Typification and nomenclature of Hedysarum boreale Nutt. (Leguminosae)

The holotype of Hedysarum boreale Nutt. is convarietal with natural populations now known as Hedysarum boreale Nutt. var. cinerascens (Rydb.) Rollins instead of var. boreale. The new combination Hedysarum boreale Nutt. var. rivulare (Williams) Northstrom is proposed for populations formerly known as var. boreale.     

Competition and niche partitioning among Pseudoroegneria spicata, Hedysarum boreale , and Centaurea maculosa

Maximizing desired plant diversity has been suggested as a means of minimizing non-indigenous plant invasion on rangeland by maximizing niche occupation. Competition between 2 desired indigenous species, Pseudoroegneria spicata (Pursh). L?ve (bluebunch wheatgrass) and Hedysarum boreale Nutt. var. boreale (northern sweetvetch), and a non-indigenous invader, Centaurea maculosa Lam. (spotted knapweed), was quantified using growth of isolated individuals and 2 three-species addition series experiments. Seeding densities of P. spicata remained constant at 0, 200, 400, and 800 seeds m -2 in both experiments. H. boreale and C. maculosa seeding densities were 0, 200, 400, and 800 seeds m -2 , respectively, in the 1st experiment and 0, 400, 800, and 1600 seeds m -2 , respectively, in the 2nd experiment. Densities were factorially arranged. Pots were place in an environmental chamber (12 C, 12-h day length, 200 μmol photons m -2 s -1 spectral light) in a randomized-complete-block design. After 90 d the growth rate of P. spicata (92.1 mg d -1 shoot growth) was greater than that of the 2 forbs (1.6 and 5.5 mg d -1 for H. boreale and C. maculosa , respectively), and growth rates of the 2 forbs were similar to one another. Curvilinear regression indicated that intraspecific competition was more important in determining shoot weight than intraspecific competition. In addition, the 2 forbs competed more directly with each other than with P. spicata . Competition coefficient ratios (1.42 and 1.53 for P. spicata with H. boreale and C. maculosa , respectively, and 1.03 for H. boreale with C. maculosa ) indicated substantial partitioning of resources between P. spicata and each of the forbs. Little or no resource partitioning occurred between forbs. This study suggests that increasing desired plant diversity may minimize weed invasion by increasing niche occupation.     

Names and types of Hedysarum L. (Fabaceae) in North America

The names and types of Hedysarum L., sensu stricto, for North America are included, along with bibliographic citations, type information and place of deposit of types, and all synonyms. Lectotypes are designated for Hedysarum auriculatum Eastw., H. carnulosum Greene, H. marginatum Greene, H. pabulare A. Nels., and H. truncatum Eastw.     

Field establishment of fourwing saltbush in processed oil shale and disturbed native soil as influenced by vesicular-arbuscular mycorrhizae

Seedlings of fourwing saltbush ( Atriplex canescens (Pursh) Nutt.) were inoculated with indigenous vesicular-arbuscular mycorrhizal (VAM) fungi in a containerized system and transplanted into processed oil shale and disturbed native soil in a semiarid rangeland environment in northwestern Colorado. After two growing seasons in the field, plants inoculated with VAM had greater aboveground biomass, cover, and height than noninoculated plants. Mycorrhizal plants were more effective in the uptake of water and phosphorus. Infection levels of inoculated plants were greatly reduced in processed shale (from 13.0 at outplanting to 3.8 at harvest), but functional VAM associations could be found after two growing seasons. Results indicate that VAM help make processed oil shale a more tractable medium for the establishment of plants representative of later successional stages by allowing these plants to make effective use of the natural resources that are limiting under conditions of high stress.        

Effects of nitrogen availability on growth and photosynthesis of Artemisia tridentata ssp. wyomingensis

This study examined the effects of alterations in soil nitrogen on the growth of Artemessia tridentata ssp. wyomingensis Nutt. Soil nitrogen content was altered by applying sugar (45 g/m 2 ), nitrate (4.5 g/m 2 ), or ammonium (4.5 g/m 2 ), and the results were compared with a control treatment (no soil amendments). Addition of either form of nitrogen significantly increased leaf nitrogen content, mean maximum length of ephemeral leaves, number of ephemeral leaves per terminal shoot, and current year's vegetative stem length over the control and sugar treatments. Both soil water and predawn xylem potentials during active growth were lower in the nitrogen-treated plots. The higher growth activity and greater leaf mass of A. tridentata in the nitrogen treatments may have been responsible for this result. Higher photosynthetic rates observed in the nitrogen treatments during an early June sampling period also lend support to this observation. This study suggests A. tridentata ssp. wyomingensis would opportunistically take advantage of increased availability of soil nitrogen. The ability of this species to respond positively to increased soil nitrogen may enhance its competitiveness over associated perennial species.     

Field study of plant survival as affected by amendments to bentonite spoil

Efforts to reclaim amended and raw bentonite spoils with six plant species (two forbs, three shrubs, and one tree) were evaluated over a 4-year period. Plant species included fourwing saltbush ( Atriplex canescens [Pursh] Nutt.), big sagebrush ( Artemisia tridentata tridentata Nutt.), Rocky Mountain Juniper ( Juniperus scopulorum Sarg.), Russian olive ( Elaeagnus angustifolia L.) common yarrow ( Achillea millifolium L.) and scarlet globemallow ( Sphaeralcea coccinea [Pursh] Rydb.). Spoil treatments included addition of gypsum, sawdust, perlite, straw, and vermiculite; the control treatment was amended. Fourwing saltbush had 52% survival across all spoil treatments, with greatest survival occurring on perlite-treated spoil (80%), followed by gypsum (70%) and vermiculite amendments (70%). Survival of other plant species ranged from 0 to 2% averaged across all treatments after 4 years. No differences in plant survival occurred among amendments when all species were considered.     

Perceptions of Utah alfalfa growers about wildlife damage to their hay crops: implications for managing wildlife on private land

We conducted a survey of Utah alfalfa ( Medicago sativa ) growers in 1993 to identify wildlife damage problems to bay crops. Such surveys can provide wildlife managers with important insights regarding landowners' wildlife damage management concerns and needs. Pocket gophers ( Thomomys spp.) and mule deer ( Odecoileus hemionus ) were perceived by growers as causing the most damage. Respondents reported a total annual loss of $350,000 or $24.79/ha (2.8% of the total crop value) because wildlife damage in alfalfa crops. Decreased hay quantity was the most frequently cited problem caused by wildlife. Compensation and incentive programs were preferred over assistance and information programs for managing wildlife damage in alfalfa crops.     

Development and longevity of ephemeral and perennial leaves on Artemisia tridentata Nutt. ssp. wyomingensis

Big sagebrush ( Artemisia tridentata Nutt.) is one of the most successful plants in the Great Basin based on its abundance and wide distribution. The development of dimorphic leaves may be an important mechanism attributing to its adaptive and competitive abilities. Development, persistence, and proportions of ephemeral and perennial leaves on Wyoming big sagebrush ( Artemisia tridentata Nutt. ssp. wyomingensis ) were studied for two years. The large ephemeral leaves are the first to develop in early spring. As early developing ephemerals mature and stems elongate, new ephemeral and perennial leaves develop in the axes of these large ephemerals. Perennial leaves expanded in the summer of their first growing season, persisting on the shrub until their abscission during summer drought of the second growing season. Plants maintained 33% of their leaf weight through the winters of 1985 and 1986. Active leaf and stem growth occurred at soil water potentials above –0.2 MPa.     

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 × 10 7 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 nif H gene sequences amplified from bacteria associated with rhizosheaths were most similar to those from Alcaligenes latus and Mesorhizobium loti .     

Notes on significant collections and additions to the flora of Glen Canyon National Recreation Area, Utah and Arizona, between 1992 and 2004

Symphyotrichum expansum (Puepp ex Spreng.) Nesom is reported new to Utah from the Escalante River drainage. A major range extension is reported for Aralia racemosa L. in the Escalante drainage, and additional populations are reported of the rare species Imperata brevifolia Vasey in Utah, including the 1st record for the Grand Staircase--Escalante National Monument. Heterotheca grandiflora Nutt. is reported new to north central Arizona. New locations and notes on an additional 22 rare species in Glen Canyon National Recreation Area are listed.     

Checklist of the mosses of Grand Teton National Park and Teton County, Wyoming

Symphyotrichum expansum (Puepp ex Spreng.) Nesom is reported new to Utah from the Escalante River drainage. A major range extension is reported for Aralia racemosa L. in the Escalante drainage, and additional populations are reported of the rare species Imperata brevifolia Vasey in Utah, including the 1st record for the Grand Staircase--Escalante National Monument. Heterotheca grandiflora Nutt. is reported new to north central Arizona. New locations and notes on an additional 22 rare species in Glen Canyon National Recreation Area are listed.     

Soil-site relationships of white locoweed on the Raft River Mountains

White locoweed ( Oxytropis sericea Nutt.) is restricted to the top and windswept ridges of the Raft River Mountains. Elevation and soil characteristics have the greatest effect on its occurrence. It is most abundant on the subalpine windswept ridge ecological site (9.2 plants/m 2 ) above 2,380 m. White locoweed apparently can tolerate the extreme environmental stresses of the shallow, rocky, windswept ridges where it is one of the dominant species. White locoweed also occurs in the deep, subalpine loam site (3.8 plants/m 2 ) above 2,865 m, but it is a minor component of this plant community. It is apparently less competitive on the deeper soils, and its population fluctuates more. It exhibits an opportunistic survival strategy on the subalpine loam site by having a large reserve of viable seeds in the soil ready to germinate and establish when environmental conditions are favorable, and then declines with competition from more robust species.     

Microhabitat-specific controls on soil respiration and denitrification in the Mojave Desert: the role of harvester ant nests and vegetation

Seed harvesting ants ( Pogonomyrmex rugosus ) concentrate organic matter and nutrients near their nests and create biogeochemical hotspots in desert soil. We examined factors regulating denitrification and soil respiration in a Mojave Desert ecosystem to determine the role harvester ant colonies play in nitrogen loss and carbon mineralization. Organic matter and nutrient storage were significantly greater in colonies than under the dominant vegetation (i.e., Pleuraphis rigida , a bunch grass) and in bare soil, with standing stocks of inorganic nitrogen in colonies nearly 4-fold greater than in the other microhabitats. Soil respiration, measured with laboratory incubations, was below detection limits under ambient soil conditions. Respiration rate in soil from bare patches and under grass was limited by water and labile organic carbon, with secondary nitrate limitation evident only once carbon limitation was alleviated. Soil respiration in ant nest soil was limited by water and labile organic carbon only. Denitrification, measured by the acetylene block technique, was elevated in bare soil and under grass with the addition of nitrate. Ant nest soil also responded to a nitrate addition; however, denitrification rate was greatest with addition of glucose. Ordinarily desert soil has low rates of respiration and denitrification due to dry ambient conditions. However, ant colonies likely function as important sites for nitrogen loss and carbon mineralization following rain storms, especially if storms coincide with seed set and the temporally pulsed input of organic matter into colonies.     

Initial survey of acetylene reduction and selected microorganisms in the feces of 19 species of mammals

Nitrogen-fixing bacteria, as demonstrated by the acetylene reduction method; yeasts, and actinomycetes were found in feces of mammals collected from St. Lawrence Island, Alaska, to the North Carolina-Tennessee border. The mammals, representing four orders and 19 species, occupy a wide variety of habitats and may play an important role in dispersing microorganisms vital to the ecosystem.     

Natural variability of vegetation, soils, and physiography in the bristlecone pine forest of the Rocky Mountains

Pinus aristata Engelm. forest vegetation in Colorado was studied to determine vegetation composition and the relationship between vegetation and environment. Species percent cover, tree size class, and environmental variables were recorded for 49 plots. Previously collected data for 4 plots form New Mexico were included. Environmental variables included latitude, longitude, elevation, slope, aspect, topographic position, parent material, percent rock cover, mean rock size, litter depth, estimated plot age class, and evidence of anthropogenic disturbance. Soils were analyzed for texture, depth, and percent carbon and nitrogen. Pinus aristata foliage was analyzed for percent nitrogen and phosphorus. Direct and indirect gradient analyses (CANOCO) were used to determine environmental factors associated with community composition. Vegetation in P. aristata forests is influenced primarily by elevation and soil pH. Substrate, soil texture, topographic position, and geographic location are secondary factors. Six plant associations were identified using cluster analysis (listed in an elevational sequence from low to high): Pinus aristata/ Festuca arizonica Vasey, Pinus aristata / Festuca thurberi Vasey, Pinus aristata / Juniperus communis L., Pinus aristata / Vaccinium myrtilus L., Pinus aristata / Ribes montigenum McClatchie, and Pinus aristata / Trifolium dasyphyllum Torr. & Gray.     

Effect of soil microtopography on seed bank distribution in the shrub-steppe

The relationship between soil surface cryptogamic crusts and seed banks was investigated in the shrubsteppe in the Lower Columbia Basin. Seventy-four percent of the seeds in a disturbed bunchgrass community were found in crevices bordering cryptogamic crust polygons. In a sagebrush/bunchgrass community, 89% of the seeds were found in crevices. In a disturbed bunchgrass community, Bromus tectorum seeds were found in both the seed bank and aboveground vegetation communities. Bromus tectorum seeds were located in the seed bank of a sagebrush/bunchgrass community, although it had a minor presence in the aboveground community. Seeds of Artemisia tridentata Nutt. were not found in either the bunchgrass or sagebrush/bunchgrass communities. The high number of seeds found in crevices bordering the cryptogamic crust suggests that crevices play a role in determining the small-scale distributional pattern of shrub-steppe plants at the Fitzner-Eberhardt Arid Lands Ecology Reserve.     

Spring denitrification rates in soils of four eastside Sierra Nevada plant communities

Denitrification rates in soils of four subalpine plant communities in the Sierra Nevada were determined by the acetylene blockage method. The study area included riparian, meadow, forest, and barren sites. Data were collected during dawn-to-dusk measurements in April 1987. Soil atmosphere samples were analyzed for N 2 O content using gas chromatography. Generally, temporal variability in denitrification rate within each plant community was insubstantial. Denitrification rate and soil temperature were found to be significantly correlated only in the riparian and barren sites. Of the four communities, the riparian site was found to have the lowest rate of denitrification overall. However, differences among sites in denitrification rate could not be conclusively attributed to variation in soil temperature, moisture, organic matter, total C and N, C:N ratio, NO 3 - N, or pH.