• Effect of breed on botanical composition of cattle diets on Chihuahuan desert range

      Winder, J. A.; Walker, D. A.; Bailey, C. C. (Society for Range Management, 1996-05-01)
      Fecal microhistology was used to estimate botanical composition of samples taken from Hereford (N = 11), Angus (N = 11) and Brangus (N = 37) 3 to 5 year-old cows in 3 seasons (October, 1991 and January and July, 1992) and from Hereford (N = 10), Angus (N = 9) and Brangus (N = 34) calves in October. Breed differences in botanical composition of diets and relationships between dam and offspring botanical composition of diets were examined. Breed differences were observed for cows in all 3 seasons and for calves in October. Brangus cows showed greater preference (P < 0.05) for Sporobolus than Hereford cows in October, January, and July. Brangus cows also showed greater preference for Sporobolus than Angus cows in January and July. Brangus and Angus calves showed greater preference for Sporobolus than Hereford calves in October (P < 0.05). Brangus cows had a stronger preference for Yucca and total shrubs in January than either Hereford or Angus cows. Hereford cows and calves had stronger preference for Aristida than either Angus or Brangus in October (P < 0.05). Regression of October calf botanical components on dam botanical components indicated significant relationships for only 2 genera, Aristida (P < 0.01) and Sporobolus (P< 0.06). These data suggest that genetic composition of the animal is an important factor determining utilization of key plant species on Chihuahuan desrt ranges.
    • Emergence date effects on resource partitioning between diffuse knapweed seedlings

      Sheley, R. L.; Larson, L. L. (Society for Range Management, 1996-05-01)
      Diffuse knapweed (Centaurea diffusa Lam.) has reduced forage production, watershed quality, and biodiversity, and increased soil erosion on millions of hectares of rangeland. Diffuse knapweed has evolved mechanisms that allow it to dominate sites in nearly monotypic stands. Understanding these mechanisms may provide useful information in developing weed management strategies. Objectives of this study were to investigate interference, growth rates, and resource partitioning between early and late emerging diffuse knapweed seedlings. Seeds of diffuse knapweed were planted 21 March (early emerging) and 14 April (late emerging) 1993 in addition series mixtures with total stand densities ranging from 1,000 7,000 plants m-2. Shoots were harvested on 1 and 2 June 1993. The greatest interference was among coemerging seedlings. Resource partitioning ratios (51 and 1398) indicated substantial partitioning between seedlings having different emergence dates. Continuous seedling emergence may allow diffuse knapweed to occupy all available safe sites.
    • Environmental effects on picloram uptake and ethylene production by broom snakeweed

      Sterling, T. M.; Lownds, N. K.; Murray, L. W. (Society for Range Management, 1996-05-01)
      Broom snakeweed [Gutierrezia sarothrae (Pursh) Britt. &Rusby] is a rangeland weed widely distributed in the western United States. Picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) uptake and picloram-induced ethylene production by broom snakeweed grown in the field were determined every 2 to 4 weeks over 36 months. For each collection date, picloram uptake and concentration in the tissue ranged from 1.5 to 46.2% of applied and 0.2 to 4.7 nmol g-1 fresh wt, respectively. Of the measured environmental variables, average precipitation and average minimum temperature 7 days prior to treatment best predicted picloram uptake and concentration in the tissue, suggesting that warmer temperatures and precipitation previous to application contribute to picloram uptake. Average minimum temperature alone also provided a good predictor for picloram concentration in the tissue. For each collection date, picloram-induced ethylene production by total tissue ranged from 50 to 791% of control. Picloram-induced ethylene production by total tissue was best predicted by the precipitation and minimum temperature 7 days prior to treatment and picloram concentration in the tissue. Therefore, the amount of picloram absorbed and the environment prior to application both contribute to the physiological sensitivity of broom snakeweed to picloram. Picloram uptake and picloram-induced ethylene production were greatest in July and August, when plants were in the phenological stages of shoot regreening or flower bud emergence and when temperatures and precipitation were high. Previous field studies have shown broom snakeweed is most responsive to field picloram application in the post-bloom stage from October to December or in April and May with high moisture and soil temperature conditions; therefore, it appears that changes in uptake and physiological sensitivity as measured by picloram-induced ethylene production are not the only factors controlling differential sensitivity to picloram.
    • Evaluation of a site conservation rating system in southeastern Arizona

      Watters, S. E.; Weltz, M. A.; Smith, E. L. (Society for Range Management, 1996-05-01)
      The objectives of this study were to identify a Site Conservation Threshold, the point at which accelerated erosion occurs, and to examine the usefulness of the Water Erosion Prediction Project (WEPP) model in determining the Site Conservation Threshold on a clay loam upland rangeland site. Sixteen sample sites were chosen to represent a wide range of species composition, ground cover, biomass and apparent soil stability to determine which of these factors could be used to evaluate the site conservation status of a clay-loam upland ecological site on a southern Arizona semi-arid desert grassland. A Site Stability Rating based on observable vegetation and soil-surface characteristics (i.e. ground surface cover and distribution of plants) was developed. A Site Stability Rating was estimated for 100 quadrats per sample site and averaged for the entire sample site. The Water Erosion Prediction Project model was used as an objective index of soil stability to assess the degree of site protection. The Soil Conservation Service soil loss tolerance value (T) was used with the sediment yield predicted by the WEPP model to establish a threshold value for the Site Stability Rating. The objective measures of standing biomass, basal cover, average distance to the nearest perennial plant, and frequency of quadrats with no rooted perennial plant showed strong relationships to the subjective Site Stability Rating. Site Conservation Thresholds were identified for standing biomass (750 kg/ha), basal cover (8%), average distance to the nearest perennial plant (15 cm), and frequency of quadrats (20 X 20 cm) with no rooted perennial plant (13%).
    • Fringed sagebrush response to sward disturbances: Seedling dynamics and plant growth

      Bai, T.; Romo, J. T. (Society for Range Management, 1996-05-01)
      Fringed sagebrush (Artemisia frigida Willd.), the most common dicotyledonous species in the Northern Mixed Prairie, often increases dramatically following disturbance. It was hypothesized that the increase could be due to release of established plants, increased recruitment of plants, or both. Experiments were conducted on a sandy range site in central Saskatchewan. Tillage, clipping, litter removal, and a combination of clipping+litter removal were compared to an undisturbed control to determine their effects on emergence and survival of fringed sagebrush seedlings and growth of established plants. In no circumstance was seedling emergence or plant growth greater in the undisturbed control than in the disturbed sward. Emergence of fringed sagebrush seedlings increased almost 80-fold the second year after tillage at 1 site, but emergence was not altered relative to the control by clipping, litter removal, or clipping+litter removal Averaged across treatments, 52 to 98% of the seedlings emerged in May and June, and 47 to 99% of these seedlings survived through the growing season and winter. Plants grew fastest in June when precipitation was highest and temperatures were moderate. Growth of plants was improved 2- to 3-fold by tillage the second year; this stimulation in growth was due to the removal of competition. Activities that reduce or remove vegetation and create bare soil surfaces promote emergence and growth of fringed sagebrush on the Northern Great Plains. Most seedlings of fringed sagebrush emerge in spring and early summer, enabling them to temporally exploit the period for optimal growth. Fringed sagebrush is well adapted to persist in Northern Mixed Prairie in a successional continuum from early to late seral stages.
    • Influence of grazing management on intake and composition of cattle diets

      Hirschfeld, D. J.; Kirby, D. R.; Caton, J. S.; Silcox, S. S.; Olson, K. C. (Society for Range Management, 1996-05-01)
      A study was conducted to evaluate the influences of seasonlong and short duration grazing management on the botanical composition, chemical composition, and organic matter intake of cattle diets in the Northern Great Plains. Four sampling periods; spring, early summer, late summer, and early fall, were conducted during the grazing seasons of 1990 and 1991. Six ruminally cannulated crossbred steers were used to collect diets while 10 ruminally cannulated crossbred heifers were used to establish intake values. In each sampling period, diet collections were obtained from the steers, allowed to graze for 60 to 90 min in each of the treatments after total rumen evacuation. Intake was estimated using an indigestible marker and twice-daily fecal collections from 5 heifers under each of the 2 treatments. The primary constituent of cattle diets in both seasonlong and short duration treatments was graminoid which was consumed in slightly greater quantity under short duration management. Nutritional content of the diet was improved under short duration management. This is most notable with regard to nitrogen and digestibility, which were higher (P < 0.05) in the short duration treatment in 5 of the sampling periods. Organic matter intake trended higher for cattle under short duration management with 3 of the analyzed sampling periods showing differences (P < 0.10). These results suggest that livestock grazing under a properly implemented rotational grazing system may be presented with an opportunity to consume more of higher quality forage.
    • Mineral dynamics in forages of the Northern Great Plains

      Grings, E. E.; Haferkamp, M. R.; Heitschmidt, R. K.; Karl, M. G. (Society for Range Management, 1996-05-01)
      Mineral concentrations of range grasses are often below that required by grazing livestock. Limited information is available on forage mineral concentrations for the Northern Great Plains and there is little data on factors influencing concentrations of forage minerals throughout the year. Therefore, a study was conducted to evaluate special and temporal variations in mineral concentrations of major forage species in the Northern Great Plains. Herbage was sampled from 4 replicates on each of 2 soils in July, August, and September 1991, April, June, July, August, and September 1992, and April 1993. Herbage was sorted by species grouping and by live and dead tissue classes. Analyses on herbage included Ca, P, Mg, K, Na, Zn, Cu, Mn, and Mo. For western wheatgrass [Pascopyrum smithii (Rydb.) Love] and annual bromes [Bromus spp.], Zn and all macrominerals except Na were greater in live than in dead tissue. Live tissues of all other species groupings contained greater amounts of P and K than did dead tissue. Live tissue Mg concentrations were greater than dead tissue concentrations for other cool-season and warm season grasses. Manganese concentrations were greater in live than dead annual brome tissues, while Cu was greater in dear than live tissue. Dead sedge tissue contained greater concentrations of Ca than live tissue. Soil type affected several nutrient but this was partially related to soil effects upon composition of species groupings and live:dead ratios. Minerals most likely to be found in quantities less than required for animal production were P, Na, K, Zn, and Cu.
    • Monitoring mule deer diet quality and intake with fecal indices

      Hodgman, T. P.; Davitt, B. B.; Nelson, J. R. (Society for Range Management, 1996-05-01)
      Few studies have evaluated fecal indices for monitoring diet quality and intake of North American deer. We conducted 11 digestion trials with black-tailed (Odocoileus hemionus columbianus Richardson) and mule deer (O. h. hemionus Rafinesque) to examine relationships between several chemical constituents of deer feces (i.e., fecal nitrogen, fecal 2,6-diaminopimelic acid (DAPA), fecal neutral detergent fiber (NDF), fecal acid detergent fiber, and fecal acid detergent lignin) and dry matter intake, digestible energy, digestible energy intake, diet crude protein content, crude protein digestibility, and digestible crude protein intake. We developed regression equations to predict diet quality and intake and also evaluated 2 alternative methods (organic matter basis and neutral detergent fiber (ndf) basis) for quantifying fecal indices. Concentrations of DAPA, fecal NDF, and fecal N were the most precise for estimating diet quality and intake. Extracts from 5 of 11 diets precipitated only small amounts of protein and influence of tannins on protein digestion probably was slight. Quantifying fecal indices per unit organic matter and neutral detergent fiber in the feces was comparable to the standard dry matter basis and under some field conditions should improve their predictive ability. We believe our best equations are suitable for management purposes where diets are similar and intake and quality are believed to be within the ranges we documented.
    • Public land policy and the market value of New Mexico ranches, 1979-94

      Torell, L. A.; Kincaid, M. E. (Society for Range Management, 1996-05-01)
      Proposals outlined in Rangeland Reform '94 have been perceived to greatly alter grazing use on public lands. In addition to new rules and regulations, the grazing fee would double under this reform proposal. The debate about these controversial policies would be expected to affect the market value of public kind grazing permits. Regression models were developed using over 700 ranch sales to determine recent trends in market value for New Mexico ranches, including public land ranches. After 1988, nominal deeded ranch values were found to have increased by 3% per annum, but remained unchanged in 1992 constant dollars. This follows a 50% decline in real value from 1982-88. Ranches heavily dependent on Bureau of Land Management (BLM) land for grazing capacity decreased in real value by about 1.8% per annum over the 1988-94 study period. The United States Forest Service (USFS) has recently had the most controversial land use polices and the highest average total grazing costs. This has been reflected in the market value of USFS ranches, with a continued decrease in permit value; USFS ranches in New Mexico have lost 75% of their real value since 1982. Doubling grazing fees on New Mexico state trust lands contributed to a downward trend in leasehold value. Somewhat surprising, given the higher grazing fee on state trust lands, these permits increased in market value in both real (1.7% per year) and nominal (5% per year) terms after controversy about state lands subsided and federal land policies became more controversial.
    • Season and sex influences on botanical composition of cattle diets in southern New Mexico

      Mohammad, A. G.; Ferrando, C. A.; Murray, L. W.; Pieper, R. D.; Wallace, J. D. (Society for Range Management, 1996-05-01)
      We conducted a study in southern New Mexico to determine seasonal variation in botanical diet composition of cattle and to compare cow and steer diets. The climate and vegetation is typical of semidesert grassland. Fecal samples were obtained from a group of cows and steers during spring, summer, fall, 1989; winter and summer, 1990. Results showed that cattle diets were highest in grass content during spring (57%), summer (78%), and winter (54%), while fortes comprised the highest proportion of cattle diets during the fall (47%). Shrubs were moderately important during winter (18%). Dropseeds (Sporobolus spp.), black grama (Bouteloua eriopoda [Torr.] Torr.), threeawn species (Aristida spp.), and leatherweed croton (Croton pottsii [Klotzch] Muell. Arg.) were key forage species for cattle. The importance of these species varied with season, availability, physiological stage, and presence of other species. Differences between cow and steer diets varied with season. The relative similarity ranged from 70% (fall) to 90% (summer). The lower fall similarity compared to that in the summer might be related to physiological variation or past differences in grazing experience between cows and steers. For practical purposes, steer diets might generally be used to represent cow diets, but caution should be exercised during periods of low forage quality.
    • Seasonal grazing of Columbia milkvetch by cattle on rangelands in British Columbia

      Majak, W.; Stroesser, L.; Hall, J. W.; Quinton, D. A.; Douwes, H. E. (Society for Range Management, 1996-05-01)
      There is a dearth of knowledge on the selection and utilization of Columbia milkvetch (Astragalus miser Dougl. ex Hook. var. serotinus) by grazing livestock on rangelands in British Columbia. Four grazing trials were conducted with cattle on Columbia milkvetch range in southern interior British Columbia. In the first 2 trials during 1990 and 1991 cattle grazed an upper grassland site in late spring. In 1992 and 1993, the animals grazed a lodgepole pine forest site during early summer. The density of Columbia milkvetch and its basal area were similar at both locations. The Columbia milkvetch was not a preferred species on the grassland site as indicated by the bite count technique that determined its percentage in the diet. Consumption of Columbia milkvetch increased gradually as other forage species were preferentially selected and depleted. On the grasslands, consumption of Columbia milkvetch by individual animals did not show an addictive pattern. At the forest site, utilization of Columbia milkvetch was determined on a weekly basis during 1992 and on a biweekly basis during 1993 by paired plots. In contrast to the grassland site, Columbia milkvetch was a preferred species at the forest site where it was utilized to a greater extent than grasses or other forbs. Approximately 80% of the Columbia milkvetch was utilized during 1992 and 60% during 1993, which was significantly greater than the utilization of grasses or other forbs. Forage nutrient analysis at the forest site indicated Columbia milkvetch had higher crude protein and lower ADF content than other forages but it caused livestock poisoning in 1993.
    • Shrub-grassland small mammal and vegetation responses to rest from grazing

      Rosenstock, S. S. (Society for Range Management, 1996-05-01)
      Between 1989-1991, I studied the effects of livestock grazing on vegetation and small mammals in semiarid shrub-grassland habitats of south-central Utah. Responses were measured at 2 spatial habitat scales; patches and macrohabitats. Patch-scale data were obtained from 4 small (<1 ha) livestock exclosures and nearby grazed areas. Macrohabitat-scale data were collected at 4 actively grazed sites and 4 comparable, excellent condition sites, ungrazed for 30+ years. Ungrazed patch and macrohabitat sites had more surface litter, greater perennial grass cover, and taller perennial grass plants, but treatment response varied among sites. Small mammal responses were apparent only at the macro-habitat scale, where ungrazed sites had 50 % greater species richness and 80% higher abundance. Small mammal reproductive activity and biomass were not affected by rest from grazing at either scale. Small mammal community composition varied greatly among sites and within treatments. This variability has important implications for ecological monitoring efforts involving these species.
    • Soil water effects on growth and nutrition in upland pastures

      MacKlon, A. E. S.; Mackie-Dawson, L. A.; Shand, C. A.; Sim, A. (Society for Range Management, 1996-05-01)
      Normally the oceanic climate of Scotland maintains soils at low levels of soil water deficit. Field data for such a year are presented and compared with those for an unusually dry year, with the objective of assessing to what degree dry spells might limit herbage production in upland pastures. One meter square plots were sampled on selected dates on reseeded pastures growing on each of 3 cambisols, each derived from different parent materials. The swards were unfertilized and maintained at nominal heights of 2, 4, 7, and 10 cm by cutting every 2 or 3 weeks to manipulate growth and demand for P and N. Overall yield was 25 to 50% lower in the dry year compared with an average year. Peaks and troughs in growth rates, measured as yield at each cutting, and in P and N content, corresponded to changes in soil water deficit in the top meter of soil. The linear correlation coefficient between soil water deficit and growth rate was -0.894 (P = 0.001). Although there was some variation in volumetric water content between soils, soil water deficits were similar in all the cambisols. Yields and nutrient contents were generally similar for herbage harvested from the 2 soils having basic parent material (one a eutric and one a dystric cambisol) and lower on the dystric cambisol derived from schists. The effects of water content largely over-rode cutting treatments, demonstrating that dry spells occasionally occurring in the oceanic climate of Scotland can significantly affect grassland production.