Plant Biology Commons^™

Integrated Weed Management Plan For The Lower Las Vegas Wash, Elizabeth Bickmore

Publications (WR)

The Las Vegas Wash (Wash) is the primary drainage for the metropolitan Las Vegas Valley, eventually finding its way into the Colorado River watershed system. Pursuant to the recommendations of the Water Quality Citizens Advisory Committee, the Las Vegas Wash Coordination Committee (LVWCC) was formed in 1998 to develop a comprehensive plan for the long-term stabilization and management of the Wash. Consisting of representatives from 28 government agencies, businesses, environmental groups and citizens, the LVWCC formulated the Las Vegas Wash Comprehensive Adaptive Management Plan (CAMP) and designated the Southern Nevada Water Authority (SNWA) as the lead agency for the implementation …

On The Relationship Between Stomatal Characters And Atmospheric Co2, C. D. Reid, H. Maherali, H. B. Johnson, S. D. Smith, S. D. Wullschleger, R. B. Jackson

Life Sciences Faculty Research

Leaf stomatal characters influence the response of terrestrial evapotranspiration to climate change and are used as proxies for the reconstruction of past atmospheric [CO2]. We examined the phenotypic response of stomatal index (SI), density (SD) and aperture (AP) to rising atmospheric CO2 in 15 species after four years exposure to a field CO2 gradient (200 to 550 μmol mol−1 atmospheric [CO2]) or at three Free Air CO2 Enrichment (FACE) sites. Along the CO2 gradient, SI and SD showed no evidence of a decline to increasing [CO2], while AP decreased slightly. There was no significant change in SI, SD or AP …

Arbuscular Mycorrhizae Of Mojave Desert Plants, J. H. Titus, P. J. Titus, R. S. Nowak, S. D. Smith

Life Sciences Faculty Research

Roots of 15 Mojave Desert plant species were assessed for arbuscular mycorrhizal (AM) colonization in spring and autumn 1999. Another 19 species were assessed in autumn only. Perennial species were AM colonized, whereas annual species contained very low levels of AM hyphae or were nonmycorrhizal. The nonnative tree Tamarix ramosissima was also nonmycorrhizal. Levels of hyphae changed over the season in 2 species, arbuscle levels increased in 1 species, and vesicles decreased in 7 species. Mycorrhizal inoculum potential (MIP) was assessed in the soils associated with spring-collected plants. All soils were found to contain MIP. MIP values were not correlated …

Effect Of Atmospheric Co2 Enrichment On Root Growth And Carbohydrate Allocation Of Phaseolus Spp., Katrina J. Salsman, Dean N. Jordan, S. D. Smith, D. S. Neuman

Life Sciences Faculty Research

A glasshouse experiment was conducted with plants of Phaseolus grown in liquid culture. Root growth parameters (biomass, diameter, length, growth rate, zone of cell division), root rheological components (wall extensibility, water potential yield threshold, water potential), shoot growth, carbon allocation, and abscisic acid (ABA) concentration were measured in Phaseolus acutifolius A. Gray at ambient (550 μmol mol−1) and elevated (700 μmol mol−1) atmospheric CO2 concentrations. For contrast, measurements of above‐ and belowground growth were conducted on Phaseolus vulgaris L. in the same treatments. Under nonlimiting conditions of water and nutrients, elevated CO2 increased root and shoot growth of P. acutifolius …

Bowen Ratio Estimates Of Evapotranspiration For Stands On The Virgin River In Southern Nevada, Dale A. Devitt, A. Sala, S. D. Smith, J. Cleverly, L. K. Shaulis, R. Hammett

Life Sciences Faculty Research

A Bowen ratio energy balance was conducted over a Tamarix ramosissima (saltcedar) stand growing in a riparian corridor along the Virgin River in southern Nevada. Measurements in two separate years were compared and contrasted on the basis of changes in growing conditions. In 1994, a drought year, record high temperatures, dry winds, and a falling water table caused partial wilt of outer smaller twigs in the canopy of many trees in the stand around the Bowen tower. Subsequently, evapotranspiration (ET) estimates declined dramatically over a 60‐day period (11 mm d−1 tod−1). In 1995, the Virgin River at the Bowen tower …

Evapotranspiration From A Saltcedar-Dominated Desert Floodplain: A Scaling Approach, S. D. Smith, A. M. Sala, Dale A. Devitt

Life Sciences Faculty Research

The purpose of this study was to investigate evapotranspiration (ET) from a variety of scales (leaf to landscape) in saltcedar-dominated floodplain vegetation along the lower Virgin River of southern Nevada. Leaf-level gas exchange indicated that saltcedar exhibits similar stomatal conductance as the sympatric phreatophytes arrowweed, mesquite, and willow. However, sap flow in saltcedar was higher per unit sapwood area than the other species, suggesting that it maintains higher leaf area per unit sapwood area. At the stand level, saltcedar ET was found to exceed potential ET early in the summer when soils were moist and the water table was near …

Fire In A Riparian Shrub Community: Postburn Water Relations In The Tamarix-Salix Association Along The Lower Colorado River, S. D. Smith, D. E. Busch

Life Sciences Faculty Research

Higher water potentials in recovering burned salt-cedar (Tamarix ramosissima) relative to unburned plants and the opposite situation in willow (Salix gooddingii) provide evidence that postfire water stress is reduced in the former but not the latter. Similarly, diurnal patterns of stomatal conductance in these taxa are consistent with the existence of more vigor in burned salt-cedar than willow. Plots of water potential and transpiration demonstrate that hydraulic efficiencies may contribute to differences in fire recovery.

Introduction And Enhancement Of Vegetative Cover At Lake Mead, Jennifer S. Haley, Lisa K. Croft, Suzanne E. Leavitt, Larry J. Paulson

Publications (WR)

Studies done by the Nevada Department of Wildlife (NDOW) and the Arizona Fish and Game between 1978 and 1981 indicate that inadequate cover may be limiting the production and survival of largemouth bass at the Lake Mead National Recreation Area (LMNRA). As a result of these studies, NDOW initiated a contract in 1986 with the Lake Mead Research Center (LMRC) to investigate means of improving habitat for game fish by introducing natural and/or artificial cover. During Phase I (1986-1987) of this contract, the shoreline of Lake Mead was surveyed for aquatic and terrestrial plant growth. Also during this time, submerged …

Water Relations Of Obligate Riparian Plants As A Function Of Streamflow Diversion On The Bishop Creek Watershed, S. D. Smith, J. L. Nachlinger, A. B. Wellington, C. A. Fox

Life Sciences Faculty Research

We investigated the water relations of obli-gate riparian plants on paired diverted and undiverted reaches on Bishop Creek, Eastern Sierra Nevada. Ri-parian plants on diverted reaches had reduced stomatal conductance and water potential compared to plants on undiverted reaches in a dry year, but not in a high runoff year. Juvenile plants on diverted reaches had reduced stomatal conductance and lower midday water potentials relative to surrounding mature trees, a trend that was not observed on undiverted reaches. Plants on diverted reaches possessed significantly smaller, thicker leaves and a reduced total leaf area relative to trees on streamside reaches. Reduced …

Riparian Plant Water Relations Along The North Fork Of The Kings River, California, J. L. Nachlinger, S. D. Smith, R. J. Risser

Life Sciences Faculty Research

Plant water relations of five obligate ripar-ian species were studied along California's North Fork Kings River. Diurnal stomatal conductance, transpi-ration, and xylem pressure potentials were measured throughout the 1986 growing season and in mid-season in 1987. Patterns were similar for all species although absolute values varied considerably. Maximum stomatal conductance occurred early in the day and season during favorable environmental conditions and decreased as air temperature and the vapor pressure difference between the leaf and air increased. Maximum transpiration rates occurred in mid-morning and mid-summer resulting in estimated daily water losses per unit sunlit leaf area of 163-328 mol H2O …

An Isotopic Analysis Of The Hydrology And Riparian Vegetation Water Sources On Bishop Creek, M. L. Space, J. W. Hess, S. D. Smith

Life Sciences Faculty Research

Five power generation plants along an eleven kilometer stretch divert Bishop Creek water for hydro-electric power. Stream diversion may be adversely affecting the riparian vegetation. Stable isotopic analysis is employed to determine surface water/ground-water interactions along the creek. surface water originates primarily from three headwater lakes. Discharge into Bishop Creek below the headwaters is primarily derived from ground water. The average δD and δ18O values are significantly different for surface water and ground water that an isotopic analysis can delineate between these two components of flow. Therefore isotopic shifts along the creek can determine gaining reaches. In addition, by knowing …

Benthic Diatom Community Dynamics In The Colorado River: Interactive Effects Of Periodic Dessication And Current Regime, Christopher Gerard Peterson

Publications (WR)

The response to periodic desiccation of periphyton communities developed in eddy environments or in areas exposed to variable, direct current was examined. Algal communities were incubated on clay tiles for between 2 and 12 weeks in the Colorado River, directly below Hoover Dam from October, 1983 - January, 1984. Mean daily discharge from the dam decreased over this period. To assess the influence of these discharge changes on community dynamics, samples collected over the first 12 weeks of the investigation were compared to samples of the same age collected over the final 8 weeks.

The small diatom taxon Achnahthes spp …