass on sites with access matting remained largely unaffected by the disturbance. Overall, low-disturbance construction methods using access matting were more effective than sod-stripping in mitigating the negative impacts of industrial development on Mixedgrass soil properties, as well as vegetation biomass, and are recommended as a best management practice during industrial disturbance.

Grazing lands provide many goods and ecosystem services, such as forage, livestock, soil carbon (C) storage, biodiversity, and recreational opportunities. Ensuring the long-term sustainability of grazing lands requires optimal management to simultaneously balance livestock productivity for sustaining human food and nutritional demands while reducing environmental impacts, such as greenhouse gases (GHG) emissions and soil degradation. In this paper, we revisit grazing management in grazing lands exposed to different grazing systems. In Section 2, we briefly review parameterization and multi-faceted goals for sustainability of grazing systems considering broader sustainability from economic to environmental aspects. We also discuss the inconsistencies between grazing researchers and ranchers’ practices. In Section 3, we review the separate experimental data to examine the impacts of multi-paddock rotational grazing on soil carbon, nutrient and GHGs. In Section 4, we present status and upcoming challenges in monitoring and upscaling of grazing ecosystem research and management. In Section 5, new concepts of multiple source monitoring networks are presented that enable the analysis of scale-dependent processes. Finally, we point out future directions for monitoring and assessment of managing soil C and GHG emissions from grazing lands. The results show that the inconsistences are essentially due to (1) effects of spatiotemporal scales on both economic and ecological outcomes, and (2) simplistic representations of multi-faceted grazing systems and sustainability. The development of multi-faceted monitoring systems needs to be further parametrized and standardized to make consistent for meaningful and comparable assessment of grazing management impacts on SOC and GHGs.

Boreal forests are increasingly exposed to industrial well site development. Little information exists on the optimal construction and reclamation strategies needed for vegetation recovery, including methods of well site preparation, soil storage, woody debris management, and revegetation. In this study we examined intermediate-term (10 yr) recovery of vegetation on 33 well sites distributed across NE Alberta, Canada, constructed and reclaimed using different site preparation methods, including high (HD), intermediate (ID), and low intensity (LD) disturbance of surface soils. Comparisons also included soil piling methods on HD sites, debris management on ID and LD sites, and tree planting on all sites. Comparisons were made to adjacent uncut forest to assess similarity, and at a subset of locations to harvested clear cuts. Ten years into recovery, vegetation was most similar between uncut forest and well sites developed using LD construction methods in species richness, diversity, and cover of vegetation growth forms and ground cover components (bare soil, litter, moss and lichen). Well sites using HD and ID had vegetation more dissimilar to uncut forest. Clear cuts harvested at the same time as the well sites also differed in composition from the forested controls, but remained more similar to the LD well sites than the HD and ID well sites. Effects of reforestation (tree planting), the technique of soil piling, and different forms of woody debris management (spreading vs windrowing) had little impact on vegetation recovery. Overall results highlight the importance of using LD well site preparation techniques where possible to keep mineral soil and embedded plant propagules intact to maximize boreal forest recovery following disturbance.

Western Canada's prairie region is extensively cultivated for agricultural production, which is a large source of greenhouse gas emissions. Agroforestry systems are common land uses across Canada, which integrate trees into the agricultural landscape and could play a substantial role in sequestering carbon and mitigating increases in atmospheric GHG concentrations. We measured soil CO2, CH4 and N2O fluxes and the global warming potential of microbe-mediated net greenhouse gas emissions (GWPm) in forest and herbland (areas without trees) soils of three agroforestry systems (hedgerow, shelterbelt and silvopasture) over two growing seasons (May through September in 2013 and 2014). We measured greenhouse gas fluxes and environmental conditions at 36 agroforestry sites (12 sites for each system) located along a south-north oriented soil/climate gradient of increasing moisture availability in central Alberta, Canada. The temperature sensitivity of soil CO2 emissions was greater in herbland (4.4) than in forest (3.1), but was not different among agroforestry systems. Over the two seasons, forest soils had 3.4% greater CO2 emission, 36% higher CH4 uptake, and 66% lower N2O emission than adjacent herbland soils. Combining the CO2 equivalents of soil CH4 and N2O fluxes with the CO2 emitted via heterotrophic (microbial) respiration, forest soils had a smaller GWPm than herbland soils (68 and 89 kg CO2 ha− 1, respectively). While emissions of total CO2 were silvopasture > hedgerow > shelterbelt, soils under silvopasture had 5% lower heterotrophic respiration, 15% greater CH4 uptake, and 44% lower N2O emission as compared with the other two agroforestry systems. Overall, the GWPm of greenhouse gas emissions was greater in hedgerow (88) and shelterbelt (85) than in the silvopasture system (76 kg CO2 ha− 1). High GWPm in the hedgerow and shelterbelt systems reflects the greater contribution from the monoculture annual crops within these systems. Opportunities exist for reducing soil greenhouse gas emissions and mitigating climate change by promoting the establishment of perennial vegetation in the agricultural landscape.

Few guidelines exist for the effective revegetation of peatlands following the removal of in-situ oil and gas infrastructure. We conducted a manipulative field study in northeast Alberta, Canada, on a well pad undergoing removal and revegetation to test different management practices for facilitating vegetation establishment and recovery of a sphagnum-dominated peatland. A randomized block design was used to evaluate the effect of various revegetation practices, including augmenting natural recovery with the use of native transplants, acrotelm transfer from a similar intact donor peatland, and the use of variable surface microtopography. Although overall survival of transplants was similar between areas smoothed and left rough, areas that were rough had greater species richness under natural recovery, including trees, shrubs, and other perennial herbs. Moreover, survival and growth of woody transplants (Picea mariana—black spruce and Ledum groenlandicum—Labrador tea) were greater when planted within the top and middle microtopographic positions rather than micro-depressions. Survival of transplanted sedges (Carex spp.) was high at all topographic positions, but benefited the most in growth from planting in depressions. Contrary to expectations, no benefits of acrotelm application were found on vegetation recovery during the first two seasons, and even reduced the presence of some native vegetation. Although transplants directly contributed to revegetation, the recovering peatland remained highly dissimilar ( 90%) in composition relative to the neighboring peatland after two years.

Changes in grazing regime and climatic conditions (such as precipitation) may affect soil N2O emissions; however, such effects have been inconsistent in grasslands. This study investigated the impact of simulated grazing, increased precipitation and N addition on soil N2O emissions, as well as soil dissolved organic carbon (DOC) concentrations, from a mixed grassland site in southern Alberta, Canada. A batch incubation study was conducted on soils (0–10 cm) collected from long-term field plots exposed to defoliation at either high intensity at low frequency (HILF) or high intensity at high frequency (HIHF) or low intensity at high frequency (LIHF) throughout the growing season (May–August). A deferred control (DC) treatment was also included where defoliation only occurred once at year end. All defoliation treatments formed a full factorial experiment with the watering treatment (ambient moisture (AM) or watering (W)) in the field. Soil N2O production was also quantified under an N addition treatment (no N and addition of 20 mg N kg−1 (NH4)2SO4) in the laboratory incubation experiment. Defoliation had no influence (p > 0.05) on soil DOC concentrations and cumulative N2O emissions. Watering increased DOC concentrations by 72–234 % but decreased N2O emissions by 33–60 %. Increments in N2O emissions after N addition were greater in the W (111–163 %) than the AM (64–67 %) treatment. Our results suggest that while defoliation regimes did not affect soil N2O emissions, watering may induce greater N2O loss in the more arid soil and N addition may further increase N2O loss under high precipitation within soils of the dry mixed grassland ecosystem.

The role of agroforestry systems in mitigating greenhouse gas (GHG) emission from agricultural soils during spring thaw (early April to mid-May) has been poorly studied. Soil CO2, CH4 and N2O fluxes were measured from treed areas and adjacent herblands (areas without trees) during spring thaw in 2014 and 2015 at 36 agroforestry sites (12 hedgerow, 12 shelterbelt and 12 silvopasture) in central Alberta, Canada. Fluxes of those GHGs varied with agroforestry systems and land-cover types. We found greater CO2 emission (P

Agroforestry practices that intentionally integrate trees with crops and/or livestock in an agricultural production system could enhance carbon (C) sequestration and reduce greenhouse gas (GHG) emissions from terrestrial ecosystems, thereby mitigating global climate change. Beneficial management practices such as enrichment planting and the application of soil amendments can affect C sequestration and GHG emissions in agroforestry systems; however, such effects are not well understood. A literature review was conducted to synthesize information on the prospects for enhancing C sequestration and reducing GHG emissions through enrichment (i.e., in-fill) tree planting, a common practice in improving stand density within existing forests, and the application of organic amendments to soils. Our review indicates that in agroforests only a few studies have examined the effect of enrichment planting, which has been reported to increase C storage in plant biomass. The effect of adding organic amendments such as biochar, compost and manure to soil on enhancing C sequestration and reducing GHG emissions is well documented, but primarily in conventional crop production systems. Within croplands, application of biochar derived from various feedstocks, has been shown to increase soil organic C content, reduce CO2 and N2O emissions, and increase CH4 uptake, as compared to no application of biochar. Depending on the feedstock used to produce biochar, biochar application can reduce N2O emission by 3% to 84% as compared to no addition of biochars. On the other hand, application of compost emits less CO2 and N2O as compared to the application of manure, while the application of pelleted manure leads to more N2O emission compared to the application of raw manure. In summary, enrichment planting and application of organic soil amendments such as compost and biochar will be better options than the application of raw manure for enhancing C sequestration and reducing GHG emissions. However, there is a shortage of data to support these practices in the field, and thus further research on the effect of these two areas of management intervention on C cycling will be imperative to developing best management practices to enhance C sequestration and minimize GHG emissions from agroforestry systems.

Agroforestry systems are common land uses across Canada and could play a substantial role in sequestering carbon (C) as part of efforts to combat climate change. We studied the impact of component land cover types (forested vs. adjacent herbland) in three agroforestry systems (hedgerow, shelterbelt and silvopasture) on organic C and nitrogen (N) distribution in three density fractions of soils at the 0–10 and 10–30 cm layers. The study evaluated 36 sites (12 hedgerows, 12 shelterbelts and 12 silvopastures) in central Alberta, Canada, distributed along a soil/climate gradient of increasing moisture availability. At the 0–10 cm layer, soil organic C (SOC) stock in the bulk soil was significantly greater in the silvopasture system (101) than in either the hedgerow (77) or shelterbelt system (67 Mg C ha−1). Soil organic C stock in both soil layers (0–10 and 10–30 cm) was also significantly greater in the forested land cover (89 and 119 Mg C ha−1, respectively) than in adjacent herblands (76 and 77 Mg C ha−1). Across all sites, 31.5, 29.1, and 35.5% of SOC was found in the light fraction ( 1.6 g cm−3) of soils, respectively. The largest pool of SOC in the more labile light fraction of the 0–10 cm layer was in the silvopasture system (50 Mg C ha−1), whereas the smallest labile light fraction component of SOC was in the shelterbelt system (17 Mg C ha−1). The largest pool of SOC in the more stable heavy fraction of both the 0–10 and 10–30 cm depth classes was in the shelterbelt (33 and 35 Mg C ha−1, respectively), while the least SOC was in the silvopasture system (26 and 20 Mg C ha−1, respectively). We conclude that the presence of Populus based silvopasture system can increase C storage in surface mineral soils, and that the establishment of Picea based shelterbelts in an otherwise annually cropped agricultural landscape enhances the size of the stable SOC pool.

On the Ground Variability in spatial and temporal patterns of herbage production is common in grasslands and can affect land uses, such as grazing. Total herbage biomass in northern mixed grass prairie was similar on loamy and sand dune ecologic sites but varied in composition. Cool-season grasses were uniformly produced throughout the grazing season, whereas warm-season grasses grew rapidly during August. Litter conservation was important for increasing cool-season grass biomass, whereas warm-season grasses remained independent of litter. Biomass and composition of herbage in the northern mixed grass varies spatially and intra-annually, affecting seasonal grazing opportunities for livestock.

How soil carbon dioxide (CO2) and methane (CH4) fluxes and above- and belowground C respond to grazing management across a grassland landscape is poorly understood. Thus, we quantified soil CO2 and CH4 fluxes, and above- and belowground C, for sandy loam and loamy sand soils within a dry mixed-grass prairie subjected to annual rotational cattle grazing (grazed) since 1970 or grazing exclusion for 4 yr (rested). Gas samples were collected weekly (May to October). The CO2 flux was 24% greater from the rested than grazed sandy loam. Higher CO2 fluxes from the rested than grazed sandy loam were associated with 49% and 68% greater water-extractable organic C concentrations in May and July, respectively, a 34% greater soil organic C concentration, and 88% greater peak aboveground vegetation C. In contrast, the rested and grazed loamy sand had similar CO2 flux and above- and belowground C, but 16% more CH4 uptake occurred in the grazed than rested. Across soil textures, water-filled pore space (WFPS) explained 5...

Climatic changes are altering Earth's hydrological cycle, resulting in altered precipitation amounts, increased interannual variability of precipitation, and more frequent extreme precipitation events. These trends will likely continue into the future, having substantial impacts on net primary productivity (NPP) and associated ecosystem services such as food production and carbon sequestration. Frequently, experimental manipulations of precipitation have linked altered precipitation regimes to changes in NPP. Yet, findings have been diverse and substantial uncertainty still surrounds generalities describing patterns of ecosystem sensitivity to altered precipitation. Additionally, we do not know whether previously observed correlations between NPP and precipitation remain accurate when precipitation changes become extreme. We synthesized results from 83 case studies of experimental precipitation manipulations in grasslands worldwide. We used meta-analytical techniques to search for generalities and asymmetries of aboveground NPP (ANPP) and belowground NPP (BNPP) responses to both the direction and magnitude of precipitation change. Sensitivity (i.e., productivity response standardized by the amount of precipitation change) of BNPP was similar under precipitation additions and reductions, but ANPP was more sensitive to precipitation additions than reductions; this was especially evident in drier ecosystems. Additionally, overall relationships between the magnitude of productivity responses and the magnitude of precipitation change were saturating in form. The saturating form of this relationship was likely driven by ANPP responses to very extreme precipitation increases, although there were limited studies imposing extreme precipitation change, and there was considerable variation among experiments. This highlights the importance of incorporating gradients of manipulations, ranging from extreme drought to extreme precipitation increases into future climate change experiments. Additionally, policy and land management decisions related to global change scenarios should consider how ANPP and BNPP responses may differ, and that ecosystem responses to extreme events might not be predicted from relationships found under moderate environmental changes. Fil: Wilcox, Kevin R.. University of Oklahoma; Estados Unidos Fil: Shi, Zheng. University of Oklahoma; Estados Unidos Fil: Gherardi, Laureano. Arizona State University; Estados Unidos Fil: Lemoine, Nathan P.. State University of Colorado - Fort Collins; Estados Unidos Fil: Koerner, Sally E.. University of South Florida; Estados Unidos Fil: Hoover, David L.. United States Department of Agriculture. Agricultural Research Service; Argentina Fil: Bork, Edward. University of Alberta; Canadá Fil: Byrne, Kerry M.. Humboldt State University; Estados Unidos Fil: Cahill Jr., James. University of Alberta; Canadá Fil: Collins, Scott L.. University of New Mexico; Estados Unidos Fil: Evans, Sarah. Michigan State University; Estados Unidos Fil: Gilgen, Anna K.. Swiss Federal Institute of Technology Zurich; Suiza Fil: Holub, Petr. Czech Academy of Sciences; República Checa Fil: Jiang, Lifen. University of Oklahoma; Estados Unidos Fil: Knapp, Alan K.. State University of Colorado - Fort Collins; Estados Unidos Fil: LeCain, Daniel. United States Department of Agriculture. Agricultural Research Service; Argentina Fil: Liang, Junyi. University of Oklahoma; Estados Unidos Fil: García Palacios, Pablo. Universidad Rey Juan Carlos; España Fil: Peñuelas, Josep. Consejo Superior de Investigaciones Científicas. Centre de Recerca Ecológica I Aplicacions Forestals; España. Universitat Autònoma de Barcelona; España Fil: Pockman, William T.. University of New Mexico; Estados Unidos Fil: Smith, Melinda D.. State University of Colorado - Fort Collins; Estados Unidos Fil: Sun, Shanghua. Northwest A & F University; China Fil: White, Shannon R.. Government of Alberta; Canadá Fil: Yahdjian, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. ; Argentina Fil: Zhu, Kai. Rice University; Estados Unidos. University of Texas; Estados Unidos Fil: Luo, Yiqi. University of Oklahoma; Estados Unidos

Significant areas of the mixedgrass prairie (MGP) in Alberta have experienced heavy equipment traffic due to industrial infrastructure development, which may change edaphic conditions that influence soil microbial communities. Direct wheeled traffic effects may be alleviated by using access mats that spread traffic impacts over a larger area; however, no scientific assessments of access mat efficacy have been conducted on soil microbial responses. Our objectives were to assess soil properties and the diversity, community structure, and size of soil microbial communities, as impacted by wheeled traffic occurring with and without access mat use on grassland. Two representative sites with differing soil texture (sandy versus loamy) were selected from a set of MGP sites established at the University of Alberta Mattheis Research Ranch in SE Alberta, Canada. Treatments at each site included non-disturbed vegetation controls, areas affected by direct traffic, and grassland with access mats placed for 12 weeks with traffic applied. Soil was sampled in July 2015 (immediately after access mat/traffic treatments ended) and in 2016 (12 months after access mat/traffic treatments) from both sites. Soil DNA was extracted and used to target N-cycling genes via qPCR and for next-generation sequencing (Illumina Miseq) of bacterial, archaeal, and fungal communities. Direct wheeled traffic without access matting increased the size of the N2O-reducing community in the sandy soil and conversely deceased the size of this community in the loamy soil. Non-metric multidimensional scaling, perMANOVA, and indicator species analyses indicated a large effect of traffic without access mat use on fungal community structure, as well as distinct bacterial and fungal indicator OTUs associated with disturbed soils compared to control soils. Fungal community structure remained affected by traffic impacts 12 months later, highlighting the extended impacts of traffic on fungal communities. Access matting mitigated some of the impacts direct traffic had on fungal community structure, but in the loamy site increased soil N and decreased the size of the N2O-reducing bacterial community. The latter indicates that ecosystem functioning of these grasslands may not only be impacted by direct wheeled traffic but also by using matting as a mitigation technique.

It is well known that climate can influence plant community assembly via a multitude of indirect and direct pathways. However, interpretations of plant diversity responses to simulated climate change experiments, and subsequent predictions of plant communities under future climate scenarios, rarely address the importance of indirect effects. Networks of direct and indirect effects are also critical in understanding linkages between climate and grazing, a common land use of grasslands, and implications for plant diversity. We characterized the roles of indirect vs. direct effects in determining plant diversity responses to climate and grazing using data from three northern temperate grasslands in which we conducted factorial experiments manipulating precipitation, air temperature, and clipping intensity. Utilizing a structural equation modeling framework to address the multivariate networks, we found warming operated directly, causing species loss at all sites. We identified shoot biomass as the key indire...

Agroforestry land-use systems have significant potential for increasing soil carbon (C) storage and mitigating increases in atmospheric greenhouse gas (GHG) concentrations. We studied the impact of three agroforestry systems (hedgerow, shelterbelt, and silvopasture) on soil organic C (SOC) and nitrogen (N) in the 0–10 cm mineral layer, by comparing SOC and N distributions in whole soils and three particle-size fractions (

Published in Agron. J. 106:33–42 (2014) doi:10.2134/agronj2013.0085 Copyright © 2014 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. The magnitude of climate change has been variable depending on location, with accelerated warming at high latitudes (Trenberth et al, 2007), including the Canadian prairies. Average temperatures in this region have increased 1.5°C in the last century, the largest temperature change across Canada (Zhang et al., 2000). Further increases up to 4.5°C are forecast for the Canadian prairies in the next 50 yr (Nyirfa and Harron, 2002). Precipitation trends with climate change are more diffi cult to assess (Christensen et al., 2007). Although precipitation is predicted to increase at high latitudes (Dore, 2005), observed increases have been lower in the prairies than in other parts of Canada (Zhang et al., 2000), and increased variability in precipitation has also been predicted, leading to drier periods (Sushama et al., 2010). Cattle grazing is a major economic activity on an estimated 13 million ha in the Canadian prairies (Vaisey and Strankman, 1999). Warming and altered precipitation have the potential to impact rangeland productivity (Izaurralde et al., 2011), with socioeconomic repercussions (Finger et al., 2010). Although several studies have evaluated the impact of warming on plant production, the results have been varied (Grime et al., 2000; Klein et al., 2007; Wu et al., 2011). Morgan et al. (2008) predicted that forage production in the Great Plains will increase with warming, and three meta-analyses of warming have concluded that plant growth will increase in grasslands (Rustad et al., 2001; Lin et al., 2010; Wu et al., 2011). Th ere is also evidence that productivity at northern latitudes is increasing due to climate change, although this trend is inconsistent across North America (Zhou et al., 2001). Warming can have negative eff ects on biomass, however, if plants are optimally adapted to their current (i.e., lower) temperature (King et al., 1995; Bertrand et al., 2008). Th e response of plant biomass to warming has also been shown to depend on other environmental variables, such as precipitation availability (Hoeppner and Dukes, 2012). Temperature aff ects plant biomass via both direct and indirect mechanisms, which can contribute to varied eff ects of warming on productivity (Shaver et al., 2000). For example, warming may decrease soil moisture (Kardol et al., 2010), in turn limiting plant biomass. Th e relationship between peak biomass and precipitation is generally positive (Sims and Singh, 1978; Wu et al., 2011), and on a continental scale, precipitation is considered the most important driver of grassland distribution and productivity (Milchunas et al., 1994; Knapp and Smith, 2001; Huston and Wolverton, 2009); however, some studies have found no relationship (Frank, 2007) or even a negative relationship (Gilgen and Buchmann, 2009) between biomass ABSTRACT

The integration of multiple uses on public rangeland requires reliable information on patterns of livestock use. We used GPS data and field plot utilization indices to examine cattle selection at the landscape and patch levels, respectively, within a heterogeneous Montane environment of SW Alberta, Canada. We also evaluated factors associated with patterns of summer cattle use, including topographic features, distance to water and roads, as well as forage quantity and quality. Cattle preferred lowland and upland grasslands, while avoiding conifer forests and clear cuts. Selection patterns differed markedly between the landscape and plot scales. At the landscape scale, forage use was related to abiotic factors, primarily slope ( β = −0.70) but also distance to water (−0.34) and distance from roads (+0.21). The negative impact of slope was greater than that observed in previous studies, and has implications for identifying primary ranges and deriving sustainable carrying capacities in Montane landscapes. At the plot (feeding patch) scale, forage use was additionally related to biomass availability ( β = +0.58), and to a lesser extent crude protein concentration (+0.16), highlighting the importance of forage characteristics in regulating cattle use. Lowland grasslands had the highest biomass and received the greatest forage use (43% utilization). Low visitation (44% of plots) and associated forage use (3% herbage utilization) by cattle within cut blocks, combined with conservative forage use across all habitats (3–43%), indicate grazing by cattle is consistent with maintaining other uses within this area, including riparian function, native grassland conservation and forest management.

Similarity between seed bank and aboveground vegetation is frequently studied in order to better understand how community composition is affected by factors such as disturbance and succession. Grassland plant communities are known to be sensitive to shifts in precipitation and increases in temperature associated with climate change, but we do not know if and how these factors interact to affect the similarity between seed bank and aboveground vegetation. Also unknown is how the impact of grazing, the dominant land-use in grasslands, will interact with climatic conditions to affect similarity. We manipulated precipitation and temperature, and cut vegetation (as a proxy for grazing) at a grassland site for three years. Percent cover of aboveground vegetation was estimated in the third year, and compared with persistent seed bank samples taken in the year prior from the same plots. Similarity increased with reduced precipitation, was unresponsive to warming, and decreased with clipping. The aboveground community responded strongly to the treatments, while the seed bank community did less so, suggesting similarity responses were largely driven by changes in aboveground vegetation. Because of the importance of the seed bank in vegetation regeneration, understanding the relationship between seed bank and aboveground vegetation will improve our understanding of plant community dynamics under climate change and varied management (grazing) intensities.

While plant litter is known to regulate soil moisture, little is known about the extent to which litter impacts moisture over and above the physical environment (i.e., ecosite) throughout the growing season, particularly in cool-temperate grasslands where moisture is considered less limiting for plant growth. In this study, we examined the relative impact of litter and ecosite on growing season soil moisture in a northern rough fescue (Festuca hallii) grassland. We also examined the relationship between litter and plant biomass throughout the growing season, including linkages between litter, plant growth, and the effects of litter on microclimate. During May, only ecosite was found to be associated with soil moisture, with a similar finding for plant biomass. Litter became important in maintaining greater soil moisture in June and July, however, likely through its corresponding negative impact on soil temperature and associated evaporation. In general, litter had a stronger and more consistent influence on soil moisture than ecosite. Finally, litter had a positive relationship with above-ground biomass, but only during June and July, the same months when litter exhibited the strongest relationship with soil moisture. Litter therefore appears to promote mid-season plant growth in these temperate grasslands, presumably through its ability to reduce evaporation and maintain greater soil water during seasonal moisture limitations.

Soil moisture can limit plant production in cool-temperate grasslands, particularly under recent increases in drought severity and predictions of future climate change. This necessitates research that examines moisture mitigation strategies under the dominant land use of grazing. We examined the effectiveness of plant litter in regulating soil moisture dynamics and associated plant production in a native grassland and tame pasture in the Aspen Parkland of Alberta, Canada during 2007/2008, specifically testing (1) how litter and defoliation (as a surrogate for grazing) alter the micro-environment at the soil surface, (2) whether litter, in combination with defoliation, alters forage production, and (3) whether production changes can be linked to observed micro-environmental changes created by litter modification. The full factorial randomized complete block design consisted of three litter treatments (litter removal, in situ control, and double litter) and three defoliation treatments (undefoliated control, light defoliation to 6.5 cm stubble height, and heavy defoliation to 2.5 cm). Soil moisture levels were assessed over four periods after summer precipitation to examine soil moisture depletion. Plant phenological development and canopy cover were also assessed throughout 2007, and biomass was measured in August 2007 and 2008. Abundant litter (up to 14,000 kg ha−1) improved soil moisture levels in both native and tame grasslands by either maintaining higher absolute moisture levels or reducing total moisture loss after rainfall. Both litter removal and double litter reduced total growing season production compared to in situ levels at the Native Site, despite highest vegetation cover in litter removal plots. High litter levels also improved growth of individual grass tillers at this site, but negatively impacted sexual production. Conversely litter removal improved overall production at the Tame Site, although litter did enhance grass tiller recovery following mid-season defoliation at both sites, in part due to positive influences on soil moisture. Treatment effects on plant production were less pronounced in 2008 than in 2007. Overall, high litter levels improve soil moisture retention and can improve or stabilize plant production particularly in native prairie sites, and can provide an important drought management strategy in the Aspen Parkland.

Decades of anthropogenic flooding to create wetlands in spring for breeding waterfowl in the Canadian Prairies have produced undesirable successional shifts from open wetlands dominated by endemic Eleocharis palustris L. (spikerush), to habitats dominated by relatively closed communities of Typha latifolia L. (cattail). Using 2 greenhouse experiments, we examined the potential of specific drying regimes to cross moisture thresholds and achieve T. latifolia control while maintaining E. palustris. We assessed the morphologic (leaf density, shoot ratio, biomass) and biochemical (root carbohydrate) responses of transplanted T. latifolia and E. palustris to different soil hydrologic treatments, including continuous flooding (CF), field capacity (FC) moisture, and 5 different drying stress (DS) treatments ranging from 4 to 12 weeks in duration, including recovery during re-inundation. Our results suggest that both plant species are susceptible to low soil moisture, as exemplified by reduced growth and survival. Although T. latifolia recovery during reflooding declined with incremental severity of moisture stress, T. latifolia was more tolerant to drought than E. palustris, with soil moisture below 5% required to induce complete root mortality. We conclude that only very low soil moisture will achieve T. latifolia control, under which E. palustris will have to re-establish from seed.

This study evaluated the impact of shrub encroachment within cool-season floodplain meadows in a portion of the Rocky Mountain Forest Reserve in southwestern Alberta, where nearly half of open grasslands have been lost since 1958. Sample transects situated in meadows, known formerly to be in open grassland, were assessed in 2001 ( n = 21) and 2002 ( n = 33) in areas ranging from 0% to 92% shrub cover. Shrub cover, density, and height were correlated to understory parameters, including herbaceous production, bunchgrass cover and density, and species richness and diversity. Additional data on soil horizon depths were obtained. Analysis was conducted using regression to assess empirical relationships between understory or soil characteristics and the overstory. Stronger empirical relationships (i.e., greater R 2 ) were found in 2002, coincident with larger sample sizes and greater rainfall. Among independent overstory variables, aggregate shrub cover for all species accounted for the greatest variation in understory characteristics. Significant ( P –1 in meadows containing less than 12% shrub cover, to 2 797 kg · ha –1 in areas where shrub cover exceeded 35%. Negative linear trends were found ( P

This study compared the suitability of LIDAR (LIght Detection And Ranging) data, three-band multispectral data, and LIDAR data integrated with multispectral information, for classifying spatially complex vegetation in the Aspen Parkland of western Canada. Classifications were performed for both a) general vegetation classes limited to three major formations of deciduous forest, shrubland and grassland, and b) eight detailed vegetation classes including upland mixed prairie and fescue grasslands, closed and semi-open aspen forests, western snowberry and silverberry shrublands, and fresh and saline riparian (lowland) meadows. A Digital Elevation Model (DEM) and Surface Elevation Model (SEM) developed from LIDAR data incorporated both topographic and biological biases in community positioning across the landscape. Using multispectral data, the original digital image mosaic, its hybrid color composite, and an intensity–hue–saturation (IHS) image were each tested. Final vegetation classification was done through integration of information from both digital images and LIDAR data to evaluate the improvement in classification accuracy. Among the land cover schedules with three and eight classes of vegetation, classification from the multispectral imagery, specifically the hybrid color composite image, had the highest accuracy, peaking at 74.6% and 59.4%, respectively. In contrast, the LIDAR classification schedules led to an average classification accuracy of 64.8% and 52.3%, respectively, for the general and detailed vegetation data. Subsequent integration of the LIDAR and digital image classification schedules resulted in accuracy improvements of 16 to 20%, resulting in a superior final accuracy of 91% and 80.3%, respectively, for the three and eight classes of vegetation. A final land cover map including 8 classes of vegetation, fresh and saline water, as well as bare ground, was created for the study area with an overall accuracy of 83.9%, highlighting the benefit of integrating LIDAR and multispectral imagery for enhanced vegetation classification in heterogenous rangeland environments.

The manner in which trembling aspen (Populus tremuloides Michx.) forest duff moisture changes during the growing season was investigated in Elk Island National Park, Alberta, Canada. A calibration-validation procedure incorpo- rating one calibration site with moisture sampling across three topographic positions was used to develop predictive mod- els, which were subsequently compared with 12 validation sites across three vegetation types throughout the Park. Duff moisture was modelled against the Duff Moisture Code and Drought Code components of the Canadian Forest Fire Weather Index System. Spring, summer, and fall rates of duff moisture change differed (P < 0.050) during calibration, with moisture loss greatest in spring. Additionally, while moisture changes on the south-facing and crest topographic positions were simi- lar during spring, moisture losses were greater (P < 0.050) at these locations compared with the north-facing landscape posi- tion. Correlation analysis indicated that duff inorganic content and bulk density were both related to duff moisture but were limited in importance compared with weather-based influences. When compared with predicted values obtained from cali- brated models, moderate predictability of duff moisture was found (mean absolute error = 20.7%-54.2%). Relative to the na- tional standard equations, unique but very different empirical relationships were developed between the Duff Moisture Code and Drought Code and the moisture content of the duff layer in aspen forest stands found in Elk Island National Park. Resume´ : La facon dont l'humiditede l'humus de la foret de peuplier faux-tremble (Populus tremuloides Michx.) evolue durant la saison de croissance a eteetudiee dans le parc national de Elk Island en Alberta, au Canada. Une methode de validation et de calibration impliquant un site de calibration oul'humiditeaeteechantillonnee dans trois positions topo- graphiques a servi adevelopper des modeles de prediction qui ont par la suite etevalides dans 12 sites repartis a travers le parc dans trois types vegetaux. L'humiditede l'humus a etemodelisee en regard des composantes de l'indice de l'humus et de l'indice de secheresse qui composent l'indice foret-meteo canadien. La variation du taux d'humiditede l'humus etait differente (P < 0,050) au printemps, en eteet al'automne durant la calibration et la perte d'humiditeetait la plus elevee au printemps. De plus, alors que la variation du taux d'humiditedans les positions topographiques exposees au sud et sur les cretes etait semblable au printemps, les pertes d'humiditeetaient les plus elevees (P < 0,050) dans ces endroits compa- rativement aux positions exposees au nord dans le paysage. L'analyse de correlation indique que la teneur en matiere inor- ganique et la densiteapparente de l'humus sont toute deux reliees al'humiditede l'humus mais ont peu d'importance comparativement a l'influence des conditions meteorologiques. L'humiditede l'humus etait moderement previsible (erreur absolue moyenne = 20,7%-54,2%) comparativement aux valeurs predites par les modeles calibres. Relativement aux equations nationales standard, des relations empiriques singulieres mais tres differentes ont etedeveloppees entre l'indice de l'humus ainsi que l'indice de secheresse et la teneur en humiditede la couche d'humus dans les peuplements forestiers de peuplier faux-tremble presents dans le parc national de Elk Island. (Traduit par la Redaction)

Question: How effective is high-resolution airborne LiDAR technology for quantifying biophysical characteristics of multiple community types within diverse rangeland environments? Location: Native Aspen Parkland vegetation in central Alberta, Canada. Methods: Vegetation within 117 reference plots stratified across eight types, including forest, shrubland, upland grassland and lowland meadow communities, were assessed in 2001 for the height, cover and density of vegetation within various strata (herb, shrub and tree layers). Actual ground data were subsequently compared against modelled values for each community type and strata derived from the analysis of airborne LiDAR data obtained in 2000. Results: LiDAR data were effective for quantifying vegetation height, cover and density of the overstory within closed- and open spulus forest communities. However, LiDAR measurements typically underestimated the height and cover of shrublands, as well as most of the herbaceous communities. Analysis of LiDAR...

Effects of three aspen (Populus tremuloides Michx.) canopy removal treatments and root trenching on understory microenvironment and moisture were tested at Parkland and Boreal sites in Alberta, Canada. Aspen canopies moderated air temperature by reducing maximums and increasing minimums, and increased the frost-free period in the understory by reducing radiative frosts. When daily differences were found among canopy treatments, maximum absolute humidity was greater with complete canopy removal. Maximum daily relative humidity was greater in openings at night than with either full or partial canopy cover. Predictably, increasing aspen cover reduced PAR reaching the understory. Soil moisture response was highly variable, changing with site, aspen density and precipitation patterns, but there were only marginal differences due to root trenching. In the Parkland site, soil moisture conservation from aspen canopy and leaf litter effects were masked by tree uptake in most periods, but a net increase in soil water (+5.2%) was observed during drought. Soil and microclimatic conditions in thinned aspen stands suggest potentially favourable production benefits from developing and adopting agroforestry systems in these northern ecosystems.

We developed a computer model (PASTURE) to simulate both condition of pastures grazed by farmed wildlife and animal performance as dual measures of system performance. For representative habitat types (e.g., aspen forest and open grasslands), the model simulates herbage growth, maturation and senescence, habitat and diet selection, and nutrient intake of several wild ruminant species. The model generated seasonal patterns of pasture productivity and animal behavior expected for Bromus-Poa pastures in aspen boreal ecosystems. Model calibration was conducted using data collected from studies conducted within the aspen boreal ecosystems at the Ministik Research Station in 1997 and 1998, and Elk Island National Park and the University of Alberta greenhouse in 1999 and parameters adjusted until the predicted and observed results were visibly close. Evaluation of the model was conducted using statistical criteria of calculating average error, root mean square, root mean square error, coefficient of residual mass and modeling efficiency and comparing these statistics against optimal values. Statistical tests indicated a good fit between predicted and observed values for cumulative phytomass, herbage use and animal performance.