Seed banks of Bromus tectorum -dominated communities in the Great Basin

We seeded Agropyron cristatum and 16 native Great Basin perennial species on Bromus tectorum -dominated sites to compare temporal patterns of seedling emergence and early survival among species. To indicate variability between sites and between years, plots were planted on 2 sites in western Utah in autumn 1994, and plantings were repeated near 1 site in autumn 1995. Two sites included burned and unburned seedbed treatments. We monitored seedling emergence and survival from early winter until July of the 1st year. Four seasonal patterns of emergence were evident, indicating considerable potential for different seasonal patterns of precipitation to favor recruitment of difference species. Emergence of all shrubs, except Ephedra nevadensis , began in February and essentially ended by April. Seedlings of Ephedra nevadensis and of the grasses Agropyron and Pseudoroegneria spicata emerged over an extended period from February through June. Most other grasses and the 2 forbs began emerging in April and continued into June. Pleuraphis jamesii emergence did not begin until May. Although many seedlings of the 3 chenopod shrubs emerged, none survived, suggesting their episodic recruitment is more a function of survival than of emergence. Survival of 2 Chrysothamnus species was also low. Pseudoroegneria and Agropyron had the highest numbers of seedlings surviving on the moister site, followed by Elymus elymoides and Stipa comata . Survival of Agropyron , but not the native Elymus , was more depressed on the drier of the 2 sites planted in 1994. Stipa, Oryzopsis hymenoides , Pleuraphis , and Ephedra survived as well on the drier site as on the moister site, or better. On the 1995 planting sites Bromus was greatly reduced by the burn treatment, and, in contrast to the effect of burn treatments on the 1994 site, survival of all species except Oryzopsis and Ephedra was higher on burned than on unburned treatments. Overall, Stipa, Oryzopsis , and Pleuraphis had low emergence but consistently higher survival.     

Grazing and passerine breeding birds in a Great Basin low-shrub desert

Densities of passerine breeding birds were compared between four range pastures variously grazed by sheep over a 50-year period. The experimental pastures, located at the Desert Experimental Range in southwestern Utah, included three grazed and one ungrazed. Grazed pastures were each heavily stocked and grazed annually at one of three winter seasons (early, middle, or late). Important structural (physiognomic) and compositional differences existed in the vegetation of the experimental pastures. Horned Larks ( Eremophila alpestris [Linnaeus]), numerically dominant in the pastures, apparently responded to those differences. Black-throated Sparrows ( Amphispiza bilineata [Cassin]) and Loggerhead Shrikes ( Lanius ludovicianus Linnaeus) were less common and found as breeding birds only in dry wash habitats. No significant differences were found between the pastures in estimates of total breeding bird populations, bird standing crop biomass, or bird species richness.     

Nest site selection by Mountain Plovers ( Charadrius montanus ) in a shrub-steppe habitat

The known Mountain Plover population breeding on the Myton Bench, Duchesne County, Utah, is small, composed roughly of 30 adults and young after each breeding season. Currently, its location is peripheral to the species main range. This shrub-steppe breeding habitat differs from the shortgrass prairie habitat with which this bird is historically associated. Between 1996 and 1998 we made observations at nesting sites located consistently in 2 concentrated areas surrounded by large tracts of similar habitat. Activity may be focused in these specific areas because of breeding-site fidelity; this behavior is common among most shorebirds and has been documented for the Mountain Plover in Colorado. Also, Mountain Plovers are social and tend to choose nest sites near others. Most nests in Utah were located within close proximity of mounds of white-tailed prairie dogs ( Cynomys leucurus ), and all were situated near roadways or oil well pads. Mountain Plovers were often observed with broods on these bare areas at night. We conclude that Mountain Plovers on the Myton Bench are distributed in clumped breeding colonies within large areas of apparently favorable habitat.     

Relationship of diurnal habitat use of native stream fishes of the eastern Great Basin to pPresence of introduced salmonids

Introduced brown trout, Salmo trutta , are common to many streams of western North America. However, the ecological interactions between brown trout and native stream fishes are not well understood, particularly the nature and extent of antipredator responses of native species. We examined the effects of brown trout presence on diurnal habitat use by 2 small native fishes at a mesohabitat scale (e.g., pool, riffle, run, backwater, etc.). Adult and juvenile southern leatherside chub ( Lepidomeda aliciae , formerly Gila copei ) and juvenile mountain sucker ( Catostomus platyrhynchus ) were located in main channel pools in the absence of brown trout, but they were found almost exclusively in backwaters and cutoff pools (i.e., off-channel habitats) in streams where brown trout were abundant. Off-channel habitat appears to provide a refuge for native fishes in streams with abundant brown trout populations. Altered or degraded streams may not include sufficient off-channel refuge habitats to allow coexistence of native species and introduced brown trout.     

Plant adaptation in the Great Basin and Colorado Plateau

Adaptive features of plants of the Great Basin are reviewed. The combination of cold winters and an arid to semiarid precipitation regime results in the distinguishing features of the vegetation in the Great Basin and Colorado Plateau. The primary effects of these climatic features arise from how they structure the hydrologic regime. Water is the most limiting factor to plant growth, and water is most reliably available in the early spring after winter recharge of soil moisture. This factor determines many characteristics of root morphology, growth phenology of roots and shoots, and photosynthetic physiology. Since winters are typically cold enough to suppress growth, and drought limits growth during the summer, the cool temperatures characteristic of the peak growing season are the second most important climatic factor influencing plant habit and performance. The combination of several distinct stress periods, including low-temperature stress in winter and spring and high-temperature stress combined with drought in summer, appears to have limited plant habit to a greater degree than found in the warm deserts to the south. Nonetheless, cool growing conditions and a more reliable spring growing season result in higher water-use efficiency and productivity in the vegetation of the cold desert than in warm deserts with equivalent total rainfall amounts. Edaphic factors are also important in structuring communities in these regions, and halophytic communities dominate many landscapes. These halophytic communities of the cold desert share more species in common with warm deserts than do the nonsaline communities. The Colorado Plateau differs from the Great Basin in having greater amounts of summer rainfall, in some regions less predictable rainfall, sandier soils, and streams which drain into river systems rather than closed basins and salt playas. One result of these climatic and edaphic differences is a more important summer growing season on the Colorado Plateau and a somewhat greater diversification of plant habit, phenology, and physiology.     

Bats associated with inactive mines in the Great Basin

We surveyed bats using echolocation calls near inactive mines in the western Great Basin from 2003 to 2007. We identified 14 species of bats during our surveys, with Myotis lucifugus and Lasionycteris noctivagans found at 9 sites and Myotis evotis and Tadarida brasiliensis at 7 sites; all other species were found at less than one-half of the sites. Euderma maculatum, a state-protected species in Nevada, was recorded at 2 sites. Our work provides information that will be useful in managing bat habitat, especially with regard to mining activities.     

Marmot distribution and habitat associations in the Great Basin

In this study I describe the distribution and habitat associations of yellow-bellied marmots ( Marmota flaviventris ) in the Great Basin, compare my findings with those of E.R. Hall during his 1929-1936 survey and later surveys, and discuss potential reasons for changes in marmot distribution over time. I found 62 marmot burrow sites in 18 mountain ranges, mostly in rocky meadows situated on well-drained slopes between 2100 m and 3000 m elevation. Marmots were generally found near burrows dug within talus slopes, talus-like rock piles, or clusters of massive boulders. Oceanspray ( Holodiscus discolor ) was the shrub most commonly associated with occupied rock formations. Marmots were most abundant in the Ruby/East Humboldt Range and were common in the Desatoya, Shoshone, Toiyabe, Toquima, Cherry Creek, Schell Creek, Deep Creek, and Stansbury Ranges. Marmots appeared to be uncommon in the Monitor Range and rare in the Clan Alpine, Roberts, and Snake Ranges. I was unable to find marmots in the Diamond, Egan, Spruce-Pequop, White Pine, and Oquirrh Ranges, although I located old, weathered marmot scats in all but the latter 2 ranges. Other evidence confirms that marmots do actually occur in the Oquirrh Range, but extensive searches of the White Pine Range, including some of the same rock formations where E.R. Hall collected marmots, revealed no sign of marmots. My distribution data suggest that marmots may have gone extinct in some Great Basin mountain ranges during the last century. These disappearances may represent a natural extinction-recolonization dynamic, but a more alarming possibility is a recent die-off linked to climate change, which is predicted to force montane vegetation zones further upslope, shrinking the habitat of associated faunas. However, marmots in this study were observed as low as 1550 m elevation, indicating an altitudinal flexibility that may allow this species to survive climatic change better than more specialized boreal species such as pikas ( Ochotona princeps ) and water shrews ( Sorex palustris ).     

Succession in pinyon-juniper woodlands following wildfire in the Great Basin

Twenty - one areas in pinyon ( Pinus monophylla ) - juniper ( Juniperus osteosperma ) woodlands burned by wildfire from approximately 1 to 60 years prior to sampling and adjacent unburned mature woodland stands were studied in Nevada and California to determine successional patterns and individual species responses to burning and to changing plant communities through time. One year after burning, all late successional woodland species were present in postburn plant communities except tree species. Increases in both cover and occurrence of annual and perennial forbs resulted in their dominance on early successional sites. Shrubs and annual grasses dominated midsuccessional sites, subsequently giving way to tree, shrub, and perennial grass dominance in late succession. North and east slopes generally supported high cover and occurrence of shrubs, perennial grasses, and perennial forbs, and south and west slopes generally supported high cover and occurrence of annual forbs and annual grasses. The ability to group species according to preferential occurrence on various aspects and successional stages can be used to predict plant community composition in time and space in the pinyon - juniper woodlands.         

Nectar-sugar concentrations and flower visitors in the western Great Basin

v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Nectar - sugar concentrations and major flower visitors were determined for 15 species of plants in the Eagle Lake area of Northeastern California. Sugar concentrations for 12 of these are reported for the first time, with means ranging from a low of 10 percent in Mentzelia laevicaulis to a high of 63 percent in Ranunculus uncinatus. The utilization of the various nectar concentrations varied with the type of flower visitor as well as with the habitat and distributional ranges of the plant and/or animal. Hummingbirds and hawkmoths were not observed visiting the flowers they typically visit in other areas (e.g. Aquilegia and Ipomopsis, or Oenothera ), but here preferred more concentrated nectar ( Cirsium spp., with mean   of 57 percent sugar). Specialization in nectar use is reported at the generic and specific level in Hymenoptera and Lepidoptera; solitary bees, as a whole, used slightly less concentrated nectar ( mean = 38 percent sugar) than butterflies ( mean = 44 percent sugar).        

Niche pattern in a Great Basin rodent fauna

Niche pattern of a desert rodent community in shrub habitats of central Utah was examined in the canonical space formed by the first four principal components of trapsite, microhabitat. Positions of species centroids differed significantly (P 1 ) increased with niche breadth (v 1 ) and decreased with increasing difference of centroids of a species from the overall mean habitat (d 1 ). V 1 was positively related to d 1 . Differences between niche pattern of this community and that of deciduous forest small mammals are discussed.     

Dam-site selection by beavers in an eastern Oregon basin

We compared physical and vegetative habitat characteristics at 14 dam sites occupied by beaver ( Castor Canadensis ) with those at 41 random unoccupied reaches to identify features important to dam-site selection in the Long Creek basin, Grant County, Oregon. Stream reaches with dams were shallower and had a lower gradient than unoccupied reaches. Beaver did not build dams at sites with a rock substrate. Bank slopes at occupied reaches were not as steep as those at unoccupied reaches; and occupied stream reaches had greater tree canopy cover, especially of thinleaf alder ( Alnus tenuifolia ), than did unused reaches. A discriminant model using transformations of bank slope, stream gradient, and hardwood cover classified all beaver dam sites correctly and 35 of 41 random sites as unoccupied sites. The 6 misclassified sites had rock substrates. We also tested four habitat suitability models for beaver in this basin. Three models produced significantly different ( P < .05) scores between occupied and random unoccupied reaches, suggesting that they might have some utility for this region.     

Breeding movements and reproductive activities of porcupine in the Great Basin Desert

I assessed movements of North American porcupines ( Erethizon dorsatum ) in the Great Basin of northwestern Nevada in relation to reproductive activities during the late summer and fall periods of 1991 and 1992. Porcupines exhibit a mate-defense polygynous mating system and I hypothesized that (1) competitively dominant males would have larger home ranges than both subordinate males and adult females, and (2) variation in home range size among adult male porcupines would be positively correlated with reproductive success. Results indicated that dominant male porcupines ranged over larger areas (average 95% minimum convex polygon home range = 20.7 ha) than subordinate males (average 95% MCP home range = 2.9 ha) and adult females (average 95% MCP home range = 8.2 ha). Analyses of movements in relation to body size and energetic requirements revealed that home ranges of dominant male porcupines were larger than predicted based on body size (approximately 10.2 ha). Breeding period home ranges of dominant male porcupines encompassed portions of the home ranges of 3 to 10 adult females, and indices of reproductive success based on observations of mate-guarding behaviors suggested a strong positive relationship between home range sizes of male porcupines and mating success. Together these data suggested that larger home ranges among dominant males were related to increased mating opportunities and not increased metabolic requirements associated with larger male body sizes. In the study area, however, female porcupines congregated around small, patchily distributed riparian areas, and dominant males with relatively small home ranges encompassing riparian areas may have gained mating access to multiple females. Finally, analyses of overlap among core home ranges (60% MCP) of adult male and adult female porcupines suggested that both sexes maintained relatively exclusive core home range areas, with males exhibiting significantly less range overlap with other males ( ￣x = 9.4%) than females with other females ( ￣x = 27.1%). It is possible that the small, patchily distributed riparian areas in this desertlike area were such a limited resource that females were unable to maintain exclusive use of their home range areas.     

Relative vulnerability to extirpation of montane breeding birds in the Great Basin

Seventy-four species of montane breeding birds were evaluated for their vulnerability to extirpation in the Great Basin. Although none of these species are endemic to the Great Basin, the montane island system results in a unique pattern of species associations. Loss of species from these montane communities could be indicative of region wide habitat degradation. I ranked susceptibility to extirpation based on seven biological variables: geographic range, population size, reproductive potential, susceptibility to cowbird parasitism, migratory status, and diet specialization. Each variable was weighted equally in its contribution to vulnerability, and scores were the sum of trait scores for each species. Different suites of life-history traits led to similar vulnerabilities. The following 10 montane bird species were categorized as most vulnerable to extirpation from the Great Basin, listed as most to least vulnerable: Olive-sided Flycatcher ( Contopus borealis ), Painted Redstart ( Myioborus pictus ), Hammond's Flycatcher ( Empidonax hammondii ), Veery ( Catharus fuscescens ), Whip-poor-will ( Caprimulgus vociferus ), Lincoln's Sparrow ( Melospiza lincolnii ), Black-backed woodpecker ( Picoides arcicus ), Three-toed Woodpecker ( P. tridactylus ), Himalayan Snowcock ( Tetraogallus himalayensis ), and Nashville Warbler ( Verminvora ruficapilla ). Species of similar vulnerability scores often were dissimilar in threats related to their vulnerability. No taxonomic patterns in vulnerability were found. This type of analysis should be used proactively to identify vulnerable species or populations and to set priorities for research management.     

Standing crops and dynamics of phytomass and minerals in two salt desert shrub communities

Of two salt desert shrub communities studied in Curlew Valley, Utah, the Atriplex confertifolia- dominated community had 15% greater total midsummer phytomass than the Ceratoides lanata community. The larger Atriplex shrubs contained much more woody tissue for support of photosynthetic tissues than did Ceratoides. Atriplex aboveground phytomass and litter were about twice those of Ceratoides. Ceratoides litter was generally fine and easily decomposable, but Atriplex litter contained about equal proportions of coarse, resistant woody tissues and fine, easily decomposable material. Atriplex root phytomass was 1.3 times that of Ceratoides at the 2&ndash;30 cm depth, but at depths below 30 cm, Ceratoides exhibited up to three times greater root phytomass and had 23% more root mass overall. Net aboveground community primary production was estimated to be about one-third greater in the Atriplex than Ceratoides community. Turnover times for readily decomposable aboveground litter were quite similar, but, because Atriplex produced coarser litter, its overall rate was somewhat slower than that of Ceratoides. Analyses of selected minerals in plant parts, litter, and soil revealed that about 90% of the mineral capital is in the soil, mostly within organic matter. Nearly equivalent pools of mineral elements were found in the two communities, except for greater Na in the Atriplex community.     

Modeling distributions of rare plants in the Great Basin, western North America

In this 2-phase study, we developed field-validated site and landscape-level predictive models for identifying potential rare and endemic plant habitat in the Great Basin of western North America. Four species were chosen to include a range of environmental variability and plant communities. Herbarium records of known occurrences were used to identify initial sample sites. The geographic coordinates, environmental attributes, and vegetation data collected at each site were used to develop 2 predictive models for each species: a field key and a probability-of-occurrence or predictor map. The field key was developed using only field data collected at the sites on environmental attributes and associated species. Predictive maps were developed with a geographic information system (GIS) containing slope, elevation, aspect, soils, and geologic data. Classification-tree (CT) software was used to generate dichotomous field keys and maps of occurrence probabilities. Predictions from both models were then field-validated during the 2nd phase of the study, and final models were developed through an iterative process, in which data collected during the field validation were incorporated into subsequent predictive models. Cross-validated models were >96% accurate and generally predicted presence with >60% accuracy. These models identified potential habitat by combining elevation, slope, aspect, rock type, and geologic process into habitat models for each species. ACRONYMS.—CEC—cation exchange capacity, CT—classification tree, DEM—digital elevation model, GAM—generalized additive model, GIS—geographic information system, GLM—generalized linear model, GPS—geographic positioning system, ROC—receiver operating curves, STATSGO—State Soil Geographic Database, USGS—United States Geological Survey, UTM—Universal Transverse Mercator. Nomenclature and distributions: Welsh et al. 2003, Shultz et al. 2005.     

Monitoring temporal change in riparian vegetation of Great Basin National Park

Disturbance in riparian areas of semiarid ecosystems involves complex interactions of pulsed hydrologic flows, herbivory, fire, climatic effects, and anthropogenic influences. We resampled riparian vegetation within ten 10-m × 100-m plots that were initially sampled in 1992 in 4 watersheds of the Snake Range, east central Nevada. Our finding of significantly lower coverage of grasses, forbs, and shrubs within plots in 2001 compared with 1992 was not consistent with the management decision to remove livestock grazing from the watersheds in 1999. Change over time in cover of life-forms or bare ground was not predicted by scat counts within plots in 2001. Cover results were also not well explained by variability between the 2 sampling periods in either density of native herbivores or annual precipitation. In contrast, Engelmann spruce ( Picea engelmannii ) exhibited reduced abundance at all but the highest-elevation plot in which it occurred in 1992, and the magnitude of change in abundance was strongly predicted by plot elevation. Abundance of white fir ( Abies concolor ) individuals increased while aspen ( Populus tremuloides ) individuals decreased at 4 of 5 sites where they were sympatric, and changes in abundance in the 2 species were negatively correlated across those sites. Utility of monitoring data to detect change over time and contribute to adaptive management will vary with sample size, observer bias, use of repeatable or published methods, and precision of measurements, among other factors.     

Diamond Pond, Harney County, Oregon: vegetation history and water table in the eastern Oregon desert

Cores obtained in 1978 from Diamond Pond, Diamond Craters, Harney County, Oregon, as part of the Steens Mountain Prehistory Project, provide a record of vegetation change on the sagebrush/shadscale ecotone and of local and perhaps regional water tables. Pollen, macrofossils, sediments, and charcoal from these radiocarbon-dated cores were analyzed. Varying abundance of juniper, grass, sagebrush, and greasewood pollen, and of aquatic to littoral plant macrofossils reflects changing regional effective moisture and local water table since 6000 B. P. Eleven dates spanning 5200 radiocarbon years and four regionally correlated volcanic ashes establish the dating of seven periods of different moisture regimes: 1. Greasewood and saltbush pollen dominance before 5400 B. P. indicates shadscale desert. Rapid accumulation of alternating silts and medium sands lacking aquatic plant macrofossils and pollen reflects periods of ephemeral ponds with water table 17 m below the present level and considerable erosion of maar slopes. 2. Increasing sagebrush pollen from 5400 to 4000 B. P. indicates sagebrush expansion into shadscale desert. Scirpus, Rumex, Ceratophyllum, and Polygonum persicaria macrofossils and finely laminated clayey silts evidence perennial pond. 3. From 4000 to 2000 B. P. abundant juniper and grass pollen reflects extensive juniper grasslands (juniper seeds from trees growing nearby fell into the pond during this period). Rising charcoal values indicate greater importance of fire. Deepest late-Holocene pond ca 3700 B. P. corresponds with postulated intensive human occupation of northern Great Basin marsh and lake locales. 4. Between 2000 and 1400 B. P. increased sagebrush pollen mirrors reduced effective moisture and reexpanding sagebrush steppe. More abundant Scirpus and Rumex macrofossils evidence shallow pond. 5. From 1400 to 900 B. P. more numerous grass pollen indicates returning greater effective moisture resulting in deeper water with abundant Potamogeton . 6. About 500 B. P. increased greasewood and saltbush pollen evidences drought. Ruppia seeds and pollen and the mollusk Musculium indicate shallow, brackish water. 7. Abundant juniper and grass pollen reflects moister conditions between 300 and 150 B. P. Numerous Ceratophyllum fruits indicate deeper, freshened water. Since the mid- 1800s man and changing climate have encouraged sagebrush reexpansion. Increased Scirpus macrofossils indicate shallower water.     

History of fish hatchery development in the Great Basin states of Utah and Nevada

Fish hatchery systems in both Utah and Nevada are now an integral part of the fishery management scheme. Historic development of hatcheries, including the early stocking of exotics, is presented. Disease control and dry pelleted feed are discussed in historical perspective and present status.     

Three new records for diatoms from the Great Basin, USA

Three diatom species recently collected from Great Basin localities represent new records of these taxa from this region of western North America. Cocconeis scutellum &nbsp; Ehr. and Melosira dubia &nbsp; Kuetz. were collected from a thermal spring in Tooele County, Utah. Nitzschia hustedtiana &nbsp; Salah was collected from newly flooded marshes at the south end of the Great Salt Lake, Tooele Countv, Utah.