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At least 343 records · Page 19Linked to original sources
USGS2005

Analysis of vegetation distribution in Interior Alaska and sensitivity to climate change using a logistic regression approach

Aim: To understand drivers of vegetation type distribution and sensitivity to climate change. Location: Interior Alaska. Methods: A logistic regression model was developed that predicts the potential equilibrium distribution of four major vegetation types: tundra, deciduous forest, black spruce forest and white spruce forest based on elevation, aspect, slope, drainage type, fire interval, average growing season temperature and total growing season precipitation. The model was run in three consecutive steps. The hierarchical logistic regression model was used to evaluate how scenarios of changes in temperature, precipitation and fire interval may influence the distribution of the four major vegetation types found in this region. Results: At the first step, tundra was distinguished from forest, which was mostly driven by elevation, precipitation and south to north aspect. At the second step, forest was separated into deciduous and spruce forest, a distinction that was primarily driven by fire interval and elevation. At the third step, the identification of black vs. white spruce was driven mainly by fire interval and elevation. The model was verified for Interior Alaska, the region used to develop the model, where it predicted vegetation distribution among the steps with an accuracy of 60-83%. When the model was independently validated for north-west Canada, it predicted vegetation distribution among the steps with an accuracy of 53-85%. Black spruce remains the dominant vegetation type under all scenarios, potentially expanding most under warming coupled with increasing fire interval. White spruce is clearly limited by moisture once average growing season temperatures exceeded a critical limit (+2 ??C). Deciduous forests expand their range the most when any two of the following scenarios are combined: decreasing fire interval, warming and increasing precipitation. Tundra can be replaced by forest under warming but expands under precipitation increase. Main conclusion: The model analyses agree with current knowledge of the responses of vegetation types to climate change and provide further insight into drivers of vegetation change. ?? 2005 Blackwell Publishing Ltd.

Journal of Biogeography↗
USGS2015

Terrain parameters of glide snow avalanches and a simple spatial glide snow avalanche model

Glide snow avalanches are dangerous and difficult to predict. Despite substantial recent research there is still inadequate understanding regarding the controls of glide snow avalanche release. Glide snow avalanches often occur in similar terrain or the same locations annually, and repeat observations and prior work suggest that specific topography may be critical. Thus, to gain a better understanding of the terrain component of these types of avalanches we examined terrain parameters associated with the specific area of glide snow avalanche release in comparison to avalanche starting zones where no glide snow avalanches were observed (i.e. non-glide snow avalanche terrain). Glide snow avalanche occurrences visible from the Going-to-the-Sun Road corridor in Glacier National Park, Montana from 2003 to 2013 are investigated using a database of all avalanche occurrences derived of daily observations each year from 1 April to 1 June. This yielded 192 glide snow avalanches in 53 distinct avalanche paths. Each avalanche was digitized in a GIS using satellite, oblique, and aerial imagery as reference. A set of 117 non-glide snow avalanche starting zones were also selected in this manner. These were start zones with avalanche activity potential, but without glide avalanches observed. Topographical parameters such as area, slope, aspect, curvature, potential incoming solar radiation, distance from ridge, and elevation were then derived for the entire dataset utilizing tools with a GIS and a 10 m DEM. Ground class and a glide factor were calculated using a four level classification index with in-situ observations and a land surface type layer in a GIS. A total of 21 terrain variables were examined using a univariate analysis between areas where glide snow avalanches occurred and areas where glide snow avalanches were never observed, despite crack formation. Only two variables were not significantly different. The significantly different variables were then used to train a classification tree to distinguish between glide and non-glide snow avalanche terrain. A 10-fold cross validated tree resulted in four decision nodes to classify the data. The nodes split on glide factor, maximum slope angle, seasonal sum of incoming solar radiation, and maximum curvature to distinguish between glide snow avalanche and non-glide snow avalanche terrain with an unweighted average accuracy (RPC) of 0.95 and probability of detection of events (POD) of 0.99. Finally, the results of the cross-validated tree were used in a GIS to examine other areas, not used in the training dataset of the classification tree, of potential glide snow avalanche release within Glacier National Park. Using this understanding of the role of topographic parameters on glide snow avalanche activity, a spatial terrain based model was developed to identify other areas with high glide snow avalanche potential outside of the immediate observation area. This simple spatial model correctly classified 78 percent of actual glide snow avalanche terrain (pixel count) of a small test area of four independent observed glide snow avalanches.

Montana↗
USGS2024

Least Bell's Vireos and Southwestern Willow Flycatchers—Breeding activities and habitat use—2023 annual report

Executive Summary We completed four protocol surveys for Least Bell’s Vireos ( Vireo bellii pusillus ; hereinafter vireo) during the breeding season, supplemented by weekly territory monitoring visits between April 6 and July 20 at the San Luis Rey Flood Risk Management Project Area (hereinafter Project Area). We identified a total of 136 territorial male vireos; 121 were confirmed as paired, and 4 were confirmed as single males. For the remaining 11 territories, we were unable to confirm breeding status. In 2023, two transient vireos were detected. The vireo population in the Project Area increased by 2 percent from 2022 to 2023. Populations in southern San Diego County also increased (by 6 percent on the Otay River) or were stable (Salt Creek/Wolf Canyon). In contrast, the vireo population at Marine Corps Base Camp Pendleton (MCBCP) and at Marine Corps Air Station decreased by 2 and 10 percent, respectively. We used an index of treatment (hereinafter Treatment Index) to evaluate the effect of ongoing vegetation clearing on the Project Area vireo population. The Treatment Index measures the cumulative effect of vegetation treatment within a territory by using the percentage area treated weighted by the number of years since treatment. We determined that the Treatment Index for an unoccupied habitat was more than four times higher than that of an occupied habitat, indicating that vireos selected habitats that were less treated in which to settle. We monitored vireo nests at three general site types: (1) within the flood channel where non-native and native vegetation removal has occurred regularly (hereinafter Channel), (2) three sites near the flood channel where limited non-native and native vegetation removal has occurred (hereinafter Off-channel), and (3) three sites that have been actively restored by planting native vegetation (hereinafter Restoration). Nesting activity was monitored in 84 territories, 4 of which were occupied by single males. Overall, 46 percent of completed nests were successful, and nest success did not differ among the three sites. In 2023, we found that territories in the Channel had greater hatching success per egg compared to Off-channel, but there were no other differences with regard to clutch size, hatching, or fledging success among Channel, Off-channel, and Restoration sites. Overall breeding success and productivity were slightly higher in 2023 than in 2022, with pairs fledging an average±standard deviation of 3.1±2.1 young and 79 percent of pairs fledging at least 1 young. To investigate if the cumulative years of treatment had an effect on vireo reproductive effort, we looked at the effects of the Treatment Index on reproductive parameters. Results from generalized linear models indicated that treatment did not have an effect on vireo nesting effort (the number of nest attempts) or the number of vireo fledglings per pair produced in 2023. Similarly, we did not detect an effect of Treatment Index on the daily survival rate (DSR) of nests. Analysis of vegetation data collected at vireo nests from 2006 to 2023 did not reveal an effect of vegetation cover at the nest on DSR. We did find, however, that Channel nests were placed higher in and farther from the edge of the host plant than Off-channel nests. Within sites, we did not detect any differences in vegetation cover between successful and unsuccessful nests. Red/arroyo willow ( Salix laevigata or Salix lasiolepis ) and mule fat ( Baccharis salicifolia ) were the species most commonly selected for nesting by vireos in all three site types. Black willow ( Salix gooddingii ) and sandbar willow ( Salix exigua ) also were commonly used. Vireos used a wider variety of species for nesting in Channel and Off-channel sites (10 and 13 species, respectively) compared to Restoration sites (2 species), although there was limited nesting in Restoration sites in 2023. There were 51 vireos banded before the 2023 breeding season that were resighted and identified at the Project Area in 2023. Two of these vireos were originally banded outside of the Project Area, at the Santa Margarita River on MCBCP. Adult birds of known age ranged from 1 to 7 years old. Between 2006 and 2023, survival of males (66±11 percent) was consistently higher than that of females (60±12 percent). First-year birds from 2006 to 2022 had an average annual survival of 15±5 percent. First-year dispersal in 2023 averaged 20.2±31.3 kilometers (km), with the longest dispersal (76.3 km) by a female that was recaptured at Wolf Canyon, a tributary to Otay River. From 2007 to 2012, most returning first-year vireos returned to the Project Area, whereas from 2014 to 2016, a greater proportion of returning birds dispersed to areas outside of the Project Area. From 2018 to 2022, the trend shifted, and more first-year vireos returned to the Project Area, except for 2022 when only one out of five first-year vireos returned to the Project Area. This trend continued in 2023: 71 percent of all first-year vireos returned to the Project Area, and 29 percent dispersed to areas outside of the Project Area (San Diego River and Wolf Canyon). Most of the returning adult male vireos showed strong between-year fidelity to their previous territories. In 2023, 94 percent of males (34/36) occupied a territory that they had defended in 2022 (within 100 meters [m]). In 2023, 33 percent of females (1/3) detected returned to a territory they occupied in 2022. The average between-year movement for returning adult vireos was 0.2±0.9 km. The amount of treatment at adults’ 2022 territories did not affect the distance adults moved to their 2023 territories. We completed four protocol surveys for the endangered Southwestern Willow Flycatcher ( Empidonax traillii extimus ; hereinafter flycatcher) at the Project Area between May 15 and July 21, 2023. In 2023, four transient Willow Flycatchers were detected in the Project Area. Two transients were detected in Reach 1, one in Reach 3a, and one in Whelan Mitigation. No resident flycatchers were documented in the Project Area in 2023. A total of 46 vegetation transects (516 points) were sampled in the Project Area in 2023. There were 71 percent (368/516) of points located in the Channel, and 22 percent (113/516) were in Upper Pond. The remaining 7 percent (35/516) of points were at the Whelan Restoration site. Foliage cover below 1 m was higher at the Channel points and Upper Pond compared to Whelan Restoration. From 1 to 3 m, foliage cover was similar at all 3 sites; however, above 3 m foliage cover was higher in the Channel compared to the Upper Pond and Whelan Restoration sites. Average canopy height was higher in the Channel (5.6±3.8 m) compared to Upper Pond (4.7±2.7 m) and Whelan Restoration (4.0±2.0 m). From 2006 to 2023, total foliage cover declined from 2 to 3 m and above 6 m in the Channel, in contrast to Upper Pond and Whelan Restoration, where little directional change in vegetation cover has occurred and where vegetation cover has largely recovered to 2006 levels. Within the Channel, the steepest declines occurred between 2009 and 2013 and between 2014 and 2016. Since 2016, we observed an increase in foliage cover, largely herbaceous, between 0 and 2 m within the Channel. Although increases were observed at all height classes after 2016, percentage cover has remained below levels measured before 2009. We sampled vegetation at 45 vireo nests and 45 random plots (territory plots) within territories in the Channel and Upper Pond after the 2023 breeding season. Vireos in the Channel established territories in areas with significantly more cover from 3 to 7 m but less cover below 1 m relative to the available habitat. Within territories, Channel vireos selected nest sites largely at random, but with significantly less foliage cover from 4 to 5 m. Vireos at Upper Pond established territories in areas with significantly more foliage cover below 4 m and from 5 to 6 m relative to available habitat. Within territories, Upper Pond vireos also selected nest sites at random except for a preference for sites with significantly less foliage cover below 1 m.

Open-File Report↗
USGS2000

Monthly variability and possible sources of nitrate in ground water beneath mixed agricultural land use, Suwannee and Lafayette Counties, Florida

In an area of mixed agricultural land use in Suwannee and Lafayette Counties of northern Florida, water samples were collected monthly from 14 wells tapping the Upper Floridan aquifer during July 1998 through June 1999 to assess hydrologic and land-use factors affecting the variability in nitrate concentrations in ground water. Unusually high amounts of rainfall in September and October 1998 (43.5 centimeters total for both months) resulted in an increase in water levels in all wells in October 1998. This was followed by unusually low amounts of rainfall during November 1998 through May 1999, when rainfall was 40.7 centimeters below 30-year mean monthly values. The presence of karst features (sinkholes, springs, solution conduits) and the highly permeable sands that overlie the Upper Floridan aquifer provide for rapid movement of water containing elevated nitrate concentrations to the aquifer. Nitrate was the dominant form of nitrogen in ground water collected at all sites and nitrate concentrations ranged from less than 0.02 to 22 milligrams per liter (mg/L), as nitrogen. Water samples from most wells showed substantial monthly or seasonal fluctuations in nitrate concentrations. Generally, water samples from wells with nitrate concentrations higher than 10 mg/L showed the greatest amount of monthly fluctuation. For example, water samples from six of eight wells had monthly nitrate concentrations that varied by at least 5 mg/L during the study period. Water from most wells with lower nitrate concentrations (less than 6 mg/L) also showed large monthly fluctuations. For instance, nitrate concentrations in water from four sites showed monthly variations of more than 50 percent. Large fluctuations in nitrate concentrations likely result from seasonal agricultural practices (fertilizer application and animal waste spreading) at a particular site. For example, an increase in nitrate concentrations observed in water samples from seven sites in February or March 1999 most likely results from application of synthetic fertilizers during the late winter months. Lower nitrate concentrations were detected in water samples from five of eight wells sampled during high-flow conditions for the Suwannee River in March 1998 compared to low-flow conditions in November 1998. Evidence for reduction of nitrate due to denitrification reactions was observed at one site (AC-1), as indicated by elevated concentrations of nitrogen gas and a corresponding increase in nitrogen isotope (d15N-NO3) values with a decrease in nitrate concentrations. Denitrification is unlikely at other sites based on the presence of dissolved oxygen concentrations greater than 2 mg/L in ground water and no observed trend between nitrate concentrations and values d15N-NO3 values. Nitrate was the dominant nitrogen species in most monthly rainfall samples; however, ammonium concentrations were similar or greater than nitrate during November and December 1998. During February through May 1999, both nitrate and ammonium concentrations were substantially higher in monthly rainfall samples collected at the study area compared to mean monthly concentrations at the Bradford Forest site located east of the study area, which is part of the National Atmospheric Deposition Program/National Trends Network. Also, higher nitrogen deposition rates in the study area compared to those at Bradford Forest could indicate that substantial amounts of ammonia are volatilized from fertilizers and animal wastes, released to the atmosphere, and incorporated as nitrate and ammonium in rainfall deposited in the middle Suwannee River Basin. Ground-water samples from most sites had d15N-NO3 values that indicated a mixture of inorganic and organic sources of nitrogen, which corresponded to multiple land uses where both synthetic fertilizers and manure are used on fields near these sites. Distinct d15N-NO3 signatures, however, were observed at some sites. For example, water samples from areas of row-crop farming as the dominant land use had d15N-NO3 values less than 4 per mil, indicating an inorganic nitrogen source such as synthetic fertilizer. In contrast, d15N-NO3 values greater than 9 per mil were found in water samples from three sites where manure from dairy and or poultry operations is spread on fields throughout the year.

Florida↗
USGS2024

Intra-urban variations in land surface phenology in a semi-arid environment

Urban vegetation is growing in importance as cities use 'green infrastructure' to mitigate the impacts of climate change, reduce extreme heat, and improve human health and comfort. However, due to the heterogeneity of city landscapes, urban vegetation experiences a diverse range of environmental conditions, potentially leading to differences in growing season timing and length within cities. Here, we investigate physical drivers of urban land surface phenology and timing within a semi-arid city (Denver, CO, USA) using four years (2018–2021) of remotely sensed vegetation indices, modelled air temperature, and land cover datasets. Within the metropolitan region study area, satellite-based vegetation index measurements indicate that growing season length is variable on sub-neighborhood spatial scales. This variability is largely due to differences in the timing of fall senescence, as opposed to early season growth. Areas with substantial fractions of irrigated land cover tend to remain greener for longer, while unirrigated and cooler areas are correlated with an earlier end to the growing season (up to ∼two months shorter). These findings complement those from non-arid cities where surface and air temperature are the dominant environmental control on phenological timing. Results here indicate the importance of soil moisture for phenology in semi-arid regions and suggest unique semi-arid urban growing season dynamics and temperature-vegetation feedbacks. These interactions have implications for water, heat, and vegetation management strategies to maximize ecosystem services in water-limited environments.

Colorado↗
USGS2018

It matters when you measure it: Using snow-cover Normalised Difference Vegetation Index (NDVI) to isolate post-fire conifer regeneration

Landsat Normalised Difference Vegetation Index (NDVI) is commonly used to monitor post-fire green-up; however, most studies do not distinguish new growth of conifer from deciduous or herbaceous species, despite potential consequences for local climate, carbon and wildlife. We found that dual season (growing and snow cover) NDVI improved our ability to distinguish conifer tree presence and density. We then examined the post-fire pattern (1984–2017) in Landsat NDVI for fires that occurred a minimum of 20 years ago (1986–1997). Points were classified into four categories depending on whether NDVI, 20 years post-fire, had returned to pre-fire values in only the growing season, only under snow cover, in both seasons or neither. We found that each category of points showed distinct patterns of NDVI change that could be used to characterise the average pre-fire and post-fire vegetation condition Of the points analysed, 43% showed a between-season disagreement if NDVI had returned to pre-fire values, suggesting that using dual-season NDVI can modify our interpretations of post-fire conditions. We also found an improved correlation between 5- and 20-year NDVI change under snow cover, potentially attributable to snow masking fast-growing herbaceous vegetation. This study suggests that snow-cover Landsat imagery can enhance characterisations of forest recovery following fire.

Arizona, Colorado, Idaho, Montana, Utah, Washingto↗
USGS2016

Consequences of seasonal variation in reservoir water level for predatory fishes: linking visual foraging and prey densities

In reservoirs, seasonal drawdown can alter the physical environment and may influence predatory fish performance. We investigated the performance of lake trout ( Salvelinus namaycush ) in a western reservoir by coupling field measurements with visual foraging and bioenergetic models at four distinct states (early summer, mid-summer, late summer, and fall). The models suggested that lake trout prey, juvenile kokanee ( Oncorhynchus nerka ), are limited seasonally by suitable temperature and dissolved oxygen. Accordingly, prey densities were greatest in late summer when reservoir volume was lowest and fish were concentrated by stratification. Prey encounter rates (up to 68 fish·day −1 ) and predator consumption are also predicted to be greatest during late summer. However, our models suggested that turbidity negatively correlates with prey detection and consumption across reservoir states. Under the most turbid conditions, lake trout did not meet physiological demands; however, during less turbid periods, predator consumption reached maximum bioenergetic efficiency. Overall, our findings demonstrate that rapid reservoir fluctuations and associated abiotic conditions can influence predator–prey interactions, and our models describe the potential impacts of water level fluctuation on valuable sport fishes.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS2021

Physiological differences in bleaching response of the coral Porites astreoides along the Florida Keys reef tract during high-temperature stress

The Florida Keys reef tract (FKRT) has a unique geological history wherein Holocene sea-level rise and bathymetry interacted, resulting in a reef-building system with notable spatial differences in reef development. Overprinted on this geologic history, recent global and local stressors have led to degraded reefs dominated by fleshy algae, soft corals, and sponges. Here, we assessed how coral physiology (calcification rate, tissue thickness, reproduction, symbiosis, and bleaching) varies seasonally (winter vs. summer) and geographically using 40 colonies of the mustard hill coral Porites astreoides from four sites across 350 km along the FKRT from 2015 to 2017. The study coincided with a high-temperature event in late summer 2015 that caused heterogeneous levels of coral bleaching across sites. Bleaching severity differed by site, with bleaching response more aligned with heat stress retroactively calculated from local degree heating weeks than those predicted by satellites. Despite differences in temperature profiles and bleaching severity, all colonies hosted Symbiodiniaceae of the same genus (formerly Clade A and subtypes). Overall, P. astreoides at Dry Tortugas National Park, the consistently coolest site, had the highest calcification rates, symbiont cell densities, and reproductive potential (all colonies were reproductive, with most planula larvae per polyp). Corals at Dry Tortugas and Fowey Rocks Light demonstrated strong seasonality in net calcification (higher in summer) and did not express visual or partial-mortality responses from the bleaching event; in contrast, colonies in the middle and southern part of the upper keys, Sombrero Key and Crocker Reef, demonstrated similar reduced fitness from bleaching, but differential recovery trajectories following the heat stress. Identifying reefs, such as Dry Tortugas and possibly Fowey Rocks Light that may serve as heat-stress refugia, is important in selecting candidate sites for adaptive reef-management strategies, such as selective propagation and assisted gene flow, to increase coral-species adaptation to ocean warming.

Florida↗
USGS2025

Seasonal movements and demographics of the endangered White River Spinedace to inform restoration and translocation

Objective Translocation is a tool being explored to restart extirpated populations or facilitate new populations of endangered spring-­dependent fish populations. Our objective was to provide information on habitat requirements for endangered White River Spinedace Lepidomeda albivallis during all seasons of the year and the population demographics that are necessary to plan conservation translocations of this species Methods We tagged and released White River Spinedace with passive integrated transponders during four twice-a-year events. Fish were subsequently recaptured or detected on six passive antennas placed throughout the Flag Springs Complex, Nevada. We evaluated movement data to understand seasonal habitat use patterns, used a Barker model to estimate monthly survival rates, adjusted counts to account for capture probability and estimate abundance, and applied reverse-time mark–recapture models to estimate recruitment to 70 mm total length. Results White River Spinedace were more active but used similar habitats during spawning seasons than during nonspawning seasons. Median life expectancy was about 5 months after tagging, and only 1% of adult White River Spinedace survived 3–4 years posttagging. The estimated population size in the Flag Springs Complex during our sampling period (November 2020 to June 2022) was fewer than a thousand White River Spinedace, and this estimate has been steady or slightly increasing. Conclusions Complex spring habitats with water temperatures ranging about 13°C to 21°C that are free from piscivorous fish are appropriate for White River Spinedace. The White River Spinedace population at Flag Springs is small but stable or increasing in size.

Transactions of the American Fisheries Society↗
USGS2024

Bee habitat, but not bee community structure, varies across grassland management in four national parks in the Mid-Atlantic, USA

National parks in the U.S. play a large role in providing habitat for native pollinators. In parks that are established to preserve cultural landscapes, park managers recognize an opportunity to improve pollinator habitat while maintaining historically accurate conditions. In this study we document floral resources and native bees within managed park grasslands, with the goal of providing managers information to help them maximize pollinator habitat while meeting other management objectives. The study was performed on 37 grassland properties in the mid-Atlantic region of the eastern U.S., distributed across four national parks; each property was managed with one of three management types: cool-season hayed, cool-season pasture, or warm-season meadows managed with multiple approaches. We surveyed bees and open flowers on 50-m transects twice each year in 2021 and 2022. Repeated measures ANOVA models revealed mean bee abundance, richness, evenness, and diversity did not vary among sites or management types. This finding was further supported by a principal coordinates analysis that showed bee community composition was similar across management types. Nonetheless, we found evidence to indicate the three management types did not produce equivalent habitat for bees. Species accumulation curves showed that the effective number of flower species was consistently lower in cool-season pastures, relative to the other two management types. Furthermore, we detected positive correlations between bee and flower diversity metrics in one of the two years, suggesting that floral metrics can influence bee communities, at least under certain conditions. Collectively, our study suggests that cool-season fields that are hayed and warm-season meadows have higher floral diversity than cool-season pastures within national parks of the mid-Atlantic region, and this higher diversity of forbs has the potential to benefit native bee diversity.

Maryland, Virginia↗
USGS2025

Wind pumping dominates landward salt transport in a weakly tidal estuary

In tidally energetic estuaries, salinity dynamics vary with tidal forcing as well as factors such as river discharge and bathymetry. However, in weakly tidal estuaries, mechanisms governing salt transport remain poorly understood. Here, we investigate salt transport processes in a weakly tidal estuary, Albemarle Sound on the U.S. East Coast, using a deterministic numerical model. In 2022, the volume averaged salinity of Albemarle Sound ranged from ∼2 to 10 psu. Although seasonal river discharge typically induces gradual salinity changes of less than 1 psu per month, four wind events caused sharp salinity increases of 1–2 psu within just a few days. We find that wind pumping, defined as the net salt transport due to temporal correlations between velocity and salinity associated with wind events, is the dominant mechanism contributing to these episodic increases in volume averaged salinity. In Albemarle Sound, wind pumping operates on timescales of several days, which is longer than the tidal timescale, and occurs intermittently throughout the year rather than following a regular repetitive pattern. Our analysis suggests that salt transport by wind pumping is typically an order of magnitude larger than by gravitational circulation and serves as the primary mechanism balancing salt loss from river flow. Isolating wind pumping requires averaging over variability of multiple days, longer than typical tidal averaging. Wind pumping likely also controls material exchange with coastal ocean, influencing biogeochemical processes in the estuary. This mechanism may be important in other systems with similar characteristics, particularly in coastal lagoons with multiple subembayments.

North Carolina↗
USGS2018

Multi-year data from satellite- and ground-based sensors show details and scale matter in assessing climate’s effects on wetland surface water, amphibians, and landscape conditions

Long-term, interdisciplinary studies of relations between climate and ecological conditions on wetland-upland landscapes have been lacking, especially studies integrated across scales meaningful for adaptive resource management. We collected data in situ at individual wetlands, and via satellite for surrounding 4-km 2 landscape blocks, to assess relations between annual weather dynamics, snow duration, phenology, wetland surface-water availability, amphibian presence and calling activity, greenness, and evapotranspiration in four U.S. conservation areas from 2008 to 2012. Amid recent decades of relatively warm growing seasons, 2012 and 2010 were the first and second warmest seasons, respectively, dating back to 1895. Accordingly, we observed the earliest starts of springtime biological activity during those two years. In all years, early-season amphibians first called soon after daily mean air temperatures were ≥ 0°C and snow had mostly melted. Similarly, satellite-based indicators suggested seasonal leaf-out happened soon after snowmelt and temperature thresholds for plant growth had occurred. Daily fluctuations in weather and water levels were related to amphibian calling activity, including decoupling the timing of the onset of calling at the start of season from the onset of calling events later in the season. Within-season variation in temperature and precipitation also was related to vegetation greenness and evapotranspiration, but more at monthly and seasonal scales. Wetland water levels were moderately to strongly associated with precipitation and early or intermittent wetland drying likely reduced amphibian reproduction success in some years, even though Pseudacris crucifer occupied sites at consistently high levels. Notably, satellite-based indicators of landscape water availability did not suggest such consequential, intra-seasonal variability in wetland surface-water availability. Our cross-disciplinary data show how temperature and precipitation interacted to affect key ecological relations and outcomes on our study landscapes. These results demonstrate the value of multi-year studies and the importance of scale for understanding actual climate-related effects in these areas.

Minnesota, Wisconsin↗
USGS2003

Structure and dynamics of mixed-species flocks in a Hawaiian rain forest

Mixed-species flocks of native and introduced birds were studied for four years in an upper elevation Hawaiian rain forest. Those flocks were characterized by strong seasonality, large size, low species richness, high intraspecific abundance, a lack of migrants, and a general lack of territoriality or any sort of dominance hierarchy. There was high variability among years in patterns of occurrence at the species level, and high variability within years at the individual level. These flocks are loosely structured social groupings with apparently open membership. The fluid, unstable movement patterns, high degree of variability in size and composition, and lack of positive interspecific associations are not consistent with the “foraging enhancement” hypothesis for flocking. Two resident, endangered insectivores, the Akepa ( Loxops coccineus ) and Hawaii Creeper ( Oreomystis mana ) served as “nuclear” species. Flock composition was compared between two study sites that differed significantly in density of these two nuclear species. Flock size was similar at the two sites, primarily because the nuclear species were over-represented relative to their density. This observation suggests that birds are attempting to achieve a more optimal flock size at the lower density site.

The Auk↗
USGS2018

Late-season movement and habitat use by Oregon spotted frogs (Rana pretiosa) in Oregon, USA

Many amphibians use multiple habitats across seasons. Information on seasonal habitat use, movement between seasonal habitat types, and habitats that may be particularly valuable is important to conservation and management. We used radio-telemetry to study late-season movement and habitat use by Oregon Spotted Frog ( Rana pretiosa ) at nine sites from four populations along the Cascade Mountains in Oregon. Movement rates declined with date and were the lowest at the end of tracking in December and January. Frogs across our sites used vegetated shallows in late summer and early fall. In fall, frogs used a range of habitat types, and at several sites moved to distinctive habitats such as springs, interstices in lava rock, and semi-terrestrial beaver channels. Distance between first and last tracking location was <250 m for 84.5% (49/58) of frogs, ranged up to 1145 m, and was greater for frogs in ditch habitats than those not in ditches. Distinctive features like springs or semi-terrestrial retreats can host multiple frogs and may represent particularly valuable wintering habitat for R. pretiosa in some sites in their Oregon range.

Oregon↗
USGS2002

Stream-aquifer relations and the potentiometric surface of the Upper Floridan aquifer in the lower Apalachicola-Chattahoochee-Flint River basin in parts of Georgia, Florida, and Alabama, 1999-2000

The Upper Floridan aquifer is the principal source of water for domestic and agricultural use in the lower Apalachicola-Chattahoochee-Flint (ACF) River Basin. Recent drought and increased water use have made understanding surface- and ground-water relations a priority for water-resource managers in the region. From July 1999 through August 2000, less than normal precipitation reduced streamflow in the area to less than 12 percent of average mean-daily streamflow and ground-water levels reached record or near-record lows. Effects of drought on stream-aquifer interactions in the basin were evaluated using baseflow estimation, ground-water seepage calculations, and potentiometric-surface maps. Ground-water discharge to streams, or baseflow, was estimated using three methods: field measurements, hydrograph separation, and linear regression analysis. Results were evaluated seasonally -- October 1999, April 2000, and August 2000 -- and for the period of record at four surface-water stations located on Kinchafoonee, Spring, Muckalee, and Turkey Creeks. Estimates of baseflow also were compared annually; ground-water discharge during the drought years, 1999 - 2000, was compared with ground-water discharge during a relatively wet year, 1994. Hydrograph separation indicated decreased base-flow of streams as the water level in the Upper Floridan aquifer declined. Mean-annual baseflow for Kinchafoonee, Spring, Muckalee, and Turkey Creeks ranged from 36 to 71 percent of total streamflow during the period of record. In 1994 baseflow accounted for only 37 to 56 percent of total streamflow, in 1999 baseflow comprised from 60 to 73 percent of total streamflow, and in 2000 baseflow comprised from 56 to 76 percent of streamflow. The percentage of total streamflow attributed to ground water increased during the drought, whereas other components of streamflow decreased (overland flow, interflow, and channel precipitation). Even though relative ground-water contributions were increased, the volume of water discharged from the aquifer to streams decreased during the drought as the Upper Floridan aquifer water level declined. Unit-area mean-annual ground-water discharge ranged from 0.60 to 0.79 cubic foot per second per square mile ([ft 3 /s]/mi2) in 1994, from 0.24 to 0.58 (ft 3 /s)/mi2 in 1999, and from 0.13 to 0.33 (ft 3 /s)/mi2 in 2000. Ground-water contributions to streamflow are high in winter, when evaporative demands are low, and low in summer, when evaporative demands are high. Linear regression analysis of stream-aquifer relations in the lower ACF River Basin shows 85- or 90-percent flow durations as reasonable estimates of baseflow.

Alabama, Florida, Georgia↗
USGS1958

A procedure for removing the effect of response bias errors from waterfowl hunter questionnaire responses

Response bias errors are studied by comparing questionnaire responses from waterfowl hunters using four large public hunting areas with actual hunting data from these areas during two hunting seasons. To the extent that the data permit, the sources of the error in the responses were studied and the contribution of each type to the total error was measured. Response bias errors, including both prestige and memory bias, were found to be very large as compared to non-response and sampling errors. Good fits were obtained with the seasonal kill distribution of the actual hunting data and the negative binomial distribution and a good fit was obtained with the distribution of total season hunting activity and the semi-logarithmic curve. A comparison of the actual seasonal distributions with the questionnaire response distributions revealed that the prestige and memory bias errors are both positive. The comparisons also revealed the tendency for memory bias errors to occur at digit frequencies divisible by five and for prestige bias errors to occur at frequencies which are multiples of the legal daily bag limit. A graphical adjustment of the response distributions was carried out by developing a smooth curve from those frequency classes not included in the predictable biased frequency classes referred to above. Group averages were used in constructing the curve, as suggested by Ezekiel [1950]. The efficiency of the technique described for reducing response bias errors in hunter questionnaire responses on seasonal waterfowl kill is high in large samples. The graphical method is not as efficient in removing response bias errors in hunter questionnaire responses on seasonal hunting activity where an average of 60 percent was removed.

Biometrics↗
USGS2020

Temporal and spatial variability of shallow soil moisture across four planar hillslopes on a tropical ocean island, San Cristóbal, Galápagos

Study Region: This paper provides a summary of findings from temporal and spatial studies of soil water content on planar hillslopes across the equatorial island of San Cristóbal, Galápagos (Ecuador). Study Focus: Soil water content (SWC) was measured to generate temporal and spatial records to determine seasonal variation and to investigate how the behavior of surface and near-surface root-zone soil water may support island-wide hydrogeology models. SWC probes were installed at four weather stations in a climosequence to generate a temporal record and spatial surveys of shallow SWC across the selected sites were completed during wet and dry seasons. Temporal differences in SWC were driven by seasonal variations in rainfall and evapotranspiration, while spatial variability remained high during both wet and dry seasons. Unsaturated hydraulic conductivity determined by mini-disk infiltrometers was highly variable across the slopes, as were other hydrologic variables. New Hydrological Insights for the Region: The high heterogeneity of soil water and hydrologic characteristics provides a means to explain why little runoff is observed at the study sites: soils do not saturate uniformly across hillslopes, allowing for runoff generated in one part of the hillslope to be conducted into the soil in adjacent parts of the hillslope. The lack of connected surface runoff helps explain how water enters the groundwater system of the island.

Journal of Hydrology: Regional Studies↗
USGS2006

Occurrence, distribution, and transport of pesticides in agricultural irrigation-return flow from four drainage basins in the Columbia Basin Project, Washington, 2002-04, and comparison with historical data

Water-quality samples were collected from sites in four irrigation return-flow drainage basins in the Columbia Basin Project from July 2002 through October 2004. Ten samples were collected throughout the irrigation season (generally April through October) and two samples were collected during the non-irrigation season. Samples were analyzed for temperature, pH, specific conductance, dissolved oxygen, major ions, trace elements, nutrients, and a suite of 107 pesticides and pesticide metabolites (pesticide transformation products) and to document the occurrence, distribution, and pesticides transport and pesticide metabolites. The four drainage basins vary in size from 19 to 710 square miles. Percentage of agricultural cropland ranges from about 35 percent in Crab Creek drainage basin to a maximum of 75 percent in Lind Coulee drainage basin. More than 95 percent of cropland in Red Rock Coulee, Crab Creek, and Sand Hollow drainage basins is irrigated, whereas only 30 percent of cropland in Lind Coulee is irrigated. Forty-two pesticides and five metabolites were detected in samples from the four irrigation return-flow drainage basins. The most compounds detected were in samples from Sand Hollow with 37, followed by Lind Coulee with 33, Red Rock Coulee with 30, and Crab Creek with 28. Herbicides were the most frequently detected pesticides, followed by insecticides, metabolites, and fungicides. Atrazine, bentazon, diuron, and 2,4-D were the most frequently detected herbicides and chlorpyrifos and azinphos-methyl were the most frequently detected insecticides. A statistical comparison of pesticide concentrations in surface-water samples collected in the mid-1990s at Crab Creek and Sand Hollow with those collected in this study showed a statistically significant increase in concentrations for diuron and a statistically significant decrease for ethoprophos and atrazine in Crab Creek. Statistically significant increases were in concentrations of bromacil, diuron, and pendimethalin at Sand Hollow and statistically significant decreases were in concentrations of 2,6-diethylanaline, alachlor, atrazine, DCPA, and EPTC. A seasonal Kendall trend test on data from Lind Coulee indicated no statistically significant trends for any pesticide for 1994 through 2004. A comparison of pesticide concentrations detected in this study with those detected in previous U.S. Geological Survey National Water-Quality Assessment studies of the Central Columbia Plateau, Yakima River basin, and national agricultural studies indicated that concentrations in this study generally were in the middle to lower end of the concentration spectrum for the most frequently detected herbicides and insecticides, but that the overall rate of detection was near the high end. Thirty-one of the 42 herbicides, insecticides, and fungicides detected in surface-water samples were applied to the major agricultural crops in the drainage basins, and 11 of the detected pesticides are sold for residential application. Eight of the pesticides detected in surface-water samples were not reported as having any agricultural or residential use. The overall pattern of pesticide use depends on which crops are grown in each drainage basin. Drainage basins with predominantly more orchards have higher amounts of insecticides applied, whereas basins with larger percentages of field crops tend to have more herbicides applied. Pesticide usage was most similar in Crab Creek and Sand Hollow, where the largest total amounts applied were the insecticides azinphos-methyl, carbaryl, and chlorpyrifos and the herbicide EPTC. In Red Rock Coulee basin, DCPA was the most heavily applied herbicide, followed by the fungicide chlorothalonil, the herbicide EPTC, and the insecticides chlorpyrifos and azinphos-methyl. In Lind Coulee, which has a large percentage of dryland agricultural area, the herbicides 2,4-D and EPTC were applied in the largest amount, followed by the fungicide chlorothalonil. The

Scientific Investigations Report↗