• Economic implications of off-stream water developments to improve riparian grazing

      Stillings, A. M.; Tanaka, J. A.; Rimbey, N. R.; DelCurto, T.; Momont, P. A.; Porath, M. L. (Society for Range Management, 2003-09-01)
      Livestock grazing in riparian areas is an important management issue on both private and public lands. A study was initiated in northeastern Oregon to evaluate the economic and ecological impacts of different cattle management practices on riparian areas. The effect of off-stream water and salt on livestock distribution and subsequent impact on riparian use, water quality, and livestock production was evaluated. A multi-period bioeconomic linear programming model is used to evaluate the long-term economic feasibility of this management practice with a riparian utilization restriction of 35% for a 300 cow-calf operation. The utilization restriction resulted in economically optimal herd sizes 10% smaller than the baseline herd size. With the management practice, cattle were distributed more evenly, consumed more upland forage before maximum riparian utilization was reached, and gained more weight. The economic impacts of these outcomes were increased with expected annual net returns to the ranch for the project ranging between 4,500 and 11,000 depending on cattle prices and precipitation levels.
    • Initial beaked hazel growth responses following protection from ungulate browsing

      Best, J. N.; Bork, E. W.; Cool, N. L. (Society for Range Management, 2003-09-01)
      Beaked hazel (Corylus cornuta Marsh) dominates the understory of many Boreal Mixedwood forests in central Alberta including those in Elk Island National Park, where this species demonstrates a high tolerance to browsing. This research quantified changes in beaked hazel stem morphology (total twig length and number) and leaf and twig biomass of current annual growth, both inside and outside 4 newly established exclosures during the growing seasons of 1999 and 2000. At 2 sites, leaf and twig current annual growth of beaked hazel shrubs recently protected from herbivory increased significantly (P < 0.05) by 85 to 114% relative to that of browsed shrubs. At another site, the removal of browsing changed the morphology of beaked hazel shrub growth (P < 0.05), with protected shrubs producing 26% more twigs that were shorter in aggregate length by 27%. The final site exhibited no significant (P > 0.05) changes in current annual growth at the individual shrub stem level, potentially due to intense intra-specific competition. These results indicate that at several locations in the Park, the recent history of intense browsing appears to be limiting the annual growth of beaked hazel, including browse production. Despite the general increase in growth of individual beaked hazel stems, however, no changes in production were evident at the community level (P > 0.05) with the removal of browsing after 2 years. Protection from browsing did increase average beaked hazel height by 40% over the same period.
    • Characterization of diversity among 3 squirreltail taxa

      Jones, T. A.; Nielson, D. C.; Arredondo, J. T.; Redinbaugh, M. G. (Society for Range Management, 2003-09-01)
      Squirreltail (Elymus elymoides, E. multisetus) is a complex of 5 taxa whose systematic interrelationships are uncertain. Our objectives were to determine whether the 3 taxa studied here, Elymus elymoides ssp. elymoides, E. elymoides ssp. brevifolius, and E. multisetus, can be distinguished by several ecological and physiological traits and whether geographical origin is correlated with these traits across accessions within taxa. A multivariate principal component analysis of materials collected in the 10 contiguous western states successfully distinguished taxa, but no pair of the 3 taxa appeared to be more ecologically similar than any other pair. Elymus elymoides ssp. elymoides, which prevails in the semi-arid cold desert, was shortest and exhibited the lowest total plant dry-matter, earliest phenology, and lowest seed mass. Elymus elymoides ssp. brevifolius, which prevails in the Rocky Mountains, exhibited slowest emergence, highest specific root length, lowest nitrate reductase activity, and lowest root-to-shoot ratio. Elymus multisetus, which is most common in areas with relatively warm springs, exhibited fastest emergence (particularly from deep seeding), greatest root length, and greatest root-to-shoot ratio. Elymus elymoides ssp. brevifolius accessions clustered into 3 groups: late-maturing high-seed mass accessions originating in Colorado, New Mexico, and Arizona (Group A), early-maturing low-seed mass accessions originating in Colorado and Utah (Group B), and intermediate-maturing low-seed mass accessions originating in the Snake River Plain of southern Idaho (Group C). The ecologically distinct subspecies and groups within ssp. brevifolius are indicative of the highly ecotypic nature of the squirreltails, suggesting that restoration practitioners should match site with genetically and ecologically appropriate plant material for these species.
    • Comparison of 2 techniques for monitoring vegetation on military lands

      Prosser, C. W.; Skinner, K. M.; Sedivec, K. K. (Society for Range Management, 2003-09-01)
      The U.S. Army is responsible for preparing a well-trained combat force while maintaining the ecological diversity and integrity of the lands it manages. The ability to efficiently collect data that accurately capture plant community diversity and percent composition is imperative to proper monitoring and land management of military lands. To ensure that the dual goals of military training and land stewardship are met on an army-wide basis, the U.S. Army Land Condition-Trend Analysis (LCTA) Program was developed. The LCTA Program specifies the Army's standard methodology for the collection, analysis, and reporting of natural resource data used for land inventory and monitoring. However, the LCTA sampling technique was developed in Colorado and Texas and little information is available on whether these methods are suitable for vegetation inventory and monitoring in other grassland ecosystems. This study compares LCTA measures of species richness and composition with quadrat sampling in the transitional area between the tall- and mixed-grass prairies of Camp Gilbert C. Grafton (South Unit) in North Dakota. Species richness was 67% higher when sampling with quadrats than using the LCTA technique, suggesting that LCTA samples did not detect a third of the plants present. Compared with the quadrat technique, LCTA samples overestimated the community contribution of Bouteloua gracilis (H.B.K.) Lag. ex Steud. (blue grama) and underestimated proportions of forbs and sedges. Moreover, LCTA samples are labor intensive and time consuming to collect. Other sampling methods may be needed to detect shifts in species composition towards a less desirable plant community or decreases in biodiversity that may be due to land-use. Thus, it is important for Camp Gilbert C. Grafton (South Unit) to re-evaluate the current standard methodology for monitoring the impacts of military training. Since military installations are located in many different ecosystems, it may be necessary for other installations to likewise examine the usefulness of LCTA techniques in their ecosystems.
    • Research observation: Hydrolyzable and condensed tannins in plants of northwest Spain forests

      González-Hernández, M. P.; Karchesy, J.; Starkey, E. E. (Society for Range Management, 2003-09-01)
      Tannins are secondary metabolites that may influence feeding by mammals on plants. We analyzed hydrolyzable and condensed tannins in 30 plant species consumed by livestock and deer, as a preliminary attempt to study their possible implications on browsing and grazing in forest ecosystems. Heathers (Ericaceae) and plants of the Rose (Rosaceae) family had tannins, while forbs, grasses and shrubs other than the heathers did not show astringency properties. We found the highest tannin content of all the species in Rubus sp., with the highest value around 180 mg TAE/g dry weight in spring. Potentilla erecta, Alnus glutinosa and Quercus robur were next with 57 to 44 mg TAE/g dw. Total tannins in heathers ranged from 22 to 36 mg TAE/g dw. Levels of condensed tannins were higher than hydrolyzable for most of the species. Only Betula alba, Calluna vulgaris, Pteridium aquilinum and Vaccinium myrtillus had 100% hydrolyzable tannins. Tannin content of the species changed seasonally with highest values during the growing season, corresponding to late winter or early spring, depending on the species.
    • Observation: Leafy spurge control in western prairie fringed orchid habitat

      Kirby, D. R.; Lym, R. G.; Sterling, J. J.; Sieg, C. H. (Society for Range Management, 2003-09-01)
      The western prairie fringed orchid (Platanthera praeclara Sheviak and Bowles) is a threatened species of the tallgrass prairie. Invasion by leafy spurge (Euphorbia esula L.) is a serious threat to western prairie fringed orchid habitat. The objectives of this study were to develop a herbicide treatment to control leafy spurge while sustaining western prairie fringed orchid populations and to evaluate the soil seedbank composition of leafy spurge-infested sites to guide long-term management strategies. Quinclorac (3,7-dichloro-8-quinolinecarboxylic acid), imazapic {(+/-)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2=yl]-5-methyl-3-pyridinecarboxylic acid}, and glyphosate [N-(phosphonomethyl)glycine] plus 2,4-D (2,4-dichlorophenoxy acetic acid) were applied in the fall for 2 consecutive years, and changes in leafy spurge cover, density, yield, and herbaceous yield were assessed. In a separate study, quinclorac, imazapic, and glyphosate plus 2,4-D were each fall-applied to 12 western prairie fringed orchids and assessed for reoccurrence and density of orchids 1-year after treatment. Quinclorac and imazapic, but not glyphosate plus 2,4-D, reduced leafy spurge cover, density, and yield without causing deleterious effects to associated native herbaceous cover and yields. Western prairie fringed orchid reoccurrence and density were unaffected by any herbicide 1 year after treatment. Soil cores were removed in spring and fall following the first year herbicide treatment, washed and placed in trays. Seedlings were allowed to germinate for 16 weeks in the greenhouse. Over 50 plant species were identified in the soil seedbank, of which approximately 60% were early seral species indicative of disturbance. Given the dominance of leafy spurge in the seed bank, a long-term management program to control this noxious species is warranted. Although these results are promising, longer-term studies need be conducted to ensure that repeated herbicide treatments do not harm the western prairie fringed orchid.
    • Non-selective grazing impacts on soil-properties of the Nama Karoo

      Beukes, P. C.; Cowling, R. M. (Society for Range Management, 2003-09-01)
      Non-selective grazing (NSG) is a relatively novel way of farming livestock in the Nama Karoo of South Africa. Our key question was how heavy grazing under this high-intensity, low-frequency grazing system would impact on certain soil properties. The study was designed to compare the impacts of NSG (treatment) with no grazing (control) in terms of: (1) amount of soil organic carbon (OC); (2) soil microbial respiration rates; (3) soil stability and infiltration properties. The treatment significantly lowered the amount of OC in the topsoil. Microbial respiration rates corresponded with the fertile patch matrix in both treatment and control with significantly higher respiration rates measured under plants compared to open, unvegetated areas. Respiration rates in treatment open areas were significantly higher than in control open areas. There was a trend (P < 0.1) for higher aggregate stability, final infiltration rate and cumulative infiltration for treatment open soils compared to controls during an initial rain event of 44 mm hour-1 in a rainfall simulator. During a second rain event on sealed soils only aggregate stability was significantly higher for treatment compared to control soils. We conclude that the short-duration, low-frequency, intensive herbivory by livestock under the non-selective grazing system resulted in a more active microbial community, which turned over organic matter more rapidly and led to higher soil stability and infiltration capacity of open, unvegetated soils. We present this as an example of conditions where herding by high densities of large herbivores can have positive impacts on soil quality.
    • Water, nitrogen and ploidy effects on Russian wildrye mineral concentrations

      Karn, J. F.; Frank, A. B.; Berdahl, J. D.; Poland, W. W. (Society for Range Management, 2003-09-01)
      High quality forage for spring and autumn grazing can be obtained from Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski], a cool-season bunchgrass. However, little is known about mineral concentrations critical to livestock production, especially in the relatively new tetraploid plants. A knowledge of plant mineral concentrations and how they can be manipulated to more nearly meet animal requirements is necessary to optimize animal production. A study was undertaken to determine the extent that concentrations of critical minerals in leaf and stem tissue of Russian wildrye were affected by ploidy level, growing-season water (50 and 150% of average), and N fertilizer (10 and 134 kg N ha-1). Plants were sampled at vegetative, boot, anthesis, and anthesis plus 10-day stages of maturity in 1994, 1995, and 1996. Ploidy level resulted in small but significant differences in some mineral concentrations, with diploid plants usually having higher levels. An exception was P in stem tissue. This finding indicates that in breeding and selection for other traits, forage quality was not adversely affected. Growing-season water level also had minimal effects on mineral concentrations, except for P which was enhanced (P < 0.05) by greater amounts of soil water. Fertilizer N increased forage levels of Ca, K, Cu, and Zn, and decreased levels of P. Higher concentrations of K are not desirable, because they increase the possibility of a grass tetany problem. Advancing plant maturity caused a decrease in P and Zn concentrations, but Ca and Mg in leaf tissue increased as plants matured. These results suggest that concentrations of P, Ca, Mg, and Cu were marginal for high producing cattle at some stages of maturity, but we found the effects of nitrogen and growing-season water did not result in leaf and stem mineral concentration changes that would adversely affect the safety and nutritive quality of Russian wildrye.
    • Wyoming big sagebrush seed production from mined and unmined rangelands

      Booth, D. T.; Bai, Y.; Roos, E. E. (Society for Range Management, 2003-09-01)
      Wyoming Coal Rules and Regulations require shrubs be returned to mined land and that revegetation "...be self renewing." We evaluated seed production and seed quality of Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis (Beetle Young)) by measuring the effect of mining, herbivory, and environmental modification on seed production at 5 sites on the Dave Johnston Coal Mine near Glenrock, Wyo. Mined-land stands ranged in age from 5 to >20 years. Single sagebrush plants on mined, and adjacent unmined land were treated by: (1) fabric mulch around the base, (2) windbreak on the north and west, (3) both mulch and windbreak, and (4) neither windbreak nor mulch. Plants were fenced and compared with unfenced, untreated, neighboring plants. Seeds were harvested for 3 years and data were collected on seed-stalk numbers, bulk weight of seeds produced, and seed quality. Fenced mined-land plants produced several times more seeds than fenced plants on adjacent unmined land. There was no difference in seed quality. Treatments to modify the plant environment resulted in some benefits but fencing had a greater effect on seed-quality parameters than did planned treatments. We conclude the sagebrush seed-production potential on reclaimed lands such as those of the Dave Johnston Coal Mine is equal to, and often several times greater than that of adjacent unmined lands. However, browsing by wild ungulates can eliminate the mined-land yield advantage.
    • Defoliation effects on reproductive biomass: importance of scale and timing

      Anderson, M. T.; Frank, D. A. (Society for Range Management, 2003-09-01)
      Community-level (per unit area) and individual tiller reproductive biomass inside and outside of long-term exclosures on the northern winter range of Yellowstone National Park, USA were compared. Grazed areas had twice the number of reproductive tillers m-2 (186 compared to 88 tillers m-2), and greater total reproductive biomass m-2 than ungrazed plots (13 compared to 7 g m-2). In contrast, seed number tiller-1 was greater for grasses in exclosures. Because of these offsetting responses, seed production (nom-2) was unaffected by herbivores. On an area basis, grazed grasses allocated proportionally more biomass to reproduction (reproductive biomass/aboveground biomass) than ungrazed grasses. We propose that altered plant demography and morphology following defoliation explain how grazers might increase the allocation of biomass to reproduction in Yellowstone grasslands. To understand these results in light of ecological and agronomic studies, we reviewed literature from 118 sources that reported the effects of defoliation on the production of reproductive biomass. The review suggested that the results of herbivory or defoliation on plant reproductive biomass depended on the scale of measurement (community vs. plant). In addition, timing of grazing or defoliation emerged as a key factor that determined whether sexual reproduction was inhibited. Like the early season grazing that is typical of Yellowstone's northern winter range, studies often showed that early season defoliation stimulated production of community-level reproductive biomass. Our results rectify disagreements in the literature that ultimately derive from differences in either timing of defoliation or measurement scale.
    • Observations of cattle use of prairie dog towns

      Guenther, D. A.; Detling, J. K. (Society for Range Management, 2003-09-01)
      We investigated the use of prairie dog towns by cattle (Bos taurus) on the shortgrass steppe of northeastern Colorado by conducting surveys of cattle and vegetation from June to August 1999. Cattle presence and behavior were recorded 3 times a week during driving surveys of 15 black-tailed prairie dog (Cynomys ludovicianus) towns. A subset of 3 pastures with prairie dog towns was intensively surveyed twice weekly wherein the habitat and activity of a randomly chosen focal animal was recorded every 6 minutes for 3.5 hours. Bite and step counts of other individuals were recorded for 5-minute intervals. Vegetation height and cover data were collected monthly on each of 6 habitats. Results from driving surveys and intensively surveyed pastures were similar; cattle neither significantly preferred nor avoided prairie dog towns. Bare ground cover on prairie dog towns did not significantly differ from most other habitats, but vegetation on prairie dog towns was significantly shorter on (mean = 6.7 cm) than that off (mean = 11.9 cm) prairie dog towns. Nevertheless, foraging observations indicated that there was no significant difference between cattle foraging rates on swales (70.9 bites/min) and prairie dog towns (69.5 bites/min). Thus, cattle on the shortgrass steppe appear to use prairie dog towns in proportion to their availability and, while there, they graze as intensively as they do on habitats not inhabited by prairie dogs.
    • Economics of sale weight, herd size, supplementation, and seasonal factors

      Tronstad, R.; Teegerstrom, T. (Society for Range Management, 2003-09-01)
      A growth function for range calves is estimated using a polynomial function of calf age that accounts for weather variation, sex, prior calf weights relative to a norm, and a compensatory gain factor. Data on rainfall plus calf weights at birth and when calves were roughly 3, 8, 12, and 20 months of age are used to estimate the growth function. This function is then used to determine the economic trade-off between herd size and calf sale weights, for both spring and fall sale dates. In addition, the profitability of feeding supplement is evaluated by increasing the rate of gain beyond that projected by the the polynomial age growth function for southeast and central Arizona grazing environments when forage and nutrients are limited. Using prices from 1980 to 1998, results indicate that the most profitable herd mix, sale date, and feeding protocol for the southeast Arizona region is 204 kg calves with no supplemental feeding and sales occurring in May. Supplemental feeding and sales occurring at 250 kg head-1 in May is the most profitable herd mix for the central Arizona region. More favorable average daily gain rates for May sales from the central versus southeast is why supplemental feeding is marginally better for the central region than feeding no supplement.
    • Remote sensing for cover change assessment in southeast Arizona

      Wallace, O. C.; Qi, J.; Heilma, P.; Marsett, R. C. (Society for Range Management, 2003-09-01)
      Understanding landscape conversion is vital for assessing the impacts of ecological and anthropogenic disturbances at regional and global scales. Since rangelands cover nearly half of the global land surface, and because a large part of rangelands is located in semi-arid ecosystems, they serve as critical land cover types for determining regional biodiversity, global biogeochemical cycles, and energy and gas fluxes. For such vast ecosystems, satellite imagery is often used to inventory biophysical materials and man-made features on Earth's surface. The large area coverage and frequent acquisition cycle of remotely sensed satellite images make earth observation data useful for monitoring land conversion rates at different spatial scales. Remote sensing could also be used for temporal assessment of semi-arid ecosystems by providing complimentary sets of rangeland health indicators. In this paper, temporal satellite data from multiple sensors were examined to quantify land use and land cover change, and to relate spatial configuration and composition to landscape structure and pattern. The findings were correlated with the role of fire to better understand ecological functionality and human and/or natural activities that are generating environmental stressors in a rapidly developing, semi-urban census division located in southeastern Arizona. Results indicate that conversion of a fire-suppressed native grassland area has 2 spatial components; in the rural areas, grass is being eliminated by increasingly homogeneous shrub and mesquite-dominated areas, whereas in the urban and suburban areas, grass as well shrubs and mesquite are being eliminated by a fragmented and expanding built landscape.
    • Spatial and temporal patterns of cattle feces deposition on rangeland

      Tate, K. W.; Atwill, E. R.; McDougald, N. K.; George, M. R. (Society for Range Management, 2003-09-01)
      The objective of this study was to identify and model environmental and management factors associated with cattle feces deposition patterns across annual rangeland watersheds in the Sierra Nevada foothills. Daily cattle fecal load accumulation rates were calculated from seasonal fecal loads measured biannually on 40 m2 permanent transects distributed across a 150.5 ha pasture in Madera County, Calif. during the 4 year period from 1995 through 1998. Associations between daily fecal load per season, livestock management, and environmental factors measured for each transect were determined using a linear mixed effects model. Cattle feces distribution patterns were significantly associated with location of livestock attractants, slope percentage, slope aspect, hydrologic position, and season. Transects located in livestock concentration areas experienced a significantly higher daily fecal load compared to transects outside of these concentration areas (P < 0.001). Percent slope was negatively associated with daily fecal load, but this association had a significant interaction with slope aspect (P = 0.02). Daily fecal load was significantly lower during the wet season compared to the dry season (P = 0.002). Daily fecal loading rates across hydrologic positions were dependent upon season. Our results illustrate the opportunities to reduce the risk of water quality contamination by strategic placement of cattle attractants, and provide a means to predict cattle feces deposition based upon inherent watershed characteristics and management factors.
    • Saltcedar recovery after herbicide-burn and mechanical clearing practices

      McDaniel, K. C.; Taylor, J. P. (Society for Range Management, 2003-09-01)
      Mechanical clearing and herbicide-burn treatments were compared to evaluate saltcedar (Tamarix chinensis Lour.) control and recovery along the Rio Grande on the Bosque del Apache National Wildlife Refuge, Socorro, N.M. The herbicide-burn treatment included an aerial application of imazapyr (+)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-pyridinecarboxylic acid] + glyphosate [N-(phosphono-methyl)glycine] (0.6 + 0.6 kg ai ha-1 rate) followed 3 years later by a prescription broadcast fire that eliminated > 99% of the standing dead stems. Six years after initial herbicide application, saltcedar mortality was 93%. Mechanical saltcedar clearing entailed removing aerial (trunks and stems) growth by blading, stacking and burning debris, followed by removal of underground plant portions (root crowns) by plowing, raking, and burning stacked material. Saltcedar mortality 3 years after mechanical clearing averaged 70%, which was deemed unsatisfactory. Thus, root plowing, raking, and pile burning was repeated. Three years later, after the second mechanical clearing, saltcedar mortality was 97%. Costs for the herbicide-burn treatment averaged 283 ha-1, whereas mechanical control costs were 884 ha-1 for the first surface and root clearing and an additional 585 ha-1 for the second root clearing. Riparian managers should consider environmental conditions and restoration strategies prior to selecting a saltcedar control approach. Although control costs were significantly lower for the herbicide-burn treatment compared to mechanical clearing in this study, the choice of methods should always consider alternative control strategies for saltcedar. Frequently, combinations of methods result in more efficient, cost-effective results.
    • Mechanism by which ammonium fertilizers kill tall larkspur

      Ralphs, M. H.; Woolsey, L.; Bowns, J. E. (Society for Range Management, 2003-09-01)
      Environmental concerns of using pesticides on public lands have greatly reduced the use of herbicides to control tall larkspur (Delphinium barbeyi Huth). An alternative method of control used ammonium sulfate placed at the base of individual plants. The objective of this study was to determine the mechanism by which fertilizers kill tall larkspur. We hypothesize the salt from the fertilizers kill the plant. We applied ammonium sulfate, ammonium nitrate and sodium chloride at equivalent salt concentrations and evaluated their effect on tall larkspur plants. There was no difference among treatments in larkspur mortality (P > 0.10). The high rate of all treatments (ammonium sulfate 400 g plant-1, ammonium nitrate 264 g, and sodium chloride 180 g, at equivalent salt concentrations) killed greater than 70% of larkspur plants. We conclude the salt in fertilizers kills tall larkspur, not the nitrogen. It is necessary to place the fertilizer or salt at the base of the plant to concentrate it in the root zone, rather than broadcast it. At the end of the study, bare areas left around the dead tall larkspur plants were only 13% of the original size of the tall larkspur plants at Yampa Colo. and Cedar Ut., and 46% at Emery Ut., indicating the surrounding vegetation was quickly filling in the vacated space. The relative cost of materials per plant for both ammonium sulfate and nitrate was 12.9 cents, and 2.6 cents for salt.
    • Clubmoss effects on plant water status and standing crop

      Colberg, T. J.; Romo, J. T. (Society for Range Management, 2003-09-01)
      Clubmoss (Selaginella densa Rydb.), a low growing, vascular cryptogam forms carpet-like mats that cover up to 80% of the ground in the Northern Mixed Prairie. Many range managers believe clubmoss competes with grasses for water or intercepts precipitation and negatively affects plant water relations and productivity. The objective of these studies was to test the hypothesis that precipitation has greater effects on leaf xylem water potentials (Leafxwp) and plant productivity than clubmoss. Studies examined the effects of clubmoss on Leafxwp of Junegrass (Koeleria cristata Pers.) and blue grama (Bouteloua gracilis [HBK.] Lag.), and productivity of forbs and graminoids by: 1) irrigating or reducing precipitation relative to natural precipitation; 2) removing clubmoss relative to clubmoss present, and; 3) irrigating with 0.0 to 25 mm of water when clubmoss was present or removed. Leafxwp of Junegrass and blue grama were unaffected by clubmoss through the growing season (P = 0.33), but Leafxwp were lowest (P or = 0.05) when precipitation was reduced relative to the control and when irrigating. Standing crop of forbs was similar in the control and clubmoss removal treatment (P = 0.22) and among precipitation treatments (P = 0.13), averaging 28 g m-2 (SE = 2.2). Graminoid standing crop was unaffected by clubmoss (P = 0.35) and was greatest (P = 0.02) when irrigated (74 g m-2), intermediate in the control (53 g m-2), and least (36 g m-2) with reduced precipitation (SE = 8.7). Clubmoss did not affect (P = 0.70) total standing crop; total standing crop declined from 102 g m-2 when irrigated to 76 g m-2 in the control, and 69 g m-2 (SE = 9.0) with reduced precipitation. Clubmoss had no influence (P = 0.06) on Leafxwp when irrigated with 0 to 25 mm of water. The decline in Leafxwp from 1 to 7 days after irrigation was the product of the interacting effects of the amount of water applied and days after irrigation (P = 0.03). More than 10 mm of irrigation water were required to impart a significant increase (P < 0.05) in Leafxwp. The hypothesis that clubmoss reduces productivity of associated plants in the Northern Mixed Prairie by increasing water stress is rejected. Similarly clubmoss does not reduce plant water stress or increase production. Precipitation amounts overshadow any effects clubmoss has on Leafxwp and plant production. Range managers in the Northern Mixed Prairie may want to consider maximizing the effectiveness of precipitation in this water-limited environment instead of focusing on reducing or attempting to eliminate clubmoss.
    • Seed germination of willow species from a desert riparian ecosystem

      Young, J. A.; Clements, C. D. (Society for Range Management, 2003-09-01)
      The restoration of riverine riparian areas following mechanical, herbicidal, or biological control of the invasive species tamarisk (Tamarix ramosissima Ledeb.) is a major issue in the western United States. Recruitment of seedlings of native woody species is necessary in these restoration efforts. Species of willow (Salix) are often considered essential in these efforts. We studied the germination of seeds of tree willow (Salix lutea Nutt.) and coyote willow (S. exigua Nutt.) at a wide range of constant or alternating incubation temperatures. Seeds were collected from native stands in the delta of the Walker River in western Nevada over a 3 year period. Seed germination was very similar for both species. On 2 of the 3 years of testing the seeds had 100% germination at some incubation temperatures and some germination over almost all of the 55 temperature regimes used in the experiments. A late frost in May of 2000 markedly reduced total germination of both species, but did not greatly restrict the temperature regimes where some germination occurred. Optimum germination, defined as that not lower than the maximum observed minus one half the confidence interval at the 0.01 level of probability, occurred over a very wide range of temperatures, but for tree willow only the temperature regimes 15/25 (15 degrees C for 12 hours and 25 degrees C for 8 hours in each 24 hour period) and 15/30 degrees C always supported optimum germination. No temperature regime always supported optimum germination of coyote willow seeds, but the most frequent optima tended to be at lower temperatures than for tree willow. Because of the similarity in germination responses and overlapping phenology, seeds of these 2 species probably compete for germination safesites.
    • Bowen ratio versus canopy chamber CO2 fluxes on sagebrush rangeland

      Johnson, D. A.; Saliendra, N. Z.; Walker, J. W.; Hendrickson, J. R. (Society for Range Management, 2003-09-01)
      Because of their expansiveness, sagebrush (Artemisia spp.)-steppe rangelands could contribute significantly to the global carbon budget. However, it is important to determine if there are differences between methods for determining CO2 fluxes on these rangelands. The objective of this study was to compare the Bowen ratio-energy balance and canopy chamber techniques for measuring CO2 fluxes in a sagebrush-steppe ecosystem. A Bowen ratio-energy balance system was installed at a sagebrush-steppe site near Dubois, Ida., U.S.A to continuously measure the vertical gradients of air temperature, water vapor, and CO2 concentration in conjunction with associated micrometeorological characteristics. The canopy chamber technique, which employed a 1-m2 (1,020 liter) clear plexiglass/plastic film chamber in combination with a portable gas exchange system, was used periodically during May through August across 4 years (1996-1999) to obtain instantaneous measurements of CO2 fluxes across 3 replicate blocks during a 2-min. measurement period. For the same measurement dates and times across the 4 years of study, CO2 fluxes ranged from -0.22 to 0.55 mg m-2 sec-1 for the Bowen ratio-energy balance technique and from -0.18 to 0.48 mg m-2 sec-1 for the canopy chamber technique. Estimates of CO2 fluxes by the 2 techniques were not statistically different (P > 0.05) for the early (May) and mid-season (June to mid-July) portions of the growing season; however, fluxes measured by the 2 techniques were significantly different (P 0.05) for the late-season period (late-July to late-August). Despite this difference during the hot-dry, late-season period, flux estimates from the 2 techniques were significantly and positively correlated during the early (r2 = 0.71), mid- (r2 = 0.88), and late- (r2 = 0.72) season periods. Thus, both techniques showed similar patterns of CO2 fluxes at our sagebrush-steppe study site across 4 years of study, although caution should be used when the canopy chamber technique is used during hot, dry conditions.