Now showing items 4335-4354 of 9911

• #### Immersive Co-production to Inform Ranch Management in Gunnison, Colorado, USA

To be successful, producers must interpret environmental stimuli and respond with management actions that help match their production operations to the ecosystem services they depend on. Climate change, and the increased variability that will likely result, may lessen the relevance of historical rules of thumb and management heuristics by altering environmental conditions and giving rise to novel systems that feature more frequent and intense periods of stress. Sustaining livestock production in the face of climate change depends on the rapid production of knowledge to inform adaptation to novel systems. Involving producers in research is often discussed as a strategy to help accomplish this goal. We propose immersive co-production, wherein a student researcher is embedded within the production operations of a working ranch while studying and conducting research, as one method of quickly developing the knowledge resources necessary to sustain livestock production in the context of environmental change. We present a case study involving a ranch near Gunnison, Colorado, as evidence of the effectiveness of this approach. Immersive co-production involves producers in research and researchers in production to develop useful ranch-level management insights and a new generation of interdisciplinary range professionals with intimate knowledge of the complexity faced by producers.

• #### 'Immigrant' forage kochia seed viability as impacted by storage methods

'Immigrant' forage kochia (Kochia prostrata (L.) Schrad.) is a valuable introduced subshrub, often used in reclamation plantings and seedings on western rangelands. Seedling establishment is best from fresh seed; however, many users plant stored seed and experience poor seeding success. One cause for failure is loss of seed viability in storage. Forage kochia seed was harvested on 4 dates in fall 1996 from 2 sites (wildland and irrigated) and tested for viability when fresh and after storage treatments. Storage treatments included low and high seed water contents (2-6% and 12-16%), cold and warm storage temperatures (2 degrees and 25 degrees C), and duration of storage (4, 8, and 12 months). Mature, highly viable forage kochia seed remains viable in storage longer than seed harvested prematurely. Low seed water content (2-6%) is essential to preserving maximum seed viability. Storing seed at a cold temperature (2 degrees C) is also helpful in maintaining viability.
• #### Impact and Control of the Range Crane Fly (Tipula simplex Doane) in the Central Valley of California

The larvae of the range crane fly (Tipula simplex) are responsible for extensive damage to rangeland of the central valley of California, but the damage occurs infrequently in years when there are extremely high densities. These outbreaks appear to be due to favorable climatic conditions during the early larval instars. Means of biological (including pheromone), mechanical, fire, and chemical control are discussed. Early detection is a key in minimizing damage.
• #### Impact of a White Grub (Phyllophaga crinita) on a Shortgrass Community and Evaluation of Selected Rehabilitation Practices

During the spring of 1973, white grubs, Phyllophaga crinita (Burm.), at a density of $46.3/{\rm m}^{2}$, reduced cover of perennial grasses by 88% in localized areas of a shortgrass community in Scurry County, Texas. Forbs and broom snakeweed were not affected. Chlordane applied to the soil surface at 3.36 kg/ha did not control white grubs. Chlordane, nitrogen fertilization (112 kg/ha of N), and a combination of the insecticide-fertilization treatments did not appreciably enhance rehabilitation of white grub-denuded rangeland. Seeding with introduced grasses was not successful because of inadequate precipitation, heavy grazing by lagomorphs on the small areas, and competitive effects of buffalograss. Forbs and broom snakeweed were not important in the early seral stages of secondary succession on the study site, but common broomweed and common sunflower were dominants on other denuded sites in the area. Most plant species had recovered by the end of the second growing season without fencing to control livestock grazing.
• #### Impact of Bentonite Mining on Selecting Arthropods

Arthropods were sampled in pitfall traps for 2 yr on bentonite mine spoils and adjacent, unmined big sagebrush (Artemisia tridentata) grasslands in southeastern Montana to assess the impacts of bentonite mining on selected arthropods, evaluate the success of early reclamation efforts in restoring arthropods to mined sites, and to identify limiting factors for colonization of spoils by arthropods. The most significant impacts on selected arthropods were on old, unreclaimed bentonite mine spoils, where after nearly 30 yr, numbers of 7 arthropod groups remained lower than on unmined sagebrush grasslands. Spoils covered with topsoil had higher captures of ground beetles (Carabidae) and crickets (Gryllidae) than unreclaimed spoils. And spoils covered with topsoil and seeded supported captures of most arachnids, Coleoptera, Hemiptera, and Formicidae similar to those on unmined sagebrush grasslands. Vegetative parameters measured in this study accounted for a portion of the variability in arthropod captures; however, microarthropod populations, arthropod vagility, and soil water contents may influence repopulation of mine spoils by some arthropods.
• #### Impact of Burning and Grazing on Soil Water Patterns in the Pinyon-Juniper Type

Soil water patterns were studied from June 1973 to February of 1977 in pinyon-juniper woodland, on pinyon-juniper areas chained and windrowed (grazed and ungrazed), and on pinyon-juniper areas chained with debris-in-place (ungrazed; burned vs. unburned). The pinyon-juniper woodland always had the least soil water, regardless of the season. Grazing did not affect soil water patterns on the chained with windrowing treatment. Burning of debris on the debris-in-place treatment had little impact on water the first year, but significantly more water was measured on the burned treatment at the beginning of the second year. Soil water patterns previously established between the unburned debris-in-place and ungrazed windrowed treatment changed in August, 1974, and the two treatments were equivalent for the balance of the study. Prior to August of 1974 the unburned debris-in-place treatment had always had more soil water than the ungrazed windrowed treatment. These changes were attributed to possibly milder winters with decreased snowfall.
• #### Impact of Burning Pinyon-Juniper Debris on Select Soil Properties

Burning had the greatest impact on soils beneath burned debris piles. Electrical conductivity, phosphorus, potassium, percent nitrogen, and percent organic carbon increased significantly at all soil depths the first year after burning debris piles. No impact was evident on phosphorus, percent nitrogen, and percent organic carbon by the second year. Impacts on burned interspace areas were generally less pronounced and few impacts were measured the second year. Impact of burning on soil pH was minor.
• #### Impact of Burrowing Activity of the Banner-tail Kangaroo Rat on Southern New Mexico Desert Rangelands

The impact of the burrowing activity of the bannertail kangaroo rat (Dipodomys spectabilis) on southern New Mexico desert rangelands was investigated. The study was conducted on black grama (Bouteloua eriopoda), dropseed (Sporobolus spp.), and mesquite (Prosopis glandulosa) grassland vegetation types. Mound density was highest in the black grama type, somewhat intermediate in the dropseed type, and lowest in the mesquite-grassland type. The surface area occupied by mounds averaged 2% over all vegetation types in the study area. Plant cover was generally greater off mounds than on mounds. Annual plant cover was greater on mounds that off mounds, suggesting that activities of bannertail kangaroo rats promote the presence of annuals.
• #### Impact of Cattle Grazing on Three Perennial Grasses in South-Central Washington

Grazing by yearling steers in a sagebrush-bluebunch wheatgrass community resulted in a reduction of growth and reproductive performance of the most important forage grass. Cusick's bluegrass was sparsely represented, but it was the most palatable and nutritious grass. It also showed the large reductions in growth of leaves and reproductive performance. Bluebunch wheatgrass and Thurber's needlegrass were not as adversely affected by grazing as Cusick's bluegrass.
• #### Impact of clipping on root systems of 3 grasses species in Tunisia

The study concerns the impact of herbivory on the root systems of 3 perennial grasses, buffelgrass (Cenchrus ciliaris), digitgrass (Digitaria commutata) and needlegrass (Stipa lagascae), growing in the arid zones of Tunisia. The study simulated animals feeding of the grasses by affecting cuttings at various times throughout the spring growing period. The following effects on the root systems of the grasses were observed. When there is continual overgazing (simulated by cutting all sprouts down the ground level along the spring), more than 65% of the roots off all 3 species are found in the salty upper 15 cm of soil. In case of medium average grazing (simulated by 2 to 3 cuttings), the root system again remains superficial for buffelgrass (C. ciliaris), with 58 to 67% of the roots located in the upper 15 cm of soil. Digitgrass (Digitaria commutata) and needlegrass (Stipa lagascae), however, develop deeper roots with 68 to 86% in the upper 30 cm of soil. When grazing is light (just one cutting), all 3 species perform all most exactly as if there had been no grazing compared to (a control plot) with 85% of the root system located in the upper 50 cm and about 15% at 50 to 75 cm of ground depth. On the basis of this experiments, it is suggested that grazing on these grasses should be allowed just once each spring, thereby allowing: 1- To take advantage of the aboveground contained in these grasses in spring. 2- Preservation of a deep root system which will thereby have a much better chance of getting through the water stress summer season.
• #### Impact of cultivation legacies on rehabilitation seedings and native species re-establishment in great basin shrublands

Little is known about how cultivation legacies affect the outcome of rehabilitation seedings in the Great Basin, even though both frequently co-occur on the same lands. Similarly, there is little known about how these legacies affect native species re-establishment into these seedings. We examined these legacy effects by comparing areas historically cultivated and seeded to adjacent areas that were seeded but never cultivated, for density of seeded crested wheatgrass (Agropyron cristatum [L.] Gaertn.) and native perennial grasses, vegetation cover, and ground cover. At half of the sites, historically cultivated areas had lower crested wheatgrass density (P<0.05), and only one site had a higher density of crested wheatgrass (P<0.05). Likewise, the native shrub Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis Beetle & Young) had lower cover (P<0.05) in historically cultivated areas at half the sites. Sandberg bluegrass (Poa secunda J. Presl.) density was consistently lower in historically cultivated areas relative to those seeded-only. At sites where black greasewood (Sarcobatus vermiculatus [Hook.] Torr.) and bottlebrush squirreltail (Elymus elymoides [Raf.] Swezey) were encountered, there was either no difference or a higher density and cover within historically cultivated areas (P<0.05). Likewise, cover of exotic forbs, especially halogeton (Halogeton glomeratus [M. Bieb.] C. A. Mey.), was either not different or higher in historically cultivated areas (P<0.05). Bare ground was greater in historically cultivated areas at three sites (P<0.05). These results suggest that cultivation legacies can affect seeding success and re-establishment of native vegetation, and therefore should not be overlooked when selecting research sites or planning land treatments that include seeding and or management to achieve greater native species diversity.

• #### Impact of Feral Herbivores on Mamane Forests of Mauna Kea, Hawaii: Bark Stripping and Diameter Class Structure Sophora chrysophylla

Management of feral and Mouflon sheep and feral goats within the Mauna Kea Forest Reserve/Game Management area has been criticized as inadequate to prevent the adverse environmental impact which these introduced herbivores have on native components of the scrub forest ecosystem. This study determined the intensity of bark stripping of mamane (Sophora chrysophylla), a small endemic leguminous tree, by these animals and assessed the impact of their browsing on the size class structure of mamane stands. In all but one of the 4 areas sampled, a high proportion of mamane trees bore bark stripping wounds. Differences in the amount of stripping between elevations in a given area, and between areas, were attributed to differences in browsing pressure, which in turn was dependent on the frequency of human disturbance and the behavioral traits of the herbivores. Tree size class distributions revealed that browsing has suppressed mamane reproduction in some areas. Suppression appeared to be the greatest in the most heavily browsed areas.
• #### Impact of Grasshopper Control on Forage Quality and Availability in Western Nebraska

Grasshopper outbreaks in Nebraska have resulted in losses over \$2 million per year due to lost forage for livestock. As much as 23% of western U.S. forage is consumed by grasshoppers annually. Controlling grasshoppers reduced grasshopper numbers without negatively impacting beneficial insects. In 2011, 29 more 318 kg steers could have grazed a 1000 hectare pasture for a 5 month growing season due to grasshopper suppression. In 2012 (a drought year), 54 more steers could have been grazed if grasshoppers were controlled. Grasshopper infestation can result in significant reduction in livestock grazing capacity especially in dry conditions.
• #### Impact of grazing on soil nutrients in a Pampean grassland

Cattle exclusion induced dramatic changes in the plant community and modifications in nutrient cycling in grazed native grasslands of the Flooding Pampa (Argentina). The study was carried out to analyze the effect of grazing on the status and spatial variability of soil organic matter, nitrogen and phosphorus. Sampling was performed in the late summer and early spring. Geostatistical methods were used to study the spatial dependence of these soil properties. Organic carbon (OC) and total nitrogen (TN) showed spatial structure only in the ungrazed area with a similar range of dependence (39 m and 36 m respectively). The occurrence of litter in this area lead to a large and spatially homogeneous C input to the soil, which would be the key factor of the spatial structure of organic carbon and total nitrogen. Mineral nitrogen content 1(NO3(-1)-N + (NH4+)-N] was higher in the ungrazed area on both sampling dates. The mineral N content showed a large short-range variability (nugget variation) independent of grazing history. A significant decrease in the extractable P (Bray & Kurtz #1) in the grazed area was found. The extractable P exhibited spatial structure only in the ungrazed area. However, its spatial pattern was different from those of organic carbon and total nitrogen: the range of dependence was higher (57 m) and the spatial structure exhibited a great irregularity. The differences between C, N, and P variability were possibly related to their dynamics in the soil. No evidence of effects of animal excrete on nutrient content or spatial variability was found.
• #### Impact of Incremental Surface Soil Depths on Infiltration Rates, Potential Sediment Losses, and Chemical Water Quality

A study was conducted between October 1974 and August 1976 to measure the effects of incremented surface soil depths on infiltration rates, potential sediment production, and chemical quality of runoff water. The treatments were incremental removals of 7.6-cm soil layers to a depth of 30.5 cm on two pinyon-juniper sites in Utah. Hydrologic parameters were measured at each 7.6-cm incremental soil depth using a Rocky Mountain infiltrometer. With one exception, no significant differences occurred in infiltration rates among treatment depths during either 1975 or 1976 at either the Blanding (southeastern Utah) or Milford (southwestern Utah) site. A significant change in infiltration capacities was noted between the 1975 and 1976 field seasons when data from both treatment depths and study sites were pooled. There were no significant differences in potential sediment production between sites or among treatment depths at a site. In terms of chemical water quality, a significant change in phosphorus content of runoff waters was observed at the Blanding site between the 1975 and 1976 field seasons. Significant differences in potassium concentrations were found between sites and among soil depths. Nitrate concentrations were very low in runoff waters from all soil depths at both sites.
• #### Impact of Incremental Surface Soil Depths on Plant Production, Transpiration Ratios, and Nitrogen Mineralization Rates

From October 1974 to August 1976, a study was conducted to measure how incremental surface soil depths from the pinyon-juniper type affected plant production, plant transpiration rates, and nitrate nitrogen mineralization rates. The treatments were incremental removals of 7.6-cm soil layers to a depth of 30.5 cm. Plant production and transpiration ratios (or water use efficiencies) were measured in greenhouse studies using Agropyron desertorum grown in specified incremental 7.6-cm soil layers taken from five study sites throughout Utah. Significant decreases in plant production and increases in transpiration ratios were measured for all sites at incremental depths beyond 7.6-cm. These changes in plant production and transpiration ratios were linearly related to the nitrate nitrogen content of the soils (as determined when the soils were collected for use in the greenhouse). Nitrate mineralization rates were measured for two 6-week periods under field conditions at two sites for each of the 7.6-cm incremental soil layers. Nitrate nitrogen mineralization was linearly correlated with the organic carbon content of the soil. Decreased mineralization rates as measured in the field at both sites were reflected in the significant increases in plant water requirements and decreases in production that were measured in greenhouse studies.
• #### Impact of Intensity and Season of Grazing on Carbohydrate Reserves of Perennial Ryegrass

Carbohydrate reserves of perennial ryegrass declined during winter and early spring and began replenishment during seed formation. The primary reserve accumulation in roots occurred during fall growth, while crowns replenished about half of their reserves from seed formation to fall and the balance during fall. Total nonstructural carbohydrate (TNC) reserves in roots were highest following a relatively wet year when compared to an average year but carbohydrate reserves were found to be more concentrated in the average year. Biomass of storage organs had a greater effect than concentration of carbohydrates on TNC reserves. Complete protection of perennial ryegrass from grazing did not induce greater accumulation of carbohydrate reserves when compared to any season of grazing treatment and they were sometimes significantly lower than for grazed treatments. No advantage from deferment of grazing in spring, summer, or fall could be determined based on carbohydrate reserves as along as stocking intensity did not exceed one ewe per 650 kg of herbage production per year. At stocking rates above this, deferment during part of the growing season should be beneficial.
• #### Impact of Land Subdivision and Sedentarization on Wildlife in Kenya’s Southern Rangelands

Subdivision and sedentarization of pastoral communities is accelerating rapidly across the African rangelands, posing a severe threat to wildlife populations, but few studies have looked quantitatively at the ecological impact of sedentarization. Here we look at the impact of sedentarization on wildlife by comparing ecologically matched subdivided and unsubdivided Maasai pastoral lands (ranches) in semiarid southern Kenya. We found no significant difference in livestock densities on the two ranches but there was a significantly higher wildlife density on the unsubdivided ranch, in both dry and wet seasons. Nonetheless, the unsubdivided ranch still had a higher percentage of grass biomass and ground cover and lower grazing pressure than the subdivided ranch. Distribution of homesteads (bomas) was mostly random on the subdivided ranch, with little area unaffected by human settlement. On the contrary, the unsubdivided ranch had a highly clumped boma distribution pattern, resulting in much of the land being relatively far from permanent human settlement. We show that the regular distribution and permanence of settlements following subdivision and sedentarization greatly reduces wildlife populations both through direct displacement and a reduction of forage. Relative to mobile pastoralism on open rangelands, sedentarization leads to reduced seasonal movements of livestock, lowered grass biomass, and slower grass recovery after very dry periods. This study points to the need to maintain mobile, large-scale herd movements to avoid the heavy impact on grasslands associated with sedentarization of pastoral settlement and herds.