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USGS2013

A natural resource condition assessment for Sequoia and Kings Canyon National Parks: Appendix 11a: giant sequoias

For natural resource managers in the southern Sierra Nevada, giant sequoia requires very little introduction. It receives great attention as an icon of western forests and as a common namesake with the areas where it occurs. While it is a single component of a very complex system, its attention in this assessment and in general is well deserved. Giant sequoia is one of the few "destination species" that attracts a wide swath of the public by nature of it simply being present. It draws people, who otherwise may not travel, to a natural environment. The result is an expansion of the public’s sense of natural resource stewardship. Because park managers could not achieve their mission without public support, this fostering role of giant sequoia is critical for park natural resources and is important for natural resources in general. Despite its social relevance and physical size, we re-emphasize here that the giant sequoia resource is a relatively small component of the ecosystems of the southern Sierra Nevada. As is the case with all of the resources assessed in the NRCA, we focus on giant sequoia with the understanding that other resources will be considered simultaneously when evaluating management decisions that impact giant sequoia. While we attempt to explicitly address the interaction of giant sequoia with other resources and stressors, we also realize that ultimately managers will integrate much more information than is presented here when making decisions that influence giant sequoia. The autecology and management issues surrounding giant sequoia have been thoroughly reviewed elsewhere (Harvey et al. 1980, Aune 1994, Stephenson 1996). Stephenson (1996), in particular, should be reviewed when considering any management decisions that potentially impact giant sequoia. For those who may not be familiar with giant sequoia ecology, a summary of basic information is provided in a table below. In some parts of this assessment, we reproduce text from Stephenson’s review because it is still relatively current for addressing some of the stressors. Numerous recent studies reported since 1996 have confirmed and expanded the understanding of giant sequoia, especially in areas related to ecophysiology and the effectiveness of restoration treatments. These recent studies are integrated into this assessment. Additionally, much unpublished work has been done that is useful for establishing baselines and evaluating trends. This work is presented in detail in order to expand upon previous work and to inform the final assessments. Instead of providing an introductory description of giant sequoia distribution and the various landowners who manage groves, we refer readers to the more recent descriptions provided by Stephenson (1996) and Willard (2000). Some of the relevant points from these descriptions with respect to giant sequoia within SEKI and Giant Sequoia National Monument (GSNM) include: - Of the native giant sequoia grove area in SEKI and GSNM approximately 38% is within SEKI and 62% is within GSNM. - 35 of the groves that make up the entire population are all or partially managed by SEKI and 33 are managed by GSNM. - As we have done above, reviewers addressing giant sequoia widely recognize its transcendence beyond an ecologically important species to one with considerable added cultural value.

California↗

USGS2013

Benthic substrate classification map: Gulf Islands National Seashore

The 2005 hurricane season was devastating for the Mississippi Gulf Coast. Hurricane Katrina caused significant degradation of the barrier islands that compose the Gulf Islands National Seashore (GUIS). Because of the ability of coastal barrier islands to help mitigate hurricane damage to the mainland, restoring these habitats prior to the onset of future storms will help protect the islands themselves and the surrounding habitats. During Hurricane Katrina, coastal barrier islands reduced storm surge by approximately 10 percent and moderated wave heights (Wamsley and others, 2009). Islands protected the mainland by preventing ocean waves from maintaining their size as they approached the mainland. In addition to storm protection, it is advantageous to restore these islands to preserve the cultural heritage present there (for example, Fort Massachusetts) and because of the influence that these islands have on marine ecology. For example, these islands help maintain a salinity regime favorable to oysters in the Mississippi Sound and provide critical habitats for many migratory birds and endangered species such as sea turtles (Chelonia mydas, Caretta caretta, and Dermochelys coriacea), Gulf sturgeon (Acipenser oxyrinchus desotoi), and piping plovers (Charadrius melodus) (U.S. Army Corps of Engineers, 2009a). As land manager for the GUIS, the National Park Service (NPS) has been working with the State of Mississippi and the Mobile District of the U.S. Army Corps of Engineers to provide a set of recommendations to the Mississippi Coastal Improvements Program (MsCIP) that will guide restoration planning. The final set of recommendations includes directly renourishing both West Ship Island (to protect Fort Massachusetts) and East Ship Island (to restore the French Warehouse archaeological site); filling Camille Cut to recreate a continuous Ship Island; and restoring natural regional sediment transport processes by placing sand in the littoral zone just east of Petit Bois Island. Prevailing sediment transport processes will provide natural renourishment of the westward islands in the barrier system (U.S. Army Corps of Engineers, 2009b). One difficulty in developing the final recommendations is that few data are available to incorporate into restoration plans related to bathymetry, sediment type, and biota. For example, the most recent bathymetry available dates to when East and West Ship Islands were a single continuous island (1917). As a result, the MsCIP program has encouraged post-hurricane bathymetric data collection for future reference. Furthermore, managing a complex environment such as this barrier island system for habitat conservation and best resource usage requires significant knowledge about those habitats and resources. To effectively address these issues, a complete and comprehensive understanding of the type, geographic extent, and condition of marine resources included within the GUIS is required. However, the data related to the GUIS marine resources are limited either spatially or temporally. Specifically, there is limited knowledge and information about the distribution of benthic habitats and the characteristics of the offshore region of the GUIS, even though these are the habitats that will be most affected by habitat restoration. The goal of this project is to develop a comprehensive map of the benthic marine habitats within the GUIS to give park managers the ability to develop strategies for coastal and ocean-resource management and to aid decisionmakers in evaluating conservation priorities.

Mississippi↗

USGS2025

Discharge and nutrients interact to determine trophic structure in a wetland: Evidence from a landscape-scale manipulation

Identifying drivers of consumer biomass patterns and community structure is complex for managed freshwater ecosystems that are sensitive to nutrients and drought. In the Florida Everglades, flow restoration is expected to reintroduce discharge across an expansive wetland, yet most research on consumers has focused on water depth and dry disturbances. Low-velocity flow can mediate nutrient availability for basal food resources, but its scaled-up effects on consumer communities remain largely untested. We quantified consumer responses to a landscape-scale flow manipulation that created discharge variability along a 2.5-km path of interconnected shallow sloughs. Over 4 yr, we repeatedly sampled macroinvertebrates, small fishes, and large predatory fishes (standard length > 8 cm) in 26 sloughs—some along a flow path experiencing pulsed water releases and others in two non-flowing reference areas. We tested the effects of antecedent discharge on consumer biomass while accounting for local nutrient concentrations (total phosphorus). Discharge increased biomass across all consumer groups, particularly in oligotrophic sloughs. Conversely, eutrophic sloughs demonstrated stronger top-down effects on small fishes and macroinvertebrates, with discharge primarily benefiting large predatory fishes. Nutrient gradients preferentially increased large fishes and caused macroinvertebrate community shifts favoring herbivorous and possibly predation-resistant taxa. Structural equation modeling similarly indicated bottom-up support from discharge but stronger top-down control in nutrient-rich sloughs. These findings demonstrate that discharge and total phosphorus interactively produce distinct consumer biomass patterns. Flow restoration in oligotrophic Everglades sloughs is hypothesized to enhance aquatic consumer biomass across trophic levels, revealing an ecological benefit to slow-flowing ecosystems not previously recognized.

Florida↗

USGS2019

Taxonomic harmonization may reveal a stronger association between diatom assemblages and total phosphorus in large datasets

Diatom data have been collected in large-scale biological assessments in the United States, such as the U.S. Environmental Protection Agency’s National Rivers and Streams Assessment (NRSA). However, the effectiveness of diatoms as indicators may suffer if inconsistent taxon identifications across different analysts obscure the relationships between assemblage composition and environmental variables. To reduce these inconsistencies, we harmonized the 2008–2009 NRSA data from nine analysts by updating names to current synonyms and by statistically identifying taxa with high analyst signal (taxa with more variation in relative abundance explained by the analyst factor, relative to environmental variables). We then screened a subset of samples with QA/QC data and combined taxa with mismatching identifications by the primary and secondary analysts. When these combined “slash groups” did not reduce analyst signal, we elevated taxa to the genus level or omitted taxa in difficult species complexes. We examined the variation explained by analyst in the original and revised datasets. Further, we examined how revising the datasets to reduce analyst signal can reduce inconsistency, thereby uncovering the variation in assemblage composition explained by total phosphorus (TP), an environmental variable of high priority for water managers. To produce a revised dataset with the greatest taxonomic consistency, we ultimately made 124 slash groups, omitted 7 taxa in the small naviculoid (e.g., Sellaphora atomoides ) species complex, and elevated Nitzschia , Diploneis , and Tryblionella taxa to the genus level. Relative to the original dataset, the revised dataset had more overlap among samples grouped by analyst in ordination space, less variation explained by the analyst factor, and more than double the variation in assemblage composition explained by TP. Elevating all taxa to the genus level did not eliminate analyst signal completely, and analyst remained the most important predictor for the genera Sellaphora , Mayamaea , and Psammodictyon , indicating that these taxa present the greatest obstacle to consistent identification in this dataset. Although our process did not completely remove analyst signal, this work provides a method to minimize analyst signal and improve detection of diatom association with TP in large datasets involving multiple analysts. Examination of variation in assemblage data explained by analyst and taxonomic harmonization may be necessary steps for improving data quality and the utility of diatoms as indicators of environmental variables.

Ecological Indicators↗

USGS2020

Forests do not limit bumble bee foraging movements in a montane meadow complex

1. Understanding the roles of habitat fragmentation and resource availability in shaping animal movement are integral for promoting species persistence and conservation. For insects like bumble bees, their movement patterns affect the survival and reproductive potential of their colonies as well as the pollen flow of plant species. However, our understanding of their mobility or the impact of putative barriers in natural environments is limited due to the technical difficulties of studying wild populations. 2. We used genetic mark-recapture to estimate the foraging distance, resource use, and site connectivity of two bumble bee species in a montane meadow complex composed of open meadows within a matrix of forest. 3. There was no evidence that forests or changes in landcover function as barriers to the fine‐scale movement for either species. Substantially greater colony‐specific foraging distances were found for Bombus vosnesenskii (maximum: 1867 m) compared to Bombus bifarius (maximum: 362 m). Despite this difference in absolute range, both species were detected across putative forest barriers at frequencies expected by uninhibited movement. Siblings separated by greater distances were more likely to be foraging on different floral species, potentially suggesting a resource‐based motivation for movement. 4. These results suggest that bumble bee foraging patterns are influenced by species-specific differences in movement capacity, with little influence of matrix composition between resource patches. They also support the perspective that habitat conservation for bumble bees should prioritize providing abundant and diverse patches of resources within species-specific movement radii with less emphasis on matrix composition.

Ecological Entomology↗

USGS2024

Geophysical identification of potential groundwater – surface water interactions in the Bonita Peak Mining District, San Juan County, Colorado

This report includes the results and interpretation of geophysical investigations to aid in the location, identification, and conceptual site model (CSM) development of the near surface groundwater and surface water hydrology of the Upper Cement Creek and California Gulch of the Animas Rivers within the Bonita Peak Mining Districts (BPMD). Mine influenced water (MIW) from numerous mine adits within the BPMD has altered the geochemistry and ecology of these ground and surface waters. Many studies of varying scales have investigated the geology, hydrogeology, geochemistry, and aqueous chemistry of these adits and impacted areas. Field investigations using non-invasive geophysical methods were conducted in the summer of 2019 to aid in identifying potential groundwater inputs to these streams and further the CSM of the near surface within and along these streams. Two field deployments were completed in August and September of 2019. In August 2019, Phase 1 was completed using multifrequency electromagnetic induction (EMI) and thermal infrared imaging (TIR) to measure the bulk electrical conductivity, magnetic susceptibility, and the temperature response at known and suspected groundwater seeps into the Upper Cement Creek and California Gulch stretches of these alpine streams. Results and interpretation from Phase 1 were used to co-locate stretches of these streams for further detailed fiber optic distributed temperature system (FODTS) monitoring of the temperature dynamics for submeter identification of potential groundwater seeps during Phase 2. Phase 2 included additional EMI measurements, FODTS measurements, and repeated some Phase 1 measurements for improved data quality. All these data were used for the combined qualitative interpretation identifying seep locations. The data from both Phase 1 and Phase 2 are available in the USGS data release at: https://www.sciencebase.gov/catalog/item/5f18a30082cef313ed84879b. These data include detailed near-surface electrical conductivity and magnetic susceptibility mapping, discrete TIR imaging, and several kilometers of FODTS data. These data were georeferenced and used to identify potential groundwater seeps into these streams. The results indicate a complex near surface geophysical and hydrogeologic regime. Seeps are classified and spatially correlated to the EMI, TIR, and geochemical sampling results. This report is a thorough compilation of the geophysical field efforts in the summer of 2019, the data processing, and interpretations of these data. These data alone should not be used for final interpretations of the complex hydrogeology within these alpine systems. Rather, these data should be combined with other known data from various investigations to further refine the CSM and guide decisions for future investigations, watershed protective measures, and other site decisions. Geographical information system (GIS) layers of these results are available to project managers for such integration and combined interpretations.

Colorado↗

USGS2010

Unbiased survival estimates and evidence for skipped breeding opportunities in females

1. &ensp;Estimates of demographic parameters for females, in many organisms, are sparse. This is particularly worrisome as more and more species are faced with high extinction probabilities and conservation increasingly depends on actions dictated by complex predictive models that require accurate estimates of demographic parameters for each sex and species. 2. &ensp;This study assesses demographic parameters, specifically temporary emigration and survival, for females, a class that has been difficult to investigate historically because of lack of data. Amphibians provide a particularly good example because there is global concern about amphibian decline; yet most demographic parameter estimates are based on data from males, which we show can lead to erroneous conclusions. 3. &ensp;We use 10 years of capture–recapture data from boreal toads ( Bufo boreas ) and the multi-state open robust design model to provide evidence for the occurrence of skipped breeding opportunities (i.e. temporary emigration) in females. This is the first time that the open robust design model has been applied to an analysis of an amphibian population that we are aware of. 4. &ensp;We determined that the transition from breeder to non-breeder is obligate and the probability of a non-breeder remaining a non-breeder is 64%; thus, temporary emigration is first-order Markovian in nature, where breeding probability is dependent on the previous year’s activity, i.e. if a female did not breed in year one, there is a 36% chance that she will breed in year two. With temporary emigration accounted for, we estimated between-year female survival at 87%. 5. &ensp;Establishing the occurrence of temporary emigration not only reduces bias in estimates of survival probabilities but also provides information about expected breeding attempts by females, a critical element in understanding the ecology of an organism and the impacts of outside stressors and conservation actions.

Methods in Ecology and Evolution↗

USGS2017

Semipermanent GPS (SPGPS) as a volcano monitoring tool: Rationale, method, and applications

Semipermanent GPS (SPGPS) is an alternative to conventional campaign or survey-mode GPS (SGPS) and to continuous GPS (CGPS) that offers several advantages for monitoring ground deformation. Unlike CGPS installations, SPGPS stations can be deployed quickly in response to changing volcanic conditions or earthquake activity such as a swarm or aftershock sequence. SPGPS networks can be more focused or more extensive than CGPS installations, because SPGPS equipment can be moved from station to station quickly to increase the total number of stations observed in a given time period. SPGPS networks are less intrusive on the landscape than CGPS installations, which makes it easier to satisfy land-use restrictions in ecologically sensitive areas. SPGPS observations are preferred over SGPS measurements because they provide better precision with only a modest increase in the amount of time, equipment, and personnel required in the field. We describe three applications of the SPGPS method that demonstrate its utility and flexibility. At the Yellowstone caldera, Wyoming, a 9-station SPGPS network serves to densify larger preexisting networks of CGPS and SGPS stations. At the Three Sisters volcanic center, Oregon, a 14-station SPGPS network complements an SGPS network and extends the geographic coverage provided by 3 CGPS stations permitted under wilderness land-use restrictions. In the Basin and Range province in northwest Nevada, a 6-station SPGPS network has been established in response to a prolonged earthquake swarm in an area with only sparse preexisting geodetic coverage. At Three Sisters, the estimated precision of station velocities based on annual ~ 3 month summertime SPGPS occupations from 2009 to 2015 is approximately half that for nearby CGPS stations. Conversely, SPGPS-derived station velocities are about twice as precise as those based on annual ~ 1 week SGPS measurements. After 5 years of SPGPS observations at Three Sisters, the precision of velocity determinations is estimated to be 0.5 mm/yr in longitude, 0.6 mm/yr in latitude, and 0.8 mm/yr in height. We conclude that an optimal approach to monitoring volcano deformation includes complementary CGPS and SPGPS networks, periodic InSAR observations, and measurements from in situ borehole sensors such as tiltmeters or strainmeters. This comprehensive approach provides the spatial and temporal detail necessary to adequately characterize a complex and evolving deformation pattern. Such information is essential to multi-parameter models of magmatic or tectonic processes that can help to guide research efforts, and also to inform hazards assessments and land-use planning decisions.

Journal of Volcanology and Geothermal Research↗

USGS2011

Refugial isolation and divergence in the Narrowheaded Gartersnake species complex (Thamnophis rufipunctatus) as revealed by multilocus DNA sequence data

Glacial–interglacial cycles of the Pleistocene are hypothesized as one of the foremost contributors to biological diversification. This is especially true for cold‐adapted montane species, where range shifts have had a pronounced effect on population‐level divergence. Gartersnakes of the Thamnophis rufipunctatus species complex are restricted to cold headwater streams in the highlands of the Sierra Madre Occidental and southwestern USA. We used coalescent and multilocus phylogenetic approaches to test whether genetic diversification of this montane‐restricted species complex is consistent with two prevailing models of range fluctuation for species affected by Pleistocene climate changes. Our concatenated nuDNA and multilocus species analyses recovered evidence for the persistence of multiple lineages that are restricted geographically, despite a mtDNA signature consistent with either more recent connectivity (and introgression) or recent expansion (and incomplete lineage sorting). Divergence times estimated using a relaxed molecular clock and fossil calibrations fall within the Late Pleistocene, and zero gene flow scenarios among current geographically isolated lineages could not be rejected. These results suggest that increased climate shifts in the Late Pleistocene have driven diversification and current range retraction patterns and that the differences between markers reflect the stochasticity of gene lineages (i.e. ancestral polymorphism) rather than gene flow and introgression. These results have important implications for the conservation of T. rufipunctatus (sensu novo), which is restricted to two drainage systems in the southwestern US and has undergone a recent and dramatic decline.

Molecular Ecology↗

USGS2017

Best practices for virtual participation in meetings: Experiences from synthesis centers

The earth environment is a complex system, in which collaborative scientific approaches can provide major benefits by bringing together diverse perspectives, methods, and data, to achieve robust, synthetic understanding (Fig. 1). Face-to-face scientific meetings remain extremely valuable because of the opportunity to build deep mutual trust and understanding, and develop new collaborations and sometimes even lifelong friendships (Alberts 2013, Cooke and Hilton 2015). However, it has been argued that ecologists should be particularly sensitive to the environmental footprint of travel (Fox et al. 2009); such concerns, along with the time demands for travel, particularly for multi-national working groups, provide strong motivation for exploring virtual attendance. While not replacing the richness of face-to-face interactions entirely, it is now feasible to virtually participate in meetings through services that allow video, audio, and file sharing, as well as other Web-enabled communication.

Bulletin of the Ecological Society of America↗

USGS2025

Shotgun sequencing of airborne eDNA achieves rapid assessment of whole biomes, population genetics and genomic variation

Biodiversity and its associated genetic diversity are being lost at an unprecedented rate. Simultaneously, the distributions of flora, fauna, fungi, microbes and pathogens are rapidly changing. Novel technology can help to capture and record genetic diversity before it is lost and to measure population shifts and pathogen distributions. Here we report the rapid application of shotgun long-read environmental DNA (eDNA) analysis for non-invasive biodiversity, genetic diversity and pathogen assessments from air. We also compared air eDNA with water and soil eDNA. Coupling long-read sequencing with established cloud-based biodiversity pipelines enabled a 2-day turnaround from airborne sample collection to completed analysis by a single investigator. To determine the full utility of airborne eDNA, we also conducted a local bioinformatic analysis and deep short-read shotgun sequencing. From outdoor air eDNA alone, comprehensive genetic analysis was performed, including population genetics (phylogenetic placement) of a charismatic mammal (bobcat, Lynx rufus ) and a venomous spider (golden silk orb weaver, Trichonephila clavipes ), and haplotyping humans ( Homo sapiens ) from natural complex community settings, such as subtropical forests and temperate locations. The rich datasets also enabled deeper analysis of specific species and genomic regions of interest, including viral variant calling, human variant analysis and antimicrobial resistance gene surveillance from airborne DNA. Our results highlight the speed, versatility and specificity of pan-biodiversity monitoring via non-invasive eDNA sampling using current benchtop/portable and cloud-based approaches. Furthermore, they reveal the future feasibility of scaling down (equipment and temporally) these approaches for near real-time analysis. Together these approaches can enable rapid simultaneous detection of all life and its genetic diversity from air, water and sediment samples for unbiased non-targeted information-rich genomics-empowered (1) biodiversity monitoring, (2) population genetics, (3) pathogen and disease-vector genomic surveillance, (4) allergen and narcotic surveillance, (5) antimicrobial resistance surveillance and (6) bioprospecting.

Nature Ecology & Evolution↗

USGS2021

Extensibility of U-net neural network model for hydrographic feature extraction and implications for hydrologic modeling

Accurate maps of regional surface water features are integral for advancing ecologic, atmospheric and land development studies. The only comprehensive surface water feature map of Alaska is the National Hydrography Dataset (NHD). NHD features are often digitized representations of historic topographic map blue lines and may be outdated. Here we test deep learning methods to automatically extract surface water features from airborne interferometric synthetic aperture radar (IfSAR) data to update and validate Alaska hydrographic databases. U-net artificial neural networks (ANN) and high-performance computing (HPC) are used for supervised hydrographic feature extraction within a study area comprised of 50 contiguous watersheds in Alaska. Surface water features derived from elevation through automated flow-routing and manual editing are used as training data. Model extensibility is tested with a series of 16 U-net models trained with increasing percentages of the study area, from about 3 to 35 percent. Hydrography is predicted by each of the models for all watersheds not used in training. Input raster layers are derived from digital terrain models, digital surface models, and intensity images from the IfSAR data. Results indicate about 15 percent of the study area is required to optimally train the ANN to extract hydrography when F1-scores for tested watersheds average between 66 and 68. Little benefit is gained by training beyond 15 percent of the study area. Fully connected hydrographic networks are generated for the U-net predictions using a novel approach that constrains a D-8 flow-routing approach to follow U-net predictions. This work demonstrates the ability of deep learning to derive surface water feature maps from complex terrain over a broad area.

Alaska↗

USGS2019

Appropriate sample sizes for monitoring burned pastures in sagebrush steppe: How many plots are enough, and can one size fit all?

Statistically defensible information on vegetation conditions is needed to guide rangeland management decisions following disturbances such as wildfire, often for heterogeneous pastures. Here we evaluate the number of plots needed to make informed adaptive management decisions using >2000 plots sampled on the 2015 Soda Fire that burned across 75 pastures and 113,000 ha in Idaho and Oregon, USA. We predicted that the number of plots required to generate a threshold of standard error/mean ≤0.2 (TSR, threshold sampling requirement) for plant cover within pasture units would vary between sampling methods (rapid ocular versus grid-point intercept) and among plot sizes (1, 6, or 531 m2), as well as relative to topography, elevation, pasture size, complexity of soils and vegetation treatments applied, and dominance by exotic annual or perennial grasses. Sampling was adequate for determining exotic annual and perennial grass cover in about half of the pastures. A tradeoff in number versus size of plots sampled was apparent, whereby TSR was attainable with less area searched using smaller plot sizes (1 compared to 531 m2) in spite of less variability between larger plots. TSR for both grass types decreased as their dominance increased (0.5-1.5 plots per % cover increment). TSR decreased for perennial grass but increased for exotic annual grass with higher elevations. TSR increased with standard deviation of elevation for perennial grass sampled with grid-point intercept. Sampling effort could be more reliably predicted from landscape variables for the grid-point compared to ocular sampling method. These findings suggest that adjusting the number and size of sample plots within a pasture or burn area using easily determined landscape variables could increase monitoring efficiency and effectiveness.

Rangeland Ecology and Management↗

USGS2007

Temporal changes of populations and trophic relationships of wintering diving ducks in Chesapeake Bay

Population and trophic relationships among diving ducks in Chesapeake Bay are diverse and complex as they include five species of bay ducks (Aythya spp.), nine species of seaducks (Tribe Mergini), and the Ruddy Duck (Oxyura jamaicensis). Here we considered the relationships between population changes and diet over the past half century to assess the importance of prey changes to wintering waterfowl in the Bay. Food habits of 643 diving ducks collected from Chesapeake Bay during 1999-2006 were determined by analyses of their gullet (esophagus and proventriculus) and gizzard contents and compared to historical data (1885-1979) of 1,541 diving ducks. Aerial waterfowl surveys, in general, suggest that six species of seaducks were more commonly located in the meso- to polyhaline areas of the Bay, whereas five species of bay ducks and Ruddy Ducks were in the oligo- to mesohaline areas. Seaducks fed on a molluscan diet of Hooked Mussel (Ischadium recurvum), Amethyst Gemclam (Gemma gemma), and Dwarf Surfclarn (Mulinia lateralis). Bay ducks and Ruddy Ducks fed more on Baltic Macoma (Macoma balthica), the adventive Atlantic Rangia (Rangia cuneata), and submerged aquatic vegetation (SAV). Mergansers were found over the widest salinity range in the Bay, probably because of their piscivorous diet. Each diving duck species appears to fill a unique foraging niche, although there is much overlap of selected prey. When current food habits are compared to historic data, only the Canvasback (Aythya valisineria) has had major diet changes, although SAV now accounts for less food volume for all diving duck species, except the Redhead (Aythya americana). Understanding the trophic-habitat relationships of diving ducks in coastal wintering areas will give managers a better understanding of the ecological effects of future environmental changes. Intensive restoration efforts on SAV and oyster beds should greatly benefit diving duck populations.

Waterbirds↗

USGS2005

Phylogeographic patterns of Hawaiian Megalagrion damselflies (Odonata: Coenagrionidae) correlate with Pleistocene island boundaries

The Pleistocene geological history of the Hawaiian Islands is becoming well understood. Numerous predictions about the influence of this history on the genetic diversity of Hawaiian organisms have been made, including the idea that changing sea levels would lead to the genetic differentiation of populations isolated on individual volcanoes during high sea stands. Here, we analyse DNA sequence data from two closely related, endemic Hawaiian damselfly species in order to test these predictions, and generate novel insights into the effects of Pleistocene glaciation and climate change on island organisms. Megalagrion xanthomelas and Megalagrion pacificum are currently restricted to five islands, including three islands of the Maui Nui super-island complex (Molokai, Lanai, and Maui) that were connected during periods of Pleistocene glaciation, and Hawaii island, which has never been subdivided. Maui Nui and Hawaii are effectively a controlled, natural experiment on the genetic effects of Pleistocene sea level change. We confirm well-defined morphological species boundaries using data from the nuclear EF-1?? gene and show that the species are reciprocally monophyletic. We perform phylogeographic analyses of 663 base pairs (bp) of cytochrome oxidase subunit II (COII) gene sequence data from 157 individuals representing 25 populations. Our results point to the importance of Pleistocene land bridges and historical island habitat availability in maintaining inter-island gene flow. We also propose that repeated bottlenecks on Maui Nui caused by sea level change and restricted habitat availability are likely responsible for low genetic diversity there. An island analogue to northern genetic purity and southern diversity is proposed, whereby islands with little suitable habitat exhibit genetic purity while islands with more exhibit genetic diversity. ?? 2005 Blackwell Publishing Ltd.

Molecular Ecology↗

USGS2009

An emerging crisis across northern prairie refuges: Prevalence of invasive plants and a plan for adaptive management

In the northern Great Plains, native prairies managed by the U.S. Fish and Wildlife Service (Service) can be pivotal in conservation of North America's biological diversity. From 2002 to 2006, we surveyed 7,338 belt transects to assess the general composition of mixed-grass and tallgrass prairie vegetation across five "complexes" (i.e., administrative groupings) of national wildlife refuges managed by the Service in North Dakota and South Dakota. Native grasses and forbs were common (mean frequency of occurrence 47%-54%) on two complexes but uncommon (4%-13%) on two others. Conversely, an introduced species of grass, smooth brome (Bromus inermis), accounted for 45% to 49% of vegetation on two complexes and another species, Kentucky bluegrass (Poa pratensis) accounted for 27% to 36% of the vegetation on three of the complexes. Our data confirm prior suspicions of widespread invasion by introduced species of plants on Service-owned tracts of native prairie, changes that likely stem in part from a common management history of little or no disturbance (e.g., defoliation by grazing or fire). However, variability in the degree and type of invasion among prairie tracts suggests that knowledge of underlying causes (e.g., edaphic or climatic factors, management histories) could help managers more effectively restore prairies. We describe an adaptive management approach to acquire such knowledge while progressing with restoration. More specifically, we propose to use data from inventories of plant communities on Service-owned prairies to design and implement, as experiments, optimal restoration strategies. We will then monitor these experiments and use the results to refine future strategies. This comprehensive, process-oriented approach should yield reliable and robust recommendations for restoration and maintenance of native prairies in the northern Great Plains. 2009 by the Board of Regents of the University of Wisconsin System.

Ecological Restoration↗

USGS2021

From satellites to frogs: Quantifying ecohydrological change, drought mitigation, and population demography in desert meadows

Increasing frequency and severity of droughts have motivated natural resource managers to mitigate harmful ecological and hydrological effects of drought, but drought mitigation is an emerging science and evaluating its effectiveness is difficult. We examined ecohydrological responses of drought mitigation actions aimed at conserving populations of the Columbia spotted frog ( Rana luteiventris ) in a semi-arid valley in Nevada, USA. Abundance of this rare frog had declined precipitously after multiple droughts. Mitigation included excavating ponds to increase available surface water and installing earthen dams to raise water tables. We assessed responses of riparian vegetation to mitigation using a 30-year time series of satellite-derived Normalized Difference Vegetation Index (NDVI) and gridded weather data. We then analyzed a 23-year mark-recapture dataset to evaluate the effects of drought mitigation and NDVI on the probability of frog survival and rates of recruitment. After accounting for interannual precipitation variability, we found that NDVI increased significantly from before to after drought mitigation, suggesting that mitigation influenced the hydrology and vegetation of the meadows. Frog survival increased with NDVI, but mitigation had a stronger effect than NDVI suggesting that excavated mitigation ponds were particularly important for frog survival during drought. In contrast, frog recruitment was associated with NDVI more than mitigation, but only in meadows where NDVI was dependent on precipitation. At meadows with available groundwater, recruitment was associated with mitigation ponds. These findings suggest that mitigation ponds are critical for juvenile frogs to recruit into the adult population, but recruitment can also be increased by raising water tables in meadows lacking groundwater sources. Lagged recruitment (i.e., effects on larvae and juveniles) was negatively associated with NDVI. This study illustrates the ecohydrological complexity of drought mitigation and demonstrates novel ways to assess the effectiveness of drought mitigation using time series of readily available satellite imagery and organismal data.

Nevada↗

USGS2023

Modeling impacts of saltwater intrusion on methane and nitrous oxide emissions in tidal forested wetlands

Emissions of methane (CH 4 ) and nitrous oxide (N 2 O) from soils to the atmosphere can offset the benefits of carbon sequestration for climate change mitigation. While past study has suggested that both CH 4 and N 2 O emissions from tidal freshwater forested wetlands (TFFW) are generally low, the impacts of coastal droughts and drought-induced saltwater intrusion on CH 4 and N 2 O emissions remain unclear. In this study, a process-driven biogeochemistry model, Tidal Freshwater Wetland DeNitrification-DeComposition (TFW-DNDC) was applied to examine the responses of CH 4 and N 2 O emissions to episodic drought-induced saltwater intrusion in TFFW along the Waccamaw River and Savannah River, USA. These sites encompass landscape gradients of both surface and porewater salinity as influenced by Atlantic Ocean tides superimposed on periodic droughts. Surprisingly, CH 4 and N 2 O emission responsiveness to coastal droughts and drought-induced saltwater intrusion varied greatly between river systems and among local geomorphologic settings. This reflected the complexity of wetland CH 4 and N 2 O emissions and suggests that simple linkages to salinity may not always be relevant, as non-linear relationships dominated our simulations. Along the Savannah River, N 2 O emissions in the moderate-oligohaline tidal forest site tended to increase dramatically under the drought condition, while CH 4 emission decreased. For the Waccamaw River, emissions of both CH 4 and N 2 O in the moderate-oligohaline tidal forest site tended to decrease under the drought condition, but the capacity of the moderate-oligohaline tidal forest to serve as a carbon sink was substantially reduced due to significant declines in net primary productivity and soil organic carbon sequestration rates as salinity killed the dominant freshwater vegetation. These changes in fluxes of CH 4 and N 2 O reflect crucial synergistic effects of soil salinity and water level on C and N dynamics in TFFW due to drought-induced seawater intrusion.

Ecological Applications↗