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Crested wheatgrass (CWG) [Agropyron cristatum (L.) Gaertn.] is a commonly introduced grass in the Canadian prairies, but concerns remain about its possible long-term effects on soil quality, and its influence on soil water repellency (SWR) has not been determined. The long-term (24 yr) effects of CWG on SWR in comparison to seeded native grasses and annual cropping were determined for a clay loam soil in southern Alberta, Canada by measuring SOC concentration and SWR using soil hydrophobicity (SH) and soil water repellency index (RI) methods. The cropping treatments were CWG, seeded native grass mix (NGM), continuous wheat, and wheat–fallow rotation, each with fertilized (nitrogen) and non-fertilized subplots, replicated four times. Mean SOC concentration, SH, and RI in samples of surface soil were similar (P > 0.05) for CWG and seeded NGM, and they did not support our hypothesis (seeded NGM > CWG). Mean SOC was significantly greater for seeded perennial grasses than annual crops by 1.7–2 times and SH by 2.1–2.5 times, which supported our hypothesis, but RI was similar among treatments. As expected, nitrogen fertilization significantly increased SOC concentrations, but the effects on SH and RI were undetectable. A strong positive correlation occurred between SOC concentration and SH (r = 0.92) but not for RI (r = 0.10). Our findings suggested that SWR was similar for CWG and seeded NGM. The SWR as measured using SH was greater for seeded perennial grasses than annual cropping but was similar using RI.

Climate change may make semiarid grasslands increasingly prone to wildfire. We studied fire seasonality and growing season condition effects on a semiarid grassland in Southern Alberta, Canada. Plots were hand-torched in either fall or spring. Response variables estimated included plant composition and diversity, plant height, aboveground net primary production (ANPP), and forage nitrogen quality. The experiment was replicated over three consecutive growing seasons, and each replicate was monitored for 3 yr thereafter. Drought conditions occurred during two of the six growing seasons. Fall fires appeared to be hotter than spring fires based on a greater fuel mass (standing litter) and exposed the soil surface to a longer period without the benefit of standing litter over winter. Although this grassland is resilient to fire, compared with spring-burned grasslands, the species composition, ANPP, and leaf length of grasses of fall burned communities took a longer time to recover to preburn conditions. Our results suggest that spring-burned grasslands should not be grazed for 1 year post burn to allow time for recovery of ANPP and litter. However, given that ANPP of fall-burned communities also exhibited higher nitrogen concentration that may make the forage more palatable to livestock, and that these communities were more severely impacted, it seems prudent to delay their grazing for more than 1 year to prevent overgrazing. The negative impacts of fire on ANPP may be ameliorated with above-average precipitation in June, which may be forecast during an El Nino year.

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.

Management intensive grazing (MIG) may not maximize plant productivity on rangelands because of morphophysiological traits of grassland vegetation. We examined defoliation and moisture effects on the biomass yield of rhizomatous and caespitose grass pairs that were either phylogenetically similar or of similar agroclimatic adaptation, including two agronomic grasses. From relatively low to high moisture regime adaptation, species pairs included western wheatgrass (Pascopyrum smithii [Rydb.] A. Love) and needle-and-thread (Hesperostipa comata [Trin. & Rupr.] Barkw.), northern wheatgrass (Elymus lanceolatus [Scribn. & J.G. Sm.]) and western porcupine grass (H. curtiseta [Hitchc.] Barkw.), plains and foothills rough fescue (Festuca hallii [Vasey] and F. campestris Rydb.), and smooth and meadow brome (Bromus inermis Leyss. and B. riparius Rehm). Response variables were shoot yield, root-shoot ratio, and water-use efficiency. We hypothesized that caespitose grasses, regardless of their origin or adaptation to agroclimate regime, would respond more determinately in biomass accumulation. Defoliation effects on shoot biomass were more pronounced under high moisture. Low intensity − high frequency defoliation yielded similarly to deferred controls in all grasses, and the same was true for high-intensity − low-frequency (HILF) defoliation in 1 rhizomatous grass. Three of the 4 rhizomatous grasses and 1 caespitose grass yielded greater under HILF defoliation compared with high-intensity − high-frequency defoliation. Caespitose grasses allocated more biomass to roots under low moisture conditions. Water-use efficiency decreased under high moisture conditions and more intense and/or frequent defoliation and peaked in agronomic grasses. Overall, our results suggested that growth patterns corresponded more with phylogenetic similarity as opposed to growth form. A conceptual model from these results showed that across all species, only the introduced bromes generated greater biomass under HILF defoliation, and this may explain why past research consistently concludes that MIG does not enhance plant productivity on rangelands.

Cultivating native rangeland can have detrimental effects on soil carbon and nitrogen storage. Understanding how vegetation and soil recover after returning marginal cultivated land to its native state is important since soil plays a key role not only in food production but also in regulating global climate change. Soil samples were taken from two sites, a mixedgrass and a dry mixedgrass prairie, which have different climates and plant species composition. Each study site included one undisturbed native plot (CK) and two cultivated treatments that were abandoned in 2008 after being cultivated for more than ten years prior to this study, one with continuous wheat (Triticum aestivum L.) and the other with wheat-fallow rotations. Soil organic carbon (SOC), total nitrogen (TN), and labile organic fraction content were measured in 2016, while plant coverage and species diversity were investigated in 2017. In both study sites, grass and sedge coverage in the previously cultivated treatments were lower than, with shrub and forb coverage similar to, the CK. The highest invasive species coverage appeared in the previously cultivated treatments. Species richness was higher with CK in the mixedgrass prairie but no differences were found in the more arid dry mixedgrass prairie. No differences were found among all treatments for species evenness, Simpson's index and Shannon–Wiener index. On average, in the 0–15 cm depth, SOC and TN contents with the previous cultivated treatments were still 20% and 16% lower than CK, respectively, whereas in the 15–30 cm depth, SOC and TN contents did not differ among all treatments except for SOC content in the mixedgrass prairie. Relative to CK, previously cultivated treatments had similar active carbon (AC), microbial respiration-carbon and NH4+-N contents but the mixedgrass prairie had lower water extractable-organic carbon and water extractable-nitrogen. In contrast, in the dry mixedgrass prairie all labile organic fraction contents, except for AC, were the same among all treatments. Negative relationships were found between plant diversity and surface soil carbon and nitrogen storage. Our results indicate that for short-term disturbed rangeland, 9 years is likely sufficient for the recovery of soil labile organic fractions and plant diversity but a longer time will be needed for the recovery of SOC and TN.

Off-stream waterers (OSWs) located in upland pastures may be effective in reducing livestock impacts on riparian areas and rivers, but little research has been conducted on the impact of OSWs located closer to rivers. We studied cattle behaviour over four years (2012–2015) for a portable OSW at two sites (18–25 m from river) along an unfenced reach, and two permanent OSWs (41–68 m from river) located adjacent to the fenced reach with restricted cattle-access along the Lower Little Bow River in southern Alberta. The number of cattle drinking from the OSW versus river or restricted access site, as well as number of cattle on the bench-terrace or riparian zone with and without OSW, was determined. Significantly (P ≤ 0.10) greater (15-fold) number of cattle per day preferred to drink from the OSW compared to the river at the first location (Site 1) along the unfenced reach in June of 2012, but there was no significant difference at the second location (Site 2) along this same reach in July–August of 2012. Significantly greater (1.7–3.4 fold) numbers of cattle were present on the bench-terrace than the riparian zone when the OSW was present along the unfenced reach. Similar number of cattle preferred to drink from the OSW and restricted river-access site along the south side of the fenced reach in 2013 and 2015, and greater (2.7 fold) number preferred to drink from the river than OSW in 2014. In contrast, the permanent OSW on the north side of the fenced reach had significantly more (2.7 fold) cattle preferring to drink from the OSW than river-access site in 2015. Our results generally supported the hypothesis that OSWs located closer (≤68 m) to rivers were effective, but there were some exceptions.

A 5 yr (2011–2015) field study was conducted to test the hypothesis that streambank fencing had a significant effect on selected vegetation and soil properties of the Mixed prairie component of a complex corridor pasture. The grazing treatments [ungrazed (UG) – periodic grazing (PG)] inside the corridor pasture were 11 yr (2001–2012) of cattle exclusion (UG), followed by 3 yr (2013–2015) of periodic grazing (PG) when the riparian soil was dry. A control treatment outside the fencing was continuous grazing (CG). Selected vegetation and soil properties were measured over the growing season at 10 paired locations in each treatment (nonreplicated) pasture over 5 yr (2011–2015), and rangeland health was measured in 2011. The UG–PG treatment significantly (P ≤ 0.10) increased the total biomass by 2- to 5-fold in all 5 yr compared with CG treatment and improved the rangeland health score of the UG phase of the UG–PG (63%) treatment compared with the CG treatment (50%) in 2011. It also significantly reduced surface soil temperature by 2.2–5.2 °C, significantly increased volumetric water content of the surface soil by 7%–10% in 3 of 5 yr, and significantly increased surface soil CO2 efflux (instantaneous) by 17%–60% in all 5 yr. Overall, the UG–PG treatment improved rangeland health, increased total biomass, soil water, and soil CO2 efflux of the Mixed prairie, but decreased soil temperature compared with the CG treatment. Excessive dead biomass, greater fire risk, and an increase in noxious weeds caused by cattle exclusion suggested that periodic grazing may be the preferred option.

Grasslands play a crucial role in offsetting greenhouse gas emissions and mitigating climate change. A moderate change in grassland carbon (C) and nitrogen (N) stocks may substantially alter the global C and N cycle and thereby influence climate. But how grassland C and N stocks respond to grazing and slope position remains uncertain. This research investigates how C and N stocks respond to cattle grazing along a landscape slope. We studied a grassland that has been grazed by cattle at four cattle stocking rates (0, 1.2, 2.4, and 4.8 animal unit months (AUM) ha−1) since 1949, representing control (CK), light (L), heavy (H), and very heavy (VH) grazing intensities, respectively. Samples were taken from the top and bottom slope positions within each paddock (only the top position in CK); C and N stocks in soil, roots, litter, and standing crop were estimated. Soil C and N stocks were estimated based on equivalent mass (1500 Mg ha−1). Root C and N stocks were estimated to the depth of 15 cm. All parameters, except for litter N stock and standing crop C stock, significantly responded to the interaction of grazing intensity and slope position. In the bottom position, soil and standing crop C and N stocks as well as litter C stock were higher with the L treatment than with VH, while no significant differences were found among the three grazed treatments for root C and litter N stocks. In the top position, soil and root C and N stocks were higher with the VH treatment than with L, whereas litter C and N stocks and standing crop C stock were lower with VH than with L. Our results provide evidence that slope position plays an important role in regulating the response of C and N stocks to grazing and may need to be considered when developing optimal grazing management strategies.

Little is known about the specific role of exotic species on measures of grassland plant diversity, including how this may vary with climatic conditions or large mammal herbivory. This study examined vegetation responses to long-term livestock grazing, including plant richness and diversity, as well as the contribution of exotic species to these metrics, across a network of 107 northern temperate grasslands in Alberta, Canada, spanning a broad aridity gradient. Exposure to grazing modestly increased plant richness, but did not alter Shannon’s diversity, Simpson’s diversity, or evenness, suggesting stability in floral diversity relative to grazing. However, grazing did increase grass cover while reducing shrub cover, the latter of which was only apparent in mesic grasslands. Unlike total plant diversity, exotic species richness and cover, together with exotic plant contributions to diversity, varied jointly with grazing and aridity. While long-term grazing increased exotic species, this response was most apparent in wetter areas, and non-grazed grasslands remained more resistant to the presence of exotics. Several exotic species were positive indicators of grazing in wetter grasslands, and coincided with lower native species cover, indicating grazing may be facilitating a shift from native to exotic vegetation under these conditions. Overall, our results indicate that while long-term grazing has altered the composition and cover of certain functional groups, including favoring exotics and minimizing woody vegetation in mesic areas, overall changes to plant diversity were limited. Additionally, these findings suggest that semi-arid northern temperate grasslands remain relatively resistant to grazing effects, including their susceptibility to exotic plant encroachment. These results improve our understanding of how ongoing grazing exposure may impact grassland diversity, including efforts to conserve native vegetation, as well as the important role of climate in altering fundamental grassland responses to grazing.

Unmanaged riparian grazing may negatively impact rivers. The objective was to determine the influence of riparian grazing by cattle on selected channel morphology properties and riparian health of ...

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

Rotational stocking theoretically enables regrazing of regrowth, but regrowth may be limited in xerophytic vegetation. We tested the hypothesis that regrowth would be slow and fixed in Hesperostipa comata (a caespitose, drought-tolerant grass), while growth would be flexible in Pascopyrum smithii (a rhizomatous, less drought-tolerant grass) under increasing defoliation and moisture, by assessing tiller growth rates, population dynamics and plant yield on marked plants in a Dry Mixed Grass prairie. Plots were clipped in late summer to simulate a deferred control, or intermittently during the growing season (May–August) at high intensity–low frequency (HILF), low intensity–high frequency (LIHF) or high intensity–high frequency and crossed with two water treatments (ambient and addition) in both a xeric upland and a mesic lowland. Growing season defoliation increased tiller growth rates of P. smithii in the upland, whereas HILF and LIHF reduced growth in the lowland. All defoliation regimes increased tiller growth for H. comata. Tiller populations of H. comata increased with frequent defoliation, while tiller populations of P. smithii decreased regardless of defoliation regime. Frequent defoliation, regardless of intensity, reduced yield relative to the deferred control for both grasses. While water addition consistently increased growth rates and reduced differences in tiller number among defoliation treatments, the regrowth of both grasses remained similar under varied defoliation with ambient moisture. High moisture conditions also promoted regrowth more in P. smithii compared to H. comata. In summary, neither grass species displayed an inherently fixed or flexible tiller or plant yield response in response to defoliation or moisture.

Long-term cattle grazing may degrade grassland soils, but how soil CO2, CH4 and N2O fluxes respond to long-term cattle grazing is poorly understood. Therefore, we quantified soil CO2, CH4 and N2O fluxes in response to four levels (none, light, heavy, very heavy) of long-term (>65 yr) cattle grazing on a rough fescue grassland in the foothills of the Rocky Mountains, Canada over three grazing seasons. The grazed grassland soils emitted 37 to 51% more CO2 than non-grazed soils. Grazed grassland soils were small CH4 sinks and small N2O sources each season, and their cumulative emissions were both significantly affected by a cattle stocking rate × year interaction, indicating the grazing effect was a function of environmental conditions. Soil CH4 uptake negatively correlated with soil moisture (r = -0.59). The 2013 grazing season had about 41% greater precipitation than average and grazing significantly decreased CH4 uptake 31 to 38% compared with non-grazed soils. The N2O emissions were 122 to 179% greater with heavy and very heavy grazing than none in the wet year, unaffected by grazing in the normal precipitation year, and 72% lower with light grazing than none in the dry year. Predicting trace gas fluxes from grazed grassland soils across space and time is difficult due to interactions amongst weather conditions, edaphic properties and grazing intensity. However, long-term cattle grazing increased soil CO2 fluxes, while the grazing effect on CH4 uptake depended on precipitation and the soil N2O flux responded as a function of grazing intensity and precipitation.

To evaluate mechanisms by which defoliation alters grassland productivity, we examined mixed grass prairie herbage yields under recurring treatments that included hand-clipping of plots over five growing seasons at high intensity and low frequency (HILF), low intensity and high frequency (LIHF), high intensity and high frequency (HIHF), or the end of the growing season (deferred control), combined with water treatments of ambient rainfall or water addition. The study was repeated in a drier upland and mesic lowland range site. Yield was assessed as annual accumulated herbage production and, for HILF and control treatments in 2012 (year 3), evaluated separately for forbs and major graminoids. Temporal changes in the proportional yield during the growing season were also examined for the HILF and HIHF treatments. Moisture addition increased accumulated herbage, especially in the upland, and exacerbated differences among defoliation effects in select years. Productivity was greatest in the deferred controls, suggesting no treatment led to overcompensation, even with moisture addition. Among growing season treatments, yields under HILF exceeded that of the HIHF in 6 of 10 different combinations of site and year, particularly early in the study and under high moisture. Observed herbage yields suggest deferred patches of grassland may boost productivity and limit the ability of HILF defoliation to increase production, a pattern magnified by a reduction in Pascopyrum smithii in lowlands before mid-July. Accumulated herbage yield did respond favorably to HILF defoliation in uplands due to increased yields of Bouteloua gracilis (Willd. ex Kunth) Lag. ex Griffiths. Overall, these results suggest that any growing season defoliation reduces yields, although where defoliation is necessary at that time, production may be more likely to be maintained under HILF defoliation. More studies examining long-term growth responses to defoliation that include variation in vegetation types, environmental conditions, and defoliation regime are warranted.

Cattle trails in grazed pastures close to rivers may adversely affect surface water quality of the adjacent river by directing runoff to it. The objective of this 3-yr study (2013-2015) in southern Alberta, Canada, was to determine if cattle trails significantly increased the risk of runoff and contaminants (sediment, nutrients) compared with the adjacent grazed pasture (control). A portable rainfall simulator was used to generate artificial rainfall (140 mm h) and runoff. The runoff properties measured were time to runoff and initial abstraction (infiltration), total runoff depth and average runoff rates, as well as concentrations and mass loads of sediment, N, and P fractions. Cattle trails significantly ( ≤ 0.10) decreased time to runoff and initial abstraction (26-32%) in the 2 yr measured and increased total runoff depth, runoff coefficients, and average runoff rates (21-51%) in 2 of 3 yr. Concentrations of sediment, N, and P fractions in runoff were not significantly greater for cattle trails than for control areas. However, mass loads of total suspended solids (57-85% increase), NH-N (31-90%), and dissolved reactive P (DRP) (30-92%) were significantly greater because of increased runoff volumes. Overall, runoff quantity and loads of sediment, NH-N, and DRP were greater for cattle trails compared with the adjacent grazed pasture, and hydrologic connection with cattle-access sites on the riverbank suggests that this could adversely affect water quality in the adjacent river. Extrapolation of the study results should be tempered by the specific conditions represented by this rainfall simulation study.

Stipa breviflora Grisb. (S. breviflora) is a dominant species in the desert steppe of northern China. Its function and role at the plant community level increases with increasing stocking rate. However, the response of spatial stability remains unclear. We selected treatment areas representing no grazing (CK), light grazing (LG), moderate grazing (MG) and heavy grazing (HG) in a long-term grazing experiment (2004–2017) in a S. breviflora desert steppe in Inner Mongolia, northern China. Using a mechanical sampling method, 40 m × 40 m representative sample plots were selected to obtain the height, coverage and density of the S. breviflora population and community, and we computed the standing crop of mechanical sampling quadrats based on a random sample of cutting quadrats. Analysis of standing crop, density of S. breviflora population and its ratio in the plant community showed that the dominant role of S. breviflora population in the plant community increased with increasing grazing intensity, while the spatial stability of S. breviflora population not only had many dimensions, but also many states. The dimension or combination of dimensions of its stability performance and its adaptive state varied under different disturbance intensities and frequencies.

Little is known about how defoliation intensity and frequency alter plant community composition and diversity in northern Great Plains mixedgrass communities. We evaluated defoliation effects in combination with watering on vascular plant composition and diversity in two contrasting ecological sites, a drier upland and more mesic lowland, in the Dry Mixedgrass natural subregion of Alberta, Canada. Treatments were applied for three growing seasons (2010 through 2012, inclusive) and included defoliation regimes of high intensity at high frequency, high intensity at low frequency, low intensity at high frequency, and defoliation deferred until the end of the growing season. Moisture regimes were ambient and elevated. Defoliation rather than moisture was the primary determinant of plant composition after 3 yr, particularly in the lowland site. Watering effects on composition were more apparent in the drier upland. All growing season defoliation regimes markedly altered composition relative to the deferred control, with relatively minor differences in composition among growing season defoliation treatments, particularly in the mesic lowland site. We conclude that growing season defoliation alters mixedgrass composition by reducing canopy dominant grasses (Pascopyrum smithii and Hesperostipa comata) and releasing shorter-statured grasses and forbs, which can either increase or decrease diversity depending on site (edaphic) conditions and the relative dominance of midgrasses and shortgrasses (Koeleria macrantha and Bouteloua gracilis). Finally, increased moisture did not ameliorate defoliation effects during the growing season, suggesting compositional responses were predictable and independent of growing season defoliation regime.

Little research has evaluated naturally vegetated buffers to retain pollutants in soil from concentrated runoff through deep (2–14 m) gullies. Soil enrichment in the flow path of 11 naturally vegetated gullies in southern Alberta, Canada, was used as a long-term signature of filtering during concentrated flow. Soil was sampled at three depth intervals (0–2.5, 2.5–5, and 5–10 cm) along two 50-m transects inside and outside the flow path of the vegetated gullies in each of 3 yr (2011–2013). The influence of soil type, flow path (inside vs. outside), distance into vegetated flow path, depth, and their interactions on enrichment of nutrients (NH4–N, NO3–N, soil test P (STP), total P) and particle size fractions (clay, silt, and sand) was determined. Significantly (P ≤ 0.05) greater enrichment of nutrients and specific particle size fractions inside than outside the flow path of the vegetated gully suggested that greater deposition occurred inside the concentrated flow path. In contrast, there was little evidence for enrichment of nutrients and sediment at the front or inlet of the buffer (except STP), or for infiltration of more soluble nutrients into the subsoil. Soil enrichment in buffers may reveal long-term filtering processes that may not be shown with short-term runoff experiments.

Semi-nomadic pastoralism was replaced by sedentary pastoralism in Inner Mongolia during the 1960's in response to changes in land use policy and increasing human population. Large increases in numbers of livestock and pastoralist households (11- and 9-fold, respectively) during the past 60 yrs have variously degraded the majority of grasslands in Inner Mongolia (78 M ha) and jeopardize the livelihoods of 24 M human inhabitants. A prevailing strategy for alleviating poverty and grassland degradation emphasizes intensification of livestock production systems to maintain both pastoral livelihoods and large livestock numbers. We consider this strategy unsustainable because maximization of livestock revenue incurs high supplemental feed costs, marginalizes net household income, and promotes larger flock sizes to create a positive feedback loop driving grassland degradation. We offer an alternative strategy that increases both livestock production efficiency and net pastoral income by marketing high quality animal products to an increasing affluent Chinese economy while simultaneously reducing livestock impacts on grasslands. We further caution that this strategy be designed and assessed within a social-ecological framework capable of coordinating market expansion for livestock products, sustainable livestock carrying capacities, modified pastoral perceptions of success, and incentives for ecosystem services to interrupt the positive feedback loop that exists between subsistence pastoralism and grassland degradation in Inner Mongolia. © 2015 Published by Elsevier Ltd.

The influence of grazing protection caused by streambank fencing on soil mesofauna density is unknown. Our objective was to determine if grazing protection (ungrazed vs. grazed), location (upland vs. riparian pasture), and seasonal (spring vs. fall) treatment effects associated with streambank fencing had a significant influence on soil mesofauna distribution and density. We collected five intact soil cores (0–5 cm depth) in June and October of 2012 from within four treatments consisting of ungrazed and grazed riparian and upland pastures associated with streambank fencing along an 800-m reach of the Lower Little Bow River in southern Alberta, Canada. Soil mesofauna were extracted and densities of Acari (mites) taxa, Collembola (springtails) taxa, and other mesofauna were determined. Grazing protection resulted in a significant (P ≤ 0.05) negative response of Astigmata mite densities for the upland pasture, and a positive response for Oribatida mites and total Collembola, and Hypogastruridae and Onychiuridae springtails for both pastures. Location and season had a significant influence on Acari and Collembola taxa, but the effects were dependent on interaction effects. We conclude that grazing protection influenced certain soil mesofauna in pastures associated with streambank fencing, and this may influence decomposition of soil organic matter, nutrient cycling, and soil structure in associated pastures.

Grazing activity can profoundly influence grassland plant community structure and ecosystem functions. However, our understanding of the effects of livestock grazing on ecological stability across different grassland types remains limited. Based on a 5-year investigation along a precipitation gradient (180 mm in desert steppe, 282 mm in typical steppe and 375 mm in meadow steppe) in temperate grasslands of Inner Mongolia, we examined the responses of the temporal stability of plant community aboveground biomass to grazing intensity at three levels (light grazing, moderate grazing and heavy grazing). We found that grazing intensity at all levels reduced biomass temporal stability across all types of grasslands. Heavy grazing intensity reduced community biomass, species richness and species asynchrony. Structural equation modeling further revealed that grazing decreased community stability mainly by decreasing species asynchrony. In addition, community-level stability was driven by grass species stability in the meadow steppe, but it was affected by the stability of forb species in the desert steppe. These findings suggest that grazing practices may alter the stability properties of grassland plant communities, highlighting the importance of understanding changes in different plant functional groups for predicting community dynamics under grazing management.

This study investigates the applicability of multivariate statistical techniques including cluster analysis (CA), discriminant analysis (DA), and factor analysis (FA) for the assessment of seasonal variations in the surface water quality of tropical pastures. The study was carried out in the TPU catchment, Kuala Lumpur, Malaysia. The dataset consisted of 1-year monitoring of 14 parameters at six sampling sites. The CA yielded two groups of similarity between the sampling sites, i.e., less polluted (LP) and moderately polluted (MP) at temporal scale. Fecal coliform (FC), NO3, DO, and pH were significantly related to the stream grouping in the dry season, whereas NH3, BOD, Escherichia coli, and FC were significantly related to the stream grouping in the rainy season. The best predictors for distinguishing clusters in temporal scale were FC, NH3, and E. coli, respectively. FC, E. coli, and BOD with strong positive loadings were introduced as the first varifactors in the dry season which indicates the biological source of variability. EC with a strong positive loading and DO with a strong negative loading were introduced as the first varifactors in the rainy season, which represents the physiochemical source of variability. Multivariate statistical techniques were effective analytical techniques for classification and processing of large datasets of water quality and the identification of major sources of water pollution in tropical pastures.

Thirteen years after cultivating native grassland and establishing continuous wheat (Triticum aestivum L.) and wheat–fallow rotations in southern Alberta, surface soil total N levels were 15% lower, and nitrate (60–90 cm) concentrations were 2.5- and 17-fold greater, than native grassland. Wheat–fallow, even without fertilization, markedly enhanced potential nitrate loss through the root zone.

The purpose of this study was to investigate the response of δ15N in herbage and cattle tail switch hair to long-term grazing pressure on a rough fescue grassland (Festuca campestris Rydb.) near Stavely, Alberta, Canada. Cattle have grazed the paddocks from 15 May to 15 November annually since 1949. Stocking rates were 0, 2.4 and 4.8 animal unit months ha−1 for non-grazing (Control), moderate grazing (MG) and heavy grazing (HG), respectively. Green standing crop (GSC) was sampled monthly throughout the grazing season in 2007. The GSC was fractioned into neutral detergent fiber (NDF), acid detergent fiber (ADF), and their total nitrogen (TN) concentration and δ15N values in NDF, ADF and GSC were determined. Tail switch hair samples from cows (>2 years old) and calves (

Grazing by large herbivores has been shown to condition vegetation in a manner that improves grassland quality for subsequent herbivory. Fescue grasslands evolved with disturbance from fire and winter grazing by bison but are now grazed primarily by cattle during summer. We examined the effect of long-term summer grazing on the seasonal forage production and quality of fescue grasslands in an examination of the hypothesis that long-term grazing had conditioned fescue grasslands to benefit livestock. This hypothesis was examined by comparing, between grazed and ungrazed plots, the biomass and composition of herbage components, concentrations of nitrogen (N) and acid detergent fiber (ADF) therein, and the ability of major plant types to maintain their biomass and quality throughout the growing season. The study was conducted in southern Alberta at five sites that had long-term exclosures (20+ yr) on grasslands that had been moderately grazed. Grazing had no effect on the N concentration of associated grasses, but grasses had lower N concentration than forbs. Concentrations of ADF followed a reciprocal trend to N. Grazing increased the mass of forbs from about 10% to 20% as a proportion of total biomass, which in turn, was not affected by grazing history. However, this grazing-induced shift to a higher quality vegetation type was not sufficient to affect total mass of N or total digestible nutrients at the community level. Rather than changes in current growth and quality, the predominant effect of summer grazing was in reducing litter mass, which also had the potential for affecting forage production and selection by herbivores. Finally, grazing reduced the relative contribution of rough fescue to total biomass by about 30%, and despite no significant effect on the potential to support summer grazing, this change could reduce the quality of these grasslands for winter grazing.

The goal of beneficial management practices (BMPs) such as off-stream watering without fencing is to direct cattle away from rivers, improve the environmental quality of the riparian zone, and prevent or reduce river pollution. We conducted a four year (2005–2008) study on an unfenced 1.3 km reach of the Lower Little Bow (LLB) River in southern Alberta, Canada where three off-stream watering systems were installed 290 to ≥730 m from the river in August, 2005. Our hypothesis was that off-stream watering would reduce cattle activity at the river, improve riparian health, prevent river pollution by cattle, and improve the soil, vegetative, and rainfall simulation runoff variables at a cattle access site near the river. Off-stream watering did not significantly ( p > 0.10) reduce the median number of cattle on the river bank, in the river, or drinking from the river one year later. However, there was a reduction of 20% ( p = 0.15) for median number of cattle on the river bank and a 72% reduction ( p = 0.20) for cattle in the river. The BMP moderately improved the riparian health score from 60% (2005) to 65% (2007). Our spatial analysis (upstream–downstream) of base-flow during the post-BMP period (2006–2008) suggested that off-stream watering prevented river pollution by cattle for the majority of water quality variables measured. Canopy cover at the cattle access site near the river was significantly ( p ≤ 0.10) increased by 26–53% one and two years after the BMP. Two years after the BMP was implemented, total basal area, biomass, and mulch were significantly increased by 37–106%, while bare soil and NO 3 -N in surface soil were decreased by 38–89%, respectively. In contrast, other vegetative and soil properties were not significantly improved. Concentrations of the majority of N and P fractions in rainfall simulation runoff were not significantly reduced, and may be related to the high precipitation in the pre-BMP year of 2005. We accept the hypothesis that off-stream watering improved riparian health, prevented river pollution by cattle, and improved certain vegetative (canopy cover, total basal area, mulch, bare soil) and soil properties (soil NO 3 -N) near the river. However, we reject the hypothesis that off-stream watering improved other vegetation (live basal area) and soil properties (bulk density, NH 4 -N, total N and C), or improved rainfall simulation runoff quality near the river. Although we cannot statistically prove that the positive benefits of off-stream watering on certain environmental variables was due to reduced cattle activity, the non-significant reductions in cattle activity suggested this may be a possibility.

We investigated the effect of increasing soil temperature and nitrogen on greenhouse gas (GHG) emissions [carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O)] from a desert steppe soil in Inner Mongolia, China. Two temperature levels (heating versus no heating) and two nitrogen (N) fertilizer application levels (0 and 100 kg N ha−1 year−1) were examined in a complete randomized design with six replications. The GHG surface fluxes and their concentrations in soil (0 to 50 cm) were collected bi-weekly from June 2006 to November 2007. Carbon dioxide and N2O emissions were not affected by heating or N treatment, but compared with other seasons, CO2 was higher in summer [average of 29.6 versus 8.6 mg carbon (C) m−2 h−1 over all other seasons] and N2O was lower in winter (average of 2.6 versus 4.0 mg N m−2 h−1 over all other seasons). Desert steppe soil is a CH4 sink with the highest rate of consumption occurring in summer. Heating decreased CH4 consumption only in the summer. Increasing surface soil te...

Landspraying while drilling (LWD) is an approved disposal method for water-based drilling mud (WBM) systems in western Canada. The mud is applied either on cultivated land, where it is incorporated by cultivation, or on vegetated land where it is not incorporated. This study examined the effects of summer WBM application (0, 15, 20, 40, and 80 m3 · ha−1) on native vegetation properties. Our results indicated that LWD increased bare ground but decreased lichen cover at the 80 m3 · ha−1 rate relative to the untreated control. Nitrogen (N), sulfur (S), and magnesium (Mg) concentrations in aboveground plant tissue increased with increasing LWD rate in samples taken 45 d after WBM application, but these differences disappeared 1 yr after treatment. Increase in tissue concentration of phosphorus (P) with LWD rate, however, was only detected 3 yr after LWD. Nonetheless, these changes in tissue chemistry were not associated with significant changes in biomass yield or species composition. Overall, our re...

Livestock performance is a critical indicator of grassland production systems and is influenced strongly by precipitation and stocking rates. However, these relationships require further investigation in the arid Desert Steppe region of northeastern China. We employed a randomized complete block design with three replications and four grazing treatments (nongrazed exclosure [Control]), lightly grazed [LG], moderately grazed [MG], and heavily grazed [HG]) by sheep in a continuously grazed system (June to November), to test the effect of stocking rate on sheep performance. The planned stocking rates were 0, 0.15, 0.30, and 0.45 sheep?ha 21 ?mo 21 ,f or the control, LG, MG, and HG treatments, respectively. However, actual stocking rates were calculated for each paddock in each year based on a 50-kg sheep equivalent (SE). Annual net primary production (ANP P) was determined at peak standing crop in August 2004 to 2008. Live weight gain was determined for the summer and fall periods, as well as the total grazing period, in each year. ANPP decreased with increasing stocking rate, and daily live weight gain per head decreased linearly with increasing stocking rates over the total grazing period but in a quadratic manner over the summer period with a plateau at the lower rates. Maximum sheep production per unit area over the total grazing season occurred at about 2 SE ha 21 for about a 5-mo grazing period, but individual gains per sheep were predicted to decline after about 1 SE ha 21 presumably because of forage limitations. However, in order to achieve stable annual production, we recommend that the Desert Steppe be grazed at about 0.77 SE ha 21 for a 5-mo period (0.15 SE ha 21 ?mo 21 ). This estimate is based on published grazing strategies that consider an averag eA NPP with a recommended utilization rate of 30%.

Question: Litter (dead leaves or stems) affects production by conserving soil moisture. However, that role is not clear for grasslands where most precipitation falls during the growing season when the demand for water is high. Our question was: Does litter affect forage production in such an environment? Location: Typical steppe, Inner Mongolia. Methods: We examined the role of plant litter in two experiments where litter was either removed or added in a protected or heavily grazed site, respectively, in autumn and in spring in a split plot design. The treatments (control, moderate and heavy litter application) were applied once in five replications but repeated at new locations in each of 3 years. This was done to examine only the direct effect of litter on annual net primary production and selected plant characteristics and not potential secondary effects. We also measured soil moisture and soil temperature. Results: Removing litter caused a reduction in the amount of grass (Leymus chinensis) that was produced, but litter addition caused an inconsistent effect among years, with moderate applications producing the most positive effects. Litter removal resulted in shorter and less dense plants of L. chinensis and Carex duriuscula, while heavy litter addition in autumn reduced plant height of both Cleistogenes squarrosa and C. duriuscula. Conclusions: Litter was effective for enhancing soil moisture status and reducing soil heat units in the typical steppe of Inner Mongolia. Therefore, litter mass may serve as an index of grassland health in such environments.

Numerous studies have examined the nutritive quality of fodder plants in different seasons but few have related this seasonal response to long-term grazing intensity. Our objective was to examine the effect of long-term grazing on the concentrations of total nitrogen, δ15N, and total phosphorus in selected forage species from the fescue grassland near Stavely, Alberta. Plants were selected from paddocks that had been stocked at 0 (control), 2.4 (moderate grazing), and 4.8 (heavy grazing) animal unit months ha–1 for 58 years. Plant material from ten species was sampled and analyzed at monthly intervals from May to September in 2007. Total N and P concentrations were not (p > 0.05) affected by grazing for most species, but total N and P concentrations in Poa. pratensis L. were higher (p < 0.05) in grazed treatments than in the control. These results reflect an altered plant phenology through defoliation and illustrate delayed phenology in P. pratensis when grazed. The higher δ15N concentration for most species in the grazed treatments than the control is an indication of accelerated nitrogen cycling through dung and urine deposition.

This study investigated how disturbances from cultivation and haying altered the soil organic C (SOC) at two sites: one (Lethbridge) in a Stipa-Agropyron-Bouteloua community (49°7" N,112°57" W) and a second (Onefour) in a more xeric Stipa-Bouteloua community (49°3" N, 110°27'' W). Seven disturbance treatments were established on previously uncultivated native grassland to assess their effect on SOC 12 or 13 yr after establishment. A randomized complete block design with four replicates was used. Soils were sampled in the fall of 1995, 1997, and 2006 at two increments (0-15 and 15-30 cm) and a third (30-90 cm) was sampled in 2006. The soils were all analyzed for their SOC and, in 2006, also for their light fraction organic C (LF OC) and mineralizable C. Breaking and immediate establishment of perennial grass monocultures had no effect on SOC, LF OC, or mineralizable C. Wheat (Triticum aestivum L.) cropping (either fallow or continuous) resulted in a 19% loss of SOC after 13 yr. The rate of loss varied from an average of about 1.7 Mg ha -1 yr -1 in the first 4 yr to about 0.32 Mg ha -1 yr -1 in the subsequent 9 yr. These results are consistent with a more rapid loss of SOC in the first decade of cropping virgin soils, a slowing rate of loss, and a new steady state within a few decades.

Limited information exists on the effect of streambank fencing on riparian zone pastures. The objective of this study was to test the hypothesis that 4 to 6 yr of streambank fencing would improve the environmental quality of the cattle-excluded pasture compared with the grazed pasture and cause the fenced pasture to act as a buffer or filter strip. Rangeland health, vegetative and soil properties, and rainfall simulation runoff were measured in the cattle-excluded and adjacent grazed native pastures along the fenced reach of the Lower Little Bow River in southern Alberta, Canada, for 3 yr (2005-2007). Rangeland health was improved (health score increase from 55 to 72%); vegetation cover (13-21%) and standing litter (38-742%) were increased; and bare soil (72-93%) and soil bulk density (6-8%) were decreased under cattle exclusion, indicating an improvement in environmental quality from streambank fencing. In contrast, other vegetation (total and live basal area, fallen litter) and soil properties (soil water and soil C, N, and P) were not improved by cattle exclusion. Cattle exclusion significantly (P

Off-stream watering troughs may reduce surface water pollution by keeping nutrients away from natural water bodies, but may increase nutrient contaminant of groundwater. The objective of this study was to determine to what extent off-stream watering troughs active for 2 to 7 yr caused enrichment and leaching of soil test P (STP) and KCl-extractable NO3-N. The study was conducted in the Lower Little Bow (LLB) River watershed of southern Alberta, Canada. Soil samples were obtained at three recently installed off-stream watering troughs, four active cattle watering sites adjacent to the LLB River, and at two sites along a fenced reach of the river with no cattle access. At each location, samples were obtained along four 100-m transects. Surface (0-5 cm) soil immediately adjacent to the LLB River was not enriched in STP or NO3-N, which was attributed to flushing of nutrients during periods of high flow. Surface soil at distances ≤ 5 m from the three water troughs was approximately three times higher in STP than surface soil obtained at distances ≥10 m and was seven times higher in NO3-N. Subsurface soil layers adjacent (3 m distance) to the three water troughs were not enriched in STP compared with background levels (100 m distance). The subsurface soil adjacent (3 m) to the longest active watering trough was enriched in NO3-N to the 60 cm depth compared with background levels (100 m). Greater nutrient enrichment at the off-stream watering troughs than at the cattle watering sites adjacent to the river suggested that this beneficial management practice (BMP) was effective in shifting nutrient distribution away from the river. Key words: Pasture, nutrient leaching, nitrate, best management practices

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.

The goal of beneficial management practices (BMPs) such as streambank fencing is to prevent or reduce water pollution of surface water bodies. We conducted a four year (2004–2007) study on a fenced 800-m reach of the Lower Little Bow (LLB) River in southern Alberta, Canada. Our hypothesis was that riparian health would be improved by streambank fencing, and that cattle exclusion would prevent water pollution within the fenced reach. Physical, chemical, and microbiological variables in the river were determined throughout the four years, and water quality variables at the upstream (control) and downstream (BMP-impact) sites during the post-BMP phase were evaluated using a paired t-test. The overall health of the riparian area, based on a visual assessment of vegetative, soils, and hydrologic features, was improved from a score of 65% (healthy but with problems) for pre-BMP phase in 2001 to 81% (healthy) for post-BMP phase in 2005. The majority of water quality variables were not significantly (P > 0.10) different at the downstream and upstream sites during streambank fencing. The evidence from our study indicated that streambank fencing improved the riparian health, and that the BMP prevented the majority of water quality variables from increasing downstream.

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.

This study investigated the effect of long-term cattle grazing on herbage production and its nutrient and mineral concentrations over the grazing season. The grazing experiment was conducted on a Rough Fescue (Festuca campestris Rydb.) grassland established in 1949. The three grazing treatments were moderate grazing (MG), heavy grazing (HG), and a non-grazed exclosure (CK) with corresponding stocking rates of 2.4, 4.8, and 0 animal unit months (AUM) ha−1, respectively. Within each of these three treatments four sampling locations were selected as four replications. Herbage biomass (green standing crop [current years’ production] and litter biomass [previous years’ production]) and its nutrient and mineral concentrations were determined monthly from May to September 2007. The green standing crop increased but litter biomass decreased with grazing and peak green standing crop for MG and HG occurred one month earlier than in the CK. For the green standing crop, total nitrogen (TN) concentration increased with grazing from 28.2 g kg−1 in the CK to 39.9 g kg−1 in the HG treatment in May while increases (12.4–15.7%) in other months were not significant. Total phosphorus (TP) (16.4%) and δ15N were higher in the HG than in the CK. For the litter, TN and Ca concentrations decreased with grazing, but TP, δ15N, K and Mg concentrations increased. The herbage feed quality also varied over the grazing season with TN, TP, K, and Mg concentrations decreasing over the grazing season while Ca concentration was lowest in spring (3.07 g kg−1) and late fall (4.08 g kg−1). Grazing appeared to accelerate nutrient cycling and improved herbage quality. These grasslands require disturbance for optimal performance but heavy grazing pressure could severely reduce their health.

Relative benefit of introducing forage species to the Northern Great Plains have been examined with contradictory conclusions. In most cases, studies were either confounded by time of establishment or treatments were not randomized and lacked independence. We examined aboveground net primary production (ANPP) in northern mixed prairie using a randomized complete block design with four treatments: crested wheatgrass ( Agropyron cristatum [L.] Gaertn.), Russian wildrye ( Psathyrostachys juncea [Fisch.] Nevski), a native control that was not harvested, and a harvested native. The experiment was conducted in a Stipa–Agropyron–Bouteloua site and a Stipa–Bouteloua site over 13 yr and 12 yr, respectively. The data were analyzed by sampling period ( Stipa–Agropyron–Bouteloua : 1, 1994 to 1997; 2, 1998 to 2001; 3, 2002 to 2006; and Stipa–Bouteloua : 1, 1995 to 1998; 2, 1999 to 2002; 3, 2003 to 2006). ANPP among treatments was influenced ( P –2 (SEM = 11.2), respectively, in the Stipa–Agropyron–Bouteloua site and 122.9, 98.2, 216.3, and 115.9 g · m –2 (SEM = 12.0), respectively, in the Stipa–Bouteloua site. Mean ANPP (SEM) within each sampling period (1 to 3) was 186.4 (9.1), 135.4 (5.8), and 263.9 (8.8) g · m –2 in the Stipa–Agropyron–Bouteloua site, respectively, and 124.5 (6.4), 138.6 (6.1), and 151.3 (10.5) g · m –2 in the Stipa–Bouteloua site, respectively. Russian wildrye in the Stipa–Bouteloua site and crested wheatgrass in both sites was relatively more productive in the first period after establishment than in subsequent years. The study confirms the relative ANPP advantage of crested wheatgrass over native on the Stipa–Bouteloua site but not on the Stipa–Agropyron–Bouteloua site, whereas Russian wildrye exhibited no ANPP advantage over the native on either site.

Grazing intensity and grassland degradation in China has increased with a growing livestock population. The Desert Steppe is vulnerable to the impacts of livestock because of relatively short and sparse ground cover and sandy soil. This study investigates the effects of historic sheep grazing on the vegetation and soil properties of a Desert Steppe community. The experiment was conducted at three sites (replicates) in Siziwang Banner in Inner Mongolia with four treatments defined along an historic grazing gradient: ungrazed (control), lightly grazed (LG), moderately grazed (MG) and heavily grazed (HG). The grazing treatments were classified based on species composition and ground cover. The vegetation and soil properties in each treatment and replicate were assessed in fall 2005. The vegetation total N (TN) and P (TP) concentrations and δ 15 N levels were not affected ( P > 0.05) by grazing. Grazing increased ( P = 0.02) soil bulk density but had no effect on soil TN and TP concentrations or δ 15 N levels ( P > 0.05). However, HG resulted in 16.4, 11.4 and 7.6% reductions in soil organic carbon (OC), TN and TP concentrations, respectively. Grazing had no effect ( P > 0.05) on the concentrations of soil available P, available N (NO 3 − and NH 4 + ), electrical conductivity, pH or soluble ions (Na + , K + , Ca 2+ , Mg 2+ , Cl − and SO 4 2− ). The vegetation of the Desert Steppe is generally tolerant of grazing pressure but is relatively unproductive, supporting a smaller number of livestock than the more mesic grasslands. Therefore, treatment differences were generally not detected. However, the combination of sandy soils (∼70%) and generally reduced litter and plant cover with increased grazing pressure suggests that the Desert Steppe is vulnerable to soil erosion. This risk may be reduced by ensuring appropriate grazing pressure and animal distribution with judicious herding.

Drilling mud systems are used by the petroleum industry to facilitate and expedite the drilling of oil and natural gas wells. In western Canada, spent water-based muds (WBM) are often applied to cropland and native prairie at low application rates as a disposal option. We speculate that application of drilling waste on native prairie in semiarid climates will alter the soil surface energy balance and adversely affect soil biophysical processes and subsequently ecosystem productivity. This study was initiated to examine the effect of application rate (0, 40, and 80 m 3 ha -1 ) of summer-applied WBM on surface albedo (α), soil temperature, and soil heat flux at the 0.05-m depth (G 0.05 ) and at the surface (G) over 42 d following application. Our results provide evidence of a significant alteration of these micrometeorological parameters with WBM application. Surface albedo decreased by 15% (relative to the control) with the application of 40 m 3 ha -1 mud and by an additional 3% when this mud rate was doubled. The lower α meant that a greater proportion of incoming shortwave solar radiation (R si ) was available for partitioning into components of the surface energy balance, including G. This coincides with observed increases in G 0.05 , G, and soil temperature at the 0.025-m depth, with higher WBM. By modifying heat flow and temperature in the root zone, WBM application may alter critical ecosystem biophysical and physiological processes, with important implications for overall biological productivity. The direction and magnitude of such changes, in conjunction with all the other ecological effects of WBM, will ultimately define the sustainability of the practice in this fragile ecosystem.

Introduced perennial grass-based pastures (e.g., crested wheatgrass, Agropyron cristatum, and Russian wildrye, Elymus junceus) are promoted as desirable alternatives to natural grasslands (Stipa-Bouteloua-Agropyron spp.) for livestock production systems on the mixed-grass prairie of Alberta. A study was conducted on plots established in 1993 to examine the surface runoff response from natural grasslands, introduced grasses and spring wheat (Triticum aestivum L.) under simulated rainfall in response to pasture and soil characteristics. The grass plots were never grazed, but herbage growth was harvested on an annual basis, while wheat was seeded each year following tillage. Both wheat and crested wheatgrass were less able to retain applied water; with low initial abstraction (5.1–5.7mm), runoff peaked earlier (14–26 min) and with higher intensity (65.1–68.8mm h-1) giving larger values of the rising limb factor (0.61–1.10). Two grasslands dominated by native species showed more desirable runoff characteristics; with high initial abstraction (9.6–13.3mm), runoff peaked later (32–54 min) and with lower intensity (32.7–45.8mm h-1) giving smaller values of the rising limb factor (0.13–0.35). Russian wildrye had an intermediary response. A linear model identified that to reduce the rising limb factor and amount of runoff generated after 30 min, the antecedent conditions of ground cover (%), litter dry matter (DM) and dead herbage DM were singularly important variables and the native grasslands had significantly higher levels of these. Importantly, fine and medium litter fragments of natural grasslands had higher water-holding capacity (>3.0 g g-1) compared with litter of the introduced species (~2.5 g g-1). However, when variables were considered in combination runoff decreased with higher ground cover and increased with higher soil water content. Levels of total N and total P in surface runoff were generally low (< 2 mg N L-1, < 1 mg P L-1), but ammonium and reactive P export from the native species was greater than for the introduced species. Suspended sediment yield did not differ among the grassland treatments, but was significantly higher for wheat. Less runoff was generated on grasslands that had high amounts of litter, dead standing herbage and ground cover. Increasing the amount of litter in pastures by using grazing management may decrease the runoff response and so avoid loss of surface water and soil nutrients. Key words: Ground cover, litter, water quality, native grasses, nutrients

The effects of grazing on grassland ecosystems must be understood to develop effective soil conservation measures and sustain livestock production. The objective of this research was to characterize the impact of dairy cow grazing intensity on C and N in soil and vegetation on a meadow steppe. The meadow steppe site, located near Hailaer, Inner Mongolia, China, has been grazed by dairy cattle for more than 30 years, with the last 23 years managed by the same herders. The study site never received any form of mineral fertilizer. Grazing intensity was classified as light (LG), moderate (MG) and heavy (HG) according to the vegetation utilization rate. Grazing affected biomass, total N (TN) and 15N levels, but not 13C, of above-ground plants. The above-ground biomass and δ15N decreased but TN content increased with the grazing intensity for all nine non-legume species while five legume species were not affected. Coarse root biomass also decreased with grazing intensity while TN or δ15N responses to grazing showed no consistent patterns. Soil OC and total N content decreased significantly with grazing intensity for all three sampling depths (0–10, 10–20 and 20–30 cm) while nitrate, ammonium and 13C levels were not affected by grazing intensity in all sampling depths. The decreases in soil OC suggest carbon storage in the meadow steppe declined as grazing intensity increased. Combined with the decreases in soil TN content, this also means heavy grazing could lead to decreases in soil quality and fertility. Uneven grazing intensity is an inherent feature of a season-long grazing system and there are risks to soil quality and environmental health associated with HG. We need to find the proper balance between light to heavy grazing intensity through proper grazing management and in some cases using judicious herding to distribute livestock. Some combination of HG, MG and LG could be desirable in sustainable rangeland grazing production.

Mountain rough fescue (Festuca campestris Rydb.) is a tufted native grass in southern Alberta and British Columbia, Canada, and has attracted interest for use in reclamation. However, its seed is often available from only a few localized sources and may not be adapted for areas removed from the collection site. We conducted a study to determine the genetic variability among rough fescue populations to assess its potential adaptation. Thirty plants were collected from each of six populations and analyzed using Random Amplified Polymorphic DNA (RAPD). One population (Kamloops, BC) was separated by several mountain ranges from the five easterly Alberta populations.The Kamloops population was also separated from the Alberta populations by genetic distance in two clusters. Of the total genetic variation present in the data, 21% was found among populations while the remaining (79%) was found within populations. Nei’s genetic distances among populations were related to their geographical distances. Genetic differences among populations appeared to be caused primarily by differences in gene frequencies rather than rare genes. Also, genetic diversity appeared to increase from west to east suggesting that the more easterly populations had greater adaptation potential. We speculate that the more easterly populations are less likely to share genes since the prevailing winds are from the west. Germplasm from the more easterly populations may be used with suitable precautions within Alberta and possibly around Kamloops. Key words: Genetic distance, geographic distance, reclamation, potential adaptation

The Bactrian camel (Camelus bactrianus ferus) is uniquely adapted to the deserts of China and Mongolia. It was domesticated about 3000 years ago but the wild Bactrian camel is endangered with less than 1000 remaining in China. We observed the foraging behaviour of 10 domestic Bactrian camels (Alashan) in a Haloxylon ammodendron C.A. Mey desert of Inner Mongolia. The Alashan Bactrian camel is one of about four breeds of the species found in the western part of Inner Mongolia. In each season, plant species selection was observed for each camel over three, 10-min periods at morning, noon and night and their primary activities were recorded over a period of 17.6, 19.2, 18.5, and 17.2 h in winter, spring, summer and autumn, respectively. Forage intake was estimated by mimicking bite size for each species and extrapolating to the total time spent grazing. Plant species preferences were calculated from estimates of their relative utilization and availability. The number of species contributing to the camels’ diet in winter, spring, summer, and autumn were 5, 6, 7, and 8, respectively. No seasonal differences (P

Fescue grasslands are well suited to dormant-season grazing, whereas spring defoliation is detrimental to rough fescue (Festuca campestris Rydb.). Dormant-season grazing may also condition fescue plants for subsequent selection in spring by removing standing litter (i.e., senesced biomass). This relationship must be understood in order to manage grazing and conserve rough fescue. This study determined the effects of standing litter on plant selection and utilization by cattle in spring. Forty dormant rough fescue plants were conditioned in fall by removing standing litter in a 4 (treatments) 3 10 (blocks) randomized complete block design. This design was repeated with the use of 2 separately grazed paddocks. Treatments were a control (no litter removal) and standing litter removed at 14-, 7-, and 2.5-cm stubble height. Nonparametric plant selection data were analyzed with the use of v 2 methods. Spring biomass utilization was estimated nondestructively through height–weight modeling techniques, and data were analyzed with the use of analysis-of-variance procedures. The stubble height of standing litter affected (P , 0.05) plant selection by cattle in the first 2 days of the trial when grazing pressure was light. By the end of the 6-d grazing period 96% of fescue plants were selected at least once. Additionally, 18% of plants were regrazed at least once after 3 days, and 48% after 6 days. Thus, the protective barrier effect of standing litter had limited effect on plant selection by cattle except when grazing pressure was light. However, the degree of spring biomass utilization increased with shorter stubble heights. After 6 days of grazing, the current growth of plants with standing litter removed at 2.5 cm was utilized at 64%, and control plants were utilized 9%. Therefore, at high grazing pressure the mass of standing litter influenced the degree of utilization, suggesting litter retention is important in limiting grazing impacts on rough fescue.

This study evaluated a non-destructive scientific method that is non-invasive to the animal, for quantifying foraging selectivity by cattle within heterogeneous pasture swards in order to test the utility of a new grazing system designed to aid conservation of native rough fescue (Festuca campestris Rydb.) rangeland in western Canada. Skim grazing is a recently developed strategy that involves a light, once-over-spring defoliation, followed by a late to dormant season grazing period. Thispractice isthoughtto conserve roughfescue ascattle areassumed toprefer invasivegrassspecies during spring when fescue is sensitive to defoliation. We examined the preferences of cattle for each of four major grass species, two native and two introduced, within rough fescue rangeland, grazing during spring, fall, or spring and fall of 2000 and 2001. We developed height‐biomass models for each grassspecies in eachgrazing period,determined biomass removalbyspecies, and despite underestimating actual herbage removal, successfully evaluated cattle preferences. Though the interpretation of established preferences are limited to the conditions of this study, rough fescue together with the introduced species, Kentucky bluegrass (Poa pratensisL.), were preferred during spring, contrary to our hypothesis. Kentucky bluegrass was also preferred within both fall and fall regrowth pastures. Smooth brome (Bromus inermis Leyss.) and Parry oat grass (Danthonia parryii Scribn.) were generally avoided. The failure of cattle to avoid rough fescue during spring indicates skim grazing

Mengli, Z., Willms, W. D., Bing, H. and Laroche, A. 2005. Effects of heavy grazing pressure on the random amplified polymorphic DNA marker diversity of mountain rough fescue (Festuca campestris Rydb.) in south western Alberta. Can. J. Plant Sci. 85: 623‐629. The Fescue Grassland is found in the western portion of the Northern Great Plains in Canada. Grazing and cultivation threaten this grassland, and a better understanding of its character is needed to preserve its integrity. Mountain rough fescue is highly sensitive to grazing during the growing season, which results in smaller plants and the death of some. The death of plants suggests the potential loss of genetic diversity. Therefore, we compared the genetic diversity of mountain rough fescue plants from sites in south western Alberta (50°12′N, 113°54′W) that had either been heavily grazed by livestock or left ungrazed for 52 yr to determine if grazing pressure had affected their genetic composition. Thirty-four and 43 plants were sampled in the spring of 2001 from very heavily grazed and ungrazed subpopulations, respectively, and their DNA was analyzed using random amplified polymorphic DNA (RAPD). Of the 15 primers used, 12 generated an average of seven polymorphic loci each. Ten loci were present at a frequency of 0.10 or less in the heavily grazed subpopulation and six in the ungrazed subpopulation. RAPD marker diversity between the heavily grazed and ungrazed subpopulations of mountain rough fescue was mainly the result of frequency differences (P < 0.05) produced by 20% of the total markers that were examined, while the subpopulations accounted for only 4.37% of total heterozygosity. Therefore, grazing affected frequency of some markers but did not eliminate genes that may be linked with grazing sensitivity or tolerance. Lack of clear genetic segregation between the subpopulations might be caused by a high gene flow (Nm = 10.92). This mechanism requires further testing in order to prescribe a suitable management response for restoring overgrazed grasslands.