• Assessing grazing impacts by remote sensing in hyper-arid environments

      Saltz, D.; Schmidt, H.; Rowen, M.; Karnieli, A.; Ward, D.; Schmidt, I. (Society for Range Management, 1999-09-01)
      Assessing vegetation status via remote sensing techniques using various vegetation indices has been successfully applied to semi-arid and arid environments. We tested the feasibility of applying such techniques for assessing grazing impact in hyper-arid environments with a high variance in soil type over space. An anticlinal erosional cirque called Makhtesh Ramon in the Negev desert, Israel, was selected for the study. The cirque is typified by low rainfall (40–90 mm per year), a variety of soil substrates and is subject to grazing by a herd of Asiatic wild asses (Equus hemionus) reintroduced into the cirque between 1984 and 1987. As a control, we used an ungrazed dry riverbed south of the cirque that runs parallel to the riverbed draining the cirque. We used 5 common vegetation indices derived from Landsat 5 satellite Thematic Mapper (TM). Four images were used, representing dry and wet seasons in above- and below-average rainfall years (1995 and 1987, respectively). To test whether we can detect changes in plant community structure via satellite data we correlated vegetation indices from the TM to ground measurements made along the altitudinal gradient of the cirque. To test whether differences in plant cover could be detected, we correlated the vegetation indices with ground measurements of cover in and out of the cirque (grazed and ungrazed areas). Although ground measurements showed that community structure changed following grazing with altitudinal gradient and ground cover was 30% lower inside the cirque than outside the cirque, none of the 5 vegetation indices correlated with the ground measurements. Transformed Soil Adjusted Vegetation Index (TSAVI) and Normalized Difference Vegetation Index (NDVI) produced the best results. We hypothesize that the low vegetation cover that typifies hyper-arid environments increases the noise to signal ratio. Thus, a 30% decline in vegetation cover in this case is only an absolute decline of 4% from 15.8 to 11.2%. Because TM is sensitive to absolute cover rather than the relative differences, it is difficult to demonstrate differences among TM images. Using ANOVA to test the effect of season and grazing status on TSAVI and NDVI, we found a significant interaction between season and grazing status in 1995 with indices declining more from wet to dry season inside the cirque than outside the cirque. No such pattern was found in 1987. These data suggest that satellite imagery may detect changes inplant cover over time but can not serve as a direct index of plant cover in hyper-arid conditions.
    • Bison use of fire-managed remnant prairies

      Biondini, M. E.; Steuter, A. A.; Hamilton, R. G. (Society for Range Management, 1999-09-01)
      This study was designed to: 1) compare the landscape distribution patterns of bison on fire-managed prairie remnants in the tallgrass (Oklahoma), and mixed prairie (Nebraska); and 2) identify the extent to which fire and range site [topoedaphic classification of the landscape] affect bison distribution patterns. This research was conducted at 2 sites: the Niobrara Valley Preserve (1990–1996), and the Tallgrass Prairie Preserve (1993–1996). At both preserves, bison selected burned areas during the growing season for 1–3 years and mostly avoided old burns and unburned areas. There was an interaction between fire and range site in selection patterns. In the absence of fire, bison mostly avoided both the Choppy Sandrange sites at the Niobrara Valley Preserve and Loamy Prairie range sites at the Tallgrass Prairie Preserve. When they were burned, however, these sites were highly selected. The main difference in bison selection patterns between the Tallgrass Prairie Preserve and the Niobrara Valley Preserve was observed during the dormant season. In the Tallgrass Prairie Preserve, burned sites continue to be preferred during the dormant period for an average of 2 years while in the Niobrara Valley Preserve selections were random. These differences can be explained by 2 mechanisms: the fall and winter re-growth of forage at the more southern latitude and the significant physiognomic changes that fire can cause in tallgrass prairies. Our study documents a continuing interaction between the ecological processes of the fire regime and bison distribution and abundance within 2 of the major prairie landscapes of the Great Plains, and provides critical details for understanding this relationship.
    • Conditioned aversion to minimize Ferula communis intake by orphaned lambs

      Landau, S. Y.; Ben-Moshe, E.; Egber, A.; Shlosberg, A.; Bellaiche, M.; Perevolotsky, A. (Society for Range Management, 1999-09-01)
      The circum-Mediterranean perennial Ferula communis L.(giant fennel) has anticoagulant constituents. Mortality from poisoning can affect 5% of the sheep grazed in infested areas and most casualties are ewe-lambs at the onset of the grazing season. In intensive sheep production systems, ewe-lambs are “orphaned”, artificially reared, and have no opportunity to acquire safe dietary habits by imitating their mothers. The aim of the present study was to evaluate the intake of F. communis in such lambs and to assess the potential of using conditioned aversion as a managerial tool to decrease the frequency of F. communis poisoning. Six lambs weighing approximately 28 kg were averted to F. communis using 2 administrations of 4g LiClin aqueous solution, given immediately after a meal of F. communis; 6 similar lambs served as unaverted controls. The intake of F. communis and the persistence of aversion were assessed over 7 observation days using a simulation of an infested field where freshly cut bunches of F. communis were tied to stakes at 10-m intervals in ryegrass (Lolium multiflorum Lam.) paddocks at the late vegetative stage. Averted lambs grazed separately from unaverted counterparts. Time spent by lambs foraging on F. communis was in the range of 0–0.015 min/hour (not significantly different from nil) in averted, and 0.15–0.24 min/hour inunaverted lambs, respectively (P = 0.002). Consequently, the rate of disappearance of F. communis was greater when grazing was by unaverted than averted lambs (0.29 and 0.15 g/min, P =0.01). The aversion persisted for 25 days after the LiCl treatment, at which time observations were discontinued. Assuming that the amount of F. communis that disappeared is close to actual intake by lambs, intake by unaverted lambs was high enough to endanger the lambs, whereas averted lambs consumed safe amounts of the poisonous plant. It is concluded that conditioned aversion has the potential to alleviate the problem of F. communis poisoning in orphaned ewe-lambs.
    • Coyote depredation control: An interface between biology and management

      Knowlton, F. F.; Gese, E. M.; Jaeger, M. M. (Society for Range Management, 1999-09-01)
      Predation by coyotes (Canis latrans) on livestock continues to plague producers in the United States. Agricultural interests are concerned about coyote predation because sheep inventories in the U.S.have declined >85% in the past 60 years, with a 25% decline between 1991 and 1996. This decline in sheep numbers has been attributed to low economic returns among producers, with coyote predation cited as a major causative factor. Generalizations about the magnitude and nature of depredations can be misleading because of the varied nature of sheep operations, including size of operations, differences in management, and environmental circumstances surrounding individual operations. Coyote depredation rates appear to be influenced by sheep management practices, coyote biology and behavior, environmental factors, and depredation management programs. Most nonlethal depredation control techniques fall within the operational purview of the producers. The major controversy regarding depredation management focuses on programs that remove coyotes to prevent or curtail predation on domestic stock, especially on public lands. Differences in the magnitude, nature, and history of problems caused by coyotes, as well as the circumstances in which they occur, dictates a need for a variety of techniques and programs to resolve problems. The resolution of coyote depredation upon livestock remains controversial for producers, resource managers, and the general public. Because various segments of society attach different values to coyotes, resolution of depredations should use management programs that integrate the social, legal, economic, and biological aspects of the animals and the problem. Preferred solutions should involve procedures that solve problems as effectively, efficiently, and economically as possible in the least intrusive and most benign ways. Predation management requires a partnership among producers and wildlife managers to tailor programs to specific damage situations so the most appropriate techniques can be selected. This paper attempts to clarify the issues surrounding depredation management, synthesize past and current research, and provide information to resource managers associated with coyote depredation management. This synthesis integrates current understandings of coyote biology and behavior, the nature of depredations upon sheep producing enterprises, and the merits of various depredation control strategies and techniques.
    • Deer damage to alfalfa and mixtures with timothy or orchardgrass

      Hall, M. H.; Stout, R. C. (Society for Range Management, 1999-09-01)
      White-tailed deer (Odocoileus virginianus L.) feed heavily on alfalfa (Medicago sativa L.) throughout Pennsylvania. Attempts to reduce deer feeding on forage crops have proven too costly or ineffective. The objective of this research was to determine the loss in yield and economic returns caused by deer feeding on pure and mixed stands of perennial forage crops. At 2 locations in central Pennsylvania, plots of pure alfalfa, timothy, and orchardgrass, and alfalfa-grass mixtures of 25, 50, and 75% alfalfa were established within areas protected (with fencing) or unprotected from deer. Forage was harvested and dry matter yields, percentage of alfalfa and grass, forage quality, and net economic returns were deter-mined. Deer reduced forage dry matter (DM) yield by 1,451 kg ha-1 yr-1. Deer feeding also reduced annual yield of pure alfalfa by an average of 54%, while yields of pure orchardgrass were reduced by only 7%, resulting in average economic losses of 198 and 59 ha-1 for pure alfalfa and pure orchardgrass, respectively. Deer fed more on plots containing timothy than those containing orchardgrass. Forage quality was unaffected by deer feeding but declined as the proportion of alfalfa to grass in the mixture declined. In unprotected areas, mixtures seeded at 50% timothy or 25 to 75% orchardgrass produced greater economic returns than pure alfalfa.
    • Diversity of the herbaceous layer in mixed bushveld

      Dörgeloh, W. G. (Society for Range Management, 1999-09-01)
      The diversity of the herbaceous layer in the Nylsvley Nature Reserve (Mixed Bushveld) was investigated to enhance the understanding of savanna ecosystems and to serve as a baseline for future monitoring to facilitate management. Species composition and density, dry weight contribution per species, and grass density was measured with a small-quadrat method. A total of 73 grass species were recorded. Plant communities were compared in terms of percentage composition and percentage dry weight per ecological group, species diversity and grass density with general linear modeling. The herbaceous layer of most plant communities consisted pre-dominantly of increaser I species (increasing in under-utilized areas), with increaser I and decreaser species (decreasing with under or over-utilization) producing the highest bio-mass. The dominance of increaser III species (becoming dominant in heavily over-grazed areas) in the Sporobolus ioclados-Acacia tortilis Savanna indicates previous over-utilization of this plant community. A generally high species diversity (Simpson’s index 1-D >0.72) in the reserve is influenced by environmental factors and is a reflection of previous low animal stocking densities and a rotational burning regime. Grass density varied from 53.07 to 219.13 grasses/m-2. A negative correlation (r = –0.6654) between grass density and species density supports the principle that species diversity is reduced in over-grazed areas. The high diversity of the herbaceous layer in the Nylsvley Nature Reserve may serve as a benchmark for comparing range diversity over time and space within this vegetation type.
    • Drought and grazing: I. Effects on quantity of forage produced

      Heitschmidt, R. K.; Haferkamp, M. R.; Karl, M. G.; Hild, A. L. (Society for Range Management, 1999-09-01)
      This research addresses the hypothesis that grazing intensity during and following drought can dramatically alter community level, post-drought recovery patterns. Research was conducted during the 1993 through 1996 growing seasons at the Fort Keogh Livestock and Range Research Laboratory located near Miles City, Mont. Study plots were twelve, 5 × 10-m non-weighing lysimeters constructed in 1992 on a gently sloping (4%) clayey range site. An automated rainout shelter was constructed to control the amount of precipitation received on 6 lysimeters during the 1992 growing season. We conclude from study results that the independent and combined effects of the imposed late spring to early fall drought and associated grazing treatments were minimal relative to soil water dynamics and aboveground net primary production although both grazing treatments reduced herbage standing crops. We attribute the absence of a strong response to the drought to its timing (i.e., late growing season) in that most herbage production in these cool-season dominated grasslands is completed by early summer. Thus, annual production processes in these grasslands avoided the major impacts of the drought. The results do not provide convincing evidence, however, that would lead us to completely reject our original hypothesis. Rather, they simply provide evidence that these grasslands are well adapted to surviving late growing season drought with or without intensive grazing by ungulates.
    • Early summer grazing effects on defoliation and tiller demography of prairie sandreed

      Cullan, A. P.; Reece, P. E.; Schacht, W. H. (Society for Range Management, 1999-09-01)
      Grazing strategies should be designed to maintain vigorous populations of plant species critical for livestock production, wildlife habitat, and/or ecosystem functions. Treatments consisting of 5- to 7-day, mid-month grazing periods in June or July at 16, 32, or 48 animal unit days (AUD) per ha, were replicated 3 times and applied to the same pastures in 1995 and 1996 to quantify cattle use and tiller recruitment and mortality of prairie sandreed [Calamovilfa longifolia (Hook) Scribn.], a rhizomatous species characterized by dispersed populations of tillers. Cumulative grazing pressure (AUD Mg-1) was used to quantify treatments because of differences in phytomass among pastures and dates. Grazing pressure ranged from 10 to 90 AUD Mg-1 and accounted for 69, 61, and 77% of the variation in percentage of tillers grazed, mean defoliation of grazed tillers, and use of prairie sandreed, respectively. As grazing pressure increased from 10 AUD Mg-1, percentage of tillers grazed increased from 48 to 90%; defoliation of grazed tillers increased from 54 to 74%; and utilization of prairies and reed increased from 27 to 67% at plateaus beginning at 50 to 60 AUD Mg-1. When spring precipitation was above average, 45 to 55% use in June or July increased tiller densities, however, these increases were not sustained or repeated in the following year with average precipitation. Utilization was 50% at 28 AUD Mg-1 and 60% at 40 AUD Mg-1. Relatively large increases in utilization per-unit-change of grazing pressure below 20 AUD Mg-1 indicated that yearling cattle selectively grazed prairie sandreed. The high degree of correlation between percentage of prairie sandreed tillers grazed and use of prairie sandreed (R2= 0.91 in June and 0.90 in July) suggests that percentage of grazed tillers can be used to monitor early-summer use of this species in the Nebraska Sandhills.
    • Goats locomotion energy expenditure under range grazing conditions: Seasonal variation

      Lachica, M.; Somlo, R.; Barroso, F. G.; Boza, J.; Prieto, C. (Society for Range Management, 1999-09-01)
      The estimation of the energy cost of various activities using calorimetric techniques in conjunction with direct field observations can be used to estimate energy expended in the daily activities of free-ranging animals. The objective of this study was to observe and quantify the grazing activities and to estimate the energy expenditure due to locomotion of goats in open range.The study was carried out at ‘Finca de Bonaya’ privately-owned site, which extends over 1,482 ha, located in the Nevada mountain-range, Almería. The local altitude varies from 1,100 to 2,000 m above sea level. The area has a mediterranean mountain climate, with annual precipitation ranging from 400 to 700 mm and average daily temperatures from 4.7 degreesC in winter to 23.0 degreesC in summer. Landscape is characterised by holm-oak wood and pinewood, degradation scrubs and hydrophilic grasses communities. The experimental flock grazed on 3 routes during the whole year. The goats were released to graze during the day and then returned to an enclosed shed. The type of goat management was considered as semi-extensive. Direct observation was used to simulate the total distance walked, the vertical ascent or descent, and to quantify other grazing activities. Data on activities on range and distance travelled were taken on 3 days in each season. The energy expenditure of locomotion was calculated from the horizontal and vertical components of travel and the corresponding costs, which had been previously obtained by calorimetry. There was no significant seasonal effect on period devoted to specific activities on range (P>0.05). However, significant changes in the estimated daily energy expenditure and extra energy expenditure due to locomotion of the animals at pasture were found in different seasons (P<0.05). Grazing and walking were the primary activities of goats throughout the study, accounting for 51.7 and 42.0% of the animals’ daily period on range, respectively. Daily travelled distances by goats on range fluctuated from 12,777 m in summer to 8,100 m in autumn, with an annual average of 9,954 m, which represents a mean speed of 20.8 m/min calculated over the whole period on range. The mean annual vertical ascent or descent was 500 m. Estimated heat production due to locomotion ranged from 130.9 to 88.5 kJ/kg^0.75 per day in summer and autumn respectively. These values account for an increased metabolizable energy (ME) requirement at pasture above maintenance of 46.6 and 31.6%, respectively, assuming a ME requirement for maintenance of 401 kJ/kg^0.75 per day for the restrained goat.
    • Inbibition temperature affects on seedling vigor: In crops and shrubs

      Booth, D. T.; Bai, Y. G. (Society for Range Management, 1999-09-01)
      Imbibition at cold temperatures reduces seedling vigor of some species, but is beneficial to others. We used 3 rangeland shrubs and 8 agronomic crop species to test for a general relationship between imbibition temperature (5 to 30 degreesC) and seedling vigor measured as post-germination growth; and to test for an effect of imbibition temperature on seed water uptake and dry weight loss during imbibition. Imbibition temperatures between 5 and 15 degreesC were correlated with greater seedling length of the shrubs while most crops were favored by imbibition temperatures between 20 and 30 degreesC. Winter wheat (Triticum aestivum L.) response to imbibition temperature was similar to that of the shrubs. Generally, shrubs had lower post-germination growth than crops, and during imbibition most crop seeds lost less weight than shrub seeds. Winter wheat had high weight loss as well as high seedling vigor. Seed water content generally increased with increasing imbibition temperature; however, winter wheat, kochia (Kochia prostrata (L.) Schrad.), and big sagebrush (Artemisia tridentata Nutt.) had significantly less water when imbibed at 30 degreesC than when imbibed at lower temperatures. The differences due to temperature suggest the relationship between imbibition temperature and seedling vigor is a general phenomenon related to the physiology of water uptake and to seed respiration (as indicated by weight loss). Therefore, we recommend that optimum imbibition temperatures be defined by species and incorporated into seed-testing guidelines. This appears particularly important for species that do not have a long history of cultivation and whose response to temperature may differ significantly from that of crops.
    • Influence of environmental factors and sheep grazing on an Andean grassland

      Adler, P. B.; Morales, J. M. (Society for Range Management, 1999-09-01)
      Chronic overgrazing in the central Andes alters vegetation and may cause erosion and loss of productivity, but quantitative studies are lacking. We measured the relative influence of environmental factors and sheep grazing on local plant species composition, diversity, and soil organic matter in a remote site in northwestern Argentina. Using redundancy analysis, we found that environmental variables explained 22% of variation in species composition between sites, while grazing-related variables explained 24% of variation. The complete model, incorporating all significant variables, explained 33% of vari-ation. Aspect, season of grazing (wet vs. dry) combined with total vegetative cover, and soil type formed the basis for the first 3 ordination axes. Unpalatable or toxic species and very low-growing species were significantly more abundant on heavily grazed sites compared to relatively protected sites. Stocking rate in wet season pastures was negatively correlated with total cover, forage volume, soil organic matter, and species richness. Season of grazing had a more dramatic effecton total cover, forage volume, species diversity and soil organic matter, which were all significantly lower in wet season pastures compared to dry season pastures. Season of grazing and aspect interacted strongly: wet season pastures on north aspects appear more susceptible to degradation and changes in species composition than south-facing sites. Our results suggest that protecting pastures during the summer rainy season may be an important complement to traditional management efforts to reduce stocking rates.
    • Intake of cattle offered normal and lodged tall fescue swards

      Dougherty, C. T.; Cornelius, P. L. (Society for Range Management, 1999-09-01)
      Grazing behavior of livestock may be altered when grass swards are lodged by trampling or wind and rain. We used a balanced change-over design to investigate the effects of lodging on the ingestive behavior of Angus cows (Bos taurus L.)(mass (M): 344 kg) grazing swards of vegetative endophyte-free ‘Kenhy’ tall fescue (Festuca arundinacea Schreb.). Animals were offered normal swards (T1), lodged swards (T2),or swards with one half of their area lodged (T3). To simulate lodging, swards were covered overnight with weighted plywood sheets that compressed sward surface height (SSH) from 34 to 14 cm and elevated sward dry matter (DM) density from 151 to 499 kg ha-1 cm-1 for herbage > 5 cm. Mean herbage DM intake per bite was 561 mg for T1, 713 mg for T2 and 792 mg for T3. Cattle grazed at 28 bites min-1 for T1, and 25 bites min-1 for both T2 and T3. Herbage DM intake rates were 0.27, 0.31, and 0.33 kg 100 kg-1 (M) hour-1 for T1, T2, and T3, respectively. In another experiment, cattle were offered equal areas of normal swards (SSH: 27 cm) and lodged swards (SSH: 16 cm), normal and partially defoliated swards (SSH: 20 cm) swards, or lodged and partially defoliated swards. When offered normal and lodged swards, 64% of DM intake came from normal swards. When offered normal and partially defoliated swards about 60% of DM intake came from normal swards. Cattle grazed equally on lodged and partially defoliated sward segments when offered that choice.
    • Land use change effects on breeding bird community composition

      Boren, J. C.; Engle, D. M.; Palmer, M. W.; Masters, R. E.; Criner, T. (Society for Range Management, 1999-09-01)
      We identified land uses, vegetation cover types, and landscape patterns associated with avian community diversity in 2 rural landscapes in a hardwood forest-tallgrass prairie ecotone that differ with regard to human population density. We obtained long-term (24 years) changes in avian community composition through records from the North American Breeding Bird Survey. We obtained historical and present land use, vegetation cover types, and landscape structure of both landscapes from high-resolution aerial photography. Avian community composition in the low density rural population landscape was primarily related to the amount of land in deciduous forest and land treated with fire or herbicides. In contrast, avian community composition in the high density rural population landscape was primarily related to the amount of land in deciduous forest, native grassland, and roads. Changes in vegetation cover type were related to changes in the avian community composition by increasing prairie habitat associated species in the low density rural population and generalist habitat associated species in the high density rural population landscapes. Loss of neotropical migrants and increased number of generalist species in the high density rural population landscape was related to decreased native vegetation, road development, and increased landscape fragmentation. Biologists and conservationists in this region should focus attention on preserving biological diversity of rural ecosystems by maintaining native plant communities.
    • Leaf area, visual obstruction, and standing crop relationships on Sandhills rangeland

      Volesky, J. D.; Schacht, W. H.; Reece, P. E. (Society for Range Management, 1999-09-01)
      The objective of this study was to determine if leaf area index (LAI) or visual obstruction (VO) could be used in an efficient double-sampling format for estimating total above-ground standing crop on upland range sites in the Nebraska Sandhills. Sampling was conducted in pastures used for summer grazing research in which treatments consisting of stocking at 16, 32, or 48 animal-unit-days (AUD) ha-1 in June or July and an ungrazed control that were replicated 3 times. During trial 1, LAI, VO, and yield of standing crop were measured in 1995and 1996 at 12 random sampling sites in each of twenty-one,1.0-ha pastures. Trial 2 compared modified LAI and VO sampling procedures against those used in trial 1. Modifications included the use of a circular 0.25 m2 sample plot area rather than a rectangular one and increasing both the number of LAI and visual obstruction readings that were used in the calculation of the mean value at each sampling site. During trial 2, data were collected from 12 sampling sites within each of 14 pastures that comprised 2 blocks of grazing treatments. There was a significant (P<0.01) linear relationship between LAI and yield of standing crop during trial 1, but only 33% of the variation in standing crop was attributable to LAI. The modified LAI sampling procedure increased R2 to 0.59. Similarly, the relationship between visual obstruction and standing crop was significant (P<0.01), but R2 values were only 0.31 and 0.41 during the first and second years of trial 1, respectively. The modified visual obstruction (VO) sampling procedure resulted in only minimal R2improvement compared to the trial 1 method. Pooling LAI or VO data for individual sample sites into stocking rate means resulted in the detection of significant (P<0.01) quadratic relationships between fall LAI or VO and summer stocking rate. Based on the sampling procedures used in this study, neither LAI nor VO would be useful as direct predictors of total standing crop at individual sample locations on upland range sites in the Nebraska Sandhills. However, with pastures as experimental units, these methods can detect the relative effects of stocking rate with replicated treatments.
    • Livestock response to multispecies and deferred-rotation grazing on forested rangeland

      Olson, K. C.; Wiedmeier, R. D.; Bowns, J. E.; Hurst, R. L. (Society for Range Management, 1999-09-01)
      Performance of cow-calf (Bos taurus) and ewe-lamb (Ovisaries) units was compared under multispecies versus single-species grazing and deferred-rotation versus continuous stocking during a 10-year grazing trial. Treatments were arranged in a 3 species (cattle, sheep, or both species) by 2 grazing method (deferred rotation or continuous) factorial using a randomized-complete block design with 2 blocks. All animals were individually weighed at initiation, mid-point, and termination of each grazing season. Livestock species and grazing method did not interact for any dependent variable (P>0.05). Average daily gain (ADG) was greater (P<0.05) when calves were alone than when mixed with sheep (1.04 vs 1.01 kg day-1, respectively), but ADG of lambs was greater (P<0.05) when mixed with cattle than alone (0.25 vs 0.23 kg day-1, respectively). Cow and ewe ADG were unaffected (P>0.05) by animal species mixture. Production of progeny (gain of calves and lambs) and total production (gain of progeny and dams) per ha was greater (P<0.05) using sheep or mixed species than cattle (17.8, 17.8, and 11.2 kg ha-1 respectively, for progeny, and 22.4, 24.5, and 17.6 kg ha-1 respectively, for total). Calves grew faster (P<0.05) under continuous than deferred-rotation grazing (1.04 vs 1.01 kg day-1). Ewes gained more rapidly (P<0.05) during the second half of the grazing season under deferred-rotation than continuous grazing (0.049 vs 0.023 kg day-1). Multispecies or sheep grazing appeared more appropriate than cattle for this environment. Deferred-rotation grazing appeared superior for sheep performance, but continuous grazing allowed greater calf performance.
    • Prescribed fire effects on biological control of leafy spurge

      Fellows, D. P.; Newton, W. E. (Society for Range Management, 1999-09-01)
      The flea beetle, Aphthona nigriscutis Foudras, is a potentially useful agent for biological control of leafy spurge (Euphorbia esula L.) in grasslands devoted to wildlife conservation. However, effects of other grassland management practices on the persistence and dynamics of flea beetle populations are not well understood. We conducted small plot tests to evaluate 1) the effect of prerelease burning on establishment of A. nigriscutis colonies, and 2) the ability of established A. nigriscutis colonies to survive prescribed fire. More colonies established on plots that were burned prior to beetle release (83% establishment) than on unburned plots (37% establishment), possibly due to litter reduction and baring of the soil surface. However, most colonies established with the aid of fire did not survive past the first generation unless the habitat was otherwise suitable for the species, and we conclude that the primary benefit of prerelease burning is increased recruitment of A. nigriscutis during the first few generations. Established colonies were not harmed by burns in October and May. Both spring and fall burns resulted in an increase in leafy spurge stem density during the first growing season, but stem density declined to the preburn level by the second growing season.
    • Spotted knapweed, forb, and grass response to 2,4-D and N-fertilizer

      Jacobs, J. S.; Sheley, R. L. (Society for Range Management, 1999-09-01)
      Herbicidal control of spotted knapweed (Centaurea maculosa Lam.) on rangeland in the western United States has been most effective using residual herbicides, such as picloram (4-amino-3,5,6-trichloropicolinic acid). However, when residual herbicides cause concerns in riparian areas and for non-target forbs, management practices that use herbicides with lower soil persistence need to be developed. The objective of this study was to quantify the interaction between 2,4-D (2,4-Dichloro-phenoxyacetic acid, dimethylamine salt) and N-fertilizer on spotted knapweed, other forbs, and grass density and biomass. Five 2,4-D rates (0.0, 0.6, 1.1, 1.6, and 2.2 kg ai ha-1) and 5 N-fertilizer rates (0, 50, 100, 150, and 200 kg ha-1) were applied to 2 spotted knapweed infested rangeland sites in a factorial combination arranged in a randomized-complete-block design during the summer of 1996 in Montana. Spotted knapweed, other forb, and grass density and biomass were measured at peak standing grass crop in 1997 and analyzed using analysis of variance. Spotted knapweed density and biomass at Rock Creek were reduced 50% and 65%, respectively, by 2,4-D of treatments of 1.1 kg ai ha-1 or greater. Spotted knapweed biomass was slightly increased by N-fertilizer at 200 kg ha-1. Grass density increased by about 50% when treated with 2,4-D of 1.1 kgai ha-1 or greater N-fertilizer did not affect grass density or biomass. At Hyalite Creek, 2,4-D at 0.6 kg ai ha-1 reduced spotted knapweed density by 30%, and rates greater than 0.6 kg ai ha-1 reduced it by 75%. Spotted knapweed biomass was reduced by 75% at all herbicide rates tested. N-fertilizer and 2,4-D interacted to increase grass density at Hyalite Creek; however, grass biomass was not affected. At Rock Creek, neither 2,4-D nor N-fertilizer affected forbs. At Hyalite Creek, 2,4-D and N-fertilizer interacted to increase aster (Aster eatonii [Gray] Howell) biomass. Death camas (Zigadenus venenosus Wats.) biomass was increased by N-fertilizer addition. Combining N-fertilizer with 2,4-D may increase long-term control of spotted knapweed when residual herbicides cannot be used. Application of 2,4-D at the bud stage of spotted knapweed growth will provide some control of spotted knapweed without affecting early season forbs.
    • Total nonstructural carbohydrate trends in Chinese tallow roots

      Conway, W. C.; Smith, L. M.; Sosebee, R. E.; Bergan, J. F. (Society for Range Management, 1999-09-01)
      Chinese tallow (Sapium sebiferum L. Roxb.) was introduced to the United States from China in the mid to late 1800s and has since naturalized throughout much of the southern U. S. Tallow continues to invade a wide variety of habitats, but control efforts have been inconsistent. We related root total nonstructural carbohydrate (TNC) levels and phenological development in Chinese tallow over an annual cycle to determine optimal timing for control treatments. Six phenological stages were recorded; (1) dormancy, (2) bud break, (3) leaf development, (4) seed formation, (5) seed maturation, and (6) leaf fall. Tallow root TNC concentrations varied by phenological stage (P<0.001), where concentrations were highest (P<0.05) during leaf fall (60.72%) and lowest during leaf development (41.11%) and seed formation (36.71%). Chinese tallow root TNC concentrations increased during the period of seed maturation until leaf fall. If foliar applied herbicides are delivered during this period of downward translocation, effective tallow control may be observed.
    • Viewpoint: The role of drought in range management

      Thurow, T. L.; Taylor, C. A. (Society for Range Management, 1999-09-01)
      Drought is an ambiguous term, subject to expectation and the weight of emphasis on meteorological, agricultural, hydrological and socio-economic dimensions. Uncertainty associated with the identification of drought often results in a lagged response in reducing stocking rates. This delay reduces vegetation cover, increasing the potential for accelerated erosion following the drought. The long-term consequences of accelerated erosion are a reduction of soil depth, a decline in soil structure and a decrease in infiltration rate and water storage capacity. Less water stored on a site hastens the onset of plant stress, effectively increasing the perceived frequency and consequences of drought. Management and policy tools must improve the integration of economic and ecological aspects of drought-induced de-stocking decisions, especially by incorporating the long-term irreversible costs of erosion.