RSS 1.0Journal of Range Management, Volume 45, Number 2 (March 1992)
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Journal of Range Management, Volume 45, Number 2 (March 1992)Society for Range Management, 1992-03-01
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Water-extractable organic matter from plant litter and soil of rough fescue grasslandLittle is known about the chemical composition of throughfall, or the water that falls through, and drips from, the grass canopy of Rough Fescue Grassland during the grazing season. Water-extractable C, N, organic acids, and monosoccharides from litter and from soil in the upper 2 cm of the Ah horizon collected at monthly intervals in 1988 were at Stavely, Alberta. Rough fescue (Festuca campestris Rydb.) were stocked at tither light (1.2 AUM/ha) or very heavy (4.8 AUM/ha) fixed rates for 39 years or were ungrazed in exclosures located within each field for an equal period of time. At the high grazing intensity, the soil and litter N was less water-extractable. The C/N ratios of the water-extractable organic matter from litter and soil averaged 11.2 and 2.3, respectively. Soil monosaccharides were essentially not water-extractable. The quality of the litter as reflected by the water-extractable constituents often differed over the season between fields. Observations at regular time intervals are essential. The effect of the quality of leachates of litter on soil was not predictable. The 3 major long-chain fatty acids identified, palmitic, stearic, and arachidic acids, from soil in grasslands that are in good condition because of the low grazing pressure, could well contribute to the resistance of those grasslands to the encroachment of invading species.
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Vegetation responses to 2 brush management practices in south TexasBrush management for improving wildlife habitat in South Texas is important because of the economic value of wildlife. We determined vegetation responses to (1) roller chopping of guajillo (Acacia berlandieri Benth.)-blackbrush acacia (A. rigidula Benth.)-dominated rangeland and (2) heavy discing of whitebrush (Aloysia lycioides Cham.)-dominated rangeland to improve white-tailed deer (Odocoileus virginianus Raf.) habitat. Canopy cover of vegetation was estimated seasonally during August 1988 to April 1990. Both treatments reduced brush canopy cover, but herbaceous response depended on rainfall. Mean herbaceous cover was 65 and 136% higher on roller chopped sites than on untreated sites when averaged across all sampling dates. Heavy discing reduced relative canopy cover of whitebrush but increased cover of spiny hackberry (Celtis pallida Torr.), an important browse species. Forb species richness was higher on roller chopped and disced sites than on untreated sites, but species diversity was similar. Because herbaceous response to brush removal may depend on rainfall, other factors such n effects on browse availability and nutritional quality may need to be considered when planning brush management strategies to improve white-tailed deer habitat.
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Seedbed ecology of winterfat: Imbibition temperature affects post-germination growthSeed imbibition is a critical first step in the awakening of an embryo plant. To determine if imbibitional conditions influenced post-germination growth, seeds of 3 winterfat (Eurotia lanata) ecotypes were imbibed at 5 temperatures from 0 to 20 degrees C, and at 5 oxygen concentrations from 0 to 40%. After a 4-day imbibition period the seeds were either dried and weighed or they were cultured in the dark at 20 degrees C. Seedling axial length was measured 5 times between 5 and 14 days post-germination to assure that maximum growth was measured. The study was repeated 3 times for each ecotype. Oxygen concentration had little effect except at 0%. As imbibition temperature increased both post-imbibition dried seed weight and seedling axil length decreased. This indicates the probability for successful termination, establishment, and survival of winterfat decreases when seeds are imbibed at 15-20 degrees C as compared to 5 degrees C. Therefore winterfat should be sown during those parts of the year when diaspores will imbibe at cool temperatures. Winterfat should be imbibed and held at 5 degrees C for 4 days, then germinated at 15 degrees C when testing germination.
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Protein supplementation and 48-hour calf removal effects on range cowsIn 1984, 99 Angus X Hereford cows (4- to 6-yr-olds) were assigned randomly to a 4-yr, 2 X 2 factorial study. Treatment assignment was permanent, and no new cows were added during the study. By 1987, 71 cows remained, and over-all, 335 complete cow-calf data sets were used. Main effect treatments were beginning time (prepartum [PRE] vs postpartum [POST]) for crude protein (CP) supplementation (twice weekly feeding of 41% CP cottonseed meal pellets at 1.58 kg cow-1 feeding-1) and temporary calf removal (48 hour [48-H] vs 0 hour [CONT]) just before the breeding season. For analyses, sex of calf was included as a third main effect (2 X 2 X 2) and year was included as a random factor; the 4-way interaction served as the testing term for repeated measures over years. Year was the dominant source of variation for most traits; we attributed this mainly to different amounts and timing of precipitation among years. Very few interactions were observed. The PRE supplemented cows had reduced (P<0.01) spring body weight losses and higher prebreeding body condition scores (4.9 vs 4.5; P<0.01) compared with POST cows. Reproductive performance did not differ between PRE and POST cows. Use of 48-H calf removal vs CONT did not influence (P>0.10) reproductive traits measured. Likewise, 48-H treatment did not impair health or reduce weaning weights of calves. In a separate, within-year analysis used to examine age of dam effects, productivity of 4-yr-old cows during 1984 was slightly below that of older cows for some traits. Cow age effects were not detected in other years. We conclude that control cows in our study were approaching optimum fertility and production levels in concert with their environment and that improvement beyond these levels with the treatments imposed was unlikely.
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Prior grazing by sheep reduces waxy larkspur consumption by cattle: An observationSheep are more resistent to larkspur poisoning than cattle. Grazing larkspur with sheep before cattle turn-in may reduce the threat of cattle poisoning. Two 2.1-ha pastures were established in Upper Ruby Valley in southwest Montana in 1987 and 1989. A band of sheep grazed 1 pasture in mid-June in both years. Sheep grazed 70% of larkspur stalks in 1987 and 35% in 1988. Because sheep grazed little larkspur in 1988, larkspur was hand decapitated to simulate the use obtained in 1987 for the subsequent cattle grazing portion of the trial. Five cows were placed in each pasture immediately following sheep grazing in 1987 and after a 3-week delay in 1998. Cattle diets were quantified by bite counts. Waxy larkspur consumption by cattle in the sheep-grazed pasture was lower than in the cattle-only pasture especially during and after rainstorms in 1987 and throughout the study in 1988. One cow died from larkspur poisoning in the cattle-only pasture in 1988. If sheep will graze waxy larkspur, subsequent consumption by cattle can apparently be reduced on this site, thus reducing the risk of poisoning.
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Observations: Potential long-term environmental impact of tebuthiuron and its metabolites in Utah juniper treesThe concentrations, distribution, and longevity of tebuthiuron [N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N'-dimethylurea] and its metabolites in Utah junipers [Juniperus osteosperma (Torr.) Little] killed by tebuthiuron are not known, causing concern about potential residues and their release into the environment from decaying plants or burning wood. Utah juniper trees killed by tebuthiuron at 3 north-central Arizona locations were assayed for tebuthiuron and its metabolites by gas chromatography with flame photometric detection. Foliage, twigs, stems, and litter from recently killed trees averaged 13.3 +/- 0.4, 0.4 +/- 0.1, 0.4 +/- 0.1, and 4.0 +/- 6.6 mg/kg of tebuthiuron plus its metabolites, respectively. Dead stems averaged 0.5 +/- 0.4 mg/kg in sapwood, 0.1 +/- 0.1 mg/kg in heartwood, and 0.4 +/- 0.7 mg/kg in bark, 3 to 9 years after application. Root bark averaged 1.1 +/- 1.9 mg/kg, and root wood averaged 0.5 +/- 1.4 mg/kg. Although long lived, these small tebuthiuron residues should have little potential environmental harm if treated Utah juniper wood is used as firewood or fence posts.
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Nebraska sedge (Carex nebraskensis Dewey): Phenology and life history at Tule Meadow, Sierra National Forest, CaliforniaTo better understand shoot development and population dynamics of Nebraska sedge (Carex nebraskensis Dewey), a valuable mountain meadow forage species, 766 shoots were tagged and studied at Tule Meadow, on the Sierra National Forest, California. A key to its vegetative and reproductive phenologic stages was developed. New shoots emerged throughout the growing season, but mostly in spring. Spring shoots reached the mature vegetative stage before autumn. Late summer and autumn shoots overwintered in juvenile vegetative stages. About 3% of each year's cohort of shoots died as juveniles. Early emerging shoots passed at least 1 winter but late emerging shoots passed at least 2 winters before flowering. Among shoots reaching the mature vegetative stage, 60% eventually flowered and died. An average of 90% of the vegetative shoots alive each autumn survived winter. A few shoots remained vegetative and had long lives—1 shoot was still alive after 7.5 years. Vegetative shoots (those not becoming reproductive) of the 1980 and 1981 cohorts lived an average of 599 +/- 50 days. Shoots that became reproductive (flowered) lived an average of 631 +/- 17 days, and time from shoot emergence to culm elongation averaged 501 +/- 18 days. Nebraska sedge appears well adapted to grazing by having long-lived vegetative shoots that can produce new herbage for several years. Nevertheless, grazing management should strive to maximize the numbers of shoots in spring because they are the ones that can flower the next season.
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Leaf development of native bluestem grasses in relation to degree-day accumulationDegree-day accumulation is commonly used to predict crop development and harvest dates. Relationships between degree-day accumulation and phenological development of range forage grasses have received less attention. This research tested the hypotheses that leaf development by big bluestem [Andropogon gerardii Vitman] and little bluestem [Schizachyrium scoparium (Michx.) Nash] is related to degree-day accumulation and that these relationships are stable over environments and years within environments. Study environments included native prairie, a space-planted garden, and a growth chamber. Individual tillers of big and little bluestem were permanently marked and fully developed leaves were counted once or twice weekly over 3 growing seasons and 1 growth chamber trial. Quadratic regression models accounted for 94 to 99% of the observed variation in leaf development for all species-environment-year combinations. Regression models were significantly different (p = 0.05) among environments and between years within environments. Lack of model stability over years was a result of high variation in total leaves produced per tiller relative to annual variation in degree-day accumulation. The simple independent variable, day of year, predicted leaf development equally as well as degree-day accumulation.
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Interdependence between public and private forage marketsThe concept of market interdependence is defined in this paper as the influence that public market quantity allocations and pricing decisions have on observed quantity and price in private markets. The existence of market interdependence violates an implicit assumption of minimal public market influence when comparable private market prices are used to appraise resource value in public markets. Under interdependence, the comparable market approach becomes inappropriate for determining a fair market value in federal resource markets because government actions have the potential to affect observed prices in private markets. In this research, a case study of the Malheur National Wildlife Refuge (MNWR) is used to empirically estimate the existence of federal/private forage market interdependence. Statistical inferences from econometric modeling show strong support for interdependence between the MNWR grazing program and the alfalfa hay market in Harney County, Ore. The results of this case study can be applied to federal grazing lands managed by BLM and FS for grazing fee policy recommendations.
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Influence of matric potential and substrate characteristics on germination of Nezpar Indian ricegrassIntact seeds (caryopses) of Indian ricegrass [Oryzopsis hymenoides (R. & S.) Ricker] are generally reported to exhibit poor germination. The cultivar Nezpar was evaluated to determine if substrate matric potential and substrate physiochemical properties influence germination. Matric potentials ranged from 0 to -1.5 MPa. Substrate variables included: 2 kinds of germination paper, the A horizon of a dune sand, and a commercial washed silica sand. Seeds of Indian ricegrass had low germination (< 5%) with an oversaturated substrate. Germination increased significantly (P less than or equal to 0.05) between -0.005 and -0.10 MPa tension (30 to 70%), then decreased at more negative matric potentials. As compared with paper substrates, the dune sand showed significantly greater (P less than or equal to 0.05) germination at matric potentials more negative than -0.30 MPa. Standard germination screening procedures, especially at high water contents, do not adequately predict the maximum germination characteristics of Indian ricegrass; thus, substrate matric potential is a critical variable to control in germination tests. Moreover, physicochemical differences among common laboratory germination substrates may lead to significantly different termination responses. Microscopic examination of cross-sections of caryopses suggests the mechanism for reduced seed germination at saturated and oversaturated conditions may be the presence of a void between the lemma and palea which, when water-filled, retards oxygen diffusion to the embryo.
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Growth, ion accumulation, and nitrogen fractioning in Atriplex barclayana grown at various salinitiesEffects of varying NaCl levels (50-400 mol/m3) on growth, ion accumulation, and nitrogen fractioning in Atriplex barclayana were studied in a greenhouse experiment using a water culture method. Relative growth rate of shoots was maintained at a high constant level at NaCl concentrations not exceeding 200 mol/m3, but fell to less than half when salt concentration was increased to 400 mol/m3. Potassium and calcium concentrations in shoots were unaffected by root media salinities up to a concentration of 200 mol/m3 but declined at 400 mol/m3. Sodium and chloride concentrations in shoots demonstrated an increase with rising salinity, particularly when NaCl level was increased from 50 to 100 mol/m3. Total nitrogen concentration in leaves was relatively high (3.51-3.72% of dw) at salinities between 50 to 200 mol/m3 NaCl but decreased significantly at 400 mol/m3 NaCl. Glycinebetaine in leaves rose slightly when culture salinity was raised from 50 to 100 mol/m3 NaCl and then remained constant up to an NaCl level of 400 mol/m3. Our results indicate that A. barclayana is a highly salt-tolerant plant with leaves rich in nitrogen, but high salt concentrations in the leaves and stems even at low salinities markedly reduce its potential as a fodder plant.
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Germination of prechilled mechanically scarified and unscarified Indian ricegrass seedSeed dormancy typically limits stand establishment of Indian ricegrass [Oryzopsis hymenoides (Roem. and Schult.) Ricker]. The mechanical and physiological mechanisms that contribute to dormancy must both be overcome before germination. Our objective was to study potential interactions between the breaking of mechanical dormancy and breaking of physiological dormancy. Germination of 13 seedlots of 'Nezpar', 'Paloma', and PI 478833, ranging in age from 4 to 19 years and in viability from 67 to 96%, was tested. Seed was scarified with an air-gun scarifier to reduce mechanical dormancy approximately 2 1/2 years before testing, or left unscarified. Over 77% of seeds remained intact following scarification. Seed was moved from 5 degrees C to room temperature 1 year before testing to reduce physiological dormancy, or left refrigerated. Seed was also prechilled for 3 weeks at 5 degrees C to reduce physiological dormancy, or left nonprechilled. Germination was determined after 2-week and 3-week 15 degrees C germination periods for prechilled and nonprechilled treatments, respectively. Scarification improved germination of undamaged seed in 12 of the 13 seedlots from 9.5 to 29.7%. Prechilling improved germination of 10 of the 13 seedlots from 8.0 to 22.8%. Room-temperature storage improved germination of 5 seedlots from 4.9 to 12.8%. In 9 seedlots prechilling improved germination of scarified seed 13.1% less than unscarified seed. In 4 seedlots room-temperature storage improved germination of scarified seed 6.5% less than unscarified seed. Depending on the vigor of the seedlot, such effects may be related to a greater reduction of either physiological dormancy or viability in scarified seed than in unscarified seed.
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Forb and shrub influences on steer nitrogen retentionTwo experiments with steers were conducted to evaluate the influence of native forbs and shrubs on nitrogen utilization by cattle. Diets in Exp. 1 were blue grams (Bouteloua gracilis [H.B.K.]) (BG), BG plus 23% alfalfa (Medicago sativa) hay (ALF), BG plus 42% forbs and BG plus 41% shrubs. Diets in Exp. 2 included barley (Hordeum vulgare L.) straw, and straw plus either 42% ALF, 63% forbs, or 62% shrubs. Forbs used in our study were scarlet globemallow (Sphaeralcea coccinea Nutt.) and leatherleaf croton (Croton pottsii Lam.). Shrubs included fourwing saltbush (Atriplex canescens [Pursh.]) and mountain mahogany (Cercocarpus montanus Raf.) Forb and shrub mixtures were 50:50 of each species. Blue grams and straw basal diets contained 7.6 and 3.5% CP, respectively. Diets containing ALF, forbs, and shrubs were isonitrogenous (10.5% CP) in both experiments. In Exp. 1, no differences (P>.10) were observed among treatments for N retention (g/d). In Exp. 2, N retention was least (P<0.5) for the straw diet, greatest for the ALF and shrub diets (P>0.05),and intermediate for the forb diet. Inclusion of forbs or shrubs with low-quality forage diets was, in most instances, comparable to inclusion of ALF. Our results indicate that maintaining palatable forbs and shrubs on rangelands should reduce the need to supply cattle with protein during periods when grasses are dormant.
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Evaluation of microhistological analysis for determining ruminant diet botanical compositionThe accuracy of microhistological techniques for analysis of herbivore diets was evaluated with cattle, sheep, and Angora goats fed grass, forb, and shrub mixtures of known botanical compositions. Two observers performed microhistological analyses on undigested diets as offered and on feces collected. Similarity indices and chi-square tests were used to determine if differences existed among actual diets, estimated diets, and fecal samples. Botanical compositions of diets fed to all 3 animal species generally were accurately estimated by fecal analyses. In some other studies, shrubs in ruminant diets have been inaccurately estimated by the microhistological technique. However, in our study, shrubs were accurately estimated with no differences between actual and observed compositions. We attribute this to the fact that shrub materials used in our study had a high proportion of current growth relative to woody materials. Woody plant parts had lower proportions of identifiable epidermal material than leaves and young stems. In grass-forb diets, forbs sometimes were overestimated and differentiation among grasses was difficult. However, in most cases, observers could precisely estimate diets of the 3 herbivore species.
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Evaluation of fecal indicators for assessing energy and nitrogen status of cattle and goatsIn vivo digestibility trials involving cattle (steers) and goats (wethers) fed shrub and nonshrub mixtures were conducted to evaluate the potential of fecal output, fecal nitrogen output, and fecal nitrogen percent for assessing diet intake, nitrogen balance, and digestibility. Two cattle digestion trials involving 8 feeds and 4 goat digestion trials involving 13 feeds were used to develop simple linear and multiple regression equations between fecal and diet characteristics. Crude protein percent (organic matter basis) of cattle diets ranged from 3.9 to 12.0%; that of goats ranged from 7.5 to 14.4%. Low-phenolic and high-phenolic shrubs were fed in separate diets to goats while cattle diets involved only low-phenolic shrubs. Fecal output of organic matter (percentage of body weight) was correlated (r2>0.80) with forage organic matter intake (percentage of body weight) for both cattle and goats when all feeds were included in the regression. Linear regression intercepts, but not slopes, differed (P<0.05) among cattle and goats. Multiple regression equations did not improve evaluation of forage intake over simple linear equations using fecal output. Fecal nitrogen output (g N/kg BW) was associated more closely with nitrogen balance (g N/kg BW) than other fecal indicators. Further, fecal N output was best associated with nitrogen bahmce for both cattle and goats (r2 = 0.64, 73, respectively) when used in multiple regression equations. Multiple regression equations showed potential for evaluating nitrogen intake (g N/kg BW) of both cattle and goats, (R2 = 0.91, 0.87, respectively). Although it is doubtful that our equations have broad applications, our approach might be useful if specific equations were developed for individual range types.
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Effect of restricted forage intake in confinement on estimated fecal output from a sustained release bolusTwo experiments were conducted to investigate the effects of restricted forage intake on patterns of chromium excretion to determine sample window duration and the accuracy and precision of fecal output estimates derived from the Captec Chrome sustained release bolus. In Experiment 1, 8 crossbred steers (mean = 243 +/- 14 kg) were assigned randomly to receive prairie hay (PH) at intake levels of either 1.12% body weight (BWT) or 0.75% BWT while maintained in individual metabolism crates and(or) pens. In Experiment 2, steers from Experiment 1 were rerandomized and assigned to receive PH at either 1.12% BWT or alfalfa hay (AH) at 1.30% BWT. The average post-dosing bolus failure rate across experiments exceeded 30%. Estimated fecal output exceeded actual fecal output under all experimental conditions (P<0.08). Averaged across experiments, fecal chromium recovery was low (mean = 55 +/- 4%). When estimated fecal output was corrected for mean marker recovery within treatment, it did not differ from actual fecal output (P>0.60). Treatment effects were similar for estimated fecal output, corrected estimated fecal output, and actual fecal output. Under conditions of pen feeding and restricted forage intake, estimated fecal output exhibited treatment differences similar to those of total fecal collection. However, unless adjusted for average marker recovery, these estimates were significantly greater than actual fecal output.
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Effect of grazing, spraying, and seeding on knapweed in British ColumbiaThe effects of late fall grazing, application of picloram (4 amino-3,5,6-trichloro-2-pyridinecarboxylic acid), and seeding on the reinfestation by knapweed (Centaurea diffusa Lam.) were investigated on a knapweed-infested grassland range in southern British Columbia. The seeding treatments were an unseeded control, crested wheatgrass (Agropyron cristatum L.), Russian wildrye (Psathyrostachys junceus (Fisch.) Nevski)), 'Drylander' alfalfa (Medicago sativa L.), and a rangeland seed mix. The spraying treatment was applied (0.56 kg a.i. per ha.) to only the unseeded control, Russian wildrye, and crested wheatgrass treatments. Re-establishment of knapweed and establishment of seeded and indigenous species were observed over 4 years. Knapweed cover never exceeded 10% on sprayed plots but ranged from 35% to 60% on unsprayed plots. Knapweed cover was greater on unsprayed grazed plots and re-establishment was more rapid on sprayed grazed plots than on ungrazed ones. Seeding produced little difference in knapweed cover but crested wheatgrass and rangeland mix (which contained crested wheatgrass) had the lowest coverage of knapweed on unsprayed plots. Russian wildrye did not establish and this failure plus the disturbance created by seeding provided ideal conditions for a surge of knapweed growth. No differences in knapweed cover were detected among seeding treatments on sprayed plots. It is concluded that spraying is far more important than seeding for controlling knapweed, and grazing pressure must be carefully controlled to prolong the effects of treatment.
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Dynamics of shrub die-off in a salt desert plant communityMortality of shadscale (Atriplex confertifolia [Torr. & Frem.] Wats.) was severe in Great Basin valley bottoms between 1983 and 1988. Puddle Valley, Utah, just west of the Great Salt Lake, typifies areas of extensive shrub loss in which density decreased from over 12,000 ha-1 to less than 200 ha-1. We analyzed vegetation along a radial transect established in the bottom of Puddle Valley in 1987. Mortality was greatest at the lowest elevations where shrubs were initially most dense. These sites occurred where soil moisture, fine-textured soils, and bulk density were greatest of all sites evaluated. Soil was most saline at the margins of the valley bottom. Higher densities of live shadscale occurred where slopes are greater, soil is more droughty, and soil moisture was lower during the 3 years of data collection. The die-off "front" continued about 5 km to the west of the valley center in 1989. Refugia of live shadscale populations were found where soil salinities were higher. Population dynamics of annuals, including summer-cypress (Kochia scoparia [L.] Schrader), cheatgrass (Bromus tectorum L.), and halogeton (Halogeton glomeratus [Bieb.] C.A. Mey.) were highly variable between 1987 and 1989.
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An integrative approach to rangeland condition and capability assessmentA comprehensive system has been designed to serve as a basis for rangeland condition and grazing capacity assessment. It is important that research information and knowledge be transferred to land managers in the most usable form. An approach has therefore been developed by which different computer technologies are combined to produce a unique and user friendly package for direct application by the grazing industry. The system can be applied universally, regardless of the pool of quantitative knowledge that exists. This is of special importance for the evaluation and monitoring of the many rangeland systems not yet understood and quantified.
