• A viewpoint on Indian ricegrass research: Its present status and future prospects

      Jones, T. A. (Society for Range Management, 1990-09-01)
      Indian ricegrass (Orysopsis hymenoides (Roem. & Schult.) Ricker) is adapted to sandy arid areas of much of the western USA and is a highly desirable species on winter range sites. Seed is typically highly dormant. Mechanical dormancy has been reduced by mechanical and sulfuric acid scarification, and physiological dormancy has been reduced with stratification, giberellic acid, and kinetin. A better understanding of the relationship between mechanical and physiological dormancy may lead to a practical procedure for breaking dormancy in harvested seed. Alternatively, a better understanding of environmental factors on seed production may lead to production of already low dormancy seed. Establishment success will also depend on development of appropriate seedbed management practices for various soils. Reduction of the currently large shattering losses would have a favorable impact on the economics of Indian ricegrass seed production. An interdisciplinary approach including seed physiology, seedbed ecology, seed technology, and plant breeding can potentially solve these problems. The potential of seeding Indian ricegrass for improving rangelands can only be realised after low dormancy seed becomes available, appropriate seedbed management practices are developed, and seed shattering losses are reduced.
    • Clipping and long-term grazing effects on biomass and carbohydrate reserves of Indian ricegrass

      Orodho, A. B.; Trlica, M. J. (Society for Range Management, 1990-01-01)
      Long-term heavy grazing had little effect on root and crown biomass of Indian ricegrass (Oryzopsis hymenoides [Roem. and Schult.] Ricker), nor did it significantly affect the total nonstructural carbohydrate (TNC) reserve levels or the seasonal cycle of reserves in this grass. Fifty years of protection from livestock use had not resulted in ecotypic differentiation in Indian ricegrass for these variables. Clipping reduced crown biomass more than root biomass and removal of 90% of the aboveground biomass resulted in more than a 50% reduction in crown biomass and reserve carbohydrate pool. Two commercial strains of Indian ricegrass ('Nezpar' and 'Paloma') were compared with native Chaco Canyon strains in a uniform garden study. The Nezpar strain was superior to Paloma and the Chaco Canyon strains in production of crown biomass and TNC reserves at the more mesic garden site. The native strains from the more arid Chaco Canyon site were superior to both cultivated strains in production of roots. The native Chaco Canyon strains were little affected by clipping and have promising genetic potential for tolerance of drought and heavy grazing.
    • Genecology and Seed Zones for Indian Ricegrass Collected in the Southwestern United States

      Johnson, R. C.; Cashman, M. J.; Vance-Borland, K. (Society for Range Management, 2012-09-01)
      Indian ricegrass (Achnatherum hymenoides [Roemer J.A. Schultes] Barkworth) is a widely distributed, highly desirable native species in desert ecosystems in the western United States. Yet there are no studies linking genetic variation in Indian ricegrass with climate across major areas of its natural distribution. In this study, seeds from 106 collection locations from the southwestern United States were established in common gardens and four phenological traits (Phen; such as blooming date), six production traits (Pro; such as dry weight), and eight morphology traits (Morph; such as leaf dimensions) were measured in 2007 and 2008. Analyses of variance revealed that all basic garden traits differed among source locations (P<0.01), indicating widespread genetic variation. Within Phen, Pro, and Morph categories, canonical correlation was completed between basic garden traits and source location temperature and precipitation. This resulted in six significant (P<0.01) canonical variates (Phen 1, Pro 1 and 2, and Morph 1, 2, and 3) representing each category of traits. Linear correlations (r> +/- 0.25, P<0.01)consistently linked monthly temperature at collection locations with Phen 1, Pro 1, and Morph 1. For precipitation, however, correlations were more dependent on month, with the strongest correlations during the spring developmental period. Using regression models between traits and climate, a map with 12 seed zones was developed representing much of the southwestern United States. This generally distinguished genetic variation between cooler and warmer regions, usually separating more northern, higher elevation areas from more southern, lower elevation areas. The correspondence between climate and genetic variation suggested climate-driven differences in natural selection, likely leading to adaptation. The seed zone map is recommended to guide and broaden germplasm collection and utilization for Indian ricegrass restoration./Indian ricegrass (Achnatherum hymenoides [Roemer & J.A. Schultes] Barkworth) presenta una amplia distribución, es una especie altamente deseable en los ecosistemas desérticos en el oeste de los estados Unidos. Sin embargo, áun no hay ning ún estudio que relacione las variaciones genéticas de Indian ricegrass con el clima a través de las áreas de su distribución natural. Eneste estudio, semillas de 106 localidades del suroeste de Estados Unidos fueron colectadas y establecidas en jardines comunes ycon cuatro características fenológicas (Phen; como día de floración), seis características productivas (Pro; como peso seco), yocho características morfológicas (Morph; como dimensión de la hoja) fueron medidas en 2007 and 2008. Análisis de varianza revelaron que todas las características básicas fueron diferentes entre las localidades de origen (P<0.01), indicando una amplia variación genética. Dentro de las categorías Phen, Pro, y Morph una correlación crónica fue completada entre las características básicas de jardín y fuente de origen, temperatura y precipitación. Esto resultó en seis variables crónicas significativas (P<0.01; Phen 1, Pro 1 and 2, and Morph 1, 2, and 3) representando cada categoría de las características. Correlaciones lineales (r> +/- 0.25, P<0.01) unieron consistentemente cada mes con la temperatura en cada colección y locación con Phen 1, Pro 1,and Morph 1. Para precipitación, sin embargo, las correlaciones fueron más dependientes de la variable mes, con las relacion es más fuerte en el periodo de desarrollo de primavera. Usando los modelos de regresión entre las características climáticas un mapa con 12 zonas de colección de semillas fue desarrollado representando la mayor parte del suroeste de Estados Unidos. Este mapa en general distinguió la variación genética entre las regiones más frías y las más cálidas, separando las localizadas más hacia el norte, con elevaciones más altas de las áreas mas hacia el sur con elevaciones más bajas. La correspondencia entre lavariación genética y climática sugiere que el clima conduce a diferencias en selección natural, probablemente llevando a la adaptación. El mapa con las zonas de semillas se recomienda para guiar y ampliar la recolección de germoplasma y su utilización para la restauración de Indian ricegrass.
    • Germination of prechilled mechanically scarified and unscarified Indian ricegrass seed

      Jones, T. A.; Nielson, D. C. (Society for Range Management, 1992-03-01)
      Seed dormancy typically limits stand establishment of Indian ricegrass [Oryzopsis hymenoides (Roem. and Schult.) Ricker]. The mechanical and physiological mechanisms that contribute to dormancy must both be overcome before germination. Our objective was to study potential interactions between the breaking of mechanical dormancy and breaking of physiological dormancy. Germination of 13 seedlots of 'Nezpar', 'Paloma', and PI 478833, ranging in age from 4 to 19 years and in viability from 67 to 96%, was tested. Seed was scarified with an air-gun scarifier to reduce mechanical dormancy approximately 2 1/2 years before testing, or left unscarified. Over 77% of seeds remained intact following scarification. Seed was moved from 5 degrees C to room temperature 1 year before testing to reduce physiological dormancy, or left refrigerated. Seed was also prechilled for 3 weeks at 5 degrees C to reduce physiological dormancy, or left nonprechilled. Germination was determined after 2-week and 3-week 15 degrees C germination periods for prechilled and nonprechilled treatments, respectively. Scarification improved germination of undamaged seed in 12 of the 13 seedlots from 9.5 to 29.7%. Prechilling improved germination of 10 of the 13 seedlots from 8.0 to 22.8%. Room-temperature storage improved germination of 5 seedlots from 4.9 to 12.8%. In 9 seedlots prechilling improved germination of scarified seed 13.1% less than unscarified seed. In 4 seedlots room-temperature storage improved germination of scarified seed 6.5% less than unscarified seed. Depending on the vigor of the seedlot, such effects may be related to a greater reduction of either physiological dormancy or viability in scarified seed than in unscarified seed.
    • Grazing Intensity and Forage Quality on the Arizona Strip

      Meen, Art (Society for Range Management, 2000-12-01)
    • High seed retention of Indian ricegrass PI 478833

      Jones, T. A.; Nielson, D. C. (Society for Range Management, 1992-01-01)
      Reduction of Indian ricegrass [Oryzopsis hymenoides (Roem. and Schult.) Ricker] seed shattering losses is of interest because it would result in more economical seed harvest. PI 478833, a genotype with glumes closely surrounding the seed, was compared with 'Paloma' for glume pair angle and seed retention parameters. Our objective was to determine its suitability as a source of seed shattering resistance for genetic transfer to an Indian ricegrass variety. Regrowth from a 19 June 1989 clipping of 'Paloma' and PI 478833 with and without supplemental irrigation was evaluated in late July. Irrigation did not affect glume pair angle or percentage intact seed (number of seeds/number of mature florets). Though Paloma and PI 478833 glume pair angles averaged 66% and 44%, respectively, percentage intact seed was 13% higher for Paloma than PI 478833 because Paloma's more indeterminate flowering pattern allowed it to replace its shattered florets more quickly than PI 478833. In a second experiment we observed individual florets of Paloma and PI 478833 for 7 weeks starting 5 September 1989. Floret opening occurred mostly during daylight hours and on warm days. Shattering events occurred when a storm followed a period of floret opening. Duration of seed retention from glume opening to shattering averaged 91% longer for PI 478833 than Paloma. After 7 weeks 83 and 35% of Paloma and PI 478833 florets had shattered, respectively. In a third experiment seed retention index (seed yield/forage dry weight) on 15 September 1989 was 0.45, 0.19, and 0.11 for PI 478833, 'Nezpar', and Paloma, respectively. PI 478833's acute glume pair angle and resultant increased seed retention make it a valuable source of shattering resistance for introduction into bred Indian ricegrass varieties.
    • Implications of desert rodent seed preferences for range remediation

      Longland, W. S.; Bateman, S. L. (Society for Range Management, 1998-11-01)
      Many desert plants germinate and establish from seed caches made by granivorous rodents. As a preliminary test of the feasibility of using rodent seed-caching activities to enhance seedling emergence of native desert plants, we tested desert heteromyid rodents for preferential consumption and/or caching of native ("target") seeds versus a commercial ("decoy") seed. The target/decoy seed concept relies on rodents caching both seeds, and preferentially consuming an inexpensive decoy seed as a sacrifice to reduce consumption of less preferred target seeds. We used cafeteria-style, paired seed choice trials to test 2 potential target seeds known to germinate from rodent scatterhoard caches (Indian ricegrass, Achnatherum hymenoides [R. & S.] Barkworth, and four-wing saltbush, Atriplex canescens [Pursh] Nutt.) against a potential decoy seed (millet, Panicum miliaceum L.). Millet was highly preferred to saltbush, and may indeed be a useful decoy seed when saltbush is the target of range restoration. Also consistent with the target/decoy seed concept, more Indian ricegrass than millet seeds were cached in laboratory trials, and all seeds were cached in scatterhoards more than in larderhoards, where the probability of seedling emergence is negligible. However, millet seed may not always be a good candidate for a decoy seed, as it was not preferred to Indian ricegrass and was cached more frequently than saltbush. Overall, we find results of these choice tests to be encouraging for applying the target/decoy seed idea. We consider the relative merits of this idea versus traditional revegetation techniques.
    • Indian ricegrass seed damage and germination responses to mechanical treatments

      Griffith, L. W.; Booth, D. T. (Society for Range Management, 1988-07-01)
      Indian ricegrass [Oryzopsis hymenoides (Roem. and Schult.) Ricker] is a valuable forage species in the western United States; however, low fresh-seed germination has limited its use in rangeland revegetation. Seed damage and germination effects were evaluated on 2 seedlots of 'Nezpar' Indian ricegrass exposed to 3 mechanical treatments. The air-gun scarifier and the Quaker Oats dehuller improved germination whereas the Forsberg dehuller decreased germination. Disruption of the seed coat before storage appears to be a practical method of reducing storage time required for improved germination of freshly harvested seed.
    • Influence of matric potential and substrate characteristics on germination of Nezpar Indian ricegrass

      Blank, R. R.; Young, J. A. (Society for Range Management, 1992-03-01)
      Intact seeds (caryopses) of Indian ricegrass [Oryzopsis hymenoides (R. & S.) Ricker] are generally reported to exhibit poor germination. The cultivar Nezpar was evaluated to determine if substrate matric potential and substrate physiochemical properties influence germination. Matric potentials ranged from 0 to -1.5 MPa. Substrate variables included: 2 kinds of germination paper, the A horizon of a dune sand, and a commercial washed silica sand. Seeds of Indian ricegrass had low germination (< 5%) with an oversaturated substrate. Germination increased significantly (P less than or equal to 0.05) between -0.005 and -0.10 MPa tension (30 to 70%), then decreased at more negative matric potentials. As compared with paper substrates, the dune sand showed significantly greater (P less than or equal to 0.05) germination at matric potentials more negative than -0.30 MPa. Standard germination screening procedures, especially at high water contents, do not adequately predict the maximum germination characteristics of Indian ricegrass; thus, substrate matric potential is a critical variable to control in germination tests. Moreover, physicochemical differences among common laboratory germination substrates may lead to significantly different termination responses. Microscopic examination of cross-sections of caryopses suggests the mechanism for reduced seed germination at saturated and oversaturated conditions may be the presence of a void between the lemma and palea which, when water-filled, retards oxygen diffusion to the embryo.
    • Intrapopulation genetic variation for seed dormancy in India ricegrass

      Jones, T. A.; Nielson, D. C. (Society for Range Management, 1999-11-01)
      Indian ricegrass (Achnatherum hymenoides [Roem. &Schult.] Barkw. = Oryzopsis hymenoides [Roem. & Schult.] Ricker = Stipa hymenoides Roem. &Schult.) may buffer its seed banks over time via morphological (lemma and palea) and physiological (seed coat) seed dormancy. However, Indian ricegrass seed dormancy has usually not been examined from a genetic perspective. Because a positive relationship between seed dormancy and seed size has long been noted within Indian ricegrass populations we wanted to determine if genetic variation for seed dormancy was present among seed morphs. We also wanted to determine if genetic variation for seed dormancy was present in material without polymorphism. The T-593 population from McKinley Co., N.M., has 3 seed morphs produced on genetically distinct plants, 'elongate' (2.24 mg/seed), 'globose' (3.00 mg/seed), and 'jumbo' (8.70 mg/seed). Following a 3-week prechill, elongate seed showed higher germination (66%) than globose seed (20%) over 6 tests (pairs of seed lots), while jumbo seed did not germinate without scarification. Jumbo seed had thicker (181 microgram) lemmas than globose (93 microgram) or elongate (52 microgram) seed. Individual plants of the nonpolymorphic cultivar, Rimrock, were selected for high or low germination following a 3-week prechill. The spring following seed harvest, germination with prechill was greater for progeny lines of the high-germination selections (45.5%) than low-germination selections (3.8%) with Rimrock intermediate (11.8%). This heritable difference in germination was accompanied by only small differences in lemma and palea thickness and no difference in seed mass. Genetic variation in seed dormancy may be found both between morphs (interpreted as variation for morphological dormancy) and within morphs (interpreted as variation for physiological dormancy). Genetic variation for seed dormancy can be as great within a population as between populations.
    • New Artificial Seeding for Rangelands

      Wilson, R. E.; Young, J. A.; Medlyn, G. W.; Deforest, S. (Society for Range Management, 2000-04-01)
    • Previous grazing or clipping affects seed of Indian ricegrass

      Orodho, A. B.; Cuany, R. L.; Trlica, M. J. (Society for Range Management, 1998-01-01)
      Previous heavy grazing for more than 50 years, compared with protection from livestock grazing, in the semi-arid area of Chaco Canyon in the southwestern United States did not result in any significant decrease in seed production potential of Indian ricegrass [Oryzopsis hymenoides (Roem. and Schult.) Ricker]. There also were no significant differences in seed production between grazed and ungrazed collections of Indian ricegrass from the Chaco Canyon study site when transplanted and grown in a common garden. This indicated that long-term protection from livestock grazing probably had not genetically (ecotypically) altered seed production potential. Both grazed and ungrazed transplants of Indian ricegrass differed in seed production from the cultivars 'Paloma' and 'Nezpar'. Nezpar produced the greatest seed yield (312 kg/ha), while Paloma had the lowest yield (78 kg/ha). Defoliation about 1 June over a 2-year period reduced seed production and nitrogen fertilization did not increase seed yield. Previous grazing history had little effect on seed germination, but there were significant differences in germination among some collections and cultivars of Indian ricegrass. Germination was less than 5% for all entries. A tetrazolium viability test showed that seed of native strains were more viable than those of Paloma. Dormancy is a troublesome, but desirable, trait of Indian ricegrass seed for use in droughty areas.
    • Seed abscission and retention in Indian ricegrass

      Whalley, R. D. B.; Jones, T. A.; Nielson, D. C.; Mueller, R. J. (Society for Range Management, 1990-07-01)
      Each spikelet of Indian ricegrass [Orysopsis hymenoides (Ram. and Schult.) Ricker] consists of a floret enclosed in a pair of glumes. As each seed matures, (1) the glumes open, (2) the lemma hairs reflex outward, and (3) the abscission layer across the rachilla fractures. This study concerned the relationship of these 3 processes to seed shattering. PI 478833 (Yellowstone Co., Mont.), had a more acute angle between the opened glumes (glume pair angle) and lower seed weight, both of which may contribute to seed retention, than ‘Paloma’ (Pueblo Co., Colo.). In Paloma and PI 478833, glume pair angle was not greater with a noret in the spikelet than without, thus the intluence of lemma hairs on opening the glumes is probably minimal. The abscission (separation) layer between the floret and rachilla of Paloma consists primarily of cells with cellulosic walls, is 1 to 2 cells thick, and lies diagonally across the rachilla. The abscission layer is distal to several layers of sclerenchyma cells with heavily lignified walls (protective layer). The abscission layer is well developed before anthesis, and it is unlikely that any genotypes lack this layer. Since lemma hairs are not related to seed retention and the abscission layer is well developed long before abscission, selection for acute glume pair angle at seed maturity may improve seed retention in Indian ricegrass, increasing harvestable seed yield.
    • Seeding Indian ricegrass in an arid environment in the Great Basin

      Young, J. A.; Blank, R. R.; Longland, W. S.; Palmquist, D. E. (Society for Range Management, 1994-01-01)
      Indian ricegrass [Oryzopsis hymenoides (R. & S.) Rickerl is a valuable forage species adapted to arid rangelands in temperate deserts. The purpose of this study was to test the influence of seeding date, depth, and rate on Indian ricegrass emergence and seedling establishment of acid scarified and intact caryopses (seeds). The seeding experiments were conducted on a wind eroding sand sheet of Lahontan age in western Nevada. During the initial year of planting, seeds of the cultivars Nezpar and Paloma Indian ricegrass were successfully established without pretreatment by acid scarification. Acid scarified seeds did not result in the established seedling stands in the field. Initial seedings were done in a season with prolonged moisture events with total precipitation about twice the average. Seedling stands of crested wheatgrass [Agropyron desertorum (Fisch.) ex Link Schult] as well as other exotic and native herbaceous and woody species were established during the first year. During the next 4 years crested wheatgrass seedlings were never again established. Indian ricegrass seedlings were established in 3 of the 4 subsequent years of seeding trials using a seeding rate of 0.8 seeds/cm of row and a seeding depth of 1 cm. Indian ricegrass seedling emergence was increased by either increasing the planting depth to 5 cm or by reducing the seeding rate to 0.03 seeds/cm of row. The ultra-low seeding rate resulted in a significant saving in seed cost.
    • Sheep grazing and plant cover dynamics of a shadscale community

      Alzerreca-Angelo, H.; Schupp, E. W.; Kitchen, S. G. (Society for Range Management, 1998-03-01)
      Despite extensive coverage and long-term use, the extent to which shadscale [Atriplex confertifolia (Torr. &Frem.) Wats.] community dynamics are driven by grazing rather than by climate and inherent plant characteristics is unresolved. We analyze a 59-year data set from the Desert Experimental Range, southwestern Utah, with the objective of discriminating between grazing and non-grazing effects on cover dynamics. Canopy cover of (5 x 20 ft) 9.3 m2 plots were estimated in 1935, 1958, 1969, 1975, and 1994. Treatments were time (5 dates), grazing (ungrazed versus grazed), and season (spring versus winter). Time was significant; total cover initially increased following release from uncontrolled grazing and improvement of climate (1935-58, P < 0.001), remained unchanged over the following dry interval (1958-69, P = 1.000), increased over a drier interval (1969-75, P < 0.001), and then decreased dramatically over the final wet period (1975-94, P < 0.001). Grazing was also significant (P < 0.001), but cover of ungrazed plots exceeded that of grazed plots only in 1975 and 1994 (P less than or equal to 0.033). The 6 dominant species showed varying responses to grazing and time, with some responding primarily to grazing (e.g., budsage, Artemisia spinescens D.C. Eaton in Wats.) and others responding primarily to time (climate, longevity, etc., e.g., Indian ricegrass, Oryzopsis hymenoides R. &S.). Similarly, seasonal effects were not universal. Shrub cover initially increased and then declined dramatically while grass cover monotonically increased. Results suggest that release from uncontrolled grazing coupled with improving climatic conditions were responsible for initial recovery of the community, but that over time, climate and inherent plant traits (e.g., longevity, establishment ecology, etc.) became relatively more important. For total cover and for many individual species, continued grazing affected the rate more than the direction of vegetation change.
    • Vegetation differences in desert shrublands of western Utah's Pine Valley between 1933 and 1989

      Yorks, T. P.; West, N. E.; Capels, K. M. (Society for Range Management, 1992-11-01)
      Changes in rangeland vegetation integrate the consequences of livestock grazing intensity and possible climate change, as well as other factors. Because vegetation changes tend to be very slow in dry environments, observational time scales that exceed a human generation are needed to separate real trends from year-to-year, weather-driven variability. An exhaustive literature search for valid starting points within the Intermountain region revealed a unique quantitative study that was more than 50 years old. In 1933, vegetation along a 37-km transect in southern Pine Valley, Utah, was read from 19-m2 plots located every 42 m. The only intentional, local management treatment in the interim has been moderation of domestic livestock grazing pressure. During a period climatically and phenologically similar to the original study, we re-examined representative segments of this transect by a more detailed updating of the original "square-foot-density" method. We found that vegetation type boundaries and ecotones were little changed after 56 years. However, canopy cover was dramatically greater in 1989, in some cases by more than tenfold for several perennial grasses, and less so for shrubs. Substantially greater understory cover as a relative proportion of total plant cover occurred in 1989 in all vegetation types examined. Some of the observed positive shifts of dominance/diversity are contrary to widely accepted expectations in the literature.