Rangeland Ecology & Management, Volume 62, Number 3 (May 2009)
ABOUT THE COLLECTIONS
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.
The most recent years of RE&M are available through membership in the Society for Range Management (SRM). Membership in SRM is a means to access current information and dialogue on rangeland management.
Your institution may also have access to current issues through library or institutional subscriptions.
Print ISSN: 0022-409x
Online ISSN: 1550-7424
Contact the University Libraries Journal Team with questions about these journals.
Chemical Composition and Ruminal Degradability of Spineless Cactus Grown in Northeastern BrazilA study was conducted to determine chemical composition and ruminal nutrient degradability of eight spineless cactus cultivars grown in northeastern Brazil. Results showed that neutral detergent fiber was similar for all cultivars and averaged 249 g kg-1 +/- 7.3 SEM. Acid detergent fiber ranged between 148 g kg-1 and 207 g kg-1 with some significant differences between cultivars. Starch and water-soluble carbohydrates were similar for all cultivars and averaged 198 g kg-1 +/- 6.3 SEM and 155 g kg-1 +/- 9.0 SEM, respectively. Protein content was less than 50 g kg-1 with some significant differences between cultivars. Calcium was the mineral with the highest concentration followed by potassium and magnesium with no differences between cultivars. Effective ruminal degradability of dry matter and neutral detergent fiber were unaffected by cultivar and averaged 701 g kg-1 +/- 8.4 SEM and 503 g kg-1 +/- 5.8 SEM, respectively. It was concluded that cultivars had little impact on chemical composition and ruminal degradability of spineless cactus. Based on chemical composition and in situ ruminal degradability, spineless cactus can be considered an excellent source of fermentable carbohydrates for grazing and nongrazing ruminants. Because of its high carbohydrate quality, spineless cactus can be used an emergency feed or as part of a complete diet providing that the diet contains an adequate amount of degradable protein.
Influence of Cow Age on Grazing Distribution in a Mixed-Conifer ForestOptimal distribution of cattle on forested rangelands has long been a subject of concern specifically related to uniform and sustainable use of forage resources. Our objective was to determine if cow age influenced distribution and resource use on forested rangelands. This study was conducted from 1991 to 2001 at the US Department of Agriculture Starkey Experimental Forest and Range, northeastern Oregon, a mixed-conifer forested rangeland. We used 43 039 locations of cattle taken from 1 h prior to sunrise until 4 h after sunrise and 4 h prior to sundown until 1 h after sundown from 15 July to 30 August to evaluate cattle distribution patterns during peak foraging time. Cattle were grouped into four age classes: 2- and 3-yr-old cattle, 4- and 5-yr-old cattle, 6- and 7- yr-old cattle, and cattle > 8 yr old. All age classes preferred areas with gentler slopes (P < 0.05), westerly aspects (P < 0.05), farther from water (P < 0.05), and with greater forage production (P < 0.05) than pasture averages. Cattle older than 3 yr of age selected areas with less canopy closure (P < 0.05) than the mean value for the pasture. Young cows (< 4 yr old) selected lower elevations and steeper slopes than the oldest cows (P<0.05). In summary, cow age and correspondingly its experience directly influences distribution patterns and forage resource use of cattle at the Starkey Experimental Forest and Range.
Dynamics of Dormancy-Status Subpopulations of Indian Ricegrass Seed Held in Dry StorageGermination of Indian ricegrass (Achnatherum hymenoides [Roem. Schult] Barkworth), a rangeland species native to western North America, is limited by persistent seed dormancy. We previously identified high-dormancy (HD) and low-dormancy (LD) genotypes from within the genetically heterogeneous cultivar Rimrock. Seed was produced in 2000 and 2001 in a common garden, stored in paper-can containers at room temperature, and tested every 3 mo with and without prechill through 2005. In 2005, tetrazolium viability of all four lots was 99%, reflective of this species’ extensive seed longevity. Over this time period, germination of nonprechilled seed increased from 1% to 53% for HD and from 15% to 79% for LD, whereas corresponding increases for prechilled seed were from 8% to 56% for HD and from 61% to 76% for LD. At first, the great majority of seeds of HD (99%) and LD (86%) were dormant, but this majority was overwhelmingly prechill nonresponsive for HD (92%) compared to roughly equal portions of prechill-nonresponsive (39%) and prechill-responsive (46%) seed for LD. At the end of the trial, most seeds of both HD (53%) and LD (79%) were nondormant, but more prechill-nonresponsive seeds were present in HD (44%) than LD (24%). Over the course of the study, the prechill-nonresponsive subpopulation declined more for HD (by 32%), the prechill-responsive subpopulation declined more for LD (by 45%), and overall dormancy (sum of the two subpopulations) declined more for HD (by 13%). The prechill-responsive subpopulation was depleted more quickly than the prechill-nonresponsive subpopulation for both genotypes. Both HD and LD genotypes were responsive to room-temperature storage without loss of viability over a 4-5-yr period. These data highlight the utility of long-term storage as a technique to improve germinability, and consequently establishment, success of Indian ricegrass.
Response of Bluebunch Wheatgrass and Medusahead to DefoliationOur objective was to determine the short-term response of bluebunch wheatgrass and medusahead to defoliation of wheatgrass designed to stimulate regrowth through tillering. We hypothesized that defoliating bluebunch wheatgrass by 20% at the 3 to 3.5 leaf stage followed by a 50% defoliation at peak standing crop would increase its tillering and biomass production. Consequently, we expected a reduction of the density and biomass of medusahead over that of bluebunch wheatgrass defoliated 50% at peak standing crop. Treatments included four initial medusahead densities (200, 333, 444, 600 plants m-2) created by hand-pulling and three defoliation regimes factorially arranged (12 treatment combinations) in a randomized complete-block design and replicated four times at two sites. In 2006 and 2007, defoliation was accomplished by hand-clipping bluebunch wheatgrass 1) by 50% once at peak standing crop (late June); 2) by 20% at the 3 to 3.5 leaf stage, then again to 50% at peak standing crop (mid May, late June); or 3) plants were not clipped. Density was sampled in 2006 and 2007, and biomass was harvested only at Star Mountain (near Riverside, Oregon) in 2007 because Warm Springs (near Drewsey, Oregon) was burned by a wildfire before final 2007 data could be collected. In 2006, no treatments applied at either site detectably altered the number of tillers produced by bluebunch wheatgrass nor did they affect bluebunch wheatgrass density or biomass in 2007 at Star Mountain. Changes in medusahead density were not detected in 2006, but this annual invasive grass increased in density and biomass in 2007 at Star Mountain in plots receiving two defoliations. The relatively short growing period caused by summer drought and the relative intolerance of bluebunch wheatgrass to grazing make the twice-over grazing an unlikely practice for arid rangelands in the western United States. In fact, it could possibly increase the risk of annual grass invasion.
Agreement Between Measurements of Shrub Cover Using Ground-Based Methods and Very Large Scale Aerial ImageryVery large scale aerial (VLSA) photography is a remote sensing method, which is collected and analyzed more efficiently than ground-based measurement methods, but agreement with ground-based measurements needs to be quantified. In this study, agreement between ground- and image-measured cover and precision, and accuracy of image locations and scale, were assessed. True image locations were determined by georeferencing images and conducting a ground search. Accuracy and precision of planned, aircraft, and georeferenced locations were evaluated by comparison with true image locations. Shrub cover was measured at true image locations using ground-based line-intercept and on the image using point-intercept. Sagebrush (Artemisia spp. L.), antelope bitterbrush (Purshia tridentata [Pursh] DC.), and spineless horsebrush (Tetradymia canescens DC.) were distinguished in the imagery. Agreement between ground- and image-based measurements was quantified using limit-of- agreement analysis. True ground locations of the VLSA images were within a 41-m radius of the aircraft location at the time of image acquisition, with 95% confidence. Using a panchromatic image from the QuickBird satellite (0.6-m pixel resolution) as a base map, 90% of true ground locations were within a 5-m radius of the location estimated from georeferencing the VLSA image to the base map. VLSA image-measured cover was, in general, unbiased with mean absolute differences between VLSA- and ground-based methods less than 1.3%. The degree of agreement and absence of bias between VLSA image-measured and ground-measured cover is sufficient to recommend using VLSA imagery to measure shrub cover.
Intensifying Beef Production on Utah Private Land: Productivity, Profitability, and RiskIt is hypothesized that Utah beef producers in certain locations could intensify private land use via improved forages and irrigation. Although intensification could increase ranch productivity and help compensate for any future restrictions in public grazing, is the approach profitable and sustainable in a dynamic environment? We investigated the efficacy of intensification using linear programming for three size-classes of model ranches. Model solutions maximize returns net of forage costs; outputs include brood-herd dynamics, optimal forage mixes, and net returns. The model is driven by 11-year risk scenarios combining high or low precipitation with high or low beef prices. We then consider current or no access to public grazing—a policy uncertainty. In general, results support the idea that intensification could be profitable, sustainable, and strategically useful under several sets of conditions. Modeled brood- herds expand and contract in response to precipitation. Optimal forage use is dominated by reliance on treated, improved, and irrigated forages. Critical irrigated forages include alfalfa hay and improved pasture. Profitability generally increases with operation size, but when public grazing is eliminated, herd sizes and profitability drop. Small and medium-sized operations respond to loss of public grazing by using more irrigated pasture and alfalfa hay, while larger operations use a wider variety of irrigated and nonirrigated forages. Sensitivity analysis indicates that optimal forage mixes for all operations remain stable even when input costs for fossil fuels double. Further increases in fuel costs, however, begin to reduce the contributions from irrigated pasture and alfalfa hay. Low precipitation (drought) has very large and negative effects on profitability in general. When drought combines with restricted access to public grazing, profitability of small and medium-sized operations drops further while profitability of large operations increases. Empirical research is needed to test model results and examine what the limiting assumptions reveal about real-world production constraints.
Contingent Valuation of Woodland-Owner Private Amenities in Spain, Portugal, and CaliforniaMost of the Mediterranean woodlands in Spain, Portugal, and California are managed as agrosilvopastoral enterprises, producing some combination of livestock, wood, cork products, and crops, as well as wildlife habitat and diverse environmental services. Private amenity benefits to landowners have been suggested as an explanation for high land prices and the persistence of such rangeland enterprises despite apparently marginal cash returns. In this study, private amenity values are estimated using a contingent valuation technique in surveys of private woodland owners as part of five case studies, using a design developed to separate landowner amenity income and capital values. Nonindustrial private landowners were asked about the maximum amount of money that they were willing to give up (to pay) before selling their property to invest in more commercially profitable assets, and the proportion of the market price of their woodland that they think is explained by privately consumed amenities. Amenity values were found to be relevant because, in all cases, landowners were willing to pay > €120 ha-1 yr-1, at 2002 prices, and attributed > 30% of land market price to amenities. These values represent an amenity profitability rate > 2% in all case studies. The data analysis shows some similarities, but mostly divergences, in the different land-simulated and amenity-simulated markets.
Primary Productivity and Precipitation-Use Efficiency in Mixed-Grass Prairie: A Comparison of Northern and Southern US SitesPrecipitation-use efficiency (PUE) is a key determinant of aboveground net primary production (ANPP). We used long-term datasets to contrast ANPP and PUE estimates between northern (southeast Montana) and southern (north Texas) mixed-grass prairies. Effects of varying amounts and temporal distribution of precipitation on PUE were examined at the Montana site, using a rainout shelter and irrigation. Results show that 1) ANPP was 21% less in Montana than Texas (188 g m-2 vs. 237 g m-2); 2) plant function type (PFT) composition varied between the two study locations, with cool-season perennial grasses (CSPG) dominating in Montana (52%) and warm-season perennial grasses (WSPG) dominating in Texas (47%); 3) production dynamics varied between the two sites with 90% of ANPP completed by 1 July in Montana as compared to 31 August in Texas; 4) average PUE estimates were greater in Montana (0.56 g dry matter m-2 mm-1 of precipitation) than Texas (0.40 g m-2 mm-1); and 5) contributions to PUE estimates varied among PFT and location, with CSPG estimates being greater in Montana than Texas (52% vs. 31%) and WSPG estimates being greater in Texas than Montana (47% vs. 27%). Seasonal droughts and supplemental irrigations at the Montana site substantially altered ANPP, PFT biomass composition, and PUE. Results show PUE was responsive to PFT composition relative to amount and seasonal distribution of precipitation. Therefore, one should expect changes in ANPP and PUE to occur with shifts in precipitation patterns until PFT composition becomes adjusted to the regime.
Surface Fuel Sampling Strategies: Linking Fuel Measurements and Fire EffectsWe assessed the effectiveness of different sampling strategies in linking fine fuel load and crown scorch of ashe (Juniperus ashei) and redberry juniper (J. pinchotii) for prescribed fires conducted in wet and dry periods of the growing season on the Edwards Plateau, Texas, USA. Our aim was to determine if spatial and temporal variation in crown scorch was best predicted by estimates of fuel load sampled with spatially explicit, multiscale sampling strategies or with traditional, simple random sampling of fuel load. We found that multiscale sampling of fuel load underneath and adjacent to juniper crowns was more effective than simple random sampling in predicting crown scorch for the 14 fires conducted in the wet period and the five conducted in the dry period. The type of sampling strategy employed was critical in relating fuel load to crown scorch during the wet period. Percent crown volume scorched ranged from 0% to 100% in these conditions. In contrast, the type of sampling strategy was less important in the dry period when crown scorch was >90% for all juniper trees. We use these findings to illustrate how a multiscale sampling design can increase prediction power, thereby improving our ability to provide resource professionals with critical values to target in management. Using such a strategy in this study revealed that fine fuel loading of 2 670 kg ha-1 were needed to scorch juniper trees 100% for the conditions present in the wet period, whereas only 1 280 kg ha-1 were needed in the dry period. To provide managers with this type of information, we suggest that researchers shift from simple, random sampling of fuels to alternate sampling designs where randomization is maintained in the designation of treatments or selection of observations (i.e., individual juniper trees) but where fuel is systematically sampled at the location of the observation of interest.
Historical and Modern Disturbance Regimes, Stand Structures, and Landscape Dynamics in Piñon-Juniper Vegetation of the Western United StatesPiñon-juniper is a major vegetation type in western North America. Effective management of these ecosystems has been hindered by inadequate understanding of 1) the variability in ecosystem structure and ecological processes that exists among the diverse combinations of pin ̃ons, junipers, and associated shrubs, herbs, and soil organisms; 2) the prehistoric and historic disturbance regimes; and 3) the mechanisms driving changes in vegetation structure and composition during the past 150 yr. This article summarizes what we know (and don’t know) about three fundamentally different kinds of piñon-juniper vegetation. Persistent woodlands are found where local soils, climate, and disturbance regimes are favorable for piñon, juniper, or a mix of both; fires have always been infrequent in these woodlands. Piñon-juniper savannas are found where local soils and climate are suitable for both trees and grasses; it is logical that low-severity fires may have maintained low tree densities before disruption of fire regimes following Euro-American settlement, but information is insufficient to support any confident statements about historical disturbance regimes in these savannas. Wooded shrublands are found where local soils and climate support a shrub community, but trees can increase during moist climatic conditions and periods without disturbance and decrease during droughts and following disturbance. Dramatic increases in tree density have occurred in portions of all three types of Piñon-juniper vegetation, although equally dramatic mortality events have also occurred in some areas. The potential mechanisms driving increases in tree density—such as recovery from past disturbance, natural range expansion, livestock grazing, fire exclusion, climatic variability, and CO2 fertilization—generally have not received enough empirical or experimental investigation to predict which is most important in any given location. The intent of this synthesis is 1) to provide a source of information for managers and policy makers; and 2) to stimulate researchers to address the most important unanswered questions.