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T-4464 Buffelgrass (Cenchrus ciliaris L.) is an introduced grass used extensively for restoring forage capacity of denuded shrublands in the arid Chaco region in central western Argentina. Currently, the technique of roller chopping and simultaneous buffelgrass seeding is widespread, but information is lacking about its effects on forage production and other vegetation attributes at the regional scale. The purpose of our study was to compare grass yield; vegetation cover and density; and species richness, diversity, and evenness, between roller chopping and simultaneous buffelgrass seeding with nontreated native degraded shrublands. Eight sites, including matched pairs of treated and nontreated areas, were studied. Grass yield, total perennial grass cover, and total perennial grass density were higher (P < 0.05) on treated areas. Increase in grass yield on treated areas compared with nontreated areas was related to the increase in total perennial grass cover due to added buffelgrass cover (r2 = 0.79). Shrub cover was lower (P < 0.05) on treated areas, but shrub density was not different between treatments (P > 0.05). Nonsignificant differences (P > 0.05) between treated and nontreated areas were detected in tree cover and density, species number, diversity index, and evenness. The results of this study indicate that, in the short term, roller chopping and simultaneous buffelgrass seeding produces rapid increases in grass cover and grass yield, and a drastic reduction in shrub cover without affecting species diversity on degraded shrublands of the arid Chaco region of Argentina.
The rapid expansion of western juniper (Juniperus occidentalis spp. occidentalis Hook.) across the northern Great Basin has diminished shrub and understory plant composition and reduced forage production. Juniper removal has accelerated during the past decade in Oregon and California to restore shrub–steppe plant communities. Livestock grazing can affect posttreatment successional dynamics, but these impacts have not received adequate study. This study evaluated herbaceous plant recovery in a cut western juniper woodland subjected to grazed and ungrazed prescriptions over 4 growing seasons. The study consisted of 4 treatments: ungrazed cut, grazed cut, ungrazed woodland, and grazed woodland. Stocking rates were 0.78 cow–calf pairs per ha for 5 days in the first year following treatment and 0.94 cow–calf pairs per ha for 4 days in the second year after treatment. The grazing portion of the study lacked true replication because grazed plots were not independent of each other (cattle had access to all plots simultaneously). This limits the strength and interpretation of the grazing results. Juniper cutting removed overstory interference and resulted in significant increases in herbaceous cover, biomass, and seed production when compared to adjacent woodlands. Herbaceous cover, standing crop, perennial grass density, and seed production all increased in the ungrazed cut treatment compared to ungrazed woodland. A similar level of response was measured in the grazed pasture where herbaceous responses were greater in the grazed cut vs. the grazed woodland. Grazing in the cut treatment did not limit herbaceous recovery except that perennial grass seed production was lower in the grazed cut than in the ungrazed cut. Rest or deferment is required the first several growing seasons after juniper cutting to provide plants the opportunity to maximize seed crops. These results imply that juniper cutting had a greater effect on herbaceous dynamics than did the grazing application.
Cattle grazing is often implicated as a factor that reduces vegetative cover and the abundance of important forage plants for wildlife. Recent declines in northern Arizona populations of pronghorn (Antilocapra americana Ord) have focused public and scientific attention on the factors contributing to low fawn recruitment and the potential benefits of cattle removal. To further understand the effects of cattle grazing, we studied the potential hiding cover provided by standing live and dead herbaceous matter as well as forb richness and canopy cover following 5 years of cattle removal. Cattle removal increased horizontal hiding cover by 8% at a distance of 5 m (P = 0.025), but had no statistically significant effect on the potential hiding cover at distances of 10 m (P = 0.105) or 25 m (P = 0.746). Forb species richness was 16% lower in exclosures than in an adjacent grazed pasture in 2001 (P = 0.036), but no differences were observed in 2002 (P = 0.636). The canopy cover of forbs was generally unaffected by cattle removal. These results suggest that curtailing or removing cattle is unlikely, by itself, to lead to rapid improvements in the hiding cover or forb availability for pronghorn on similar rangelands in northern Arizona. In this region, where immediate improvements in fawn survival and recruitment are important to population persistence, additional management actions should be considered.
Perennial grass production on the Chihuahuan Desert Rangeland Research Center in south-central New Mexico was correlated with precipitation characteristics over a 34-year period. Total December through September precipitation was highly correlated (r = 0.77, n = 34) with perennial grass production. Practical generalized indices were developed that could be broadly applied by managers for predicting perennial grass production from precipitation characteristics. Perennial grass production and precipitation data on 3 separate pastures were collected over a 6-year period to evaluate the reliability of models to predict perennial grass production. Simple linear, 2-variable, quadratic, and polynomial regression models gave perennial grass production estimates that were well correlated with actual values (r = 0.85 to 0.91, n = 17) across the 3 pastures. The quadratic regression model (Y = 4.04 − 0.24X 0.012 X2, X = December through September precipitation, Y = forage production, n = 34, r = 0.85) gave the most accurate predicted values. Our quadratic regression model should be of practical use to ranchers and range managers on Chihuahuan Desert upland rangelands receiving 200–300 mm annual precipitation, with loamy to sandy loam soils and in mid- to late-seral ecological condition. These conditions match those generally found on Chihuahuan Desert Uplands. We consider our quadratic regression model to be highly useful over large areas to ranchers in southern New Mexico, southeastern Arizona, southwestern Texas, and north-central Mexico.
A modeling approach that assesses impacts of alternative management decisions prior to field implementation would reduce decision-making risk for rangeland and livestock production system managers. However, the accuracy and functionality of models should be verified before they are used as decision-making tools. The goal of this study was to evaluate the functionality of the Great Plains Framework for Agricultural Resource Management (GPFARM) model in simulating forage and cow–calf production in the central Great Plains. The forage production module was tested in shortgrass prairie using April–October monthly biomass values from 2000 through 2002 for warm-season grasses (WSG), cool-season grasses (CSG), shrubs, and forbs. The forage module displayed excellent (99% explained variance) agreement in the 2001 calibration year in tracking growth and senescence trends of WSG and CSG, which constitute the vast majority of the aboveground biomass. Less agreement (35%–39% explained variance) was observed for shrubs and forbs. The model-explained variances of biomass in 2000 and 2002 (verification years) were 80% for WSG, 67% for CSG, 78% for shrubs, and 82% for forbs. Further development is needed to improve predicted plant response to environmental stresses. The cow–calf production module was tested in northern mixed-grass prairie using June–November monthly average cow and calf weights from 1996 through 2001 for March-calving, moderately stocked Hereford pairs. Overall, GPFARM performed well and tracked cow (81% explained variance) and calf (94% explained variance) pre- and postweaning weights. The GPFARM model has functional utility for simulating forage and cow–calf production with satisfactory accuracy at semiarid-temperate sites, such as southeastern Wyoming and northeastern Colorado. Continued development will focus on improving plant response to environmental stresses and testing the model's functionality as a decision support tool for strategic and tactical ranch management.
Global positioning systems (GPSs) enable continuous and automatic tracking of an animal's position. The value of such spatial–temporal information can be improved if the corresponding activity of the animal is known. We evaluated the potential of Lotek GPS collars to predict activity of beef cattle on extensive rangeland in 2 contrasting foraging environments. Collars were configured to record animal location at intervals of 20 minutes (United States) or 5 minutes (Israel), together with counts from 2 motion sensors. Synchronized field observations of collared cows were conducted in 1999 (United States) and in 2002 and 2003 (Israel). Grazing, traveling (without grazing), and resting activities were recorded as minutes out of 20 for each category (United States), or as a single category (Israel). For the US data, stepwise regression models of grazing, traveling, and resting time accounted for 74%–84% of the variation, on the basis of the motion sensor counts for the left–right axis and the distances between GPS fixes. Regression tree analysis of grazing time yielded a simple model (4 splits) that accounted for 85% of the variation. For the Israeli data, the misclassification rates obtained by discriminant analysis and classification tree analysis of animal activity were 14% and 12%, respectively. In both analyses, almost all grazing observations were correctly classified, but other activities were sometimes misclassified as grazing. Distance alone is a poor indicator of animal activity, but grazing, traveling, and resting activities of free-ranging cattle can be inferred with reasonable accuracy from data provided by Lotek GPS collars.
This 2-year study was designed to quantify the influence of terrestrial and stream habitats on cattle distribution and behavior in a riparian pasture with access to active chinook salmon (Oncorhynchus tshawytscha) spawning. The active salmon redds accessible to cattle were at a density of 4.6 redds per km in 1996 and 6.1 redds per km in 1997. The stocking rate was maintained at 0.82 ha·AUM−1 for 28 days. Cattle spent approximately 94% of their time in the terrestrial habitats (meadow, disturbance, low shrub, tall shrub, and trees) that supported herbivory-type activities (travel, graze, and rest), the remaining time was spent in stream habitats, which consisted of gravel bar (5%) and in aquatic (< 1%) habitats. Cattle spent approximately 88% of their time on nonherbivory-type activities while in the aquatic habitat. Individual cows were observed during the daylight hours for 18 of 28 days each year they were in the pasture and were never observed in direct contact with a redd. Cattle spent over half of their time drinking and < 0.01% of their time defecating while they were in the aquatic habitat. Defecation was proportional to time spent in each habitat; so about 2% of the manure was directly deposited in the stream.
The study addressed the interaction between cattle and spawning spring chinook salmon late in the summer, when it is common for cattle to be present in pastures that have streams where spawning occurs. We addressed the occurrence of spawning in the study area and 2 potential impacts of cattle behavior during chinook salmon spawning: 1) disruption of spawning behavior by the presence of cattle near the redd and 2) the frequency of actual cattle contact with redds. Frequency of salmon redds was not significantly different in the stream reaches accessible to cattle compared with excluded reaches. Salmon continued preexisting patterns of behavior while cattle were within visible range of a redd. Cattle were seldom close to a redd and the chance for direct interaction to occur was minimal. When cattle were visibly near the active redd, cattle remained greater than 3.0 m from the active redd 84% of the time. Of the total time redds were observed, cattle contacted the redds <0.01% of the time. Previous studies have shown salmon that are harassed during spawning can retain eggs and even go completely unspawned. All salmon fully spawned in the study area in both years of the study.
Understanding the survival and transport of Escherichia coli in feces on land and in water is important when trying to assess contamination of water by grazing animals. A fecal-pat experiment was conducted in July and August of 2003 to investigate the survival of E. coli under 4 levels of solar exposure controlled by using shade cloth. Fresh beef cattle manure was uniformly blended to produce 2.5- and 1.6-kg fecal pats, which were placed in plastic trays or in contact with the soil and covered with 0%, 40%, 80%, or 100% shade cloth treatments and replicated 5 times. Samples from each fecal pat were collected at Time 0 to establish E. coli levels; sampling was repeated at Day 1, Day 3, and approximately weekly thereafter for 45 days to determine die-off. E. coli concentration and percent moisture were measured for each fecal sample. At the end of the experiment, fecal pats under the 0% shade cloth had the lowest E. coli concentrations, followed by the 40%, 80%, and 100% treatments, with 0.018, 0.040, 0.11, and 0.44 × 106 colony-forming units (CFU) · g−1, respectively. Fecal-pat size was significant only on Day 17, when large fecal pats had higher concentrations of E. coli (P < .0001). There was no significant difference (P = 0.43) in E. coli concentration between the fecal pats in contact with the soil vs. those in plastic trays. Percent moisture of fecal pats was not a good covariate. Age of fecal pats, as well as exposure to solar radiation negatively influences the survival of E. coli. From a management perspective, E. coli in fecal pats under forested situations would survive longer than in open grasslands due to shading, and any possible contamination by E. coli would be greatest within 7 days of removing cattle from a riparian area or pasture.
Adoption of effective brush management methods is critical to achieving many rangeland management objectives. However, landowners have often been reluctant to adopt new practices. In April 2000, a questionnaire was mailed to the 1 058 landowners in 48 Texas counties to identify factors that influence land management decisions, especially with respect to brush management practices, including Brush Busters treatments. Brush Busters is a Texas-based program developed to expedite the adoption of “select” individual plant treatments through the use of environmentally safe methods. Overall, landowners were “neutral” to “dissatisfied” with regard to the amount of brush on their land. Two primary reasons for wanting to decrease brush were to increase forage production and to conserve water. Kind of brush and cost of brush control were important factors determining the preferred treatment type. In general, the most effective methods were considered to be mechanical treatments for juniper (Juniperus ashei) and individual plant herbicide treatments for mesquite (Prosopis glandulosa) and prickly pear (Opuntia spp.). Mechanical treatments and aerial herbicide applications were perceived to be the most expensive methods, followed by individual plant herbicide treatments, and fire was considered to be the least expensive method. Our study indicated that landowners' satisfaction with Brush Busters' select methods will likely result in an increase in the use of individual plant herbicide treatments for controlling brush. Our study emphasized that a key for enhancing the adoption of sound rangeland management practices is the development and effective dissemination of user-friendly information about low-cost techniques that produce quick results. Easily visible demonstration sites and the establishment of cooperative groups could accelerate the adoption of such practices.
Seedlings of 2 varieties of honey mesquite (Prosopis glandulosa var. glandulosa and P. glandulosa var. torreyana) were exposed to 2 concentrations of atmospheric carbon dioxide (CO2) (368 and 704 μmol · mol−1) in environmentally controlled glasshouses under near-optimal temperature and soil water conditions to determine if CO2 enrichment alters above- and belowground growth responses. CO2 enrichment substantially enhanced both above- and belowground growth variables of both varieties for all harvest dates (8, 16, and 24 days postemergence). This growth enhancement was greater for aboveground variables (21%–35%) at the first harvest, greater for belowground variables (36%–40%) at the second harvest, and similar for both above- (13%–68%) and belowground (10%–40%) variables at the last harvest. Differences in temporal growth enhancement associated with CO2 enrichment suggest changing carbon allocation priorities, with initial carbon investment allocated primarily aboveground to develop photosynthetic machinery, and later carbon allocations predominately directed toward increased investment in roots. The absence of significant CO2 × variety interactions at any harvest date provides evidence that CO2 enrichment did not exaggerate growth responses between the 2 varieties. These results suggest that varietal differences in rooting and other characteristics did not modify the size advantage of the glandulosa over the torreyana variety, as the absolute differences in sizes did not change as a function of CO2 treatment. Although CO2 enrichment did not exaggerate growth differences between varieties in this species, it is evident that honey mesquite seedlings possess the capacity to respond markedly to CO2 enrichment. The greater root depth of honey mesquite seedlings exposed to CO2 enrichment confers a competitive advantage to mesquite seedlings over grass seedlings, assuming that C3 and C4 grass seedlings will not respond as vigorously to CO2 enrichment. As such, this species should continue to aggressively encroach into grasslands in future CO2-enriched environments.
Clones of superior pollen- and seed-producing plants of 4 fourwing saltbush (Atriplex canescens [Pursh] Nutt.) ecotypes were planted in a seed orchard in west-central Texas to determine if seed production and quality could be enhanced by irrigation and fertilization. Subplots of nitrogen (N) at 112 kg·ha−1, phosphorous (P) at 112 kg·ha−1, N P at 112 112 kg·ha−1, or no fertilizer were superimposed on irrigated or dryland main-plots. Neither irrigation nor fertilization affected estimated seed yields or utricle fill during the third growing season after planting. Fertilization did not affect seed germination of any of the saltbush ecotypes on irrigated plots or that of the 2 more xeric ecotypes (Grandfalls and Valentine) on dryland plots. Fertilizer N on dryland plots increased germination of the San Angelo ecotype, and N P increased germination of the Texon ecotype. Estimated gross value of the first seed crop was about $4 648·ha−1 even though the superior reproductive traits of parental pistillate plants were poorly expressed by the clones. Fertilization did not affect estimated seed yields in irrigated plots, but N and N P increased seed yields in dryland plots in the fourth growing season. Fertilization effects on seed weights varied among irrigated and dryland plots and among saltbush ecotypes. Mortality of the shrubs during the period extending from 1988 to 1990 was not affected by irrigation or fertilization but increased among ecotypes as the xeric nature of their sites of origin increased and as the distance of their sites of origin from the seed orchard increased. Evidence from this study did not strongly support cloning, irrigation, or fertilization for improving seed harvests of fourwing saltbush in west-central Texas.
Seasonal variation in production and quality of warm-season grasses is a limitation for livestock productivity. The use of high quality forage legumes to aid in overcoming this problem can be a management alternative. The objective of this study was to evaluate the nutrient content of kleingrass (Panicum coloratum L.)–bundleflower (Desmanthus sp.) mixtures during the establishment year. Plots were drilled at a 0.15 m row-spacing with kleingrass sown either alone or in association with Illinois bundleflower (Desmanthus illinoensis [Michx.] MacM.) or desmanthus (Desmanthus pubescens [L.] Willd), which was previously identified as Desmanthus virgatus. Spacings of 0.30, 0.60, and 0.90 m between rows of bundleflower were used. Plots were planted in April and nutritive value was determined on samples harvested at 60, 90, and 120 days after planting. Age reduced kleingrass crude protein (CP) and increased fiber concentration. The CP concentration of desmanthus leaves was greater than that of Illinois bundleflower; however, the CP on a whole-plant basis was greater in Illinois bundleflower. Associations had greater CP yield than did the kleingrass monoculture. The tannin content was higher in desmanthus than in Illinois bundleflower. In both legumes the leaves had the greatest tannin concentrations, with a mean of 2.1% and 1.69% in desmanthus and Illinois bundleflower, respectively. With the exception of calcium (Ca), mineral content declined with increased age in both legumes and the grass. Levels of potassium, sodium, copper, and manganese were greater in kleingrass than in the legumes, while the legumes had greater concentrations of Ca and magnesium (Mg). Phosphorus and zinc concentrations were similar for kleingrass and legumes. The legumes did not affect the nutrient content of kleingrass when established in association, and the high CP of both legumes and their high levels of Ca and Mg suggest that animals grazing kleingrass-desmanthus associations may benefit nutritionally.
The effective use of plant materials for an array of objectives including conservation, restoration, renovation, landscaping, and bioremediation requires knowledge of the adaptation of each species and, more specifically, knowledge of the adaptation of cultivars, strains, accessions, or ecotypes of a species to specific sites or regions. For agronomic and horticultural plants, specific adaptation information has been and continues to be developed by extensive testing. Rangeland, grassland, park, and restoration project managers often lack the resources to determine adaptation areas for plant materials because of the large number of species that are used and the extensive geographical areas that are serviced. Problems often arise in delineating adaptation areas for plant materials of both native and introduced species. Since ecoregion and plant hardiness zone classification systems integrate many climatic and geographic variables that determine plant adaptation, these 2 systems can be combined to develop Plant Adaptation Regions (PARs). A PAR map of the contiguous United States was developed by merging a widely used ecoregion map with the USDA Plant Hardiness Zone map, and is available in GIS format. Based on their geographic origins and/or test results, plant materials and their general areas of adaptation can be classified using PARs.
During the summer of 1996, 50 radio-tagged, pen-reared Attwater's prairie chickens (Tympanuchus cupido attwateri) were released on Attwater Prairie Chicken National Wildlife Refuge in a restoration effort to supplement a wild population. We evaluated fine-scale habitat use of pen-reared Attwater's prairie chickens during the 1997 nesting season based on 4 variables: obstruction of vision, plant height, litter depth, and percentage of bare ground. Low obstruction of vision (mean = 1.5 dm), plant height (mean = 67.3 cm), and litter depth (mean = 2.7 cm) characterized preferred habitats. Bare ground averaged 16.5% at Attwater's prairie chicken locations compared with 8.2% at random locations. Use locations differed from random locations with respect to visual obstruction (P < 0.001), plant height (P < 0.001), litter depth (P < 0.001), and bare ground (P = 0.007). Potential release sites should be managed using prescribed burning and controlled grazing to produce vegetative structure with an obstruction of vision ≤ 1.5 dm, plant height ≤ 67.3 cm, litter depth ≤ 2.7 cm, and percentage of bare ground ≥ 16.5%), the preferred habitat of pen-reared Attwater's prairie chickens.
Goats avoid eating redberry juniper (Juniperus pinchottii Sudw.) when other palatable forages are available but will increase intake of juniper when exposed to the plant for several days. Intake of redberry juniper also differs among breeds and individual goats. Selection based on foraging habits could further improve juniper intake. The purpose of this study was to determine the influence of sires on juniper consumption. Heritability of redberry juniper intake was assessed for 3 years (1997, 1998, 2000) by placing male Boer-Spanish cross goats from 4–8 sires (the number of sires differed among years) in individual pens and feeding juniper (200 g) daily for 2 hours over 5 to 10 days. Feeding juniper was done after weaning kid goats each year. Juniper intake was similar among sire groups within years. Heritability of juniper consumption was low (11%) across the 3 years of this study. Goats increased juniper intake daily while in individual pens. These results suggest that an acceptance of juniper by goats can be conditioned through exposure to the plant after weaning, and that juniper consumption does not appear to be a highly heritable trait.