Fall Line Research Articles

The Australian Desert Fireball Network: a new era for planetary science

Through an international collaboration between Imperial College London, the Ondřejov Observatory in the Czech Republic and the Western Australian Museum, the installation of the Australian Desert Fireball Network in the Nullarbor Region of Western Australia was completed in 2007. Currently, the Network, which is the first to be established in the southern hemisphere, comprises four all-sky autonomous observatories providing precise triangulation of fireball records to constrain pre-atmospheric orbits and fall positions of meteorites over an area of approximately 200 000 km2. To date, the Network has led to the successful recovery of two observed meteorite falls. The first recovery was three fragments (174, 150 and 14.9 g) of the same meteorite fall recorded on 20 July 2007 at 19 h 13 m 53.2 s±0.1 s UT that were found within 100 m of the predicted fall line. Named Bunburra Rockhole, the meteorite is a basaltic achondrite with an oxygen isotopic composition (Δ17O = −0.112 ‰) distinguishing it from basaltic meteorites belonging to the Howardite–Eucrite–Diogenite clan thought to be derived from asteroid 4Vesta, and therefore must have come from another differentiated asteroid in the terrestrial planet region. Bunburra Rockhole was delivered to Earth from an Aten-like orbit that was almost entirely contained within the Earth's orbit. The second recovered fall was detected by the Network on 13 April 2010 and led to the recovery of a 24.54 g meteorite fragment that is yet to be fully described. To date, the Network has recorded ∼550 fireballs. Records from which precise orbits and trajectories can be determined number ∼150. In addition to the two recovered falls twelve fireballs are considered to have resulted in meteorite falls. Of these, four are probable falls (10's–100 g), and five are certain falls (>100 g). Having proved the potential of the Network, ultimately a large dataset of meteorites with orbits will provide the spatial context for the interpretation of meteorite composition that is currently lacking in planetary science.

A porewater-based stable isotope approach for the investigation of subsurface hydrological processes

Abstract. Predicting and understanding subsurface flowpaths is still a crucial issue in hydrological research. We present an experimental approach to reveal present and past subsurface flowpaths of water in the unsaturated and saturated zone. Two hillslopes in a humid mountainous catchment have been investigated. The H2O(liquid) – H2O(vapor) equilibration laser spectroscopy method was used to obtain high resolution δ2H vertical depth profiles of pore water at various points along two fall lines of a pasture hillslope in the southern Black Forest, Germany. The Porewater-based Stable Isotope Profile (PSIP) approach was developed to use the integrated information of several vertical depth profiles of deuterium along transects at the hillslope. Different shapes of depth profiles were observed in relation to hillslope position. The statistical variability (inter-quartile range and standard deviation) of each profile was used to characterize different types of depth profiles. The profiles upslope or with a weak affinity for saturation as indicated by a low topographic wetness index preserve the isotopic input signal by precipitation with a distinct seasonal variability. These observations indicate mainly vertical movement of soil water in the upper part of the hillslope before sampling. The profiles downslope or at locations with a strong affinity for saturation do not show a similar seasonal isotopic signal. The input signal is erased in the foothills and a large proportion of pore water samples are close to the isotopic values of δ2H in streamwater during base flow conditions indicating the importance of the groundwater component in the catchment. Near the stream indications for efficient mixing of water from lateral subsurface flow paths with vertical percolation are found.

Modeling the Impact of Winter Maintenance on Pavement Marking Retroreflectivity

This paper investigates the change in retained retroreflectivity of waterborne paint and spray thermoplastic pavement markings before and after winter maintenance in a typical Snowbelt state. The research hypothesis is that if pertinent initial conditions such as fall retroreflectivity, marking material, and line type are known, it is possible to predict future performance for a given variable such as annual winter maintenance. Individual pairs of fall and spring retroreflectivity readings from hundreds of separate statewide sites are analyzed to show, among other things, that fall retroreflectivity and product type are predictors of spring retroreflectivity. In general, as fall retroreflectivity increases, the percent retroreflectivity retained by spring decreases in a predictable fashion for both waterborne and spray thermoplastic pavement markings.

Portage and Path Dependence

The authors examine portage sites in the U.S. South, Mid-Atlantic, and Midwest, including those on the fall line, a geomorphological feature in the southeastern U.S. marking the final rapids on rivers before the ocean. Historically, waterborne transport of goods required portage around the falls at these points, while some falls provided water power during early industrialization. These factors attracted commerce and manufacturing. Although these original advantages have long since been made obsolete, the authors document the continuing importance of these portage sites over time. They interpret these results as path dependence and contrast explanations based on sunk costs interacting with decreasing versus increasing returns to scale.

Kinetic Analysis of Ski Turns Based on Measured Ground Reaction Forces

The objective of this study was to devise a method of kinetic analysis of the ground reaction force that enables the durations and magnitudes of forces acting during the individual phases of ski turns to be described exactly. The method is based on a theoretical analysis of physical forces acting during the ski turn. Two elementary phases were defined: (1) preparing to turn (initiation) and (2) actual turning, during which the center of gravity of the skier-ski system moves along a curvilinear trajectory (steering). The starting point of the turn analysis is a dynamometric record of the resultant acting ground reaction force applied perpendicularly on the ski surface. The method was applied to six expert skiers. They completed a slalom course comprising five gates arranged on the fall line of a 26° slope at a competition speed using symmetrical carving turns (30 evaluated turns). A dynamometric measurement system was placed on the carving skis (168 cm long, radius 16 m, data were recorded at 100 Hz). MATLAB procedures were used to evaluate eight variables during each turn: five time variables and three force variables. Comparison of the turn analysis results between individuals showed that the method is useful for answering various research questions associated with ski turns.

Novel Phylogeographic Patterns in a Lowland Fish,Etheostoma proeliare(Percidae)

Abstract Etheostoma proeliare is distributed in the Gulf Coastal Plain of southeastern North America from the Colorado River of eastern Texas through the Choctawhatchee River of eastern Alabama, north to the Fall Line, and upstream along the Arkansas River valley into eastern Oklahoma. Parsimony and Bayesian analysis of the ND2 gene from 28 populations recovered a monophyletic E. proeliare (PP: 1.0) containing a basal split between a novel clade of populations in the northern apex of the Mississippi embayment, from the Black and St. Francis rivers to the west of, through the Yazoo River to the east of, the main channel of the Mississippi River, and all other populations (PB:99, PP: 1.0). Southern populations are resolved into three clades: Trinity plus Neches Rivers (PB: 100, PP: 1.0), Sabine River east through western tributaries to the Mississippi River plus the Lake Pontchartrain drainage (PP: 1.0), and eastern tributaries to the Mississippi River east through the Escambia River (PP:0.99). The eastern ...

Distance decay of similarity in temperate aquatic communities: effects of environmental transition zones, distance measure, and life histories

The decay of community similarity with distance (distance decay) is reported for many taxa in a variety of geographic settings. However, the importance of scale, distance measure, ecoregions, and ecological transition zones to distance decay has not been thoroughly examined. The goal of our study was to test the effects of these factors on distance decay in two freshwater assemblages (benthic macroinvertebrates and fish) with differing dispersal abilities in small streams within the Patuxent River basin, Maryland, USA. The Patuxent basin contains a geologic Fall Line, an ecological transition zone separating the two main regions of the basin. For both assemblages, we examined distance decay in similarity at several extents: entire Patuxent, Piedmont sub-region, and Plains sub-region using both linear geographic and stream network distances. Decay patterns were observed across all extents and distances. At the Patuxent extent decay rates differed

An Overlooked Hotspot? Rapid Biodiversity Assessment Reveals a Region of Exceptional Herpetofaunal Richness in the Southeastern United States

We conducted a competitive bioblitz survey in four Georgia counties to raise awareness of a unique and species rich herpetofauna in the Pine Mountain/ Fall Line Sandhills Region of Georgia, and compared documented species of these counties to other herpetofaunas of the southeast that have known high richness and/ or were subject to thorough collection efforts. Our results demonstrate the efficacy of bioblitzes for documenting large numbers of species in a limited amount of time (62 amphibian and reptile species in only seven days, including 36 new county records and documentation of three protected species). Compared to areas of similar size, this area is among the most species-rich herpetofaunas in North America north of Mexico, with only three areas having higher documented richness. However, all areas we compared our site to have experienced much higher collection effort and contain much larger tracts of protected land. Thus, our data suggest the Pine Mountain/Fall Line Sandhills region is among the most important regions for amphibian and reptile conservation in North America.

Portage: Path Dependence and Increasing Returns in U.S. History

The authors examine portage sites in the U.S. South, Mid-Atlantic, and Midwest, including those on the fall line, a geomorphologic feature in the southeastern U.S. marking the final rapids on rivers before the ocean. Historically, waterborne transport of goods required portage around the falls at these points, while some falls provided water power during early industrialization. These factors attracted commerce and manufacturing. Although these original advantages have long since been made obsolete, the authors document the continuing-and even increasing-importance of these portage sites over time. They interpret this finding in a model with path dependence arising from local increasing returns to scale.

Migration and Spawning of American Shad in the James River, Virginia

AbstractAcoustic telemetry and ichthyoplankton surveys were used to characterize the migratory behavior and spawning grounds of American shad Alosa sapidissima in the James River, Virginia. Seven acoustic monitoring stations spanned a distance of 95 river kilometers extending downstream from just below the fall line in Richmond to the estuarine portion of the river at Hog Island. Ninety‐three fish were tagged in the estuarine portion of the river near Hog Island on 21 March 2005. Eighty‐six fish exhibited fallback behavior, and 45 of these fish eventually abandoned the migration. Forty‐six fish were eventually detected upstream at the mouths of the two major James River tributaries (Appomattox and Chickahominy rivers), within the main‐stem James River up to the fall line, or both. Upstream movements detected by stationary hydrophones during the prespawning migration were significantly related to flooding tides, and movements downstream during the postspawning emigration were significantly related to ebbing tides. However, there was no significant relationship between time of day and movements during the prespawning or postspawning migration phase. Movement patterns suggested three primary areas of residency located within the 65‐km reach below the fall line downstream to Upper Brandon Plantation, although some fish exhibited behaviors that were inconsistent with a specific residence area. Ichthyoplankton collections of eggs and yolk sac larvae indicated that the principal spawning grounds were located in a 33.5‐km reach extending downstream from the fall line, a finding consistent with repeated detection of a majority of the tagged cohort within this reach.

Direct connectivity between upstream and downstream promotes rapid response of lower coastal‐plain rivers to land‐use change

Low‐relief fluvial systems that originate in the lower coastal plain and discharge into estuaries are common along passive margins. These watersheds are thought to be disconnected from their termini by floodplains, which buffer the sediment‐routing system by sequestration. Here, we present a detailed study of the Newport River, a typical lower coastal‐plain system, which reveals high connectivity between watershed and delta. Connectivity is measured as the time lag between initiation of a silviculture operation, which increased landscape erosion, and when the sediment appeared at the bay‐head delta. The time lag, measured from aerial photographs and sedimentation rates calculated from 210Pb‐ and 137Cs‐activities in cores from the watershed and delta, is <3 years. Most lower coastal‐plain rivers are steeper and have less floodplain accommodation available for storage than their larger counterparts that originate landward of the fall line, which promotes higher connectivity between upstream and downstream.

Planters' Progress: Modernizing Confederate Georgia (review)

Reviewed by: Planters' Progress: Modernizing Confederate Georgia William Harris Bragg Planters' Progress: Modernizing Confederate Georgia. By Chad Morgan. (Gainesville: University Press of Florida, 2005. Pp. xii, 163. $55.00 cloth.) The pleasantly alliterative title of Chad Morgan's excellent first book echoes John Bunyan's The Pilgrim's Progress. Most similarities between the books end there, however. Morgan's concept of "progress"—unlike Bunyan's meaning: a journey toward a goal—is "material progress, the material improvement of the lot of all classes in a society . . . generally associated with a substantial degree of industrialization and urbanization" (124n13). Nonetheless, while the idea of a journey toward a goal remains, the author demonstrates that Georgia's planters fell far short of reaching theirs: long-term "industrialization in a slave society" (2). Indeed, Bunyan's protagonist's point of departure, the City of Destruction, became the planters' destination. Morgan satisfyingly explains the link between what might seem opposites—planters and industrialization—by providing succinct histories of both. He painstakingly traces the roots of planters' power, quite disproportionate to their numbers, to the late 1700s and early 1800s. Political decisions during that period sanctioned the primacy of planters in politics by creating property-holding qualifications for officeholders. Adoption of the federal ratio for representation in the state legislature (which appointed the governor until 1824) further strengthened the planters. By the time the government became more democratized in the 1840s, planter dominance was firmly established. Early Southern industrialization, on the other hand, failed to flourish. Factory expansion came mainly at the sufferance of the planters, who comprised only 20 percent of the South's industrialists. During the early decades of the Industrial Revolution, factory owners depended on water to transport goods to major markets from their water-powered plants on the fall line. The distance from Lowell to the Massachusetts coast was around twenty miles; that [End Page 315] from Macon to Georgia's Atlantic seaboard was closer to two hundred. This made quite a difference. By the 1840s rail transportation somewhat reduced this disparity, but by then northern industrial dominance had been as well established as planter political power. The planters tended to support railroad construction and even found ways for slave property to further rail expansion; consequently, Georgia's rail mileage would exceed all but Virginia's when the Civil War came to the American southeast. But other factors limited expansion of the state's industrial base: the superior momentum and skill of Northern industries—even in manufacturing cotton products, weaknesses in the Southern banking system, and deficits in industrial tradition and experience—translating into "amateur manufacturing" (12). Morgan records pro-industrial sentiments in the antebellum South, quoting thinkers who understood that a mixed economy of agriculture and industry promised independence. These observers also knew that lack of industry helped explain the South's non-competitive population growth, which was draining the region's national political power. Consequently, many Georgians were heartened by the Confederacy's incredibly rapid wartime industrial expansion. One 1862 Georgia newspaper even hoped wistfully for a longer, rather than a shorter war, for "a too speedy peace . . . would expose [Southerners] to a worse danger than that of war—the danger of being kept in our former commercial vassalage" (33). Modernization thus came to Confederate Georgia and its sister states, adding the Southern Confederacy to those other almost instantaneously modernized nation-states of the mid-1800s, Germany and Japan—a membership that would also be quickly revoked. This modernization, "nonrevolutionary [and] overseen by a landed elite" (1), combined "industrialization, urbanization, and . . . the expansion of state power" (118n1). Consequently, long before the first Union army crossed Georgia's borders, the state's industrial base and potential, its abundant population, and its rail-linked towns had made it a battleground for Confederate and Georgia authorities, all seeking to expand their powers in the midst of war. Modernized Georgia's industries were quickly harnessed to meet the needs of the soldiers on whom the Confederacy's independence depended—producing the food, arms, clothing, and shelter vital to the nation's troops. Morgan sees that national conscription was central not only to keeping adequate forces in the field, but to controlling the industrial labor...

Retention of Riverine Sediment and Nutrient Loads by Coastal Plain Floodplains

Despite the frequent citation of wetlands as effective regulators of water quality, few quantitative estimates exist for their cumulative retention of the annual river loads of nutrients or sediments. Here we report measurements of sediment accretion and associated carbon, nitrogen, and phosphorus accumulation as sedimentation over feldspar marker horizons placed on floodplains of the non-tidal, freshwater Coastal Plain reaches of seven rivers in the Chesapeake Bay watershed, USA. We then scale these accumulation rates to the entire extent of non-tidal floodplain in the Coastal Plain of each river, defined as riparian area extending from the Fall Line to the upper limit of tidal influence, and compare them to annual river loads. Floodplains accumulated a very large amount of material compared to their annual river loads of sediment (median among rivers = 119%), nitrogen (24%), and phosphorus (59%). Systems with larger floodplain areas and longer floodplain inundation retained greater proportions of riverine loads of nitrogen and phosphorus, but systems with larger riverine loads retained a smaller proportion of that load on floodplains. Although the source and long-term fate of deposited sediment and associated nutrients are uncertain, these fluxes represent the interception of large amounts of material that otherwise could have been exported downstream. Coastal Plain floodplain ecosystems are important regulators of sediment, carbon, and nutrient transport in watersheds of the Chesapeake Bay.

“CRACKER CULTURE”: A PRELIMINARY DEFINITION

IN THE STUDY of modern societies it is of value to the social scientist to distinguish and describe the regional variations which occur within a larger society. It is important to understand the various regional specializations in which man has established in order to conceptualize the nature of the contemporary modern world. Alfred Kroeber1 has correctly suggested that the culture is a subject matter for the social scientist; he defines culture as the natural region within which several communities have similar cultural and social norms. The variations from community to community within the area serve to distinguish the communities of the area from each other and from those in surrounding regions. It is the purpose of this paper to describe in broad terms the general cultural configuration of such a cultural area in Southeast Georgia and North Central Florida. The inhabitants refer to themselves and are referred to by others as Crackers, and we have used this name as a general term to denote the particular of these people. In describing this we attempt to develop a device for understanding the nature of contemporary modern society by placing it in the proper area context. Cracker Culture is a sub-type within the larger regional denoted as Southern. It is distinguished by three factors: the geographic features (topography, flora, fauna, and weather); the logic of its social order (social organization); and the sacred logic (rationale) which supports and gives meaning to the culture. The outstanding geographic features of the area are its mild waters, hot, humid summers, and the red clay upland soils; they are the sedimentary soils of the terraces that resulted from the progressive up-lift of the Atlantic littoral. They are the sand and sandy clay loams, whose primary drainage system consists of the east-west rivers such as the Savannah, Satilla, Altamaha and the Ogeechee, originating above the fall line in the uplands. The rivers serve as channels of migration from the sea-island region of the coast into the fertile areas of the uplands and Piedmont. The relatively infertile soils between these rivers discouraged settlers in search of the wealth that came from cotton production. A typical plant of the area is the Long-Leaf Pine which occurred in such profusion that the early settlers termed the area the

Distribution of the Brown Recluse Spider (Araneae: Sicariidae) in Georgia with Comparison to Poison Center Reports of Envenomations

Georgia is on the southeastern margin of the native range of the brown recluse spider, Loxosceles reclusa Gertsch and Mulaik. The brown recluse is not a common Georgia spider and has limited distribution in the state. Using recent submissions, previously published records, and examination of museum specimens, we document the spider's presence in 31 (19.5%) of Georgia's 159 counties, with almost all being found in the northern portion. The spider was collected almost exclusively north of the Fall Line (a transition zone separating the Piedmont and the Coastal Plain geological provinces). Only two locations in the southern Coastal Plain province produced L. reclusa specimens; these southern finds are considered spiders that were transported outside their range. There were six finds of the non-native world tramp species, L. rufescens (Dufour), three south of the Fall Line. In conspicuous contrast, over a 5-yr period, a Georgia poison center database recorded 963 reports of brown recluse spider bites from 103 counties. These figures greatly outnumber the historic verifications of brown recluses in the state for both specimen quantity and county occurrence, indicating improbable spider involvement and the overdiagnosis of bites. In the southern half of the state, medical diagnoses of brown recluse spider bites have virtually zero probability of being correct. Bite diagnoses should be made with caution in north Georgia given the spider's spotty distribution with low frequency of occurrence.

Mapping snow avalanche chutes in the Canadian Rockies using Landsat TM and DEM data

Snow avalanches are a common occurrence within the Canadian Rockies. Such features result in a distinctive biogeographic response that can be associated with characteristic land cover patterns. These patterns are most visible when avalanches penetrate through mature forest stands, leaving a narrow track of open ground aligned parallel to the fall line. The recurrence of avalanches in the same location perpetuates the disruption of the forest canopy, leaving more avalanche-resistant shrubs and herbs to colonize these areas. To date, no reliable method to map snow avalanche features using satellite sensor data has been reported. The use of image segmentation and digital elevation model (DEM) derivatives provides a solution to this shortcoming. Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) data covering areas in the Canadian Rockies are used in conjunction with specific geomorphometry and image segmentation to isolate image objects that conform to the geomorphic and spectral characteristics consistent with avalanche tracks. Accuracy assessment using a database derived from manual inspection of stereo aerial photographs indicates approximately 80% accuracy for both errors of omission and errors of commission.

Research Note: Alignment of Elongated Nassella pulchra Plants with Hill-Slope Contours

On 10 sloped grassland sites, 175 Nassella pulchra plants were randomly selected and their basal geometry measured. Plants were not circular ( p < 0.001) with an average elongation of 30.3% + 20.7 and 89% of the plants had greater than 10% elongation. Sixty-six percent of the plants had the elongation oriented along the contours. Elongation was correlated with slope steepness ( p = 0.003, r 2 = 0.06), but unrelated to the angle the long axis was deflected from the slope fall line ( p = 0.21, r 2 = 0.02). This elongation and orientation potentially reduced overland flow compared to circular plants.

English

Deep row incorporation of biosolids is a unique alternative land application method that will prevent odor problems and may permit the application of considerably higher than currently permitted biosolids rates. The goal of our research is to assess environmental consequences of employing deep row incorporation of biosolids to restore productivity of mined land for the production of hybrid poplar as a potential bioenergy crop. Our objectives are to quantify the transformations of nitrogen and phosphorus applied to the soil as entrenched biosolids. The study is being conducted on a mineral sands mine reclamation site near the Coastal Plain-Piedmont fall line in Dinwiddie County, Virginia. The experimental design consists of 5 treatments - two biosolids types each applied in subsurface trenches at two rates and an unamended control. Application rates were 328 and 656 Mg ha -1 for the lime-stabilized biosolids and 213 and 426 Mg ha -1 for the anaerobically digested biosolids. Each treatment was replicated four times and arranged in a randomized complete block design. The site has been instrumented with suction and zero-tension lysimeters for collection and analysis of leachate from which were determined subsurface loss of nitrogen and phosphorus. Gas chambers have been used to collect soil air samples for accounting of denitrification rates from the entrenched biosolids. Redox potential was determined in the incorporated biosolids to describe the biosolids environment influencing nitrogen and phosphorus chemical transformations. During the first 10-14 months following biosolids application, initial nitrogen loss occurred largely as ammonium and organic N and, after 7-10 months, mostly as nitrate N. There was no significant leaching of phosphorus. Low redox potential in the biosolids' seam validated the occurrence of anaerobic conditions. Higher nitrous oxide emissions occurred from the anaerobically digested biosolids than from the lime stabilized biosolids. The deep row biosolids incorporation technology, when applied to coarse-textured soils, does not appear to be environmentally viable with respect to potential nitrogen loss to groundwater.

Increased Terrestrial to Ocean Sediment and Carbon Fluxes in the Northern Chesapeake Bay Associated With Twentieth Century Land Alteration

We calculated Chesapeake Bay (CB) sediment and carbon fluxes before and after major anthropogenic land clearance using robust monitoring, modeling and sedimentary data. Four distinct fluxes in the estuarine system were considered including (1) the flux of eroded material from the watershed to streams, (2) the flux of suspended sediment at river fall lines, (3) the burial flux in tributary sediments, and (4) the burial flux in main CB sediments. The sedimentary maximum in Ambrosia (ragweed) pollen marked peak land clearance (~1900 a.d.). Rivers feeding CB had a total organic carbon (TOC)/total suspended solids of 0.24 ± 0.12, and we used this observation to calculate TOC fluxes from sediment fluxes. Sediment and carbon fluxes increased by 138–269% across all four regions after land clearance. Our results demonstrate that sediment delivery to CB is subject to significant lags and that excess post-land clearance sediment loads have not reached the ocean. Post-land clearance increases in erosional flux from watersheds, and burial in estuaries are important processes that must be considered to calculate accurate global sediment and carbon budgets.

Life History of the Tricolor Shiner, Cyprinella trichroistia (Teleostei: Cyprinidae), in Alabama

Relatively little is known about the life history of Cyprinella trichroistia (Tricolor Shiner), a species endemic to the Coosa and Cahaba rivers in Alabama, Georgia, and Tennessee above the Fall Line. The life history of this species was investigated using a series of collections obtained through the University of Alabama Ichthyological Collection spanning 27 months and collected from Hubbard Creek in the Coosa River System. A total of 6366 specimens were examined for age and growth, reproductive cycle, food habits, parasites, habitat, and associated species. Males and females have similar length-weight relationships, but males attain a larger size. Data analysis and field observations indicate that the species has a single reproductive season beginning in April and ending in August with peak activity in June. Numbers of mature ova of females ranged from 32 to 148, and was highly correlated to female size and weight. At any given time in the population, there were three (possibly four) age classes noted. The habitat for the Tricolor Shiner was primarily clear, flowing streams with a rocky substrate suitable for crevice spawning to occur. The diet consisted mainly of aquatic insects; the only parasites observed were internal nematodes and external trematodes.