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Research about Southeastern United States

Source-linked reports with geographic coverage including Southeastern United States.

11 recordsLinked to original sources
USGS2025

Modelling and mapping burn severity of prescribed and wildfires across the southeastern United States (2000-2022)

Background The southeastern United States (‘Southeast’) experiences high levels of fire activity, but the preponderance of small and prescribed fires means that existing burn severity products are incomplete across the region. Aims We developed and applied a burn severity model across the Southeast to enhance our understanding of regional burn severity patterns. Methods We used Composite Burn Index (CBI) plot data from across the conterminous US (CONUS) to train a gradient-boosted decision tree model. The model was optimised for the Southeast and applied to the annual Landsat Burned Area product for 2000–2022 across the region. Key results The burn severity model had a root mean square error (RMSE) of 0.48 ( R 2 = 0.70) and 0.50 ( R 2 = 0.37) for the CONUS and Southeast, respectively. The Southeast, relative to CONUS, had lower mean absolute residuals in low and moderate burn severity categories. Burn severity was consistently lower in areas affected by prescribed burns relative to wildfires. Conclusions Although regional performance was limited by a lack of high burn severity CBI plots, the burn severity dataset demonstrated patterns consistent with low-severity, frequent fire regimes characteristic of Southeastern ecosystems. Implications More complete data on burn severity will enhance regional management of fire-dependent ecosystems and improve estimates of fuels and fire emissions.

Southeastern United States↗
USGS2025

Differential habitat use of wintering Whooping Cranes throughout the range of the Eastern Migratory Population

In 2001, a reintroduced population of whooping cranes (Grus americana), the Eastern Migratory Population (EMP), was established in the eastern United States. There has been no assessment of habitat use of the EMP across the current winter distribution. During 2 winters, we used radio-telemetry to track groups of cranes each for 1 day. We grouped sites into 3 regions, based on natural clustering: north (Illinois, Indiana, Kentucky), central (Tennessee, Alabama), and south (Georgia, Florida, Louisiana). Home ranges decreased in size from north to south (4.9 ± 2.8, 3.1 ± 1.0, and 2.3 ± 0.5 km 2 , respectively). In the north and central regions, cranes often used agricultural areas, including those with hydric soil that were potentially inundated during winter (e.g., flooded fields). Home ranges in the south had the greatest proportion of wetlands (south: 37%, central: 7%, north: 1%). Wintering sites in the south potentially had higher habitat quality than other regions (small home ranges with many wetlands); however, many individuals wintered further north, indicating there was a potential tradeoff with migration distance or cranes adapted to new habitats. More research on the effects of winter habitat use on the population growth of the EMP may clarify the importance of high-quality habitat.

Southeastern United States↗
USGS2020

Highly competent native snake hosts extend the range of an introduced parasite beyond its invasive Burmese python host

Invasive Burmese pythons ( Python bivittatus ) have introduced a nonnative pentastomid parasite ( Raillietiella orientalis ) to southern Florida that has spilled over to infect native snakes. However, the extent of spillover, regarding prevalence and intensity, is unknown. We examined native snakes ( n = 523) and invasive pythons ( n = 1003) collected from Florida to determine the degree to which parasite spillover is occurring. We found R. orientalis has infected 13 species of native snakes collected from areas of sympatry with pythons. Prevalence and infection intensity of R. orientalis were significantly higher among native snakes compared with pythons. Moreover, adult female pentastomes achieved larger sizes and represented a greater proportion of the overall parasite population in native snakes vs. pythons, indicating native snakes are more competent hosts of R. orientalis than pythons. We also examined native snakes from regions of allopatry with pythons to determine how far R. orientalis has spread. We found an infected native snake 348 km north of the northernmost infected python. Our data show that native snakes are highly competent hosts of R. orientalis and have facilitated the rapid spread of this nonnative pentastome beyond the range of its invasive host.

Alabama, Florida, Georgia↗
USGS2020

Spatially referenced models of streamflow and nitrogen, phosphorus, and suspended-sediment loads in the southeastern United States

Spatially Referenced Regression On Watershed attributes (SPARROW) models were applied to describe and estimate mean-annual streamflow and transport of total nitrogen (TN), total phosphorus (TP), and suspended sediment (SS) in streams and delivered to coastal waters of the southeastern United States on the basis of inputs and management practices centered near 2012, the base year of the model. Previously published TN and TP models for 2002 served as a starting point and reference for comparison. The datasets developed for the 2012 models not only represent updates of previous conditions but also incorporate new approaches for characterizing sources and transport processes that were not available for previous models. Variability in streamflow across the southeastern United States was explained as a function of precipitation adjusted for evapotranspiration, spring discharge, and municipal and domestic wastewater discharges to streams. Results from the streamflow model were used as input to the water-quality SPARROW models, and areas with large streamflow prediction errors—urban areas and karst areas—were used to provide guidance on where additional data are needed to improve routing of flow. Variability in TN transport in Southeast streams was explained by the following five sources in order of decreasing mass contribution to streams: atmospheric deposition, agricultural fertilizer, municipal wastewater, manure from livestock, and urban land. Variable rates of TN delivery from source to stream were attributed to variation among catchments in climate, soil texture, and vegetative cover, including the extent of cover crops in the watershed. Variability in TP transport in Southeast streams was explained by the following six sources in order of decreasing mass contribution to streams: parent-rock minerals, urban land, manure from livestock, municipal wastewater, agricultural fertilizer, and phosphate mining. Varying rates of TP delivery were attributed to variation in climate, soil erodibility, depth to water table, and the extent of conservation tillage practices in the watershed. Variability in SS transport in Southeast streams was explained by variable sediment export rates for different combinations of land cover and geologic setting (for upland sources of sediment) and by gains in stream power caused by longitudinal changes in channel hydraulics (for channel sources of sediment). Sediment yields for the transitional land cover (shrub, scrub, herbaceous, and barren) varied widely depending on geologic setting and on agricultural land cover. Varying rates of SS delivery, like those for TP, were attributed to variation in climate, soil erodibility, and the extent of conservation tillage practices in the watershed, as well as to areal extent of canopy land cover in the 100-meter buffer along the channel. Relatively large uncertainty, compared to the other three models, for almost all the SS source coefficients indicates the need for caution when interpreting the results from the sediment model. TN, TP, and SS inputs to streams from sources were balanced in the models with losses from physical processes in streams and reservoirs and with water withdrawals. The losses in streams and reservoirs along with withdrawals removed 35, 44, and 65 percent of the TN, TP, and SS load, respectively, that entered streams before reaching coastal waters.

Scientific Investigations Report↗
USGS2009

Spatial analysis of instream nitrogen loads and factors controlling nitrogen delivery to streams in the southeastern United States using spatially referenced regression on watershed attributes (SPARROW) and regional classification frameworks

Understanding how nitrogen transport across the landscape varies with landscape characteristics is important for developing sound nitrogen management policies. We used a spatially referenced regression analysis (SPARROW) to examine landscape characteristics influencing delivery of nitrogen from sources in a watershed to stream channels. Modelled landscape delivery ratio varies widely (by a factor of 4) among watersheds in the southeastern United States—higher in the western part (Tennessee, Alabama, and Mississippi) than in the eastern part, and the average value for the region is lower compared to other parts of the nation. When we model landscape delivery ratio as a continuous function of local-scale landscape characteristics, we estimate a spatial pattern that varies as a function of soil and climate characteristics but exhibits spatial structure in residuals (observed load minus predicted load). The spatial pattern of modelled landscape delivery ratio and the spatial pattern of residuals coincide spatially with Level III ecoregions and also with hydrologic landscape regions. Subsequent incorporation into the model of these frameworks as regional scale variables improves estimation of landscape delivery ratio, evidenced by reduced spatial bias in residuals, and suggests that cross-scale processes affect nitrogen attenuation on the landscape. The model-fitted coefficient values are logically consistent with the hypothesis that broad-scale classifications of hydrologic response help to explain differential rates of nitrogen attenuation, controlling for local-scale landscape characteristics. Negative model coefficients for hydrologic landscape regions where the primary flow path is shallow ground water suggest that a lower fraction of nitrogen mass will be delivered to streams; this relation is reversed for regions where the primary flow path is overland flow.

Alabama, Florida, Georgia, Mississippi, North Caro↗
USGS1966

Hydrology of limestone terranes in the coastal plain of the Southeastern United States

T he very productive limestone aquifers of Tertiary and Quaternary age in the Coastal Plain of the Southeastern States contain a water-table circulation system where aquifers are at or near the land surface; the Tertiary limestone unit is a homoclinal artesian system confined beneath younger beds in coastal areas. The Tertiary limestone has a total thickness of several thousand feet and ranges in age from Paleocene to Pliocene. The part of the limestone that represents a hydrologic unit, as much as 1000 feet thick, ranges in age from middle Eocene to middle Miocene. That unit is the principal artesian aquifer in Florida and southeastern Georgia. It is also an aquifer, but of lesser importance, in South Carolina, North Carolina, and Alabama. In southeastern Florida the Quaternary limestone forms a shallow, although highly productive, aquifer. In general, the Tertiary formations dip gently toward the coast, except where the regional dip is interrupted by folds such as the Cape Fear arch, the Ocala uplift, and the Chattahoochee anticline, or by faults such as those on the Ocala uplift. A piezometric map showing the head of water in the principal artesian aquifer in Florida and southeastern Georgia reveals chief areas of recharge where limestone crops out in interstream areas and where sinkholes breach overlying beds; it reveals principal discharge areas in certain stream valleys, springs, and offshore. Lateral movement of the water in the limestone is generally controlled by the hydraulic gradient to the nearest discharge area. The movement may be either controlled by or independent of faults and folds; it may be along joints for short distances. Solution by downward movement of water in the zone of aeration to the water table has formed vertical tubular openings or shafts. Lateral movement of the water from areas of recharge to areas of discharge has formed caves and other solution channels, chiefly in the upper part of the zone of saturation. Since they were formed, some caves have been drowned, and others have been exposed in the zone of aeration as the water rose and fell, chiefly in Pleistocene time. The principal aquifer in Florida probably has caves and solution channels comparable in size and extent to those of Mammoth Cave, Kentucky; however, only a small percentage of these are above the water table at the present time. In a large part of the region the most noticeable change in chemical quality of the water in the limestone resulting from circulation of water is the freshening accompanying removal of salty water from the aquifer. Changes in sea level during Pleistocene time have raised and lowered the water table; thus the position of the upper part of the zone of saturation, in which conditions were most favorable for solution and for the formation of cavities, has changed repeatedly. At the lowest stand of the Pleistocene sea, it is conceivable that the water level in part of the limestone in north-central Florida was a few hundred feet lower than at present. The present pattern of solution openings probably was developed in Pleistocene time.

Southeastern United States↗
USGS1966

Development of permeability and storage in the tertiary limestones of the southeastern states, USA

Permeability and storage characteristics in the Tertiary limestone system of southern United States have developed progressively but non-uniformly as circulation of water and solution in the limestone have changed during the geologic and hydrologic history. The limestone formations, predominantly of Eocene age and subordinated of Oligocene and Miocene age, are widespread at and beneath the surface. They commonly dip gently seaward and are covered in coastal areas by Miocene to Recent clays and sands. Sinkholes and other karst features are common, but topographic relief is generally not great. Circulation of water under water-table conditions when the limestone was exposed to meteoric weathering, before middle Miocene time, resulted in development of secondary permeability as solution channels in near-surface parts of the limestone, Marine deposition of middle and late Miocene clays and later emergence converted part of the water-table circulation system to the present great artesian system. Later, Pleistocene changes in sea level caused changed in places where water discharged, which in turn caused changes in rates of circulation and changes in rates and positions of solution of limestone. Both present and past circulation of water have contributed to changes in permeability and storage of this limestone system.

Southeastern United States↗