RSS 1.0Journal of Range Management, Volume 50, Number 3 (May 1997)
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Welcome to the Rangeland Ecology & Management archives. The journal Rangeland Ecology & Management (RE&M; v58, 2005-present) is the successor to the Journal of Range Management (JRM; v. 1-57, 1948-2004.) The archives provide public access, in a "rolling window" agreement with the Society for Range Management, to both titles (JRM and RE&M), from v.1 up to five years from the present year.
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Print ISSN: 0022-409x
Online ISSN: 1550-7424
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Recent Submissions
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Journal of Range Management, Volume 50, Number 3 (May 1997)Society for Range Management, 1997-05-01
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Viewpoint: The importance of range science to federal grazing policyThe value of science to policy design is questioned by many, including political scientists. Critics view scientific expertise as subject to monopolization by an elite technocracy; a process with antidemocratic consequences. Science has been influential in the development of federal grazing policy by creating the Clementsian paradigm, by affecting the policy agenda, and by defining terms of discussion. Science has been less influential in the implementation of grazing policy. In contrast with many policy issues, science is important to sound grazing policy, because western rangelands are isolated from the thought process of the general public by geographic, demographic, and temporal features. In America, good policy is that which solves important problems and fosters democracy. Democratic forums in which grazing policies are born are enlightened by the disciplined competency of science. More than any other form of knowing, science represents concentrated, devoted study of a topic. Range science should provide the basis of public information and opinion that is converted, via the political process, into federal grazing policy.
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Viewpoint: atmospheric CO2, soil water, and shrub/grass ratios on rangelandsThe abundance of woody plants on grasslands and savannas often is controlled by the availability of water and its location in soil. Water availability to plants is limited by precipitation, but the distribution of soil water and period over which it is available in these ecosystems are influenced by the transpiration rates of grasses. We discuss implications of recent and projected increases in atmospheric CO2 concentration for transpiration, soil water availability, and the balance of grasses and shrubs. An increase in CO2 concentration often reduces potential transpiration/leaf area by reducing stomatal conductance. On grasslands where effects of stomatal closure on transpiration are not negated by an increase in leaf temperature and leaf area, rising CO2 concentration should slow the depletion of soil water by grasses and potentially favor shrubs and other species that might otherwise succumb to water stress. Predicted effects of CO2 are supported by results from CO2-enrichment studies in the field and are compatible with recent models of interactions between resource levels and vegetation pattern and structure.
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Techniques for computer-assisted mapping of rangeland changeManagement of grasslands subject to replacement by woody species requires an understanding of the scales and patterns of change and how to detect and express them. We used the Jornada del Muerto Basin of southern New Mexico as a case study, testing the suitability of Landsat Multi-Spectral Scanner (MSS) data for detecting vegetation changes. Cycles of drought and heavy grazing have apparently changed the once extensive grasslands of the upland Jornada and surrounding areas gradually into a patchwork of shrublands and relict grasslands. Integrated remote sensing and geographic information system (GIS) techniques can facilitate automated detection of these rangeland changes. A GIS was used to store and process two 4-band, co-registered multi-temporal Landsat MSS scenes collected in July 1983 and August 1992. Scene-to-scene radiometric calibration was performed using a regression technique. The data were then evaluated for changes 3 different ways using algorithms based on differences between the 'red' (chlorophyll absorption) bands for the 2 scenes; the Euclidean distances between the 'red' and 'near-infrared' bands for the 2 scenes; and a standardized principal components analysis using all 8 MSS bands. A threshold of 3 standard deviations above the mean was applied to each of the 3 resulting 'change' images to represent areas of extreme change. Correlations among these images ranged between 0.83 and 0.95. We conclude these techniques can identify successfully the patterns and extent of extreme change, and thus have potential value for management of our rangelands resources.
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Technical note: Comparison of simulated ground nest types for grazing/trampling researchOrnithologists often use simulated nests consisting of game bird or domestic poultry eggs to study nest survival. Researchers investigating cattle trampling of ground nests have sometimes used clay targets instead of actual eggs to avoid the confounding effects of nest depredation. To determine whether livestock respond similarly to clay targets and egg nests, we compared inadvertent trampling and intentional disturbance of clay targets versus clutches of 3 pheasant eggs by Angus X Holstein heifers. Overall trampling levels for clay target- and egg-nests were similar (35 and 36%, respectively). Cattle noticed and responded to both types of nests. When noticed, simulated nests were kicked, sniffed, licked, or picked up in the mouth. Cattle disturbed an average of 25% of the clay targets and 8% of the egg nests during 4 trials. Our results suggest that cattle are as likely to inadvertently trample egg nests as they are clay targets, but targets are more likely to attract attention and are therefore disturbed more often than egg nests. The greater likelihood of intentional disturbance of clay targets by cattle reduces the confidence of extrapolating the fate of this type of simulated nest to that of actual nests.
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Soil depth and fertility effects on biomass and nutrient allocation in jaraguagrassThe African perennial C4 grass Hyparrhenia rufa (Nees) Stapf has successfully invaded the lowland non-flooded savannas of Venezuela except in isolated sites with a shallow lithoplinthic hardpan. To study the mechanism of this invasion process, an experiment was designed to determine the effect of soil fertility and depth of the lithoplinthic hardpan on growth, biomass, and nutrient allocation of H. rufa. The main treatments were fertilization with nitrogen, phosphorus and potassium and mechanical disruption of the lithoplinthic horizon prior to seeding with H. rufa at the beginning of the rainy season. Soil fertility rather than soil depth is the predominant abiotic variable regulating the invasion and growth of H. rufa in savanna sites with a shallow lithoplinthic horizon. H. rufa exhibited flexibility in phenology, morphology, productivity and biomass allocation patterns in response to nutrient availability. These responses are typical of successful invader plants. Fertilization significantly increased plant growth through increased tillering and leaf production. Fertilization increased total and organ biomass by approximately 1,000% and the highest proportion was allocated to reproductive tillers. In unfertilized plants, live leaves comprised the highest fraction (approximately 40%) of total biomass whereas the root/shoot ratio was about 0.3 in all treatments. N concentration was approximately 50% higher in roots and rhizomes than in other organs at the beginning of the dry season and under all treatments. Live leaves of unfertilized plants had higher N concentration than leaves of fertilized plants. Phosphorus and K concentrations were similar among vegetative organs but approximately 400% greater in reproductive tillers of fertilized plants. Fertilized plants bad the greatest total content of mineral nutrients due to increased biomass production.
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Seasonal variation of locomotion and energy expenditure in goats under range grazing conditionsEnergy cost of various activities can be used in conjunction with direct field observations to estimate energy expended in the daily activities of free-ranging animals. The objective of this study was to estimate the energy expenditure due to locomotion of goats on open range. The study was carried out at the 130-ha "Los Pajares" pilot zone, located in the Filabres mountain-range, Almeria. Average elevation is 865 m above sea level. The area has a Mediterranean climate. The mean annual precipitation is 324 mm. The average daily temperatures range from 8.9 degrees C in January to 23.0 degrees C in August. The landscape is characterized by woody plants and perennial grasses. The experimental flock was grazed on its customary routes for 2 days during 4 seasons. The goats were released to graze during the day and then returned to an enclosed shed. Direct observation was used to simulate the total distance walked, the vertical ascent or descent, and to quantify other grazing activities. 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. Daily travel distances by goats on range fluctuated from 5,763 m in summer to 3,482 m in autumn, with an annual average of 4,295 m, which represents a mean speed of 10.8 m/min. The mean annual vertical ascent or descent was 168 m. Estimated heat production due to locomotion ranged from 56.9 to 34.8 kJ/kg(0.75) per day in summer and autumn respectively. These values account for an increased energy requirement at pasture above maintenance of 14.2 and 8.7%, respectively.
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Response of spotted knapweed and grass to picloram and fertilizer combinationsSpotted knapweed (Centaurea maculosa Lam.) has reduced forage production, increased soil erosion, and lowered biodiversity on millions of hectares of rangeland throughout the western United States. Objectives of this study were to quantify the interaction between picloram (4-amino-3,5,6-trichloropicolinic acid) and fertilizer on spotted knapweed density and grass yield. Four picloram rates (0.0, 0.14, 0.28, and 0.42 kg ha-1) and 4 fertilizer rates (N+P: 0.0+0.0, 10.5+12.2, 21.1+26.4, and 31.7+39.6 kg ha-1) were applied to 3 spotted knapweed infested rangeland sites in a factorial combination arranged in a randomized-complete-block design during the spring of 1994. Grass yield and spotted knapweed density were measured at peak standing grass crop in 1994 and 1995. Data were analyzed as a split-plot in time using analysis of variance. Picloram and fertilizer did not interact to affect either spotted knapweed density or grass yield. All picloram treatments reduced spotted knapweed density to nearly zero. By 1995, all picloram treatments increased grass yield by an average of 1,500 kg ha-1. Fertilization did not affect spotted knapweed density, but the highest rates increased grass yield on those sites with a substantial residual grass understory. Combining fertilizer with picloram may enhance grass yield on sites with a residual of highly productive grasses.
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Research observation: Influence of over-wintering feed regimen on consumption of locoweed by steersMany producers believe cattle grazing wheat pasture during the winter are likely to graze actively growing locoweed when turned onto short-grass prairie in the spring. White locoweed (Oxytropis sericea Nutt, ex T&G) consumption was compared in a spring grazing study between steers wintered on irrigated 'TAM 105' wheat (Triticum aestivum L.) pasture (Wheat) and steers wintered on native range (Range). Range steers consumed locoweed for 43% of bites compared to 17% for the Wheat steers, and began eating locoweed before steers in the Wheat group. We rejected the hypothesis that steers wintered on wheat are more inclined to graze locoweed than steers wintered on native range.
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Relationships among Idaho fescue defoliation, soil water, and spotted knapweed emergence and growthDeveloping rangeland management strategies to minimize spotted knapweed (Centaurea maculosa Lam.) invasion will require understanding the effects of intensity, frequency, and season of grazing on weed establishment. We studied the effects of hand-clipping 2-year-old Idaho fescue (Festuca idahoensis Elmer) plants 0, 30, 60, or 90%, 1, 2, or 3 times (14-day intervals) on spotted knapweed seedling emergence and growth in pots watered with 150 ml once weekly or 50 ml 3 times weekly. Pots were seeded with 5,000 spotted knapweed seeds m-2, replicated twice, and placed in a growth chamber in a completely randomized design. The experiment was repeated once. Plants were harvested after 50 days. Treatment effects on soil moisture, Idaho fescue and spotted knapweed shoot and root weight, and leaf area were compared using analysis of variance and regression analysis. At final harvest, Idaho fescue shoot weight and leaf area decreased with increasing defoliation level and frequency. Idaho fescue root weight was not affected by any treatment. A single Idaho fescue defoliation at 30% and 90% increased spotted knapweed weight and numbers per pot respectively, over those pots with undefoliated plants. The level of defoliation necessary to enhance spotted knapweed numbers was lower as defoliation frequency increased. As defoliation level and frequency increased, soil water content increased resulting in a corresponding increase in spotted knapweed emergence and growth.
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Post-burn recovery in the flooding Pampa: Impact of an invasive legumeWinter burning of Paspalum quadrifarium Lam. stands ("pajonales") promotes colonization of denuded spaces by several alien species. Lotus tenuis Waldst et Kit. ("lotus"), a recent invader of the region, is able to reach very high densities between the resprouting bunches of the dominant species. Results of a removal experiment performed to evaluate the impact of natural establishment of lotus on post-born colonization of pajonal stands are reported. Seedlings of lotus were removed shortly after their emergence between burned bunches of P. quadrifarium. Eighty days after burning, approximately 30% of the soil surface remained uncovered within removal plots, whereas canopy cover was complete within controls. Furthermore, final (137 days post-burn) total aboveground biomass was 2.7 times higher in control than in removal plots. Removal of lotus significantly (p
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Observations of white-tailed deer cattle diets in MexicoMost rangelands in northern Nuevo Leon, Mexico, have been grazed intensely for more than 10 years simultaneously by cattle and white-tailed deer (Odocoileus virginianus texanus). There is a lack of information concerning diet selection of white-tailed deer and cattle in this region. We observed the dietary preferences of these ungulates in northeastern Nuevo Leon for a 6 month period. Two adjacent areas were subjected to rotational grazing (RG) and continuous cattle grazing (CG). Fecal analysis was used to determine dietary overlap of these 2 sympatric ruminants. Cattle diets averaged 70% grasses, 23% browse, and 4% forbs. Deer diets were 63% browse, 24% forbs and 12% grasses in both areas. The preferred species for cattle in both areas were grasses. Deer preferred fortes on the continuous grazed area and grasses on rotational grazed area. Zacate toboso [Hilaria mutica (Buckl.] Benth.) was the most preferred species by both ruminants in both management systems. Differences between cattle and deer diets were significant (P < 0.05). The similarity index was higher on the rotational grazed (23%) than on the continuous grazed area (15%) (P < 0.05). The higher similarity index in RG area may have been a result of the altered forage preferences of deer. Zacate toboso under RG could be an important feed resource in those areas where white-tailed deer and cattle graze in common.
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Landscape structure and change in a hardwood forest-tall-grass prairie ecotoneTemporal changes in land use, vegetation cover types, and landscape structure were examined in a hardwood forest-tallgrass prairie ecotone in northern Oklahoma using a Geographic Information System. Our objective was to examine relationships between human activity, changes in land use and vegetation cover type, and landscape structure in rural landscapes between 1966 and 1990. Cover types in most of the high density rural population landscape in this study require more intensive inputs and management, which resulted in a landscape with lower diversity, higher homogeneity, and greater patch fragmentation compared to the low density rural population landscape. Both native grasslands and forests were less fragmented in the low density rural population landscape whereas forests were increasingly fragmented in the high density rural population landscape. Native grasslands were less fragmented than forests for all years in both the low density rural population and high density rural population landscapes. Our study suggests conservationists should focus their concerns on fragmentation and losses in biological diversity that accompany increased human activity in densely populated rural landscapes that surround urban centers. Extensively managed landscapes dominated by native vegetation that are under less pressure from expanding human influence are in less peril.
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Gas exchange of Idaho fescue in response to defoliation and grazing historyWe tested the hypothesis that prior grazing history would influence the defoliation responses of Idaho fescue (Festuca idahoensis) growing in a common garden environment. Plants were taken from a grazed pasture and adjacent exclosure which had not been grazed since 1937, and established in a common garden at 1 m spacings during spring of 1989. Plants from defoliated and nondefoliated treatments within the 2 populations were sampled during 1992 and 1993. Photosynthesis, conductance to H2O, and xylem potentials were measured during the 2 growing seasons, and carbon isotope ratio (delta 13C) was measured for senescent leaf tissue. Both within exclosure and outside exclosure defoliated plants exhibited compensatory photosynthesis that averaged a 12% increase the first year, and a 52% increase during the second year, compared with nondefoliated plants. No differences in photosynthesis occurred between the 2 collections. However, outside exclosure plants had higher stomatal conductance than did exclosure plants for the dry year 1992. Also, outside exclosure plants exhibited more negative delta 13C (thus lower water use efficiency) than exclosure plants for 1992 and 1993. We suggest that the higher conductance of previously-grazed plants relative to nongrazed plant populations may be an adaptive response to greater soil moisture often found in grazed sites.
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Estimation of green-Ampt effective hydraulic conductivity for rangelandsEffective hydraulic conductivity (Ke) is an important parameter for the prediction of infiltration and runoff volume from storms. The Water Erosion Prediction Project (WEPP) model, which uses a modified Green-Ampt equation, is sensitive to the hydraulic conductivity parameter in the prediction of runoff volume and peak discharge. Two sets of algorithms developed from cropland data to predict Ke have previously been used in the WEPP model. When tested with data collected on rangelands, these equations resulted in low predictions of Ke which significantly over-estimated runoff volume. The errors in runoff prediction were propagated through the model and resulted in poor predictions of peak discharge and sediment yield. The objective of this research was to develop a new predictive equation to calculate Ke specifically for use on rangelands using field data collected in 8 western states on 15 different soil/vegetation complexes. A distinction was made between ground cover parameters located outside and underneath plant canopy in an effort to account for the significant spatial variability that occurs on most rangelands. Optimized Ke values were determined using the WEPP model and observed runoff data. A regression model (r2=0.60) was then developed to predict Ke using measured soil, canopy cover, and spatially distributed ground cover data from 44 plots. Independent rangeland data sets are now required to test the new equation to determine how well the relationships developed from the data used in this study extend to other rangeland areas.
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Comparison of forage value on private and public grazing leasesFederal land grazing fees have been set by a formula that uses a base rate developed from a 1966 study comparing total grazing costs on private and public lands. A similar market comparison was recently conducted in Idaho, New Mexico, and Wyoming. Total grazing costs were adhered through personal interviews from 258 ranchers using 245 public grazing permits and 149 private leases. Public land grazing permit values were also estimated in each state. This study demonstrated that many public land ranchers have been willing to pay more for grazing than the apparent value implied from the private forage market. With the 1992 grazing fee of 1.92/animal unit month (AUM), 34% of Bureau of Land Management (BLM) cattle producers, 62% of U.S. Forest Service (USFS) cattle producers, 60% of BLM sheep producers and 92% of USFS sheep producers paid more for grazing public lands than did those grazing privately leased lands. Estimated forage values averaged 3.63/AUM for cattle grazing BLM land, and were negative for cattle using USFS lands and for sheep using both BLM and USFS allotments. Using a 3.35% interest rate to amortize permit value, the annual value of public land forage was estimated to be from 3 to 5/AUM. Doubts were cast about the standard assumptions that ranchers have profit maximization as their primary goal, that permit value measures only excess forage value, and that sufficient private leases are available for a valid comparison between private and public forage markets.
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Classifying ecological types and evaluating site degradationAn analytical method for classifying ecological types was developed and tested for mountain meadows in central Nevada. Six ecological types were identified by plot sampling of vegetation and soil-site variables. Two-way indicator species analysis and canonical correspondence analysis were used to identify ecological types and to compare the discriminating abilities of different ecosystem components. Each ecological type was a characteristic combination of landform, soil, and vegetation. Changes in vegetation and soil conditions were assessed along a gradient of degradation within one ecological type—the dry graminoid/Cryoboroll/trough drainageway type. Direct gradient analysis was used to display changes in plant composition and indicators of site degradation. Plant and soil indicators of degradation were basal cover of vegetation, standing crop production of 3 key grass species, rates of infiltration, and soil compaction. Three states of range degradation were identified along the gradient. The grass-dominated state was the most desirable in terms of forage production, basal cover of vegetation and infiltration, while the grass/forb/shrub state represented the most degraded and least productive state.
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Cattle as dispersers of hound's-tongue on rangeland in southeastern British ColumbiaHound's-tongue (Cynoglossum officinale L.) is a noxious weed on forested range of western North America (N.A.), which produces barbed nutlets (burrs) that attach to animals. There is anecdotal evidence that cattle are important dispersers of hound's-tongue in N.A., although European studies suggest animal dispersal of hound's-tongue burrs is minimal. The objectives of this research were to examine the role of cattle as hound's-tongue dispersers, and to develop a method of estimating hound's-tongue burr and plant density on rangeland that may be useful to researchers and range managers. To determine the movement of burrs onto cattle, the number of burrs on marked stalks, before and after grazing, were counted. In 1993 and 1994, about 65% of the burrs stalk-1 were picked up by grazing cattle, whereas, only 14% of the burrs stalk-1 were lost in a paddock ungrazed by cattle in 1994. Individual cows were monitored for burr gains and losses during monthly moves between paddocks by photographing their faces, and counting the burrs face-1 from projected slides. Cattle also were photographed every 2 weeks while in-situ on paddocks. Within 2 to 4 weeks, cows acquired and then lost burrs as they moved within and between paddocks. These experiments suggest that cattle are major dispersers of hound's-tongue on rangelands. There was a positive, linear relationship (R2=0.77; p
