Grazing-Induced Modifications to Peak Standing Crop in Northern Mixed-grass Prairie

Selective grazing can modify the productive capacity of rangelands by reducing competitiveness of productive, palatable species and increasing the composition of more grazing-resistant species. A grazing system (season-long and short-duration rotational grazing) × stocking rate (light: 16 steers · 80 ha^-1, moderate: 4 steers · 12 ha^-1, and heavy: 4 steers · 9 ha^-1) study was initiated in 1982 on northern mixed-grass prairie. Here, we report on the final 16 years of this study (1991–2006). Spring (April + May + June) precipitation explained at least 54% of the variation in peak standing crop. The percentage of variation explained by spring precipitation was similar between stocking rates with short-duration grazing but decreased with increasing stocking rate for season-long grazing. April precipitation explained the greatest percentage of the variation in peak standing crop for the light stocking rate (45%), May precipitation for the moderate stocking rate (49%), and June precipitation for the heavy stocking rate (34%). Peak standing crop was 23%–29% greater with light (1 495 ± 66 kg · ha^-1, mean ± 1 SE) compared to moderate (1 218 ± 64 kg · ha^-1) and heavy (1 156 ± 56 kg · ha^-1) stocking rates, which did not differ. Differences in peak standing crop among stocking rates occurred during average and wet but not dry springs. Neither the interaction of grazing system and stocking rate nor grazing system alone affected standing crop across all years or dry, average, or wet springs. Grazing-induced modification of productive capacity in this northern mixed-grass prairie is attributed to changes in species composition with increasing stocking rate as the less productive, warm-season shortgrass blue grama (Bouteloua gracilis [H.B.K.] Lag. ex Griffiths) increases at the expense of more productive, cool-season midheight grasses. Land managers may need to substantially modify management to offset these losses in productive capacity.     

Temperature and Precipitation Affect Steer Weight Gains Differentially by Stocking Rate in Northern Mixed-Grass Prairie

Cattle weight gain responses to seasonal weather variability are difficult to predict for rangelands because few long-term (>20 yr) studies have been conducted. However, an increased understanding of temperature and precipitation influences on cattle weight gains is needed to optimize stocking rates and reduce enterprise risk associated with climatic variability. Yearling steer weight gain data collected at the USDA-ARS High Plains Grasslands Research Station at light, moderate, and heavy stocking rates for 30 years (1982–2011) were used to examine the effects of spring (April–June) and summer (July–September) temperature and precipitation, as well as prior-growing-season (prior April–September) and fall/winter (October–March) precipitation, on beef production (kg · ha^?1). At heavier stocking rates, steer production was more sensitive to seasonal weather variations. A novel finding was that temperature (relatively cool springs and warm summers) played a large predictive role on beef production. At heavier stocking rates, beef production was highest during years with cool, wet springs and warm, wet summers, corresponding to optimum growth conditions for this mixed C₃–C₄ plant community. The novelty and utility of these findings may increase the efficacy of stocking rate decision support tools. The parsimonious model structure presented here includes three-month seasonal clusters that are forecasted and freely available from the US National Oceanic and Atmospheric Administration up to a year in advance. These seasonal weather forecasts can provide ranchers with an increased predictive capacity to adjust stocking rates (in advance of the grazing season) according to predicted seasonal weather conditions, thereby reducing enterprise risk.     

Nondestructive Estimation of Standing Crop and Fuel Moisture Content in Tallgrass Prairie

Accurate estimation of standing crop and herbaceous fuel moisture content (FMC) are important for grazing management and wildfire preparedness. Destructive sampling techniques have been used to accurately estimate standing crop and FMC, but those techniques are laborious and time consuming. Existing nondestructive methods for estimating standing crop in tallgrass prairie have limitations, and few studies have examined nondestructive estimation techniques for FMC in this environment. Therefore, our objective was to develop robust models for nondestructive estimation of standing crop and FMC in tallgrass prairie. We calibrated and validated stepwise multiple linear regression (SMLR) and artificial neural network (ANN) models for standing crop and FMC using data collected in tallgrass prairies near Stillwater, Oklahoma. Day of year (DOY), canopy height (CH), Normalized Difference Vegetation Index (NDVI), and percent reflectance in five wavelength bands were candidate input variables for the models. The study spanned two growing seasons and nine patches located within three pastures under patch burn management, and the resulting data set with > 3 000 observations was split randomly with 85% for model calibration and 15% withheld for validation. Standing crop ranged from 0 to 852 g m^? 2, and FMC ranged from 0% to 204%. With DOY, CH, and NDVI as predictors, the SMLR model for standing crop produced a root mean squared error (RMSE) of 119 g m^? 2 on the validation data, while the RMSE of the corresponding ANN model was 116 g m^? 2. With the same predictors, the SMLR model for FMC produced an RMSE of 26.7% compared with 23.8% for the corresponding ANN model. Thus, the ANN models provided better prediction accuracy but at the cost of added computational complexity. Given the large variability in the underlying datasets, the models developed here may prove useful for nondestructive estimation of standing crop and FMC in other similar grassland environments.     

Habitat Targets for Imperiled Grassland Birds in Northern Mixed-Grass Prairie

Grassland bird populations are declining faster than any other avian guild in North America, and promotion of favorable habitat conditions in rangeland breeding cores is important for their maintenance. There is much information on associations between breeding grassland songbirds and vegetation attributes. However, previous results have been difficult to translate into management practices due to mismatch between the scale and metrics used in biological sampling and those used in management. Here, we evaluate the response of imperiled grassland bird species to vegetation conditions using metrics and scales accessible to managers. We focus on four species that are experiencing particularly severe population declines: Baird's sparrow (Centronyx bairdii), chestnut-collared longspur (Calcarius ornatus), McCown's longspur (Rynchophanes mccownii), and Sprague's pipit (Anthus spragueii). In 2017 and 2018, we evaluated the abundances of these species within their core distributions in northern Montana. We used temporally replicated point-counts and hierarchical models to estimate abundance and associations with plot-level (9-ha) vegetation conditions while accounting for spatially and temporally variable detectability. Exotic grass encroachment and shrub cover had negative or neutral effects on all species. Birds responded strongly to biomass at this scale, with chestnut-collared longspurs and Sprague's pipit preferring a range of 1 100 kg ha⁻¹ to 1 400 kg ha⁻¹, and McCown's longspurs selecting for the lowest available. Residual grass and litter cover were important for Baird's sparrows. Variable results among species emphasize the need for heterogeneity in vegetation structure and composition at scales larger than the plot. Our results provide guidance for managers interested in improving habitat for these species.     

Effects of Livestock Grazing Management on Grassland Birds in a Northern Mixed-Grass Prairie Ecosystem

Grassland birds have undergone substantial population declines throughout much of their historic ranges in North America. Most of the remaining grassland bird habitat is restricted to rangelands managed for livestock production, so grazing management has strong implications for grassland bird conservation efforts. We conducted 1 830 point-count surveys at 305 sites during 2016–2017 to evaluate the relative effects of three livestock grazing systems on the abundance and community composition of grassland birds in a northern mixed-grass prairie ecosystem of eastern Montana, United States. Our objectives were to 1) evaluate effects of grazing management on abundance and community composition of grassland obligate birds, focusing specifically on grazing systems, stocking rates, and interactions with rangeland productivity; 2) evaluate the importance of local vegetation characteristics for grassland birds within grazing systems; and 3) assess the effectiveness of rest-rotation grazing to create patch-heterogeneity in rangeland vegetation through the alteration of structural components and the response of grassland birds to these treatments. Overall, we found inconsistent responses in abundances of grassland birds relative to livestock grazing systems and no discernable differences among grazing systems relative to community composition. However, local abundances were often driven by interactions between grazing system and rangeland production potential, suggesting the effects of livestock grazing management were generally mediated by rangeland productivity. In addition, associations between avian abundance and grazing management parameters (e.g., stocking rate) were species specific. Ubiquitous guidelines for livestock grazing systems may be inappropriate for grassland bird conservation efforts in the northern mixed-grass prairie, and high stocking rates may negatively impact populations of dense-grass obligate grassland birds in this region.     

Pipeline Impacts and Recovery of Dry Mixed-Grass Prairie Soil and Plant Communities

Agricultural practices have historically dominated disturbance on North American grasslands. Disturbances from oil and gas have become increasingly common and problematic for grassland conservation. With growing demand for oil and gas, industry is actively implementing minimal disturbance techniques during construction to reduce impacts on grasslands. This study aimed to determine impacts of a large-diameter pipeline right of way (ROW) on dry mixed-grass prairie to determine if and how far these impacts extended beyond the ROW and the effect of time on grassland recovery on and off ROW. Soil and vegetation on the ROW and on transects extending 300 m on either side of the ROW were assessed over a 10-yr period, starting the yr of construction, at six sites along a pipeline route in southern Alberta, Canada. There were significant impacts to soil and vegetation on the ROW and within 5 m of the ROW in the first yr. The trench was most impacted, followed by work and storage areas. Within 2 yr, soil and plant communities were on a trajectory toward reference prairie conditions. Ten yr following construction, only soil pH and bare ground were greater, and litter was less, on the trench than on work and storage areas, and relative to reference prairie. While native grass richness, dominance, and cover were similar on and off ROW, abundance of some native forb species was less on ROW. Non-native species cover was < 2% in all yr and locations. Although ruderal weed species were abundant on ROW the yr following construction, they disappeared by the following yr. Use of minimal-disturbance construction techniques reduced the size and intensity of the disturbance footprint, allowing for even sensitive arid habitat to recover within a short period of time. Similar approaches to other grassland disturbances can increase ecosystem resiliency.     

Vegetation Response to a One-Time Spent Drilling Mud Application to Semiarid,Mixed-Grass Prairie

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 results suggest that single WBM applications at rates (≤ 20 m³ · ha^?1) commonly used in western Canada, if properly managed, are unlikely to adversely affect native prairie vegetation.     

Effects of Defoliation,Litter, and Moss on Bromus arvensis in a Northern Mixed-Grass Prairie

Exotic winter annual grasses (Bromus spp.) are a problem in North American rangelands. Defoliation, litter, and mosses are thought to regulate invasive annual Bromus species. We conducted a field experiment that tested effects of mechanical mowing and fungicide applications on Bromus arvensis, other and total graminoids, forbs, litter, and moss. Treatments caused litter biomass and moss cover to vary, which enabled testing whether litter and mosses explain variation in B. arvensis biomass. Two yr after cessation of experimental treatments, mowing treatments caused persistent reductions in B. arvensis, total graminoid, and litter biomasses but had no effect on other graminoid and forb biomasses. We detected a positive relationship between litter and B. arvensis. Fungicide applications increased moss cover and other and total graminoid biomasses, thereby suggesting mosses and several graminoids were released from the suppressive effects of biota (e.g., lichen, pathogenic fungi) susceptible to the fungicide. We found no relationship, however, between moss cover and B. arvensis. In temperate and semiarid ecosystems, mowing during flowering and before seed drop coupled with removal of clippings is likely to help control invasive bromes and fungicide additions may increase grass production.     

Plant Interspaces Resulting From Contrasting Grazing Management in Northern Mixed-Grass Prairie: Implications for Ecosystem Function

We assessed plant interspaces in July 2007 using continuous line intercepts in twice-replicated pastures of northern mixed-grass prairie with contrasting grazing treatments: 1) long-term (25 yr) heavily grazed, dominated by the bunchgrass blue grama (Bouteloua gracilis), and 2) ungrazed, dominated by the rhizomatous grass western wheatgrass (Pascopyrum smithii). The number of plant interspaces was 26% higher in pastures heavily grazed, but the amount of soil surface occupied by plant interspaces was 27% greater without grazing. Plant interspaces were larger without grazing (14.8 ±  cm, mean ± 1 SE) than heavily grazed (8.9 ±  cm). Plant interspaces represented 87% and 68% of the total soil surface in the ungrazed and heavily grazed communities, respectively. The percentage of soil surface covered by plant interspaces < 20 cm was higher for the heavily grazed (94%) compared to the ungrazed (79%). Litter cover in the plant interspaces was higher without grazing (80 ± 1%) compared to the heavily grazed (57 ± 3%). Grazing-induced structural changes from a rhizomatous- to a bunchgrass-dominated vegetation community were manifest in the size and distribution of plant interspaces. Ecological consequences for erosion from raindrop impacts in larger plant interspaces in the ungrazed community are likely offset by greater litter cover in these communities; conversely, lower litter cover in heavily grazed pastures may increase erosion potential despite occurrence of smaller plant interspaces and less proportion of the soil surface covered by interspaces. Management practices that increase the cover of litter in plant interspaces should reduce the potential of erosion from water and wind in this semiarid rangeland.     

Primary Productivity and Precipitation-Use Efficiency in Mixed-Grass Prairie: A Comparison of Northern and Southern US Sites

Precipitation-use efficiency (PUE) is a key determinant of aboveground net primary production (ANPP). We used long-term datasets to contrast ANPP and PUE estimates between northern (southeast Montana) and southern (north Texas) mixed-grass prairies. Effects of varying amounts and temporal distribution of precipitation on PUE were examined at the Montana site, using a rainout shelter and irrigation. Results show that 1) ANPP was 21% less in Montana than Texas (188 g · m^-2 vs. 237 g · m^-2); 2) plant function type (PFT) composition varied between the two study locations, with cool-season perennial grasses (CSPG) dominating in Montana (52%) and warm-season perennial grasses (WSPG) dominating in Texas (47%); 3) production dynamics varied between the two sites with 90% of ANPP completed by 1 July in Montana as compared to 31 August in Texas; 4) average PUE estimates were greater in Montana (0.56 g dry matter · m^-2 · mm^-1 of precipitation) than Texas (0.40 g · m^-2 · mm^-1); and 5) contributions to PUE estimates varied among PFT and location, with CSPG estimates being greater in Montana than Texas (52% vs. 31%) and WSPG estimates being greater in Texas than Montana (47% vs. 27%). Seasonal droughts and supplemental irrigations at the Montana site substantially altered ANPP, PFT biomass composition, and PUE. Results show PUE was responsive to PFT composition relative to amount and seasonal distribution of precipitation. Therefore, one should expect changes in ANPP and PUE to occur with shifts in precipitation patterns until PFT composition becomes adjusted to the regime.     

Evaluation of Pentobarbital as a Drug for Standing Sedation in Cattle

Pentobarbital (1.0, 1.5, and 2.0 mg/kg intravenously [IV]) was administered to four adult cows to determine a dose suitable for producing standing sedation in adult cattle, and to evaluate its effects on cardiopulmonary function and rumen motility. The response was assessed after 15, 30, 60, and 90 minutes. The 1.0 and 1.5 mg/kg doses induced mild sedation at 15 and 30 minutes, and no sedation at 60 and 90 minutes. The 2.0 mg/kg dose produced moderate sedation at 15 and 30 minutes, and mild sedation at 60 minutes. The 2.0 mg/kg dose was judged to be the most suitable. The effects of pentobarbital (2.0 mg/kg IV) on heart rate, blood pressure, respiratory rate, blood gases, and rumen motility were measured in five cows during a 90 minute period. Respiratory rate was significantly depressed at 15, 30, and 60 minutes, but there were no significant changes in the other variables. Pentobarbital (2.0 mg/kg IV) is reliable in adult cattle for standing sedation of short duration.     

春制越年春用秋蚕品种对春蚕生产影响初探

春蚕饲养秋蚕品种,嘉兴市秀洲区从2000年试点.2002年全面饲养至今已有7年,多年的饲养比较、总结,在相同的叶质、气候条件下,秋蚕品种的抗氟性、抗逆性比春蚕品种强.     

春期原种催青日期的确定

阐述了春期原蚕种催青日期确定的原则 ,列举了浙江省和全国主要蚕区历来春期原种催青开始日期     

A Nondestructive Method to Estimate Standing Crop of Purple Threeawn and Blue Grama

We used multiple regression analysis to develop models to predict standing crop of purple threeawn (Aristida purpurea Nutt.) and blue grama (Bouteloua gracilis [H.B.K.] Griffiths) nondestructively. Data were collected for 3 yr on the Texas Tech University Native Rangeland, Lubbock, TX, USA. Independent variables included plant length and area measurements (basal area and cross-sectional area at a 7.5-cm plant height and at 50% of total plant height). One hundred randomly selected plants of each species were measured in June 2008; 50 plants of each species were measured in June 2009 and 2010. Coefficients of determination exceeded 0.91 for both species in all 3 yr of measurement. For both species and years, cross-sectional area at 7.5 cm was the most important single predictor variable. For each species, models differed among years. Our regression models were successful at predicting mid- to late-season standing crop of purple threeawn and blue grama grass and provide an effective method for nondestructive monitoring of these species. This approach should be applicable to similar morphotypes of these species.     

The Use of a Metabolic Disorder Index as a Predictor for Metabolic Eliminations in Endurance Horses

The equine endurance race involves both aerobic and anaerobic metabolisms of the horse. The intense physical activity over an extended period often causes susceptible horses to develop metabolic signs or problems resulting in elimination from races. Thus, the objective of this study was to develop a method for prediction and validation of a metabolic disorder index (MDI) to be used before endurance races. Three hundred seventy-five Arabian (n = 152) and Arabian cross (n = 223) endurance horses aged from 6 to 15 years and weighing between 350 and 450 kg were selected for the study in Malaysia. Blood samples were collected at pre- and post-race periods. The significant (P < .05) findings in horses with metabolic disorder were packed cell volume (0.50 ± 0.06 LL−1), creatine kinase (1,275.89 ± 121.45 UL−1), interleukin-6 (2.01 ± 0.89 ng/mL), decreased glutathione reductase (26.57 ± 3.95 ng/mL), and chloride (94.98 ± 8.12 mmol/L). A new method called MDI was developed as a predictor for horses with the potential to develop metabolic disorders in endurance races. The MDI indicated a higher value greater than 5.5 for those eliminated and lower value below 5.5 for those that completed the race successfully, this proved to be accurate in the prediction of metabolic disorder in endurance horses. The MDI is an innovative and simple method used as a prediction method that will assist the equine endurance society to reduce the rate of elimination and to safeguard against serious medical problems during endurance races in the tropics.     

Standing low-field magnetic resonance imaging as a diagnostic modality for solar keratoma in a horse

A 22-year-old Friesian gelding was presented with a history of chronic, nonresolving lameness localised to the right front foot. Radiographs showed a smoothly marginated circular lucent area with a rim of increased opacity adjacent to the solar canal of the distal phalanx. The magnetic resonance imaging (MRI) revealed a reversed V-shaped smoothly demarcated space-occupying mass causing invagination of the solar laminae towards the solar canal arch and deformity of the adjacent surface of the distal phalanx. The mass was removed surgically and submitted for histopathology, which revealed a keratoma and periosteal fibrosis. Six weeks post-surgery the horse returned to the previous work level and 8 months follow-up showed no recurrence of keratoma. This report highlights the usefulness of MRI as a diagnostic modality for solar keratoma.     

射阳县推广二春蚕的可行性及其必须注意的几个技术环节

二春蚕是在春蚕结束后,桑园暂不夏伐,利用其新梢继续生长的桑叶而饲养的一批蚕.近几年来,二春蚕在江苏省不少地方进行了试验、示范和推广,并取得了良好的经济效益和社会效果.受其影响,射阳县前几年也有少数养蚕农户开始试养,2002～2003年县蚕桑生产服务站组织重点镇、村进行了批量试养,试养效果颇佳.现根据近年来的试养实践,笔者就二春蚕在射阳推广的可行性及其注意的几个技术环节谈一些体会,供从事农村蚕桑技术推广工作的同志们作参考.     

海盐县今年春茧高产原因分析

今年我县2003年春蚕生产获得了大面积、大幅度优质高产。全县饲养的52766张蚕种,平均张产49.36kg,创造了全县历史最高水平。蚕茧质量得到了全面提升,其中解舒率接近近年最好年份。解舒丝长、一茧丝长、光折分别达到了738m、1133m、256kg,比去年同期的629.2m、898.3m、276kg分别增长了17.29%、26.13%与9.42%。分析在茧丝绸形势低迷情况下,我县一举夺取春茧张产超历史的优异成绩,笔者认为主要有以下几点:1抓好增产基础,为平衡高产提供了大量优质桑叶为夺取今年春蚕丰收,我县在桑叶基础工作上首先是抓发动工作,向蚕农宣传蚕桑产业在我县的传统…