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At least 559 records · Page 31Linked to original sources
USGS1993

Early Proterozoic ties between two suspect terranes and the Mojave crustal block of the Southwestern U.S

Southern California and adjacent areas contain two suspect or exotic terranes comprised largely of ancient continental crust, namely the Tujunga (San Gabriel) and Joshua Tree terranes, that have been considered part of a larger displaced terrane, the Santa Lucia-Orocopia allochthon. Paleomagnetic data for the allochthon indicate northward transport in excess of 2000 km and, thus, an origin extraneous to North America. However, Early Proterozoic plutons of the Mojave crustal block and the Joshua Tree and Tujunga terranes have strikingly comparable features, including: (1) crystallization ages of 1.63 to 1.68 Ga; (2) biotite + sphene + magnetite hornblende garnet mineralogy; (3) high LIL and enriched HFS elemental composition; (4) WPG (within-plate granite) trace element chemistry; (5) similar and unique oxygen isotopic compositions; and (6) distinct Pb and Nd isotopic signatures. These features of the Mojave block, which clearly originated as part of native North America, nevertheless distinguish it from crust elsewhere in North America. On the basis of data presented here, we conclude that the Tujunga terrane is a disrupted portion of the Mojave crustal block and is neither far-traveled nor exotic to North America. Its apparent "exotic" nature stems from derivation out of the middle crust. We also conclude that the Joshua Tree terrane is correlative to the Mojave block. We have found no significant evidence for its displacement and consider Joshua Tree to be contiguous with the Mojave block and thus not a valid terrane. The Tujunga (San Gabriel) and Joshua Tree terranes should not be considered as part of, or having shared the same transport as, the Santa Lucia-Orocopia allocthon.

The Journal of Geology↗
USGS2020

Natural and anthropogenic processes affecting radon releases during mining and early stage reclamation activities, Pinenut uranium mine, Arizona, USA

Radon (Rnair) was monitored in open air in publicly accessible areas surrounding the Pinenut uranium (U) mine during mining and reclamation activities in 2015–16 to address concerns about mining related effects to areas surrounding Grand Canyon National Park (GCNP) in Arizona, USA. During July 2015, Rnair concentrations associated with the ore storage pile monitoring site were larger than those at the mine vent monitoring site and likely resulted from the relatively large amount of ore stored on site during this period. Higher wind velocities at the ore pile monitoring site generally resulted in lower Rnair concentrations; however, wind velocity did not appear to be an important factor in controlling Rnair concentrations at the mine vent monitoring site. Physical disturbances of the ore pile by heavy equipment did not coincide with elevated Rnair concentrations at the ore storage pile or mine vent monitoring sites. The relative size of the ore storage pile showed a positive trend with the daily mean Rnair concentration measured at the ore pile monitoring site. Principal component analysis (PCA) was applied to the ore pile and mine vent multivariate data sets for simultaneous comparison of all measured variables during 230 days of the study period. A significant positive coefficient for Rnair was associated with a significant negative coefficient for wind speed for principal component (PC) 2ore pile. Significant, positive PC2mine vent coefficients included Rnair, wind direction, and relative ore pile size indicating that Rnair variations at the mine vent monitoring site may be affected by Rn sourced from the ore pile. The ore pile is located about 200 m south of the mine vent Rn monitor with the prevalent wind direction coming from the south. All data generated during the field study and laboratory verification tests were published by Naftz et al. (2018) and are available online at:

Journal of Environmental Radioactivity↗
USGS2019

Numerical simulations of depressurization-induced gas production from an interbedded turbidite gas hydrate-bearing sedimentary section in the offshore India: Site NGHP-02-16 (Area-B)

The recent National Gas Hydrate Program Expedition 02 (NGHP-02) identified the existence of gas hydrate-bearing sand reservoirs at a number of sites in the offshore of India including Site NGHP-02-16 in Area-B of the Krishna-Godavari Basin. The architecture of that gas hydrate accumulation is characterized by thin, gas hydrate-bearing, high quality sand layers interbedded with mud layers within a turbidite interval. The lowest gas hydrate-bearing layer contacting a thinly-interbedded saline aquifer designates the base of the gas hydrate stability zone (BGHSZ). The proximity of the BGHSZ and the average temperature around 20oC make the reservoir a favorable target for hydrate destabilization by means of the depressurization method. The results of the reservoir simulations indicate high gas production potential from this marine gas hydrate deposit with manageable concomitant water production using a well completion design that hydraulically isolates layers with water-saturated sands. Using a detailed geological input model, the predicted cumulative gas rates reach 3.1 x 104 m3/day (1.1 mmscf/day) after 90 days of continuous depressurization and demonstrate sustained production rates of 3.0 x 104 m3/day (1.0 mmscf/day) after 5 years of production. The interbedded nature of this gas hydrate occurrence promotes the development of horizontal dissociation interfaces between gas hydrate-bearing sand and mud layers. As a result, non-uniform gas production along the horizontal interfaces becomes a primary determinant of reservoir performance. Simulation cases have been executed to determine the impact of the uncertainty in in situ reservoir permeability and the manner in which intrinsic permeability dynamically changes during dissociation in response to the imposed effective stress increase. The cases where effective permeability is initially low and compaction is highly sensitive to stress result in the least favorable production predictions.

Journal of Marine and Petroleum Geology↗
USGS2020

Assessment of two techniques for remediation of lacustrine rocky reef spawning habitat

Rocky reef habitats in lacustrine systems constitute important areas for lithophilic‐spawning fishes. Interstitial spaces created by the structure of rocky reefs form microenvironments where incubating embryos and juvenile fish are potentially protected from predators and physical displacement. However, if interstitial spaces are filled or blocked by sediment or biofouling, the reef structure may lose these benefits. Common practices to restore reef habitat include augmentation of existing reef structures or construction of new reefs, though these practices can be costly. We explored an alternative approach for reef remediation. In 2018, we developed two benthic sled cleaning devices that used either propulsion or pressurized water jets and were towed behind a small vessel to clean reefs. We used the devices to clean two impaired natural rocky reefs in Saginaw Bay, Lake Huron. We indexed effectiveness of cleaning by measured changes in substrate relative hardness before and after cleaning. A biological response to reef cleaning was also measured by egg deposition of fall (Lake Whitefish Coregonus clupeaformis ) and spring (Walleye Sander vitreus ) lithophilic spawners. We found that our propulsion cleaning device was more effective in increasing substrate relative hardness than was the water jet device, although this was not consistent among all study locations. We also found that egg deposition on study plots was variable, but in general, egg deposition was highest on study plots that had the greatest increases in relative hardness post‐cleaning. The practicality of cleaning devices is likely related to the magnitude of site‐specific degradation. Our results indicate that the use of these or similar devices can potentially increase the quality of spawning habitat by displacing sediments that have deposited on reef structures.

North American Journal of Fisheries Management↗
USGS2005

Estimation of nutrient sources and transport for New Zealand using the hybrid mechanistic-statistical model SPARROW

The hybrid mechanistic-statistical catchment model SPARROW was applied to predict the mean annual load of nitrogen and phosphorus in streams throughout New Zealand (270,000 km2). The loads from land areas, point sources, and erosion are routed through the drainage network (576,300 reaches) with first-order stream decay and attenuation in lakes and reservoirs. Model parameters were determined by calibration against loads measured in the national water quality network (77 sites). For nitrogen, the model predicted the measured loads well (R2 of 0.956 and RMSE of 0.33 in natural-log space), while for phosphorus the model fit was not as good (R2 of 0.900 and RMSE of 0.58). The predictions of exported yields for streams with catchments > 20 km2 are broadly comparable with previous compilations of yields for various land-use classes for nitrogen, but are larger than the previous measurements for phosphorus. The calibrated stream attenuation and lake/reservoir rates were broadly consistent with previous measurements. The predicted load of total nitrogen (TN) delivered to the coast was 167,700 t yr-1, which is 45% of the loads entering the streams. For total phosphorus (TP) the predicted load to the coast was 63,100 t yr-1, 44% of the load entering the streams. Reservoir/lake attenuation makes a relatively small contribution to the overall attenuation compared with in-stream attenuation (3.5% for nitrogen and 8.5% for phosphorus). The largest contribution of total nitrogen is from pastoral land uses, together accounting for 70% of the total nitrogen load to the coast. Land used for dairying makes a disproportionately large contribution to the load of total nitrogen in relation to the area of land (37% of the load versus 6.8% of the land). For total phosphorus, the highest contribution of the load to the coast is from erosion (53.2%). Point sources contribute only a small proportion of the load to the coast (3.2% for nitrogen, 1.8% for total phosphorus). The monitoring network does not include streams with catchments smaller than 10 km2, so model predictions for streams smaller than 10 km2 should be used with caution. ?? New Zealand Hydrological Society (2005).

Journal of Hydrology New Zealand↗
USGS2004

Ecological impacts of wheat seeding after a Sierra Nevada wildfire

The Highway Fire burned 1680 ha of mixed ponderosa pine–oak–chaparral in the newly created Giant Sequoia National Monument and the adjacent Sequoia National Forest of Fresno County, California in August 2001. The USDA Forest Service Burned Area Emergency Rehabilitation (BAER) program recommended that portions of the burned forest be seeded with a non-persistent variety of wheat at a density of 157 kg ha –1 (140 lb/ac). The present study compared the vascular plant diversity and cover in seeded and unseeded parts of this burn to evaluate the ecological impact of seeding an alien grass. In the first post-fire growing season, the natural regeneration of unseeded control sites averaged ~55% ground surface covered. Wheat seeding enhanced the ground cover, averaging 95% ground surface cover. Wheat was the dominant species on the seeded sites, comprising 67% of the total cover. Dominance–diversity curves were markedly affected by the seeding and indicated a disruption in the natural ecological structure of these communities. On seeded sites, wheat dominated and all other species were poorly represented whereas, on unseeded control sites, there was a more equitable distribution of species. Correlated with the wheat cover was a significant decrease in species richness at all scales examined. Total species richness was reduced from 152 species across all unseeded sites to 104 species on all seeded sites. Average species richness, at scales from 1 to 1000 m 2 , was 30–40% lower on seeded sites. Species most strongly inhibited were post-fire endemics whose lifecycle is restricted to immediate post-fire environments. Seeded sites had fewer alien species than unseeded sites; however, this may not have any lasting effect since other studies show the primary alien threat is not in the first post-fire year. Seeding was also associated with an order of magnitude drop in Pinus ponderosa seedling recruitment and, coupled with the massive thatch still remaining on the site, it is likely that recruitment will be inhibited in subsequent years.

International Journal of Wildland Fire↗
USGS2013

Wildfire and aspect effects on hydrologic states after the 2010 Fourmile Canyon Fire

Wildfire can change how soils take in, store, and release water. This study examined differences in how burned and unburned plots on north versus south-facing slope aspects respond to rainfall. The largest wildfire impacts were litter/duff combustion on burned north-facing slopes versus soil-water retention reduction on burned south-facing slopes. Wildfire is one of the most significant disturbances in mountainous landscapes, affecting water supply and ecologic function and setting the stage for natural hazards such as flash floods. The impacts of wildfire can affect the entire hydrologic cycle. Measurements of soil-water content and matric potential in the near surface (top 30 cm) captured the hydrologic state in both burned and unburned hillslopes during the first spring through fall period (1 June–1 Oct. 2011) after the 2010 Fourmile Canyon Fire near Boulder, CO. This time span included different hydrologic periods characterized by cyclonic frontal storms (low-intensity, long duration), convective storms (high-intensity, short duration), and dry periods. In mountainous environments, aspect can also control hydrologic states, so north- vs. south-facing slopes were compared. Wildfire tended to homogenize soil-water contents across aspects and with depth in the soil, yet it also may have introduced an aspect control on matric potential that was not observed in unburned soils. Post-wildfire changes in hydrologic state were observed in south-facing soils, probably reflecting decreased soil-water retention after wildfire. North-facing soils were impacted the most, in terms of hydrologic state, by the loss of water storage in the combusted litter–duff layer and forest canopy, which had provided a large “hydrologic buffering” capacity when unburned. Unsaturated zone measurements showed increased variability in hydrologic states and more rapid state transitions in wildfire-impacted soils. A simple, qualitative analysis suggested that the range of unsaturated-zone processes along the gravity–capillarity–adsorption continuum was expanded by wildfire for a given soil. The small number of experimental plots in this study suggests that further work is needed before these conclusions can be generalized to other geographic areas.

Vadose Zone Journal↗
USGS1954

Studies on avian malaria in vectors and hosts of encephalitis in Kern County, California. I. Infections in avian hosts

An epizoological study of Plasmodium infections in wild birds of Kern County, California, in the years 1946 through 1951 greatly extended knowledge of the occurrence of these parasites and their behavior in nature. Examination of 10,459 blood smears from 8,674 birds representing 73 species resulted in the observation of Plasmodium spp. in 1,094 smears representing 888 individual birds of 27 species. Seven species of Plasmodium were found: relictum, elongatum, hexamerium, nucleophilum, polare, rouxi and vaughani. Plasmodium relictum was by far the most frequently observed species, occurring in at least 79 per cent of the infected birds. Twelve new host species are recorded for this parasite. Sufficient morphological variation was observed to indicate that two strains of this species probably exist in nature. Numerous new host records were made of plasmodia with elongate gametocytes. The finding of parasites believed to be P. rouxi in two new host species represents the first record of the occurrence of this Plasmodium outside of Algeria. Multiple smears were obtained from a number of individual birds over varying time periods. Evidence of prolonged parasitemia was unusual, but some individuals had parasitemia on consecutive months and even for three successive years. In most individuals, parasitemias were of short duration. The inoculation of blood from wild birds into canaries led to the demonstration of many infections not observed on blood smear examination of donors. Use of these two complementary techniques led to more complete host records and a truer picture of the prevalence of infection. Three age classes of birds were studied--nestling, immature (less than 1 year of age) and adult. Parasites were observed in all three groups but infections in the younger individuals were most susceptible to interpretation. As to time of onset, numerous records were obtained of infection in nestling birds. Prevalence rates in immature birds after a single season's exposure ranged from 64 to 100 per cent in the house finch and 17 to 68 per cent in the English sparrow in different areas and years. Marked differences were found in the prevalence rates in different summer months, years and areas. It is believed these differences reflect variation in a number of environmental factors. This study indicates the extensive distribution of Plasmodium infection in a wide range of wild avian hosts. The observations are of possible importance in epidemiological studies of other arthropod-borne diseases such as the viral encephalitides for which these birds serve as hosts.

California↗
USGS2022

Debris flows originating from soil slips during rainstorms in Southern California

Debris flows generated during rainstorms present a greater risk of death and injury to southern California residents than all other kinds of slope failure combined. During the years 1962-1971, twenty-three people in the greater Los Angeles area died from being buried or struck by debris flows, all of which probably originated as soil slips. Soil slips and debris flows are recurring major natural geomorphological processes in the region. Soil slips are reconstituted into debris flows when the initial movement (sliding failure) of slabs of soil and wedges of ravine fill causes remoulding of the saturated moving mass into viscous, debris-laden mud, which then flows down available drainage courses. This change of state results in a marked reduction in resistance to shear, permitting masses to accelerate down the same slopes on which, only moments earlier, the slabs of soil mantle had barely overcome the resistance to sliding. Many flows reach avalanche speeds and do not begin to deposit significant amounts of detritus until they reach lower gradients far from their sources. The deposits form steep ‘alluvial’ fans at the mouths of short, steep drainage basins tributary to broad valleys, and form debris trains in and along narrow trunk canyons below the mouths of short, steep tributaries. The exceptional storm period of January 18th to 26th, 1969, was accompanied by thousands of soil slips and provided an unusual opportunity to determine the times of occurrence of numerous debris flows, establish their origin from soil slips, and compare the times of those events with rainfall records from an extensive network of continuously recording rain gauges and a sequential set of radar weather maps. An empirical association between soil slips and rainfall suggests that a 10 inch antecedent rainfall is required to bring most of the colluvial soil of the area to field capacity, and 0.25 inch-per-hour is the minimum rate at which surface infiltration exceeds subsoil drainage for most of the colluvial soils of the area so that pore pressures are raised in a zone above the less permeable parent materials. Soil moisture of this level also appears to be sufficient so that most of the colluvial soils of the area will become at least partly liquid when disturbed. GeoRef Subject

California↗
USGS1997

Selection of the Mars Pathfinder landing site

The Mars Pathfinder spacecraft will land on a depositional fan near the mouth of the catastrophic outflow channel, Ares Vallis (19.5°N, 32.8°W). This site offers the prospect of analyzing a variety of rock types from the ancient cratered highlands, intermediate-age ridged plains, and reworked channel deposits. Analyses of these rocks by Pathfinder instruments will enable first-order scientific questions to be addressed, such as differentiation of the crust, the development of weathering products, and the nature of the early environment, as well as their subsequent evolution on Mars. Constraints imposed by (1) spacecraft and rover designs (which are robust), (2) entry, descent, and landing, (3) scientific potential at various sites, and (4) safety were important considerations in site selection. Engineering constraints require a 70 km by 200 km smooth, flat (low slopes) area located between 10° and 20°N that is below 0 km elevation, with average radar reflectivity, little dust, and moderate rock abundance. Three regions on Mars are between 10° and 20°N and below 0 km elevation: Chryse, Amazonis, and Isidis-Elysium. Science considerations favor sites at the mouths of outflow channels (grab bag sites offer an assay of rock types on Mars), highland sites (early crustal differentiation and climate), and sites covered with dark (unoxidized) material. Sites are considered safe if they are clearly below 0 km elevation, appear acceptably free of hazards in high-resolution (<50 m/pixel) Viking orbiter images and have acceptable reflectivity and roughness at radar wavelengths, thermal inertia, rock abundance, red to violet ratio, and albedo. Recent 3.5-cm wavelength radar observations were used to verify elevation, reflectivity, and roughness within the landing ellipses. Three sites meet all of these criteria: Ares Vallis, Tritonis Lacus, and Isidis. Although Isidis appears to be safer than Tritonis and Ares, the greater scientific potential at Ares Vallis resulted in its selection. Comparisons of the Grand Coulee (channel) and the depositional Ephrata Fan of the Channeled Scabland in eastern Washington, with Ares Vallis and its depositional fan also suggest the Ares Vallis landing site is safe and scientifically interesting.

Journal of Geophysical Research Planets↗
USGS2016

Deriving habitat models for northern long-eared bats from historical detection data: A case study using the Fernow Experimental Forest

The listing of the northern long-eared bat ( Myotis septentrionalis ) as federally threatened under the Endangered Species Act following severe population declines from white-nose syndrome presents considerable challenges to natural resource managers. Because the northern long-eared bat is a forest habitat generalist, development of effective conservation measures will depend on appropriate understanding of its habitat relationships at individual locations. However, severely reduced population sizes make gathering data for such models difficult. As a result, historical data may be essential in development of habitat models. To date, there has been little evaluation of how effective historical bat presence data, such as data derived from mist-net captures, acoustic detection, and day-roost locations, may be in developing habitat models, nor is it clear how models created using different data sources may differ. We explored this issue by creating presence probability models for the northern long-eared bat on the Fernow Experimental Forest in the central Appalachian Mountains of West Virginia using a historical, presence-only data set. Each presence data type produced outputs that were dissimilar but that still corresponded with known traits of the northern long-eared bat or are easily explained in the context of the particular data collection protocol. However, our results also highlight potential limitations of individual data types. For example, models from mist-net capture data only showed high probability of presence along the dendritic network of riparian areas, an obvious artifact of sampling methodology. Development of ecological niche and presence models for northern long-eared bat populations could be highly valuable for resource managers going forward with this species. We caution, however, that efforts to create such models should consider the substantial limitations of models derived from historical data, and address model assumptions.

West Virginia↗
USGS2015

Re-colonization by common eiders Somateria mollissima in the Aleutian Archipelago following removal of introduced arctic foxes Vulpes lagopus

Islands provide refuges for populations of many species where they find safety from predators, but the introduction of predators frequently results in elimination or dramatic reductions in island-dwelling organisms. When predators are removed, re-colonization for some species occurs naturally, and inter-island phylogeographic relationships and current movement patterns can illuminate processes of colonization. We studied a case of re-colonization of common eiders Somateria mollissima following removal of introduced arctic foxes Vulpes lagopus in the Aleutian Archipelago, Alaska. We expected common eiders to resume nesting on islands cleared of foxes and to re-colonize from nearby islets, islands, and island groups. We thus expected common eiders to show limited genetic structure indicative of extensive mixing among island populations. Satellite telemetry was used to record current movement patterns of female common eiders from six islands across three island groups. We collected genetic data from these and other nesting common eiders at 14 microsatellite loci and the mitochondrial DNA control region to examine population genetic structure, historical fluctuations in population demography, and gene flow. Our results suggest recent interchange among islands. Analysis of microsatellite data supports satellite telemetry data of increased dispersal of common eiders to nearby areas and little between island groups. Although evidence from mtDNA is suggestive of female dispersal among island groups, gene flow is insufficient to account for recolonization and rapid population growth. Instead, near-by remnant populations of common eiders contributed substantially to population expansion, without which re-colonization would have likely occurred at a much lower rate. Genetic and morphometric data of common eiders within one island group two and three decades after re-colonization suggests reduced movement of eiders among islands and little movement between island groups after populations were re-established. We predict that re-colonization of an island group where all common eiders are extirpated could take decades.

Alaska↗
USGS2006

Multiphase, multicomponent parameter estimation for liquid and vapor fluxes in deep arid systems using hydrologic data and natural environmental tracers

Multiphase, multicomponent numerical models of long-term unsaturated-zone liquid and vapor movement were created for a thick alluvial basin at the Nevada Test Site to predict present-day liquid and vapor fluxes. The numerical models are based on recently developed conceptual models of unsaturated-zone moisture movement in thick alluvium that explain present-day water potential and tracer profiles in terms of major climate and vegetation transitions that have occurred during the past 10 000 yr or more. The numerical models were calibrated using borehole hydrologic and environmental tracer data available from a low-level radioactive waste management site located in a former nuclear weapons testing area. The environmental tracer data used in the model calibration includes tracers that migrate in both the liquid and vapor phases (δD, δ 18 O) and tracers that migrate solely as dissolved solutes (Cl), thus enabling the estimation of some gas-phase as well as liquid-phase transport parameters. Parameter uncertainties and correlations identified during model calibration were used to generate parameter combinations for a set of Monte Carlo simulations to more fully characterize the uncertainty in liquid and vapor fluxes. The calculated background liquid and vapor fluxes decrease as the estimated time since the transition to the present-day arid climate increases. However, on the whole, the estimated fluxes display relatively little variability because correlations among parameters tend to create parameter sets for which changes in some parameters offset the effects of others in the set. Independent estimates on the timing since the climate transition established from packrat midden data were essential for constraining the model calibration results. The study demonstrates the utility of environmental tracer data in developing numerical models of liquid- and gas-phase moisture movement and the importance of considering parameter correlations when using Monte Carlo analysis to characterize the uncertainty in moisture fluxes.

Vadose Zone Journal↗
USGS2011

Trap style influences wild pig behavior and trapping success

Despite the efforts of many natural resource professionals, wild pig ( Sus scrofa ) populations are expanding in many areas of the world. Although many creative techniques for controlling pig populations are being explored, trapping has been and still is the most commonly used method of population control for many public and private land managers. We conducted an observational study to examine the efficiency of 2 frequently used trap styles: a small, portable box‐style trap and a larger, semi‐permanent, corral‐style trap. We used game cameras to examine patterns of trap entry by wild pigs around each style of trap, and we conducted a trapping session to compare trapping success between trap styles. Adult female and juvenile wild pigs entered both styles of trap more readily than did adult males, and adult males seemed particularly averse to entering box traps. Less than 10% of adult male visits to box traps resulted in entries, easily the least percentage of any class at any style of trap. Adult females entered corral traps approximately 2.2 times more often per visit than box traps and re‐entered corral traps >2 times more frequently. Juveniles entered and re‐entered both box and corral traps at similar rates. Overall (all‐class) entry‐per‐visit rates at corral traps (0.71) were nearly double that of box traps (0.37). Subsequent trapping data supported these preliminary entry data; the capture rate for corral traps was >4 times that of box traps. Our data suggest that corral traps are temporally and economically superior to box traps with respect to efficiency; that is, corral traps effectively trap more pigs per trap night at a lower cost per pig than do box traps

Georgia↗
USGS2025

Physical habitat is more than a sediment issue: A multi-dimensional habitat assessment indicates new approaches for river management

Degraded physical habitat is a common stressor affecting river ecosystems and typically addressed in the United States (US) through a regulatory focus on sediment. However, a narrow regulatory focus on sediment may overlook other aspects of physical habitat and the processes for its creation, maintenance, and degradation. In addition, there exist few “ready-to-use” regional assessments of the multiple dimensions of physical habitat to better understand continuous patterns of condition and prioritize management efforts across a large spatial scale. In this study, we use rapid habitat monitoring data to train a machine-learning ( i.e., random forest) model to predict twelve physical habitat metrics for nearly 120,000 km of nontidal rivers and streams across the Chesapeake Bay watershed, US. We capture a range of habitat conditions driven by both natural variables and anthropogenic pressures. Covariation among habitat metrics indicated two major dimensions of habitat variation: 1) coarse bed substrate and hydromorphic heterogeneity and 2) bank stability and riparian condition. The model predicted localized changes from 2001 to 2019, and the predicted areas of deterioration roughly balanced improvements across the watershed, indicating little progress towards long-term watershed management goals. To evaluate connections to regulatory and management endpoints, we compared our physical habitat predictions to paired estimates of sediment and flow alteration across the region. Sediment concentrations were greater in reaches with less bank stability and lower riparian quality; however, the relation was weak for coarse bed condition metrics, including embeddedness, which is frequently used for establishing regulatory sediment restrictions. For flow alteration, most habitat metrics had lower scores with altered flow metrics, but metrics of instream habitat heterogeneity and coarse substrate condition were most strongly affected. Increased flashy, high flows negatively affected most metrics, but coarse substrate metrics were also negatively affected by greater low flow severity. This study highlights a potential disconnect between a narrow focus on regulatory sediment targets given the multiple dimensions and responses of physical habitat. A more holistic approach to physical habitat in management interventions – one that considers hydromorphic processes, diversity and variability in microhabitats, and explicit consideration of alterations to both low and high flows – may be warranted. By providing direct estimates of multiple aspects of physical habitat, this model can help support managers in the Chesapeake Bay watershed to better understand the range of habitat conditions, identify high-quality reaches for conservation, and target potential management actions tailored to localized conditions.

Delaware, Maryland, New York, Pennsylvania, Virgin↗
USGS2005

Effects of forest structure and composition on food availability for Varecia variegata at Ranomafana National Park, Madagascar

We present a summary of a long-term field study that examined the effects of forest disturbance on the availability of palatable fruit and its utilization by V. variegata. Forest structure and tree species composition were measured in three adjacent study areas, with different histories of disturbance, in Ranomafana National Park (RNP), Madagascar. V. variegata abundance was monitored by frequent encounters with resident groups and periodic censuses conducted along trails. Finally, the abundance of mature fruit in species used by V. variegata was scored monthly at representative trees at several locations. V. variegata abundance was most consistent in the least anthropogenically disturbed site, while no established lemur groups were observed in the heavily logged site for over a decade post-harvest. Lemur abundance was variable in the selectively logged site. The presence of select food trees, particularly specimens with voluminous crowns capable of producing abundant fruit crops, appears to be key to the establishment and expansion of V variegata groups. Our analysis of year-long fruit utilization revealed a high degree of preference for several species of trees. Two species exhibited mature fruit in a low percentage of stems but were available for a protracted period of time, while two additional species showed high intraspecific fruiting synchrony and were available for a shorter period of time. These contrasting phenologies, rather than the individual tree species, may be most important to V. variegata due to their coincident timing of fruit maturation with key lemur life-history events. Any disturbance-natural or anthropogenic-that disrupts the phenology cycles of food trees has the potential to impact lemur abundance and dispersion. Intense disturbances, such as heavy logging or severe cyclones, have long-lasting impacts on fruit production, while selective logging or moderate cyclonic windthrow cause more transient impacts. V. variegata is adapted to deal with an intrinsically erratic food supply by virtue of its reproductive biology and social behavior.

American Journal of Primatology↗
USGS2016

An empirical assessment of which inland floods can be managed

Riverine flooding is a significant global issue. Although it is well documented that the influence of landscape structure on floods decreases as flood size increases, studies that define a threshold flood-return period, above which landscape features such as topography, land cover and impoundments can curtail floods, are lacking. Further, the relative influences of natural versus built features on floods is poorly understood. Assumptions about the types of floods that can be managed have considerable implications for the cost-effectiveness of decisions to invest in transforming land cover (e.g., reforestation) and in constructing structures (e.g., storm-water ponds) to control floods. This study defines parameters of floods for which changes in landscape structure can have an impact. We compare nine flood-return periods across 31 watersheds with widely varying topography and land cover in the southeastern United States, using long-term hydrologic records (&ge;20 years). We also assess the effects of built flow-regulating features (best management practices and artificial water bodies) on selected flood metrics across urban watersheds. We show that landscape features affect magnitude and duration of only those floods with return periods &le;10 years, which suggests that larger floods cannot be managed effectively by manipulating landscape structure. Overall, urban watersheds exhibited larger (270 m 3 /s) but quicker (0.41 days) floods than non-urban watersheds (50 m 3 /s and 1.5 days). However, urban watersheds with more flow-regulating features had lower flood magnitudes (154 m 3 /s), but similar flood durations (0.55 days), compared to urban watersheds with fewer flow-regulating features (360 m 3 /s and 0.23 days). Our analysis provides insight into the magnitude, duration and count of floods that can be curtailed by landscape structure and its management. Our findings are relevant to other areas with similar climate, topography, and land use, and can help ensure that investments in flood management are made wisely after considering the limitations of landscape features to regulate floods.

Journal of Environmental Management↗
USGS2021

Aerial strip-transect surveys: Indexing autumn–winter waterbird abundance and distribution in South Carolina

Aerial surveys integrating probability-based sample designs have been implemented successfully to estimate relative abundance of wintering ducks in Arkansas, Louisiana, Mississippi, and Missouri, but these approaches have not been evaluated in the Atlantic Flyway except for American black ducks ( Anas rubripes ) along the Atlantic coast. Furthermore, these surveys have not been used to index abundance of other nonbreeding waterbirds. Given elimination or reduction of resources allocated to the Midwinter Waterfowl Survey in the Atlantic Flyway and elsewhere, the South Carolina Department of Natural Resources (SCDNR) expressed a need for reliable surveys to monitor waterfowl and other waterbirds during autumn through winter. We designed stratified aerial strip-transect surveys to estimate population indices for migrating and wintering dabbling ducks (Anatini), diving ducks (Aythini, Mergini, Oxyurini), pelagic and piscivorous waterbirds (Anhingidae, Laridae, Pelicanidae, Phalacrocoracidae), and wading birds (Ardeidae, Ciconiidae, Threskiornithidae) in coastal and inland regions of South Carolina during autumn-winter 2017–2019. We used unequal probability random sampling to estimate population indices with deemed adequate precision (i.e., coefficient of variation [CV] ≤ 20%) and estimated theoretical survey efforts needed to achieve desired precision for future aerial surveys. Indices met our goal for precision in September and January 2018 for wading birds, in February and November 2018 for pelagic waterbirds, and in February 2018 for diving ducks, but never for other ducks during South Carolina waterfowl hunting season. We detected peak abundance of dabbling and diving ducks in January and wading birds and wood storks ( Mycteria americana ) in September. We estimated ~2.5 times greater survey effort was needed across waterbird taxa than was expended to achieve a CV=20%. We also used survey data to depict spatiotemporal variation in waterbird distributions across the study area. Our surveys are applicable for the SCDNR and other agencies seeking to monitor autumn-winter waterbird populations. Although survey refinements are necessary to increase precision in South Carolina, our waterbird indices are useful to assess population trends through time, guide habitat management and restoration efforts, refine local harvest regulations, inform law enforcement to detected illicit activities (e.g., baiting), and monitor possible shifting waterbird distributions in response to land-use and climate change.

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