Geology topics

E. P. Glenn

Publications and source records attributed to E. P. Glenn.

15 recordsLinked to original sources

USGS2014

Indirect effects of biocontrol of an invasive riparian plant ( Tamarix ) alters habitat and reduces herpetofauna abundance

The biological control agent (tamarisk leaf beetle, Diorhabda spp.) is actively being used to defoliate exotic saltcedar or tamarisk ( Tamarix spp.) in riparian ecosystems in western USA. The Virgin River in Arizona and Nevada is a system where tamarisk leaf beetle populations are spreading. Saltcedar biocontrol, like other control methods, has the potential to affect non-target species. Because amphibians and reptiles respond to vegetation changes in habitat and forage in areas where beetles are active, herpetofauna are model taxa to investigate potential impacts of biocontrol defoliation. Our objectives related herpetofauna abundance to vegetation cover and indices (normalized difference vegetation index, NDVI; enhanced vegetation index, EVI) and timing of biocontrol defoliation. We captured herpetofauna and ground-dwelling arthropods in trap arrays and measured vegetation using remotely sensed images and on-the-ground measurements at 16–21 sites 2 years before (2009–2010) and 2 years following (2011–2012) biocontrol defoliation. Following defoliation, riparian stands (including stands mixed with native and exotic trees and stands of monotypic exotic saltcedar) had significantly lower NDVI and EVI values and fewer captures of marked lizards. Total captures of herpetofauna (toads, lizards, and snakes) were related to higher vegetation cover and sites with a lower proportion of saltcedar. Our results suggest that effects of biocontrol defoliation are likely to be site-specific and depend upon the proportion of native riparian trees established prior to biocontrol introduction and defoliation. The mechanisms by which habitat structure, microclimate, and ultimately vertebrate species are affected by exotic plant biocontrol riparian areas should be a focus of natural-resource managers.

Mojave Desert↗

USGS2013

Plot- and landscape-level changes in climate and vegetation following defoliation of exotic saltcedar (Tamarix sp.) from the biocontrol agent Diorhabda carinulata along a stream in the Mojave Desert (USA)

The biocontrol agent, northern tamarisk beetle (Diorhabda carinulata), has been used to defoliate non-native saltcedar (Tamarix spp.) in USA western riparian systems since 2001. Biocontrol has the potential to impact biotic communities and climatic conditions in affected riparian areas. To determine the relationships between biocontrol establishment and effects on vegetation and climate at the plot and landscape scales, we measured temperature, relative humidity, foliage canopy, solar radiation, and used satellite imagery to assess saltcedar defoliation and evapotranspiration (ET) along the Virgin River in the Mojave Desert. Following defoliation solar radiation increased, daily humidity decreased, and maximum daily temperatures tended to increase. MODIS and Landsat satellite imagery showed defoliation was widespread, resulting in reductions in ET and vegetation indices. Because biocontrol beetles are spreading into new saltcedar habitats on arid western rivers, and the eventual equilibrium between beetles and saltcedar is unknown, it is necessary to monitor trends for ecosystem functions and higher trophic-level responses in habitats impacted by biocontrol.

Mojave Desert↗

USGS2012

Roles of saltcedar (Tamarix spp.) and capillary rise in salinizing a non-flooding terrace on a flow-regulated desert river

Tamarix spp. (saltcedar) secretes salts and has been considered to be a major factor contributing to the salinization of river terraces in western US riparian zones. However, salinization can also occur from the capillary rise of salts from the aquifer into the vadose zone. We investigated the roles of saltcedar and physical factors in salinizing the soil profile of a non-flooding terrace at sites on the Cibola National Wildlife Refuge on the Lower Colorado River, USA. We placed salt traps under and between saltcedar shrubs and estimated the annual deposition rate of salts from saltcedar. These were then compared to the quantities and distribution on of salts in the soil profile. Dense stands of saltcedar deposited 0.159 kg m −2 yr −1 of salts to the soil surface. If this rate was constant since seasonal flooding ceased in 1938 and all of the salts were retained in the soil profile, they could account for 11.4 kg m −2 of salt, about 30% of total salts in the profile today. Eliminating saltcedar would not necessarily reduce salts, because vegetation reduces the upward migration of salts in bulk flow from the aquifer. The densest saltcedar stand had the lowest salt levels in the vadose zone in this study.

California↗

USGS2012

A simple method for estimating basin-scale groundwater discharge by vegetation in the basin and range province of Arizona using remote sensing information and geographic information systems

Groundwater is a vital water resource in the arid to semi-arid southwestern United States. Accurate accounting of inflows to and outflows from the groundwater system is necessary to effectively manage this shared resource, including the important outflow component of groundwater discharge by vegetation. A simple method for estimating basin-scale groundwater discharge by vegetation is presented that uses remote sensing data from satellites, geographic information systems (GIS) land cover and stream location information, and a regression equation developed within the Southern Arizona study area relating the Enhanced Vegetation Index from the MODIS sensors on the Terra satellite to measured evapotranspiration. Results computed for 16-day composited satellite passes over the study area during the 2000 through 2007 time period demonstrate a sinusoidal pattern of annual groundwater discharge by vegetation with median values ranging from around 0.3 mm per day in the cooler winter months to around 1.5 mm per day during summer. Maximum estimated annual volume of groundwater discharge by vegetation was between 1.4 and 1.9 billion m 3 per year with an annual average of 1.6 billion m 3 . A simplified accounting of the contribution of precipitation to vegetation greenness was developed whereby monthly precipitation data were subtracted from computed vegetation discharge values, resulting in estimates of minimum groundwater discharge by vegetation. Basin-scale estimates of minimum and maximum groundwater discharge by vegetation produced by this simple method are useful bounding values for groundwater budgets and groundwater flow models, and the method may be applicable to other areas with similar vegetation types.

Arizona↗

USGS2011

Estimating basin scale evapotranspiration (ET) by water balance and remote sensing methods

Evapotranspiration (ET) is an important hydrological process that can be studied and estimated at multiple spatial scales ranging from a leaf to a river basin. We present a review of methods in estimating basin scale ET and its applications in understanding basin water balance dynamics. The review focuses on two aspects of ET: (i) how the basin scale water balance approach is used to estimate ET; and (ii) how ‘direct’ measurement and modelling approaches are used to estimate basin scale ET. Obviously, the basin water balance-based ET requires the availability of good precipitation and discharge data to calculate ET as a residual on longer time scales (annual) where net storage changes are assumed to be negligible. ET estimated from such a basin water balance principle is generally used for validating the performance of ET models. On the other hand, many of the direct estimation methods involve the use of remotely sensed data to estimate spatially explicit ET and use basin-wide averaging to estimate basin scale ET. The direct methods can be grouped into soil moisture balance modelling, satellite-based vegetation index methods, and methods based on satellite land surface temperature measurements that convert potential ET into actual ET using a proportionality relationship. The review also includes the use of complementary ET estimation principles for large area applications. The review identifies the need to compare and evaluate the different ET approaches using standard data sets in basins covering different hydro-climatic regions of the world.

Hydrological Processes↗

USGS2011

Potential for water salvage by removal of non-native woody vegetation from dryland river systems

Globally, expansion of non-native woody vegetation across floodplains has raised concern of increased evapotranspiration (ET) water loss with consequent reduced river flows and groundwater supplies. Water salvage programs, established to meet water supply demands by removing introduced species, show little documented evidence of program effectiveness. We use two case studies in the USA and Australia to illustrate factors that contribute to water salvage feasibility for a given ecological setting. In the USA, saltcedar (Tamarix spp.) has become widespread on western rivers, with water salvage programs attempted over a 50-year period. Some studies document riparian transpiration or ET reduction after saltcedar removal, but detectable increases in river base flow are not conclusively shown. Furthermore, measurements of riparian vegetation ET in natural settings show saltcedar ET overlaps the range measured for native riparian species, thereby constraining the possibility of water salvage by replacing saltcedar with native vegetation. In Australia, introduced willows (Salix spp.) have become widespread in riparian systems in the Murray-Darling Basin. Although large-scale removal projects have been undertaken, no attempts have been made to quantify increases in base flows. Recent studies of ET indicate that willows growing in permanently inundated stream beds have high transpiration rates, indicating water savings could be achieved from removal. In contrast, native Eucalyptus trees and willows growing on stream banks show similar ET rates with no net water salvage from replacing willows with native trees. We conclude that water salvage feasibility is highly dependent on the ecohydrological setting in which the non-native trees occur. We provide an overview of conditions favorable to water salvage. Copyright ?? 2011 John Wiley & Sons, Ltd.

Hydrological Processes↗

USGS2011

Vegetation index-based crop coefficients to estimate evapotranspiration by remote sensing in agricultural and natural ecosystems

Crop coefficients were developed to determine crop water needs based on the evapotranspiration (ET) of a reference crop under a given set of meteorological conditions. Starting in the 1980s, crop coefficients developed through lysimeter studies or set by expert opinion began to be supplemented by remotely sensed vegetation indices (VI) that measured the actual status of the crop on a field-by-field basis. VIs measure the density of green foliage based on the reflectance of visible and near infrared (NIR) light from the canopy, and are highly correlated with plant physiological processes that depend on light absorption by a canopy such as ET and photosynthesis. Reflectance-based crop coefficients have now been developed for numerous individual crops, including corn, wheat, alfalfa, cotton, potato, sugar beet, vegetables, grapes and orchard crops. Other research has shown that VIs can be used to predict ET over fields of mixed crops, allowing them to be used to monitor ET over entire irrigation districts. VI-based crop coefficients can help reduce agricultural water use by matching irrigation rates to the actual water needs of a crop as it grows instead of to a modeled crop growing under optimal conditions. Recently, the concept has been applied to natural ecosystems at the local, regional and continental scales of measurement, using time-series satellite data from the MODIS sensors on the Terra satellite. VIs or other visible-NIR band algorithms are combined with meteorological data to predict ET in numerous biome types, from deserts, to arctic tundra, to tropical rainforests. These methods often closely match ET measured on the ground at the global FluxNet array of eddy covariance moisture and carbon flux towers. The primary advantage of VI methods for estimating ET is that transpiration is closely related to radiation absorbed by the plant canopy, which is closely related to VIs. The primary disadvantage is that they cannot capture stress effects or soil evaporation. Copyright ?? 2011 John Wiley & Sons, Ltd.

Hydrological Processes↗

USGS2010

Sap flux-scaled transpiration by tamarisk (Tamarix spp.) before, during and after episodic defoliation by the saltcedar leaf beetle (Diorhabda carinulata)

The release of the saltcedar beetle (Diorhabda carinulata) has resulted in the periodic defoliation of tamarisk (Tamarix spp.) along more than 1000 river km in the upper Colorado River Basin and is expected to spread along many other river reaches throughout the upper basin, and possibly into the lower Colorado River Basin. Identifying the impacts of these release programs on tamarisk water use and subsequent water cycling in arid riparian systems are largely unknown, due in part to the difficulty of measuring water fluxes in these systems. We used lab-calibrated, modified heat-dissipation sap flux sensors to monitor tamarisk water use (n=20 trees) before, during and after defoliation by the saltcedar leaf beetle during the 2008 and 2009 growing seasons (May-October) in southeastern Utah. We incorporated a simple model that related mean stem sap flux density (Js) with atmospheric vapor pressure deficit (vpd) before the onset of defoliation in 2008. The model was used to calculate differences between predicted Js and Js measured throughout the two growing seasons. Episodic defoliation resulted in a 16% reduction in mean annual rates of Js in both 2008 and 2009, with decreases occurring only during the periods in which the trees were defoliated (about 6-8 weeks per growing season). In other words, rates of Js rebounded to values predicted by the model when the trees produced new leaves after defoliation. Sap flux data were scaled to stand water use by constructing a tamarisk-specific allometric equation to relate conducting sapwood area to stem diameter, and by measuring the size distribution of stems within the stand. Total water use in both years was 0.224m, representing a reduction of about 0.04myr-1. Results showed that repeated defoliation/refoliation cycles did not result in a progressive decrease in either leaf production or water use over the duration of the study. This investigation improves ground-based estimates of tamarisk water use, and will support future efforts to characterize impacts of the beetle on basin-wide hydrologic processes. ?? 2010 Elsevier B.V.

Agricultural and Forest Meteorology↗

USGS2010

On the irrigation requirements of cottonwood (Populus fremontii and Populus deltoides var. wislizenii) and willow (Salix gooddingii) grown in a desert environment

Native tree plots have been established in river irrigation districts in the western U.S. to provide habitat for threatened and endangered birds. Information is needed on the effective irrigation requirements of the target species. Cottonwood (Populus spp.) and willow (Salix gooddingii) trees were grown for seven years in an outdoor plot in a desert environment in Tucson, Arizona. Plants were allowed to achieve a nearly complete canopy cover over the first four years, then were subjected to three daily summer irrigation schedules of 6.20??mm??d -1 ; 8.26??mm??d -1 and 15.7??mm??d -1 . The lowest irrigation rate was sufficient to maintain growth and high leaf area index for cottonwoods over three years, while willows suffered considerable die-back on this rate in years six and seven. These irrigation rates were applied April 15-September 15, but only 0.88??mm??d -1 was applied during the dormant period of the year. Expressed as a fraction of reference crop evapotranspiration (ET o ), recommended annual water applications plus precipitation (and including some deep drainage) were 0.83 ET o for cottonwood and 1.01 ET o for willow. Current practices tend to over-irrigate restoration plots, and this study can provide guidelines for more efficient water use. ?? 2010 Elsevier Ltd.

Journal of Arid Environments↗

USGS2009

Deficit irrigation of a landscape halophyte for reuse of saline waste water in a desert city

Saline waste waters from industrial and water treatment processes are an under-utilized resource in desert urban environments. Management practices to safely use these water sources are still in development. We used a deeprooted native halophyte, Atriplex lentiformis (quailbush), to absorb mildly saline effluent (1800 mg l-1 total dissolved solids, mainly sodium sulfate) from a water treatment plant in the desert community of Twentynine Palms, California. We developed a deficit irrigation strategy to avoid discharging water past the root zone to the aquifer. The plants were irrigated at about one-third the rate of reference evapotranspiration (ETo) calculated from meteorological data over five years and soil moisture levels were monitored to a soil depth of 4.7 m at monthly intervals with a neutron hydroprobe. The deficit irrigation schedule maintained the soil below field capacity throughout the study. Water was presented on a more or less constant schedule, so that the application rates were less than ETo in summer and equal to or slightly greater than ETo in winter, but the plants were able to consume water stored in the profile in winter to support summer ET. Sodium salts gradually increased in the soil profile over the study but sulfate levels remained low, due to formation of gypsum in the calcic soil. The high salt tolerance, deep roots, and drought tolerance of desert halophytes such as A. lentiformis lend these plants to use as deficit-irrigated landscape plants for disposal of effluents in urban setting when protection of the aquifer is important. ?? 2008 Elsevier B.V.

Landscape and Urban Planning↗

USGS2009

Remote monitoring of tamarisk defoliation and evapotranspiration following saltcedar leaf beetle attack

Tamarisk (Tamarix spp.) has invaded riparian ecosystems throughout the Western United States, including significant portions of riparian ecosystems within U.S. National Parks and Monuments. Recently, the saltcedar leaf beetle (Diorhabda elongata) was released as a tamarisk biocontrol agent. Although initial releases have been monitored, no comprehensive program is currently in place to monitor the rapid spread of Diorhabda that has resulted from numerous subsequent releases by county and state agencies. Long term monitoring of tamarisk defoliation and its impacts on habitat and water resources is needed. This study examines the potential for using higher spatial resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and lower spatial resolution Moderate Resolution Imaging Spectroradiometer (MODIS) data for monitoring defoliation caused by Diorhabda and subsequent changes in evapotranspiration (ET). Widespread tamarisk defoliation was observed in an eastern Utah study area during summer 2007. ASTER normalized difference vegetation index (NDVI) showed only minor changes between 2005 and 2006, but a significant drop in NDVI was found within riparian areas between 2006 and 2007. The decrease in NDVI caused by defoliation was apparent despite partial refoliation within the study area. MODIS time series data revealed that absolute decline in EVI varied by site, but that the timing of EVI decline during summer 2007 was early with respect to phenological patterns from 2001 through 2006. Defoliation caused decreases in ET values estimated from both ASTER and MODIS data. MODIS estimated ET declined earlier than in previous years, although annual ET was not significantly different than ET in previous years due to high year-to-year variability. Challenges to detection and monitoring of tamarisk defoliation include spectral mixing of tamarisk and other cover types at subpixel spatial resolution, spatial coregistration of time series images, the timing of image acquisition, and changes unrelated to defoliation in non-tamarisk land cover over time. Continued development of the techniques presented in this paper may allow monitoring the spread of Diorhabda and assessment of potential water salvage resulting from biocontrol of tamarisk. ?? 2009 Elsevier Inc.

Remote Sensing of Environment↗

USGS2008

Assessing the extent and diversity of riparian ecosystems in Sonora, Mexico

Conservation of forested riparian ecosystems is of international concern. Relatively little is known of the structure, composition, diversity, and extent of riparian ecosystems in Mexico. We used high- and low-resolution satellite imagery from 2000 to 2006, and ground-based sampling in 2006, to assess the spatial pattern, extent, and woody plant composition of riparian forests across a range of spatial scales for the state of Sonora, Mexico. For all 3rd and higher order streams, river bottomlands with riparian forests occupied a total area of 2,301 km2. Where forested bottomlands remained, on average, 34% of the area had been converted to agriculture while 39% remained forested. We estimated that the total area of riparian forest along the principal streams was 897 km2. Including fencerow trees, the total forested riparian area was 944 km2, or 0.5% of the total land area of Sonora. Ground-based sampling of woody riparian vegetation consisted of 92, 50 m radius circular plots. About 79 woody plant species were noted. The most important tree species, based on cover and frequency, were willow species Salix spp. (primarily S. goodingii and S. bonplandiana), mesquite species Prosopis spp. (primarily P. velutina), and Fremont cottonwood Populus fremontii. Woody riparian taxa at the reach scale showed a trend of increasing diversity from north to south within Sonora. Species richness was greatest in the willow-bald cypress Taxodium distichum var. mexicanum-Mexican cottonwood P. mexicana subsp. dimorphia ecosystem. The non-native tamarisk Tamarix spp. was rare, occurring at just three study reaches. Relatively natural stream flow patterns and fluvial disturbance regimes likely limit its establishment and spread. ?? 2008 Springer Science + Business Media BV.

Biodiversity and Conservation↗

USGS2008

Wide-area estimates of stand structure and water use of tamarix spp. on the lower colorado river: Implications for restoration and water management projects

Tamarix spp. removal has been proposed to salvage water and allow native vegetation to recolonize western U.S. riparian corridors. We conducted wide-area studies on the Lower Colorado River to answer some of the scientific questions about Tamarix water use and the consequences of removal, combining ground surveys with remote sensing methods. Tamarix stands had moderate rates of evapotranspiration (ET), based on remote sensing estimates, averaging 1.1 m/yr, similar to rates determined for other locations on the river and other rivers. Leaf area index values were also moderate, and stands were relatively open, with areas of bare soil interspersed within stands. At three Tamarix sites in the Cibola National Wildlife Refuge, groundwater salinity at the site nearest to the river (200 m) was relatively low (circa 2,250 mg/L) and was within 3 m of the surface. However, 750 and 1,500 m from the river, the groundwater salinity was 5,000-10,000 mg/L due to removal of water by the Tamarix stands. Despite the high groundwater salinity, the sites away from the river did not have saline surface soils. Only 1% of the mean annual river flow is lost to Tamarix ET on the Lower Colorado River in the United States, and the opportunities for water salvage through Tamarix removal are constrained by its modest ET rates. A possible alternative to Tamarix removal is to intersperse native plants among the stands to improve the habitat value of the riparian zone. ?? 2008 Society for Ecological Restoration International.

Restoration Ecology↗

USGS2007

Relationship between evapotranspiration and precipitation pulses in a semiarid rangeland estimated by moisture flux towers and MODIS vegetation indices

We used moisture Bowen ratio flux tower data and the enhanced vegetation index (EVI) from the moderate resolution imaging spectrometer (MODIS) on the Terra satellite to measure and scale evapotranspiration (ET) over sparsely vegetated grassland and shrubland sites in a semiarid watershed in southeastern Arizona from 2000 to 2004. The grassland tower site had higher mean annual ET (336 mm yr-1) than the shrubland tower site (266 mm yr-1) (P<0.001). ET measured at the individual tower sites was strongly correlated with EVI (r=0.80-0.94). ET was moderately correlated with precipitation (P), and only weakly correlated with net radiation or air temperature. The strong correlation between ET and EVI, as opposed to the moderate correlation with rainfall, suggests that transpiration (T) is the dominant process controlling ET at these sites. ET could be adequately predicted from EVI and P across seasons and tower sites (r2 = 0.74) by a single multiple regression equation. The regression equation relating ET to EVI and P was used to scale ET over 25 km2 areas of grassland and shrubland around each tower site. Over the study, ratios of T to ET ranged from 0.75 to 1.0. Winter rains stimulated spring ET, and a large rain event in fall, 2000, stimulated ET above T through the following year, indicating that winter rain stored in the soil profile can be an important component of the plants' water budget during the warm season in this ecosystem. We conclude that remotely sensed vegetation indices can be used to scale ground measurements of ET over larger landscape units in semiarid ranglelands, and that the vegetation communities in this landscape effectively harvest the available precipitation over a period of years, even though precipitation patterns are variably seasonally and interannually. ?? 2007 Elsevier Ltd. All rights reserved.

Journal of Arid Environments↗

USGS2001

Selenium, selected inorganic elements, and organochlorine pesticides in bottom material and biota from the Colorado River delta

Concentrations of selenium (Se) in bottom material ranged from 0.6 to 5.0 μg g −1 , and from 0.5 to 18.3 μg g −1 in biota; 23% of samples exceeded the toxic threshold. Concentrations of DDE in biota exceeded the toxic threshold in 30% of the samples. Greater concentrations of selenium in biota were found at sites with strongly reducing conditions, no output, alternating periods of drying and flooding or dredging activities, and at sites that received water directly from the Colorado River. The smallest Se concentrations in biota were found at sites where an outflow and exposure or physical disturbance of the bottom material were uncommon.

Journal of Arid Environments↗