Indian Ricegrass Research Articles

Plant growth and survival of five introduced and two native/naturalized perennial grass genotypes exposed to two defoliation managements in arid Argentina

AbstractThe field performance of the native Pappophorum vaginatum, the naturalized Eragrostis curvula and various cultivars of the introduced Achnatherum hymenoides and Leymus cinereus was evaluated as potential forage resources in rangelands of arid Argentina during the warm seasons of 2007/2008 and 2008/2009. Plants of these grass species, obtained from seeds, were transplanted to the field in 2006, when they were 1 year old. During the study years, there were two defoliation managements: plants of all study genotypes either remained undefoliated (controls) or were defoliated twice a year during spring at 5 cm stubble height. Despite tiller number being lower (P < 0·05) on defoliated than on undefoliated plants, and total leaf length per unit basal area being similar (P > 0·05) between defoliation managements by mid‐spring, there were no differences (P > 0·05) in dry weight production between defoliated and undefoliated plants in all genotypes at the end of the second growing season. Plants of one or more of the introduced genotypes showed a similar (P > 0·05) or greater (P < 0·05), but not lower, tiller number per plant and per square centimetre, daughter tiller production, total leaf length and dry weight production per unit basal area than the native species at the end of the first and/or second growing seasons. These morphological variables were similar (P > 0·05) or greater (P < 0·05) in the native than in the naturalized genotype. Plant survival, however, was lower (P < 0·05, overall mean = 20%) in the introduced than in the native (>70%) or naturalized (>39%) genotypes at the end of the first or second growing seasons.

Cultivation legacies alter soil nutrients and differentially affect plant species performance nearly a century after abandonment

Cultivation legacies affect native vegeta- tion in old fields of the Great Basin, USA for nearly a century after these fields are abandoned. We hypoth- esized that cultivation lowered soil nutrients and that this legacy would differentially impact plant perfor- mance of four representative Great Basin species. To test these hypotheses, we compared soil nutrients (C, N, P, K, Mg and Ca) between two formerly cultivated and adjacent noncultivated sites in two soil series. We then compared the plant growth and foliar nutrient content of an exotic grass (Bromus tectorum L.), two native grasses (Elymus elymoides (Raf.) Swezey and Achnatherum hymenoides (Roem. and Schult.) Barkworth), and a native forb (Sphaeralcea grossu- lariifolia (Hook. and Arn.) Rydb) grown in these soils in the greenhouse and in the field. Only one sampling site had reduced soil nutrients associated with culti- vation legacies, where most of the negative effects on plant performance were found. E. elymoides appeared to be less affected by cultivation legacies than did A. hymenoides, which had a reduced survivorship and 20 % less above-ground biomass in cultivated soils. No species, including B. tectorum, were favored by cultivation. Our findings suggest that cultivation legacies can affect plant performance of different species in different ways and that altered soil nutrients may interact with other abiotic and biotic cultivation legacies in complex ways.

Establishing Cool‐Season Grasses on a Degraded Arid Rangeland of the Colorado Plateau

AbstractReestablishing cool‐season (C3) grass communities on low elevation rangelands of the Colorado Plateau is notoriously difficult, raising questions about the viability of restoring native species and continuing to actively graze these landscapes. We conducted a seeding experiment on an arid (15.4 cm rain/year), historically heavily‐grazed rangeland in Northern Arizona to test the effects of seeding technique and simulated seasonal climate scenarios on germination and recruitment of four species of native, cool‐season bunchgrasses: Achnatherum hymenoides, Hesperostipa comata, Poa secunda, and Elymus elymoides. Initial results indicated that C3 grasses germinated significantly more in drill‐seeded treatments under simulated high precipitation years than in other treatment types. Five years post‐treatment, P. secunda and E. elymoides were not observed but simulated drill‐seeded treatments, had significantly higher densities of A. hymenoides and H. comata recruits relative to most other treatment types. Simulated drill seeding also increased soil disturbance which increased the establishment of the invasive weed Salsola tragus in year 1, but not thereafter. Although it appears critical to coordinate effective seeding techniques with high winter–spring precipitation, predicting such events may not be possible at some sites, suggesting that seeding low elevation, arid rangelands of the Colorado Plateau may not always be realistic under a future climate that is drier and less predictable.

Seed harvesting is influenced by associational effects in mixed seed neighbourhoods, not just by seed density

Summary Rodents frequently forage in a density‐dependent manner, increasing harvesting in patches with greater seed densities. Although seldom considered, seed harvesting may also depend on the species identities of other individuals in the seed neighbourhood. When the seed harvest of a focal species increases in association with another seed species, the focal species suffers from Associational Susceptibility. In contrast, if seeds of the focal species are harvested less when in association with a second species, the focal species benefits from Associational Resistance. To evaluate density dependence and associational effects among seeds in mixtures, we conducted seed removal experiments using a completely additive design patterned after a two‐species competition experiment using seeds of either Achnatherum hymenoides (Indian ricegrass), Leymus cinereus (basin wildrye) or Pseudoroegneria spicata (bluebunch wheatgrass), all native perennial grasses, combined with seeds of Bromus tectorum (cheatgrass), a non‐native annual grass. The experiment involved placing five fixed quantities of the native seeds mixed with five fixed quantities of B. tectorum seeds in a factorial design, resulting in 35 seed mixture combinations. The seed‐eating rodent community at our study sites, in order of abundance, is composed of Peromyscus maniculatus (North American deer mouse), Dipodomys ordii (Ord's kangaroo rat) and Perognathus parvus (Great Basin pocket mouse). Native seed harvesting was density dependent, with a greater proportion of seeds being harvested as density increased. In the mixed density model, the presence of B. tectorum did not affect harvest of any of the native species' seeds when analysed individually. However, when all three native species were analysed together, increasing quantities of B. tectorum resulted in reduced harvest of native seeds, demonstrating weak but significant Associational Resistance. In contrast, harvest of B. tectorum seeds increased when in combination with any of the native seed species individually, indicating relatively strong Associational Susceptibility. These results demonstrate that seed harvest is determined not just by seed density, but also by the local seed neighbourhood and suggest that associational effects between native seeds and B. tectorum can occur in field conditions. The ecological implications of seed selection and associational effects on plant populations in natural and managed systems are also discussed.

Stand Establishment and Persistence of Perennial Cool-Season Grasses in the Intermountain West and the Central and Northern Great Plains

The choice of plant materials is an important component of revegetation following disturbance. To determine the utility and effectiveness of various perennial grass species for revegetation on varied landscapes, a meta analysis was used to evaluate the stand establishment and persistence of 18 perennial cool-season grass species in 34 field studies in the Intermountain and Great Plains regions of the United States under monoculture conditions. Combined across the 34 studies, stand establishment values ranged from 79% to 43% and stand persistence values ranged from 70% to 0%. Intermediate wheatgrass (Thinopyrum intermedium [Host] Barkworth & D. R. Dewey), tall wheatgrass (Thinopyrum ponticum [Podp.] Z.-W. Liu & R.-C. Wang), crested wheatgrass (Agropyron spp.), Siberian wheatgrass (Agropyron fragile [Roth] P. Candargy), and meadow brome (Bromus riparius Rehmann) possessed the highest stand establishment (≥ 69%). There were no significant differences among the 12 species with the largest stand persistence values. Basin wildrye (Leymus cinereus (Scribn. & Merr.) Á. Löve), Altai wildrye (Leymus angustus [Trin.] Pilg.), slender wheatgrass (Elymus trachycaulus [Link] Gould ex Shinners), squirreltail (Elymus spp.), and Indian ricegrass (Achnatherum hymenoides [Roem. & Schult.] Barkworth) possessed lower stand persistence (≤ 32%) than the majority of the other species, and Indian ricegrass (0%) possessed the lowest stand persistence of any of the species. Correlations between environmental conditions and stand establishment and persistence showed mean annual study precipitation to have the most consistent, although moderate effect (r = ∼0.40) for establishment and persistence. This relationship was shown by the relatively poor stand establishment and persistence of most species at sites receiving less than 310mm of annual precipitation. These results will be a tool for land managers to make decisions concerning the importance of stand establishment, stand persistence, and annual precipitation for revegetation projects on disturbed sites.

Lignocellulosic Fermentation of Wild Grass Employing Recombinant Hydrolytic Enzymes and Fermentative Microbes with Effective Bioethanol Recovery

Simultaneous saccharification and fermentation (SSF) studies of steam exploded and alkali pretreated different leafy biomass were accomplished by recombinant Clostridium thermocellum hydrolytic enzymes and fermentative microbes for bioethanol production. The recombinant C. thermocellum GH5 cellulase and GH43 hemicellulase genes expressed in Escherichia coli cells were grown in repetitive batch mode, with the aim of enhancing the cell biomass production and enzyme activity. In batch mode, the cell biomass (A 600 nm) of E. coli cells and enzyme activities of GH5 cellulase and GH43 hemicellulase were 1.4 and 1.6 with 2.8 and 2.2 U·mg−1, which were augmented to 2.8 and 2.9 with 5.6 and 3.8 U·mg−1 in repetitive batch mode, respectively. Steam exploded wild grass (Achnatherum hymenoides) provided the best ethanol titres as compared to other biomasses. Mixed enzyme (GH5 cellulase, GH43 hemicellulase) mixed culture (Saccharomyces cerevisiae, Candida shehatae) system gave 2-fold higher ethanol titre than single enzyme (GH5 cellulase) single culture (Saccharomyces cerevisiae) system employing 1% (w/v) pretreated substrate. 5% (w/v) substrate gave 11.2 g·L−1 of ethanol at shake flask level which on scaling up to 2 L bioreactor resulted in 23 g·L−1 ethanol. 91.6% (v/v) ethanol was recovered by rotary evaporator with 21.2% purification efficiency.

Impacts of Tamarix‐mediated soil changes on restoration plant growth

AbstractQuestionDo soils impacted by Tamarix spp. affect the growth of plants used for restoration through altered soil chemistry and/or plant‐soil feedbacks?LocationThe Bighorn River, the Yellowstone River and the Fort Peck Reservoir, Montana, western USA.MethodsSoil was collected from paired subsites where Tamarix was either present or absent along three water bodies. To evaluate chemical and biological soil effects on plant growth, eight plant species (Achnatherum hymenoides, Astragalus cicer, Dalea candida, Elymus lanceolatus, Leymus cinereus, Pascopyrum smithii, Ratibida columnifera and Trifolium pratense) commonly used in restoration projects at Tamarix‐invaded sites were grown in the collected soil. Plant‐soil feedbacks were evaluated by growing two species (D. candida and P. smithii) in greenhouse soils inoculated with small amounts of the field soils. Germination, emergence and growth characteristics were compared between Tamarix‐invaded and un‐invaded subsites and across water bodies.ResultsSeedling emergence and plant relative growth rate, total biomass production and allocation of resources to roots and shoots were not negatively affected in field soils or in greenhouse soil inoculated with soil from areas where Tamarix was present. In fact, overall, plants emerged earlier and produced more biomass in soils affected by Tamarix than in soils from where Tamarix was not present. These results indicate that for sites in the northern range of Tamarix, restoration would not be inhibited by Tamarix‐induced soil changes.ConclusionsTamarix is a relatively new invader in the northern USA, and little is known about its impacts in this area or the potential implications for restoration. However, our results indicate that neither altered soil chemistry nor plant‐soil feedbacks negatively impact native plant growth, and restoration efforts would not be hindered by Tamarix‐induced changes to soil chemistry or microbiota.

Genecology and Seed Zones for Indian Ricegrass Collected in the Southwestern United States

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 .6 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.

Ecosystem Services from Keystone Species: Diversionary Seeding and Seed‐Caching Desert Rodents Can Enhance Indian Ricegrass Seedling Establishment

AbstractSeeds of Indian ricegrass (Achnatherum hymenoides), a native bunchgrass common to sandy soils on arid western rangelands, are naturally dispersed by seed‐caching rodent species, particularlyDipodomysspp. (kangaroo rats). These animals cache large quantities of seeds when mature seeds are available on or beneath plants and recover most of their caches for consumption during the remainder of the year. Unrecovered seeds in caches account for the vast majority of Indian ricegrass seedling recruitment. We applied three different densities of white millet (Panicum miliaceum) seeds as “diversionary foods” to plots at three Great Basin study sites in an attempt to reduce rodents' over‐winter cache recovery so that more Indian ricegrass seeds would remain in soil seedbanks and potentially establish new seedlings. One year after diversionary seed application, a moderate level of Indian ricegrass seedling recruitment occurred at two of our study sites in western Nevada, although there was no recruitment at the third site in eastern California. At both Nevada sites, the number of Indian ricegrass seedlings sampled along transects was significantly greater on all plots treated with diversionary seeds than on non‐seeded control plots. However, the density of diversionary seeds applied to plots had a marginally non‐significant effect on seedling recruitment, and it was not correlated with recruitment patterns among plots. Results suggest that application of a diversionary seed type that is preferred by seed‐caching rodents provides a promising passive restoration strategy for target plant species that are dispersed by these rodents.

Bioconversion of Agricultural Waste to Ethanol by SSF Using Recombinant Cellulase fromClostridium thermocellum

The effect of different pretreatment methods, temperature, and enzyme concentration on ethanol production from 8 lignocellulosic agrowaste by simultaneous saccharification and fermentation (SSF) using recombinant cellulase and Saccharomyces cerevisiae were studied. Recombinant cellulase was isolated from E. coli BL21 cells transformed with CtLic26A-Cel5-CBM11 full-length gene from Clostridium thermocellum and produced in both batch and fed-batch processes. The maximum cell OD and specific activity in batch mode were 1.6 and 1.91 U/mg, respectively, whereas in the fed-batch mode, maximum cell OD and specific activity were 3.8 and 3.5 U/mg, respectively, displaying a 2-fold increase. Eight substrates, Syzygium cumini (jamun), Azadirachta indica (neem), Saracens indica (asoka), bambusa dendrocalmus (bamboo), Populas nigra (poplar), Achnatherum hymenoides (wild grass), Eucalyptus marginata (eucalyptus), and Mangifera indica (mango), were subjected to SSF. Of three pretreatments, acid, alkali, and steam explosion, acid pretreatment Syzygium cumini (Jamun) at 30°C gave maximum ethanol yield of 1.42 g/L.

Defoliation effects on the arbuscular mycorrhizas of ten perennial grass genotypes in arid Patagonia, Argentina

Pappophorum vaginatum is the most abundant C 4, warm-season perennial grass in rangelands of northeastern, arid Patagonia, which is often exposed to continuous grazing. Eragrostis curvula is the only naturalized, C 4 warm-season genotype that has successfully established from seed during moist years in the study region, that is characterized by a scarce forage availability to livestock during the spring and summer. Successful introduction of perennial forage genotypes is then critical in that region. No studies have yet been conducted to determine the greater abundance of P. vaginatum compared to that of other native C 4 grass genotypes ( Aristida subulata, A. spegazzinii, Sporobolus cryptandrus) in the study area. The effect of defoliation on arbuscular mycorrhizal colonization was investigated on the four native, one naturalized and five introduced, C 3 perennial grass genotypes ( Leymus cinereus cvs. “Magnar” and “Trailhead”, and Achnatherum hymenoides cvs. “Paloma”, “Rimrock” and “Nezpar”) growing at the field. We hypothesized that the magnitude of mycorrhizal colonization (1) is similar on defoliated than on undefoliated plants of the native and naturalized genotypes, (2) is greater in the native and naturalized than in the introduced genotypes, and (3) is greatest in P. vaginatum than in all remaining genotypes. Plants of all ten genotypes were either exposed or not to a severe defoliation twice in the growing seasons of 2007/2008 and 2008/2009. The results showed that all studied genotypes maintained arbuscular mycorrhizal colonization levels following defoliation similar to undefoliated controls. The greatest arbuscular mycorrhizal colonization was often found on both cultivars of L. cinereus among all genotypes. The greatest arbuscular mycorrhizal colonization in P. vaginatum than in the other native genotypes at the end of the study, parameter that contributes to defoliation tolerance, could help to explain its greater abundance in rangelands of central Argentina. The higher arbuscular mycorrhizal colonization in both cultivars of L. cinereus might contribute to their successful establishment and survival in rangelands of northeastern, arid Patagonia. Genotype introduction in these rangelands is likely to affect community dynamics because of variable effects of the mycorrhizal symbiosis on the various plant genotypes.

Effects of rodent species, seed species, and predator cues on seed fate

Seed selection, removal and subsequent management by granivorous animals is thought to be a complex interaction of factors including qualities of the seeds themselves (e.g., seed size, nutritional quality) and features of the local habitat (e.g. perceived predator risk). At the same time, differential seed selection and dispersal is thought to have profound effects on seed fate and potentially vegetation dynamics. In a feeding arena, we tested whether rodent species, seed species, and indirect and direct predation cues influence seed selection and handling behaviors (e.g., scatter hoarding versus larder hoarding) of two heteromyid rodents, Ord’s kangaroo rat ( Dipodomys ordii) and the Great Basin pocket mouse ( Perognathus parvus). The indirect cue was shrub cover, a feature of the environment. Direct cues, presented individually, were (1) control, (2) coyote ( Canis latrans) vocalization, (3) coyote scent, (4) red fox ( Vulpes vulpes) scent, or (5) short-eared owl ( Asio flammeus) vocalization. We offered seeds of three sizes: two native grasses, Indian ricegrass ( Achnatherum hymenoides) and bluebunch wheatgrass ( Pseudoroegneria spicata), and the non-native cereal rye ( Secale cereale), each in separate trays. Kangaroo rats preferentially harvested Indian ricegrass while pocket mice predominately harvested Indian ricegrass and cereal rye. Pocket mice were more likely to scatter hoard preferred seeds, whereas kangaroo rats mostly consumed and/or larder hoarded preferred seeds. No predator cue significantly affected seed preferences. However, both species altered seed handling behavior in response to direct predation cues by leaving more seeds available in the seed pool, though they responded to different predator cues. If these results translate to natural dynamics on the landscape, the two rodents are expected to have different impacts on seed survival and plant recruitment via their different seed selection and seed handling behaviors.

Coexisting desert rodents differ in selection of microhabitats for cache placement and pilferage

Seed caching by desert rodents in the family Heteromyidae is an important behavioral adaptation for animals living in environments with limited and unpredictable food resources. Heteromyids cache seeds throughout their home ranges, either concentrated in 1 location (larder hoard) or in multiple, small seed piles (scatter hoards). To minimize cache pilferage by other rodents, coexisting species may scatter hoard seeds in distinct microhabitats. We examined interspecific differences in caching and pilfering behaviors of 3 coexisting heteromyid rodents, Merriam's kangaroo rat (Dipodomys merriami), the pale kangaroo mouse (Microdipodops pallidus), and the little pocket mouse (Perognathus longimembris), to determine if caching microhabitat affects likelihood of pilferage. In outdoor enclosures we tracked cache placement and measured pilferage of artificial caches using radiolabeled Indian ricegrass (Achnatherum hymenoides) seeds. M. pallidus and P. longimembris placed seed caches mostly under shrubs, whereas D. merriami placed caches predominately in open microhabitat. However, D. merriami showed a significant preference for pilfering caches under shrubs, whereas P. longimembris did not show a significant preference for pilfering caches in either open or undershrub microhabitats. The 2 species pilfered similar numbers of caches. Coexisting heteroymid rodent species may contribute to spatial heterogeneity of available resources by caching in different microhabitats, thereby reducing but not eliminating cache pilferage by other species.

Notice of release of White River Germplasm Indian ricegrass

White River Germplasm Indian ricegrass ( Achnatherum hymenoides (Roem. & Schult.) Barkworth [Poaceae]) has been released for use in rangeland seedings. This plant material traces from a seed morph collected in northwestern Colorado in Rio Blanco County, near the White River. White River Germplasm displays good germinability in a species characterized by high levels of seed dormancy. We anticipate this material will be used in the Upper Colorado Plateau of eastern Utah and western Colorado and the Basin Province of southern Wyoming.

Nutritional Quality of Natural Foods of Juvenile and Adult Desert Tortoises (Gopherus agassizii): Calcium, Phosphorus, and Magnesium Digestibility

Abstract Exotic plants can make up a major component of the diet for some Desert Tortoises (Gopherus agassizii) in the Mojave Desert. If introduced plants differ nutritionally from native plants, they may influence the growth and welfare of young tortoises. Minerals available from a native grass (Achnatherum hymenoides), an introduced grass (Schismus barbatus), a native forb (Malacothrix glabrata), and an introduced forb (Erodium cicutarium) were measured for juvenile Desert Tortoises voluntarily eating single-species diets. We offered tortoises weighed amounts of chopped foods daily for ∼130 days (dry grasses; summer diet) or ∼90 days (green forbs; spring diet). Orts and feces were collected daily and dried to constant mass, and calcium, phosphorus, and magnesium contents of food and feces were measured and used to calculate nutrient digestibilities. Overall, tortoises gained more minerals from forbs than from grasses. Tortoises lost small but significant amounts of phosphorus when eating grasses, which ...

Root-associated fungal communities colonizing two dominant semiarid grasses: Hilaria sp. and Stipa sp.

AbstractWe conducted a preliminary survey of the fungal communities associated with roots of Stipa hymenoides and Hilaria jamesii, two grasses native to the southwestern United States. Root samples from 10 different plants were collected at a semiarid grassland in Utah. Fungal communities were assessed using microscopic and molecular methods. Roots were cleared with KOH and stained using blue ink to visualize mycorrhizal and endophytic fungi. A total of 100 root segments were surface sterilized and plated on malt extract agar with antibiotics. Fungal endophytes were identified using nrITS primers. Results/Conclusions Microscopic analyses showed that all root samples from both Hillaria and Stipa were colonized by dark septate and arbuscular mycorrhizal fungi. Vesicles and hyaline hyphae also were observed in all the roots. Sclerotia, a characteristic structure of some dark septate fungi were also found. Approximately 75 fungi were isolated representing at least 45 morphotypes. Molecular identification showed that both grasses are colonized by endophytes in the orders Pleosporales, Hypocreales, and Sordariales commonly found in semiarid grasses, liverworts, and mosses.

English

The Stucky Ridge test plot is located approximately two miles northeast of Anaconda, Montana. Sparse vegetation includes quaking aspen, Wood's rose, currant species, rubber rabbitbrush, horsebrush, redtop and basin wildrye. In November 2002, 22 tons/acre lime kiln dust was disced to a 12‖ depth. Prior to spring seeding, 500 bulk-pounds of fertilizer were applied/incorporated to a 6‖ depth. Thirty-six grass, two subshrub accessions, and four seed mixtures were arranged in a Randomized Complete Block with four replications. Plots were drill-seeded in May 2003 at 50 Pure Live Seeds per linear row foot. Soil sampling for arsenic and heavy metals occurred after planting. A significant amount of new grass seedling emergence was detected during the June 2004 evaluation, particularly for Indian ricegrass, western wheatgrass, Nevada bluegrass, and basin wildrye. Following the 2004, 2005, and 2006 evaluations for cover and vigor rating, each plot was sampled for biomass production. Tissue analyses indicated heavy metal concentrations were generally within limits for livestock and wildlife use. In single-species plots, ‗local source' plants exhibiting superior performance included Copperhead and 9081621 slender wheatgrass, Opportunity Nevada bluegrass, 9081968 western wheatgrass, 9081624 and Washoe Germplasm basin wildrye, 9081628 Indian ricegrass, 9081636 bluebunch wheatgrass and 9081635 Canbyi bluegrass. In 2003, Open Range Germplasm winterfat was the only broad-leaved entry demonstrating significant emergence. In 2007, the only broad-leaved plants surviving were Open Range winterfat and 9081632 silverleaf phacelia. Old Works fuzzytongue penstemon and silverleaf phacelia were only detected in alternating years. In the Seed Mixture Trials, the ‗Experimental' mixes containing native ‗local source' were far superior to the ‗Developed' mixes consisting of native ‗nonlocal source' (Upland Mix) and introduced cultivars (Waste Management Areas). However, it was estimated the majority of plants in the Experimental mixtures were Copperhead slender wheatgrass, the best overall performer on the test site.

Dynamics of Dormancy-Status Subpopulations of Indian Ricegrass Seed Held in Dry Storage

Germination of Indian ricegrass (Achnatherum hymenoides [Roem. & Schult] Barkworth), a rangeland species native to western North America, is limited by persistent seed dormancy. We previously identified high-dormancy (HD) and low-dormancy (LD) genotypes from within the genetically heterogeneous cultivar Rimrock. Seed was produced in 2000 and 2001 in a common garden, stored in paper-can containers at room temperature, and tested every 3 mo with and without prechill through 2005. In 2005, tetrazolium viability of all four lots was 99%, reflective of this species' extensive seed longevity. Over this time period, germination of nonprechilled seed increased from 1% to 53% for HD and from 15% to 79% for LD, whereas corresponding increases for prechilled seed were from 8% to 56% for HD and from 61% to 76% for LD. At first, the great majority of seeds of HD (99%) and LD (86%) were dormant, but this majority was overwhelmingly prechill nonresponsive for HD (92%) compared to roughly equal portions of prechill-nonresponsive (39%) and prechill-responsive (46%) seed for LD. At the end of the trial, most seeds of both HD (53%) and LD (79%) were nondormant, but more prechill-nonresponsive seeds were present in HD (44%) than LD (24%). Over the course of the study, the prechill-nonresponsive subpopulation declined more for HD (by 32%), the prechill-responsive subpopulation declined more for LD (by 45%), and overall dormancy (sum of the two subpopulations) declined more for HD (by 13%). The prechill-responsive subpopulation was depleted more quickly than the prechill-nonresponsive subpopulation for both genotypes. Both HD and LD genotypes were responsive to room-temperature storage without loss of viability over a 4–5-yr period. These data highlight the utility of long-term storage as a technique to improve germinability, and consequently establishment, success of Indian ricegrass. La germinación de Indian ricegrass (Achnatherum hymenoides [Roem. & Schult] Barkworth), una especie nativa de los pastizales del oeste de Norte América, es limitada por una persistente dormancia de la semilla. Inicialmente se identificaron genotipos con alta (AD) y baja dormancia (BD) dentro del cultivar Rimrock, un cultivar genéticamente heterogéneo. La semilla fue producida en 2000 y 2001 en un jardín común, almacenada en contenedores de papel a temperatura ambiente y evaluada cada tres meses con y sin frio previo a través de 2005. En 2005, la viabilidad en tetrazolio de los cuatro lotes fue de 99%, un reflejo de la extensa longevidad de esta especie. Por encima de este periodo de tiempo, la germinación de semilla no almacenada en frio incrementó de 1% a 53% para AD y de 15% a 79% para BD, mientras que la germinación observada en semilla almacenada en frio fue de 8% a 56% para AD y de 61% a 76% para BD. Al principio, la gran mayoría de las semillas AD (99%) y BD (86%) estuvieron latentes, pero la mayoría presentó una respuesta negativa a la exposición al frio para AD (92%) comparada con porciones iguales de semilla BD que no presentó respuesta al frio (39%) y otra que respondió positivamente al frio (46%). Al final de la prueba, la mayoría de las semillas en AD (53%) y BD (79%) estuvieron no latentes, pero una mayor cantidad de semillas con respuesta negativa al frio fueron observadas en AD (44%) comparadas con BD (24%). Durante el resto del estudio, la sub-población de semilla que no respondió a la aplicación del frio declinó (32%), para AD y (45%) para BD y la latencia general (suma de las dos sub-poblaciones) declinó mas para AD (13%). La sub-población que respondió al frio fue agotada más rápidamente que la sub-población que no respondió al frio en ambos genotipos. Los genotipos de AD y BD respondieron al almacenaje a temperatura ambiente sin perdidas en la viabilidad por encima de un período de cuatro a cinco años. Estos resultados resaltan la utilidad del almacenamiento a largo plazo para mejorar la germinación y consecuentemente el éxito en el establecimiento del Indian ricegrass.

Grass Rhizosheaths: Associated Bacterial Communities and Potential for Nitrogen Fixation

Rhizosheaths are structures composed of mucilage secreted from plants and adherent soil particles that form a cylinder around the root. Using scanning electron microscopy (SEM), we observed bacteria associated with rhizosheaths of the grasses Achnatherum hymenoides, Calamovilfa longifolia, Hesperostipa comata, and Pascopyrum smithii from a sand dune area in Harding County in northwestern South Dakota. The greatest numbers of bacteria, observed with SEM (529 mm-2), and the greatest number of culturable bacteria (9.9 × 107 CFU · g-1 or 5178 CFU · mm-2) were on rhizosheaths of C. longifolia. Rhizosheaths of all the grasses examined contained a higher density of bacteria than the surrounding soil. Nitrogen fixation, as assayed by reduction of acetylene to ethylene, was present in some rhizosheaths. Bacterial nifH gene sequences amplified from bacteria associated with rhizosheaths were most similar to those from Alcaligenes latus and Mesorhizobium loti.

Nutritional Quality of Natural Foods of Juvenile Desert Tortoises (Gopherus agassizii): Energy, Nitrogen, and Fiber Digestibility

Wild Desert Tortoises, Gopherus agassizii, are eating different foods now than they were decades ago, because exotic plant species have invaded and flourished in the Mojave Desert over the last century. Reservations about the nutritional quality of exotic vegetation compared to native vegetation led us to conduct feeding experiments with growing, juvenile Desert Tortoises. We determined the digestibility of dry matter, energy, fiber, and nitrogen in four foods: Achnatherum hymenoides (a native grass), Schismus barbatus (an exotic grass), Malacothrix glabrata (a native forb), and Erodium cicutarium (an exotic forb). The largest nutritional differences among diets were between food types (fresh forbs and dry grasses) rather than between native and exotic species. The two grass diets were higher in fiber content and they contained less digestible energy than the two forb diets. The grasses contained little protein, and tortoises actually lost mass and body nitrogen while eating them. The exotic forb yielded more energy and nitrogen per unit dry mass than did the native forb, but this may be related to differences in phenological stages and associated fiber contents of these foods when they were collected. Juvenile tortoises gained weight rapidly when eating forbs and showed no evidence of having a lower digestive capability than did adults, despite their small size and immaturity. Estimates of nitrogen requirements compared to annual nitrogen intake on these diets suggested that growth of juveniles may be limited in part by dietary nitrogen.