Big Spring Research Articles

Wind tunnel study of twelve dust samples by large particle size

Due to the lack of data by large dust and sand particle, the fluid dynamics characteristics, hence the collection efficiencies of different twelve dust samplers have been experimentally investigated. Wind tunnel tests were carried out at wind velocities ranging from 1 up to 5.5 ms−1. As a large solid particle of 0.5 and 1 mm in diameter, Polystyrene pellets called STYRO Beads or polystyrene sphere were used instead of sand or dust. The results demonstrate that the collection efficiency is relatively acceptable only of eight tested sampler and lie between 60 and 80% depending on the wind velocity and particle size. These samplers are: the Cox Sand Catcher (CSC), the British Standard Directional Dust Gauge (BSD), the Big Spring Number Eight (BSNE), the Suspended Sediment Trap (SUSTRA), the Modified Wilson and Cooke (MWAC), the Wedge Dust Flux Gauge (WDFG), the Model Series Number 680 (SIERRA) and the Pollet Catcher (POLCA). Generally they can be slightly recommended as suitable dust samplers but with collecting error of 20 up to 40%. However the BSNE verify the best performance with a catching error of about 20% and can be with caution selected as a suitable dust sampler. Quite the contrary, the other four tested samplers which are the Marble Dust Collector (MDCO), the United States Geological Survey (USGS), the Inverted Frisbee Sampler (IFS) and the Inverted Frisbee Shaped Collecting Bowl (IFSCB) cannot be recommended due to their very low collection efficiency of 5 up to 40%. In total the efficiency of sampler may be below 0.5, depending on the frictional losses (caused by the sampler geometry) in the fluid and the particle's motion, and on the intensity of airflow acceleration near the sampler inlet. Therefore, the literature data of dust are defective and insufficient. To avoid false collecting data and hence inaccurate mass flux modeling, the geometry of the dust sampler should be considered and furthermore improved.

Evidence of Strong Land Degradation by Wind Erosion as a Result of Rainfed Cropping in the Algerian Steppe: A Case Study at Laghouat

AbstractIn Algeria, overgrazing has long threatened the sustainable use of the nearly 20 million hectares of steppe lands. More recently, governmental policies favouring extensive rainfed cereal cropping in the steppe region have increased anthropic pressure on this fragile environment. Low rainfall, weak crop development and sandy soils lead to a high risk of wind erosion, yet no studies have been carried out in this region to this date to quantify the effect of steppe conversion on wind erosion. A 1·3‐ha field in the central steppe of Algeria (Laghouat) was converted to cropland (Hordeum Vulgare L.) and equipped with a weather station and Big Spring Number Eight sand straps to monitor climate‐related parameters and sediment fluxes over a 25‐month period. Threshold wind velocities (3·6 m height) varied between 6 and 7 m s−1 with a weak seasonal variation. More than 70% of the saltation‐producing winds originated from the NW. For these winds, a soil loss of 155 Mg ha−1 was measured. Half of the sediment loss occurred during a single, 12‐day period. Deposition of 26·5 Mg ha−1 was observed for SW winds. The measured erosion rates by far exceeded all norms of tolerable soil loss, indicating that rainfed cereal cropping is a highly unsustainable form of land use in the steppe region around Laghouat. National agricultural policies should be revised to take this into account. © 2014 The Authors. Land Degradation and Development published by John Wiley & Sons, Ltd.

Potential nitrogen and carbon processing in a landscape rich in milldam legacy sediments

Recent identification of the widespread distribution of legacy sediments deposited in historic mill ponds has increased concern regarding their role in controlling land–water nutrient transfers in the mid-Atlantic region of the US. At Big Spring Run in Lancaster, Pennsylvania, legacy sediments now overlay a buried relict hydric soil (a former wetland soil). We compared C and N processing in legacy sediment to upland soils to identify soil zones that may be sources or sinks for N transported toward streams. We hypothesized that legacy sediments would have high nitrification rates (due to recent agricultural N inputs), while relict hydric soils buried beneath the legacy sediments would be N sinks revealed via negative net nitrification and/or positive denitrification (because the buried former wetland soils are C rich but low in O2). Potential net nitrification ranged from 9.2 to 77.9 g m−2 year−1 and potential C mineralization ranged from 223 to 1,737 g m−2 year−1, with the highest rates in surface soils for both legacy sediments and uplands. Potential denitrification ranged from 0.37 to 21.72 g m−2 year−1, with the buried relict hydric soils denitrifying an average of 6.2 g m−2 year−1. Contrary to our hypothesis, relict hydric layers did not have negative potential nitrification or high positive potential denitrification rates, in part because microbial activity was low relative to surface soils, as indicated by low nitrifier population activity, low substrate induced respiration, and low exoenzyme activity. Despite high soil C concentrations, buried relict hydric soils do not provide the ecological services expected from a wetland soil. Thus, legacy sediments may dampen N removal pathways in buried relict hydric soils, while also acting as substantial sources of NO3− to waterways.

Aeolian sediment and dust fluxes during predominant “background” wind conditions for unburned and burned semiarid grassland: Interplay between particle size and temporal scale

Abstract Monitoring of aeolian transport is needed for assessment and management of human health risks as well as for soil resources. Human health risks are assessed based on duration of exposure as well as concentration. Many aeolian studies focus on periods of high wind speed when concentrations are greatest but few studies focus on “background” conditions when concentrations are likely lower but which represent the most prevalent conditions. Such “background” conditions might be especially important at sites with recent disturbance such as fire. Exposure assessments also require improved understanding relating longer-term (days to weeks) measurements of saltation of larger particles to shorter-term (minutes to hours) measurements of smaller inhalable dust particles. To address these issues, we employed three commonly used instruments for measuring dust emissions for unburned and recently-burned sites: Big Springs Number Eight (BSNE) samplers for larger saltating soil particles (>50 μm) with weekly to monthly sampling resolution, DustTraks for suspended particles (diameters

Aqueous geochemistry of the Thermopolis hydrothermal system, southern Bighorn Basin, Wyoming, U.S.A.

The Thermopolis hydrothermal system is located in the southern portion of the Bighorn Basin, in and around the town of Thermopolis, in northwest Wyoming. It is the largest hydrothermal system in Wyoming outside of Yellowstone National Park. The system includes hot springs, travertine deposits, and thermal wells. Published models for the hydrothermal system propose the Owl Creek Mountains as the recharge zone, simple conductive heating at depth, and resurfacing of thermal waters up the Thermopolis Anticline. The geochemistry of the thermal waters of three active hot springs—Big Spring, White Sulphur Spring, and Teepee Fountain—is similar in composition and characteristic of carbonate or carbonate-bearing siliciclastic aquifers. Previous studies of the Thermopolis hydrothermal system postulate that the thermal waters are a mixture of waters from Paleozoic formations. Major element geochemical analyses available for waters from these formations are not of sufficient quality to determine whether the thermal waters are a mixture of the Paleozoic aquifers. In the time frame of this study (one year), the geochemistry of all three springs was constant through all four seasons, spanning spring snowmelt and recharge as well as late-summer and fall dryness. This relationship is consistent with a deep source not influenced by shallow, local hydrogeology. Anomalies are evident in the historic data set for the geochemistry of Big Spring. We speculate that anomalies occurring between 1906 and 1926 suggest mixing of source waters of Big Spring with waters from a siliciclastic formation, and that anomalies occurring between 1926 and 1933 suggest mixing with waters from a formation containing gypsum or anhydrite. Decreased concentrations measured in our study—relative to concentrations measured between 1933 and 1976—may reflect mixing of thermal waters with more dilute waters. Current data are not sufficient to rigorously test these suggestions, and events of sufficient scale taking place in these timeframes have not been identified.

A new stable isotope record of Neogene paleoenvironments and mammalian paleoecologies in the western Great Plains during the expansion of C4 grasslands

Stable isotopes in horse teeth from the North American Great Plains show that equids began to incorporate C4 plants in their diets about 6.5million years ago as C4 grasslands expanded. However, the ecological response of many other ungulates to this expansion is poorly documented. We use stable carbon isotopes in mammalian tooth enamel to test whether other ungulates adapted by incorporating C4 vegetation in their diets. The openness of habitats before the expansion of C4 grasslands is uncertain, with plant phytolith studies suggesting a patchy environment with open-habitat grasses and forest, and pollen and macrofloral studies suggesting more forested habitats. To address this problem we use a model that predicts carbon isotope values for tooth enamel for a variety of environments, based on values in modern plants. Carbon and oxygen isotopes were analyzed in medium to large herbivores from three late Miocene and three Pliocene local faunas comprising a total of 13 and 7 genera, respectively, and 59 and 42 individuals. Results indicate that before the expansion of C4 grasslands, taxa with high-crowned teeth were consuming predominantly C3 vegetation. In contrast, by the late Pliocene most taxa studied were consuming a component of C4 vegetation and only the peccary Platygonus sp. had a pure C3 diet. C4 consumption increased in the late Pliocene (~3.0Ma) Big Springs local fauna probably in response to increased C4 biomass. Most landscapes in the late Miocene of Nebraska were open, such as woodland-savanna or C3 grassland, although low carbon values from the Pratt Slide local fauna suggest a denser, presumably forested area. This general pattern suggests an expansion of open-habitats no later than 12Ma (early Clarendonian). Through the Miocene–Pliocene transition there was an overall shift to lower δ18O enamel values, which parallels the long-term decrease in global mean annual temperature inferred from the marine record. Our results indicate that major changes in the diets of medium and large herbivores broadly corresponded with increased C4 biomass and cooling climate from the latest Miocene to the late Pliocene.

Distribution and Movement of Big Spring Spinedace (Lepidomeda mollispinis pratensis) in Condor Canyon, Meadow Valley Wash, Nevada

Big Spring spinedace (Lepidomeda mollispinis pratensis) is a cyprinid whose entire population occurs within a section of Meadow Valley Wash, Nevada. Other spinedace species have suffered population and range declines (one species is extinct). Managers, concerned about the vulnerability of Big Spring spinedace, have considered habitat restoration actions or translocation, but they have lacked data on distribution or habitat use. Our study occurred in an 8.2-km section of Meadow Valley Wash, including about 7.2 km in Condor Canyon and 0.8 km upstream of the canyon. Big Spring spinedace were present upstream of the currently listed critical habitat, including in the tributary Kill Wash. We found no Big Spring spinedace in the lower 3.3 km of Condor Canyon. We tagged Big Spring spinedace ≥70 mm fork length (range 70–103 mm) with passive integrated transponder tags during October 2008 (n = 100) and March 2009 (n = 103) to document movement. At least 47 of these individuals moved from their release location (up to 2 km). Thirty-nine individuals moved to Kill Wash or the confluence area with Meadow Valley Wash. Ninety-three percent of movement occurred in spring 2009. Fish moved both upstream and downstream. We found no movement downstream over a small waterfall at river km 7.9 and recorded only one fish that moved downstream over Delmue Falls (a 12-m drop) at river km 6.1. At the time of tagging, there was no significant difference in fork length or condition between Big Spring Spinedace that were later detected moving and those not detected moving. We found no significant difference in fork length or condition at time of tagging of Big Spring spinedace ≥70 mm fork length that were detected moving and those not detected moving. Kill Wash and its confluence area appeared important to Big Spring spinedace; connectivity with these areas may be key to species persistence. These areas may provide a habitat template for restoration or translocation. The lower 3.3 km of Meadow Valley Wash in Condor Canyon may be a good candidate section for habitat restoration actions.

How It Works

Los Angeles Department of Water and Power public relations officer Chris Plakos describes how the Los Angeles Aqueduct works, from its headwaters near Big Springs to the Los Angeles Aqueduct filtration plant in Sylmar.

WATER TEMPERATURE PATTERNS BELOW LARGE GROUNDWATER SPRINGS: MANAGEMENT IMPLICATIONS FOR COHO SALMON IN THE SHASTA RIVER, CALIFORNIA

ABSTRACTElevated stream temperature is a primary factor limiting the coho salmon (Oncorhynchus kisutch) population in California's Shasta River Basin. Understanding the mechanisms driving spatial and temporal trends in water temperature throughout the Shasta River is critical to prioritising river restoration efforts aimed at protecting this threatened species. During the summer, the majority of streamflow in the Shasta River comes from large‐volume, cold‐water springs at the head of the tributary Big Springs Creek. In this study, we evaluated the initial character of this spring water, as well as the downstream fate and transport of these groundwater inflows during July and August 2008. Our results indicated that Big Springs Creek paradoxically provided both cool and warm waters to the Shasta River. During this period, cool groundwater inflows heated rapidly in the downstream direction in response to thermal loads from incoming solar radiation. During the night time, groundwater inflows did not appreciably heat in transit through Big Springs Creek. These diurnally varying water temperature conditions were inherited by the Shasta River, producing longitudinal temperature patterns that were out of phase with ambient meteorological conditions up to 23 km downstream. Findings from this study suggest that large, constant temperature spring sources and spring‐fed rivers impart unique stream temperature patterns on downstream river reaches that can determine reach‐scale habitat suitability for cold‐water fishes such as coho salmon. Recognising and quantifying the spatiotemporal patterns of water temperature downstream from large spring inflows can help identify and prioritize river restoration actions in locations where temperature patterns will allow rearing of cold‐water fishes. Copyright © 2013 John Wiley & Sons, Ltd.

Soil organic carbon enrichment of dust emissions: magnitude, mechanisms and its implications for the carbon cycle

ABSTRACTSoil erosion is an important component of the global carbon cycle. However, little attention has been given to the role of aeolian processes in influencing soil organic carbon (SOC) flux and the release of greenhouse gasses, such as carbon dioxide (CO2), to the atmosphere. Understanding the magnitude and mechanisms of SOC enrichment in dust emissions is necessary to evaluate the impact of wind erosion on the carbon cycle. This research examines the SOC content and enrichment of dust emissions measured using Big Spring Number Eight (BSNE) wind‐vane samplers across five land types in the rangelands of western Queensland, Australia. Our results show that sandy soils and finer particulate quartz‐rich soils are more efficient at SOC emission and have larger SOC dust enrichment than clay‐rich aggregated soils. The SOC enrichment ratios of dusts originating from sites with sand‐rich soil ranged from 2·1–41·9, while the mean enrichment ratio for dusts originating from the clay soil was 2·1. We hypothesize that stronger inter‐particle bonds and the low grain density of the aggregated clay soil explain its reduced capacity to release SOC during saltation, relative to the particulate sandy soils. We also show that size‐selective sorting of SOC during transport may lead to further enrichment of SOC dust emissions. Two dust samples from regional transport events were found to contain 15–20% SOC. These preliminary results provide impetus for additional research into dust SOC enrichment processes to elucidate the impact of wind erosion on SOC flux and reduce uncertainty about the role of soil erosion in the global carbon cycle. Copyright © 2013 John Wiley & Sons, Ltd.

Using Water Chemistry, Isotopes and Microbiology to Evaluate Groundwater Sources, Flow Paths and Geochemical Reactions in the Death Valley Flow System, USA

Springs of Ash Meadows and Furnace Creek (near or in Death Valley, CA) have nearly constant flow, temperature, chemistry, and similar δ2H and δ18O signatures. These factors indicate shared water sources and/or analogous geochemical reactions along similar flow paths. DNA-based (16S rRNA gene) microbial diversity assessments further illuminate these relationships. Whereas, all Ash Meadows springs share related archaeal populations, variations in carbon-14 (Crystal Spring) and strontium isotopes, Na+, SO2-, and methane concentrations (Big Spring), correspond with microbial differences within and between the two discharge areas. Similar geochemical signatures linking Ash Meadows and Furnace Creek springs appear to support a distinct end member at Big Spring in Ash Meadows, which is also supported by coincident enrichment in microbial methanogens and methanotrophs. Conversely, DNA libraries from a deep carbonate well (878 m) located between Ash Meadows and Furnace Creek (BLM-1), indicate no shared microbial diversity between Ash Meadows or Furnace Creek springs.

Quantifying concentrated and diffuse recharge in two marble karst aquifers: Big Spring and Tufa Spring, Sequoia and Kings Canyon National Parks, California, USA

To improve water management in mountain systems, it is essential that we understand how water moves through them. Researchers have documented the importance of porous-media aquifers in mountain river systems, but no previous research has explicitly included mountain karst as part of conceptual models. To do so, we used discharge and geochemical parameters measured along upstream- to-downstream transects under high- and low-flow conditions in 2010 to assess storage characteristics and geochemical properties of two mountain marble-karst systems, the Big Spring and Tufa Spring systems in Sequoia and Kings Canyon National Parks, California. During both high- and low-flow conditions, we quantified the relative contributions of concentrated and diffuse recharge in both karst systems, and we used a simple linear mixing model to calculate specific conductance in unsampled diffuse sources that ranged from 34 m Sc m 21 to 257 m Sc m 21 . Data show that the Big Spring system has a much higher seasonal storage capacity than the Tufa Spring system, and that diffuse sources dominate discharge and geochemistry under baseflow conditions in both aquifer systems. Baseflow in Big Spring was 0.114 m 3 s 21 and in Tufa Spring it was 0.022 m 3 s 21 . Snowmelt-derived allogenic recharge dominates both systems during high discharge periods, measured at Big Spring as 0.182 m 3 s 21 and Tufa Spring as 0.220 m 3 s 21 . A conceptual model is proposed that explicitly includes the effects of karst aquifers on mountain hydrology when karst is present in the basin.

Can BSNE (Big Spring Number Eight) samplers be used to measure PM10, respirable dust, PM2.5 and PM1.0?

Abstract Wind tunnel and field measurements were conducted to evaluate whether the Big Spring Number Eight (BSNE) sampler can be used to measure ambient concentrations of PM10 (particles less that 10 μm), respirable dust (particles less than 4 μm or PM4), PM2.5 (particles less than 2.5 μm) and PM1.0 (particles less than 1 μm). The BSNE was tested against the DustTrak Aerosol Monitor and relationships with several other active automated samplers were investigated. Concentrations obtained from BSNE and DustTrak samplers tend to be comparable (less than 50% difference) within the wind speed interval 2–7 m s −1 (PM10) or 2–9 m s −1 (PM4, PM2.5, and PM1.0) provided appropriate corrections are made for sampler efficiency, cut-off percentage and data transfer from mass to volume (or reverse). For wind speeds −1 the DustTrak significantly underestimates the concentration compared to the BSNE. No data were available from this study for wind speeds >10 m s −1 . Field measurements confirmed the wind tunnel data, but only for PM10. No field information was available for PM4, PM2.5 and PM1.0. Comparisons with data from the literature suggest that the BSNE behaves similar to several active automated gravimetric samplers, at least for PM10 and within the wind speed interval 1–5 m s −1 . No data were available to confirm this conclusion for higher wind speeds or other size fractions.

A field experiment on dust emission by wind erosion in the Taklimakan Desert

Dust emission by wind erosion in surface is a serious problem in many arid regions around the world, and it is harmful to the ecological environment, human health, and social economy. To monitor the characteristics of saltation activity and to calculate the threshold wind velocity and sediment discharge under field conditions have significance on the research of dust emission by wind erosion. Therefore, a field experiment was conducted over the flat sand in the hinterland of the Taklimakan Desert. One sampling system was installed on the flat sand surface at Tazhong, consisting of a meteorological tower with a height of 2 m, a piezoelectric saltation sensor (Sensit), and a Big Spring Number Eight (BSNE) sampler station. Occurrence of saltation activity was recorded every second using the Sensit. Each BSNE station consisted of five BSNE samplers with the lowest sampler at 0.05 m and the highest sampler at 1.0 m above the soil surface. Sediment was collected from the samplers every 24 h. It is found that saltation activity was detected for only 21.5% of the hours measured, and the longest period of saltation activity occurring continuously was not longer than 5 min under the field conditions. The threshold wind velocity was variable, its minimum value was 4.9 m s−1, the maximum value was 9.2 m s−1, and the average value was 7.0 m s−1. The threshold wind velocity presented a positive linear increase during the measurement period. The observation site had a sediment discharge of 82.1 kg m−1 over a period of 24 h. Based on hourly saltation counts, hourly sediment discharge was estimated. Overall, there was no obvious linear or other functional relationship between the hourly sediment discharge and wind velocity. The results show that the changes of sediment discharge do not quite depend on wind velocity.

Field wind erosion measurements with Big Spring Number Eight (BSNE) and Modified Wilson and Cook (MWAC) samplers

The aim of this study was to compare the horizontal mass flux (HMF) of Aeolian sediment obtained from field wind erosion measurements with the Modified Wilson and Cook (MWAC) and Big Spring Number Eight (BSNE) and to analyze the effectiveness of exponential, power, logarithmic and rational equations to calculate the horizontal mass transport (HMT) for each sampler type. With this purpose wind erosion was measured on fine sandy loam soil in 10 erosion events between December 4, 2008 and July 1, 2009. The relative efficiency of the MWAC related to BSNE (RE W/B, quotient between the HMF of MWAC and the HMF of BSNE multiplied by 100) was 247% while RE W/B obtained from the absolute efficiency of the BSNE (85% to 95%) and MWAC (44% to 120%) found in previous studies, was between 51% and 141%. The RE W/B increased with height, as a consequence of the wind speed increase and particle size decrease, which reduces the efficiency of the BSNE while the efficiency of the MWAC remains constant. Depending on the equation used, the HMT of MWAC was from 2.1 to 2.53 times higher than the HMT of BSNE indicating that if the HMF is corrected by the RE W/B, found in this study, the HMT obtained with the MWAC and BSNE is similar. The HMT obtained from exponential equations was 16% higher than the power equation and, 62% and 11% lower than logarithmic and rational equations respectively. In spite of this, the HMT obtained with different equations presented a good relationship with each other (p < 0.05), indicating that the HMT can be corrected and compared between equations. This study shows that the HMF and HMT data obtained from field measurements with the BSNE and MWAC are different. Nevertheless, comparable measurements of wind erosion can be obtained with both samplers taking into account the relative efficiency and the relationship between equations found in this study.

Technical Note: Aeolian Materials Sampler for Measuring Surface Flux of Soil Nitrogen and Carbon During Wind Erosion Events in the Sahel, West Africa

In the Sahel, determining the effects of wind erosion on soil fertility and soil carbon balance is crucial for achieving sustainable agriculture and for carbon sequestration, respectively. We designed the Aeolian Materials Sampler (AMS) to measure the surface flux of soil nitrogen and carbon, which limit crop production as well as water in the Sahel. The AMS should not be used alone, but with the Big Spring Number Eight (BSNE) sampler, which is a quasi-isokinetic sampler. We examined the performance of the AMS in estimating the surface flux of soil nitrogen and carbon by conducting wind-tunnel and field experiments. In the former experiment, we measured the trapping efficiency of the AMS for nitrogen and carbon content in coarse organic matter (COM) and soil particles. We observed that the AMS allows estimation of the surface flux of soil nitrogen and carbon associated with the movement of COM and soil particles; wind data and empirical equations were used for the estimation. In the field experiment, we assessed the contribution of the inherent error of the AMS to the total measurement error and found that the inherent error was negligible and did not increase the total measurement error in the estimation of the surface flux of soil nitrogen and carbon. Therefore, we concluded that the combination of the AMS and the BSNE sampler could be effectively used to evaluate the effects of wind erosion on soil fertility and soil carbon balance in the Sahel.

Fast, Regional Conduit Flow to an Exceptional-Value Spring-Fed Creek: Implications for Source-Water Protection in Mantled Karst of South-Central Pennsylvania

Karst springs of Cumberland County, Pennsylvania, are important water resources, but their sources and flow paths are unknown. We traced flow in a mantled- karst groundwater system in the Great Valley section of the Valley and Ridge Physiographic Province using fluorescent dyes, with focus on Big Spring Creek. Upper Big Spring Creek is assigned High Quality/Exceptional Value status by Pennsylvania based on its high water quality and value as a multi-use resource with exceptional recreational or ecological significance. Subsurface flow followed the geologic strike after Sulpho Rhodamine B (Acid Red 52) dye was released on exposed carbonates. Subsurface flow had a maximum effective linear velocity of 2.5 km d 21 , which is 8 times greater than sodium fluorescein (Acid Yellow 73) dye released separately into a losing stream over colluvium (0.3 km d 21 ). Sulpho Rhodamine B was detected strongly 8.9 km away at Big Spring Creek's largest source spring (,250 ppt water; 50 ppb eluate), but weakly in an east source (2.5 ppb eluate). Sodium fluorescein was detected after four weeks at 0.07 to 0.15 ppb in eluate at springs at Huntsdale Hatchery, 9.5 km from release atop the colluvial mantle. Slow flow derived from losing streams on the colluvial mantle likely maintains water quality of Big Spring Creek and similar systems. However, this recharge is distant, and the flow passes below karst recharge features in the valley center, creating many opportunities for contamination. Future studies of contaminant and sediment loadings to subterranean basins and of source-water protection strategies that recognize these patterns are necessary to protect these streams.

Arboreal Spider Ecology on Saltcedar (Tamarix) at Big Spring, Howard County, Texas

The arboreal species of spiders on saltcedar, Tamarix spp., at Big Spring, Howard County, TX, were surveyed to determine which species could pose a threat to the success of the biological control agent Diorhabda elongata (Brulle) (Coleoptera: Chrysomelidae). This resulted in a list of the spider genera and species found on tamarisk and some initial information on spider ecology in association with this weed tree. Of the 1,495 specimens of spiders collected above ground level during the 3 years of study at the site, 55 spider species in 15 families were found on saltcedar trees. The most abundant species of spiders were mapped to determine their habitat on the trees and in relation to other species. Orb-weavers (Araneidae) and jumping spiders (Salticidae) were the most diverse families, as well as being common, but mesh web-weavers (Dictynidae), while less diverse, were individually numerous. Only orb-weavers were observed to feed on D. elongata in the field.

Application of Dyar's Law to Life Stages ofSigara mathesoni(Heteroptera: Corixidae)

Sigara mathesoni, collected from Big Spring Creek in south-central Pennsylvania, were observed under laboratory and field conditions in 2007 in order to test Dyar's law in predicting developmental stage from head width. In the laboratory, eggs were collected with subsequent hatch- ing. Head width was obtained at each developmental stage. It was found that Dyar's law accurately modeled growth of S. mathesoni and instar number is easily determined by head width measurement. In the final two stages of growth, head width and body length were sexually dimorphic. Female head width was larger than male head width.

A Darcian Model for the Flow of Big Spring and the hydraulic head in the Ozark aquifer, Missouri, USA

The complex discharge hydrographfor Big Spring, Missouri, can be described as the sum of two terms governed by Darcy’s Law. The dominant, long-term component is proportional to the regional hydraulic gradient, and constitutes about 80% of the average flow of 12.6 m 3 /s. Superimposed on this is a tran­sient component witha time-constant of about 1.5 days that represents the Darcian response to sharp, rainfall-driven pulses on the head of the shallow groundwater system. This tran­sient component delivers about 20% of the average total flow, but over short intervals can exceed the long-term component. However, the long-term component is so large that the ratio of record highflows to the average flow is only about 4x for Big Spring, and 1.5 to 4.5x for most other large Ozark springs; for comparison, this ratio is 10 to 3000x for most surface streams in Missouri . The strong correlation between the discharge of the large springs and the head in the Ozark aquifer permits the extension of the Darcian rainfall-runoff model to predict groundwater levels in wells.