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At least 1,189 records · Page 66Linked to original sources
USGS2014

SAFRR tsunami scenario: Impacts on California ecosystems, species, marine natural resources, and fisheries

We evaluate the effects of the SAFRR Tsunami Scenario on California’s ecosystems, species, natural resources, and fisheries. We discuss mitigation and preparedness approaches that can be useful in Tsunami planning. The chapter provides an introduction to the role of ecosystems and natural resources in tsunami events (Section 1). A separate section focuses on specific impacts of the SAFRR Tsunami Scenario on California’s ecosystems and endangered species (Section 2). A section on commercial fisheries and the fishing fleet (Section 3) documents the plausible effects on California’s commercial fishery resources, fishing fleets, and communities. Sections 2 and 3 each include practical preparedness options for communities and suggestions on information needs or research. Our evaluation indicates that many low-lying coastal habitats, including beaches, marshes and sloughs, rivers and waterways connected to the sea, as well as nearshore submarine habitats will be damaged by the SAFRR Tsunami Scenario. Beach erosion and complex or high volumes of tsunami-generated debris would pose major challenges for ecological communities. Several endangered species and protected areas are at risk. Commercial fisheries and fishing fleets will be affected directly by the tsunami and indirectly by dependencies on infrastructure that is damaged. There is evidence that in some areas intact ecosystems, notably sand dunes, will act as natural defenses against the tsunami waves. However, ecosystems do not provide blanket protection against tsunami surge. The consequences of ecological and natural resource damage are estimated in the millions of dollars. These costs are driven partly by the loss of ecosystem services, as well as cumulative and follow-on impacts where, for example, increased erosion during the tsunami can in turn lead to subsequent damage and loss to coastal properties. Recovery of ecosystems, natural resources and fisheries is likely to be lengthy and expensive. Preparedness is key to enhancing resilience to ecological impacts.

California↗
USGS2020

Simulation modeling of complex climate, wildfire, and vegetation dynamics to address wicked problems in land management

Complex, reciprocal interactions among climate, disturbance, and vegetation dramatically alter spatial landscape patterns and influence ecosystem dynamics. As climate and disturbance regimes shift, historical analogs and past empirical studies may not be entirely appropriate as templates for future management. The need for a better understanding of the potential impacts of climate changes on ecosystems is reaching a new level of urgency, especially in highly perturbed or vulnerable ecological systems. Simulation models are extremely useful tools for guiding management decisions in an era of rapid change, thus providing potential solutions for wicked problems in land management—those that are difficult to solve and inherently resistant to easily definable solutions. We identify three experimental approaches for landscape modeling that address management challenges in the context of uncertain climate futures and complex ecological interactions: (1) an historical comparative approach, (2) a future comparative approach, and (3) threshold detection. We provide examples of each approach from previously published studies of simulated climate, disturbance, and landscape dynamics in forested landscapes of the western United States, modeled with the FireBGCv2 ecosystem process model. Cumulatively, model outcomes indicate that typical land management strategies will likely not be sufficient to counteract the impacts of rapid climate change and altered disturbance regimes that threaten the stability of ecosystems. Without implementation of new, adaptive management strategies, future landscapes are very likely to be different than historical or contemporary ones, with significant and sometimes persistent changes triggered by interactions of climate and wildfire.

Montana, New Mexico, Wyoming↗
USGS2015

How are your berries? Perspectives of Alaska’s environmental managers on trends in wild berry abundance

Background : Wild berries are a valued traditional food in Alaska. Phytochemicals in wild berries may contribute to the prevention of vascular disease, cancer and cognitive decline, making berry consumption important to community health in rural areas. Little was known regarding which species of berries were important to Alaskan communities, the number of species typically picked in communities and whether recent environmental change has affected berry abundance or quality. Objective : To identify species of wild berries that were consumed by people in different ecological regions of Alaska and to determine if perceived berry abundance was changing for some species or in some regions. Design : We asked tribal environmental managers throughout Alaska for their views on which among 12 types of wild berries were important to their communities and whether berry harvests over the past decade were different than in previous years. We received responses from 96 individuals in 73 communities. Results : Berries that were considered very important to communities differed among ecological regions of Alaska. Low-bush blueberry ( Vaccinium uliginosum and V. caespitosum ), cloudberry ( Rubus chamaemorus ) and salmonberry ( Rubus spectabilis ) were most frequently identified as very important berries for communities in the boreal, polar and maritime ecoregions, respectively. For 7 of the 12 berries on the survey, a majority of respondents indicated that in the past decade abundance had either declined or become more variable. Conclusions : Our study is an example of how environmental managers and participants in local observer networks can report on the status of wild resources in rural Alaska. Their observations suggest that there have been changes in the productivity of some wild berries in the past decade, resulting in greater uncertainty among communities regarding the security of berry harvests. Monitoring and experimental studies are needed to determine how environmental change may affect berry abundance.

Alaska↗
USGS2017

Operationalizing the telecoupling framework for migratory species using the spatial subsidies approach to examine ecosystem services provided by Mexican free-tailed bats

Drivers of environmental change in one location can have profound effects on ecosystem services and human well-being in distant locations, often across international borders. The telecoupling provides a conceptual framework for describing these interactions—for example, locations can be defined as sending areas (sources of flows of ecosystem services, energy, or information) or receiving areas (recipients of flows). However, the ability to quantify feedbacks between ecosystem change in one area and societal benefits in other areas requires analytical approaches. We use spatial subsidies—an approach developed to measure the degree to which a migratory species’ ability to provide services in one location depends on habitat in another location—as an example of how telecoupling can be operationalized. Using the cotton pest control and ecotourism services of Mexican free-tailed bats as an example, we determined that of the 16 states in the United States and Mexico where the species resides, three states (Texas, New Mexico, and Colorado) are receiving areas, while the rest of the states are sending areas. In addition, the magnitude of spatial subsidy can be used as an indicator of the degree to which different locations are telecoupled to other locations. In this example, the Mexican free-tailed bat ecosystem services to cotton production and ecotourism in Texas and New Mexico are heavily dependent on winter habitat in four states in central and southern Mexico. In sum, spatial subsidies can be used to operationalize the telecoupling conceptual framework by identifying sending and receiving areas, and by indicating the degree to which locations are telecoupled to other locations.

Ecology and Society↗
USGS2017

California Gull population growth and ecological impacts in the San Francisco Bay estuary, 1980–2016

The breeding population of California Gulls (Larus californicus) in the San Francisco Bay estuary increased from 24 individuals in 1980 to a peak of over 53,000 in 2014, then declined to 38,040 in 2016. The expansion of the breeding population may be related to the availability of suitable nesting sites in close proximity to anthropogenic food subsidies at landfills. Telemetry data indicate that California Gull movements are largely dictated by the two primary landfills in South San Francisco Bay. The large population of California Gulls has had negative effects on locally breeding shorebirds and terns, especially the Forster’s Tern (Sterna forsteri), American Avocet (Recurvirostra americana), and Western Snowy Plover (Charadrius nivosus nivosus). In South San Francisco Bay, California Gulls were responsible for 13% and 38% of egg predation events at nests of American Avocets and Snowy Plovers, respectively, and 55% and 54% of chick predation events of American Avocets and Forster’s Terns, respectively. The forced relocation of the largest gull colony (~24,000) at Pond A6 in 2010 resulted in increased survival of Forster’s Tern chicks at the adjacent colony at Pond A7 in 2011. The California Gull population and its effects on locally breeding shorebirds and terns are among the most pressing concerns for wetland managers within the San Francisco Bay estuary, especially for the South Bay Salt Pond Restoration Project. Further research is needed to evaluate the gull’s reproductive rates, habitat use, and annual movements and so to clarify its demographics and to quantify its effects on other breeding birds.

Book chapter↗
USGS2019

Northern forest winters have lost cold, snowy conditions that are important for ecosystems and human communities

Winter is an understudied but key period for the socio-ecological systems of northeastern North American forests. A growing awareness of the importance of the winter season to forest ecosystems and surrounding communities has inspired several decades of research, both across the northern forest and at other mid- and high-latitude ecosystems around the globe. Despite these efforts, we lack a synthetic understanding of how winter climate change may impact hydrological and biogeochemical processes and the social and economic activities they support. Here we take advantage of 100 years of meteorological observations across the northern forest region of the northeastern U.S. and eastern Canada to develop a suite of indicators that enable a cross-cutting understanding of 1) how winter temperatures and snow cover have been changing and 2) how these shifts may impact both ecosystems and surrounding human communities. We show that cold and snow-covered conditions have generally decreased over the past 100 years. These trends suggest positive outcomes for tree health as related to reduced fine root mortality and nutrient loss associated with winter frost but negative outcomes as related to the northward advancement and proliferation of forest insect pests. In addition to effects on vegetation, reductions in cold temperatures and snow cover are likely to have negative impacts on the ecology of the northern forest through impacts on water, soils, and wildlife. The overall loss of coldness and snow cover may also have negative consequences for logging and forest products, vector-borne diseases and human health, recreation and tourism, and cultural practices, which together represent important social and economic dimensions for the northern forest region. These findings advance our understanding of how our changing winters may transform the socio- ecological system of a region that has been defined by the contrasting rhythm of the seasons. Our research also identifies a trajectory of change that informs our expectations for the future as the climate continues to warm.

Ecological Applications↗
USGS1993

Behavioral ecology of black-legged kittiwakes during chick rearing in a failing colony

Compared with their Atlantic counterparts, Black-legged Kittiwakes ( Rissa tridactyla ) in North Pacific colonies are notably unproductive. A large colony on Middleton Island, Alaska, has in most years since 1981 seen complete breeding failure and the population has declined by half. We compared parent-offspring behaviors in this colony during two years that differed in overall breeding success. Potential indicators of food stress included parental attendance at the nest, foraging trip lengths, chick feeding and begging rates, and sibling aggression. Whereas chick feeding and begging rates were strongly correlated with overall breeding performance, patterns of time allocation by adults (nest attendance and foraging trips) were not. Contrasts between years and comparisons with data from other colonies in and outside Alaska point to food shortage as the likely cause of recurrent breeding failure on Middleton.

Alaska↗
USGS2006

Migratory connectivity of a widely distributed songbird, the American redstart (Setophaga ruticilla)

Determining the degree of connectivity between breeding and wintering populations is critical for understanding the ecology and evolution of migratory systems. We analyzed stable hydrogen isotopic compositions in tail feathers ($Dw) collected from 26 sites in 11 countries throughout the wintering range of the American Redstart (Setophaga ruticilla), a Nearctic- Neotropical migratory passerine bird. Feathers were assumed to have molted on the breeding grounds, and $Dw was used to estimate breeding origin. Values of $Dw were highly correlated with longitude of sampling location, indicating that breeding populations were generally distributed along the east-west axis of the wintering grounds. Within the Caribbean region, Florida, and Bahamas, $Dw values were negatively correlated with winter latitude, which suggests that American Redstarts exhibit a pattern of chain migration in which individuals wintering at northern latitudes are also the most northern breeders. To identify the most probable breeding regions, we used a likelihood-assignment test incorporated with a prior probability of breeding abundance using Bayes?s rule. Expected $D values of feathers from five breeding regions were based on interpolated $D values from a model of continent-wide growing-season $D values in precipitation ($Dp) and were adjusted to account for a discrimination factor between precipitation and feathers. At most wintering locations, breeding assignments were significantly different from expected frequencies based on relative breeding abundance. Birds wintering in eastern and western Mexico had a high probability of breeding in northwest and midwest North America, whereas birds in the Greater and Lesser Antilles were likely to have originated from breeding regions in the northeast and southeast, respectively. Migratory connectivity, such as we report here, implies that the dynamics of breeding and nonbreeding populations may be linked at a regional scale. These results provide a key opportunity for studying the year-round ecology and evolution of spatially connected populations in a migratory species.

Book chapter↗
USGS2016

Tidal hydrodynamics under future sea level rise and coastal morphology in the Northern Gulf of Mexico

This study examines the integrated influence of sea level rise (SLR) and future morphology on tidal hydrodynamics along the Northern Gulf of Mexico (NGOM) coast including seven embayments and three ecologically and economically significant estuaries. A large-domain hydrodynamic model was used to simulate astronomic tides for present and future conditions (circa 2050 and 2100). Future conditions were simulated by imposing four SLR scenarios to alter hydrodynamic boundary conditions and updating shoreline position and dune heights using a probabilistic model that is coupled to SLR. Under the highest SLR scenario, tidal amplitudes within the bays increased as much as 67% (10.0 cm) because of increases in the inlet cross-sectional area. Changes in harmonic constituent phases indicated that tidal propagation was faster in the future scenarios within most of the bays. Maximum tidal velocities increased in all of the bays, especially in Grand Bay where velocities doubled under the highest SLR scenario. In addition, the ratio of the maximum flood to maximum ebb velocity decreased in the future scenarios (i.e., currents became more ebb dominant) by as much as 26% and 39% in Weeks Bay and Apalachicola, respectively. In Grand Bay, the flood-ebb ratio increased (i.e., currents became more flood dominant) by 25% under the lower SLR scenarios, but decreased by 16% under the higher SLR as a result of the offshore barrier islands being overtopped, which altered the tidal prism. Results from this study can inform future storm surge and ecological assessments of SLR, and improve monitoring and management decisions within the NGOM.

Florida, Louisiana↗
USGS2017

Use of fish telemetry in rehabilitation planning, management, and monitoring in Areas of Concern in the Laurentian Great Lakes

Freshwater ecosystems provide many ecosystem services; however, they are often degraded as a result of human activity. To address ecosystem degradation in the Laurentian Great Lakes, Canada and the United States of America established the Great Lakes Water Quality Agreement (GLWQA). In 1987, 43 highly polluted and impacted areas were identified under the GLWQA as having one or more of 14 Beneficial Use Impairments (BUIs) to the physical and chemical habitat for fish, wildlife and humans, and were designated as Areas of Concern (AOC). Subnational jurisdictions combined with local stakeholders, with support from federal governments, developed plans to remediate and restore these sites. Biotelemetry (the tracking of animals using electronic tags) provides information on the spatial ecology of fish in the wild relevant to habitat management and stock assessment. Here, seven case studies are presented where biotelemetry data were directly incorporated within the AOC Remedial Action Plan (RAP) process. Specific applications include determining seasonal fish–habitat associations to inform habitat restoration plans, identifying the distribution of pollutant-indicator species to identify exposure risk to contamination sources, informing the development of fish passage facilities to enable fish to access fragmented upstream habitats, and assessing fish use of created or restored habitats. With growing capacity for fish biotelemetry research in the Great Lakes, we discuss the strengths and weaknesses of incorporating biotelemetry into AOC RAP processes to improve the science and practice of restoration and to facilitate the delisting of AOCs.

Great Lakes↗
USGS2024

A conceptual framework to assess post-wildfire water quality: State of the science and knowledge gaps

Wildfire substantially alters aquatic ecosystems by inducing moderate to catastrophic physical and chemical changes. However, the relations of environmental and watershed variables that drive those effects are complex. We present a Driver-Factor-Stressor-Effect (DFSE) conceptual framework to assess the current state of the science related to post-wildfire water-quality. We reviewed 64 peer-reviewed papers using the DFSE framework to identify drivers, factors, stressors, and effects associated with each study. A total of five drivers were identified and ranked according to their frequency of occurrence in the literature: atmospheric processes > fire characteristics > ecologic processes and characteristics > land surface characteristics > soil characteristics. Commonly reported stressors include increased nutrients, runoff, and sediment transport. Furthermore, although several different factors have been used at least once to explain water-quality effects, relatively few factors outside of precipitation and fire characteristics are frequently studied. We identified several gaps indicating the need for long-term monitoring, multi-factor studies, consideration of organic contaminants, consideration of groundwater, and inclusion of soil characteristics. This assessment expands on other reviews and meta-analyses by exploring causal linkages between influential variables and overall effects in post-wildfire watersheds. Information gathered from our assessment and the framework itself can be used to inform future monitoring plans and as a guide for modeling efforts focused on better understanding specific processes or to mitigate potential risks of post-wildfire water quality.

Water Resources Research↗
USGS2011

Evolutionary relationships among sympatric life history forms of Dolly Varden inhabiting the landlocked Kronotsky Lake, Kamchatka, and a neighboring anadromous population

We investigated the evolutionary relationships among five sympatric morphs of Dolly Varden Salvelinus malma (white, Schmidti, longhead, river, and dwarf) inhabiting landlocked Kronotsky Lake on the Kamchatka Peninsula, Russia, and an anadromous population below the barrier waterfall on the outflowing Kronotsky River. Morphological analyses indicated phenotypic differentiation corresponding to preferred habitat, the longhead (a limnetic piscivorous morph) having a fusiform body, long jaw, and short fins and the Schmidti (a benthic morph) having a robust body, small jaw, and long fins. Analysis of molecular variance among the Kronotsky Lake morphs indicated that contemporary gene flow is restricted both among morphs within locations and among locations within morphs. Gene flow from Kronotsky Lake into the anadromous population also appears to be restricted. Our findings indicate that there are two divergent evolutionary lineages, one consisting of the white, Schmidti, river, and dwarf morphs and the other of the longhead morph and the anadromous population, which suggests that Kronotsky Lake was subject to separate waves of immigration. The Kronotsky Lake Dolly Varden morphs may represent an example of ecological speciation in progress, and we present a working hypothesis for the diversification of morphs within Kronotsky Lake.

Transactions of the American Fisheries Society↗
USGS2013

Beaver dams maintain fish biodiversity by increasing habitat heterogeneity throughout a low-gradient stream network

Understanding the relationship between heterogeneity and biodiversity is an active focus of ecological research. Although habitat heterogeneity is conceptually linked to biodiversity, the amount and configuration of heterogeneity that maintains biodiversity within ecosystems is not well understood, especially for an entire stream network. Here, we tested alternative outcomes about how habitat alterations caused by beaver dams affected native fish biodiversity. Specifically, we quantified in-stream habitat and fish assemblages above and below all beaver dams ( n = 15) and selected control sites ( n = 9), adjacent to beaver dams, within an entire, low-gradient stream network (Fish Brook, MA, U.S.A.). Beaver dams altered habitat within streams in four ways based on upstream versus downstream differences in stream width, depth, velocity and substratum. In general, habitat heterogeneity, measured using two indices, was greater at beaver dams than control sites. The diversity and abundance of fish around beaver dams were positively related to habitat heterogeneity. Faster water and the coarser substratum below beaver dams increased the amount of fluvial habitat available to native fish. This alteration can be critical for fish with life histories that depend on flowing water and hard substrata. In summary, within a stream network, beaver dams maintained fish biodiversity by altering in-stream habitat and increasing habitat heterogeneity. Understanding the relationship between habitat heterogeneity and biodiversity can advance basic freshwater ecology and provide science-based support for applied aquatic conservation

Massachusetts↗
USGS2011

Stopover ecology of a migratory ungulate

1. Birds that migrate long distances use stopover sites to optimize fuel loads and complete migration as quickly as possible. Stopover use has been predicted to facilitate a time-minimization strategy in land migrants as well, but empirical tests have been lacking, and alternative migration strategies have not been considered. 2. We used fine-scale movement data to evaluate the ecological role of stopovers in migratory mule deer Odocoileus hemionus — a land migrant whose fitness is strongly influenced by energy intake rather than migration speed. 3. Although deer could easily complete migrations (range 18–144 km) in several days, they took an average of 3 weeks and spent 95% of that time in a series of stopover sites that had higher forage quality than movement corridors. Forage quality of stopovers increased with elevation and distance from winter range. Mule deer use of stopovers corresponded with a narrow phenological range, such that deer occupied stopovers 44 days prior to peak green-up, when forage quality was presumed to be highest. Mule deer used one stopover for every 5∙3 and 6∙7 km travelled during spring and autumn migrations, respectively, and used the same stopovers in consecutive years. 4. Study findings indicate that stopovers play a key role in the migration strategy of mule deer by allowing individuals to migrate in concert with plant phenology and maximize energy intake rather than speed. Our results suggest that stopover use may be more common among non-avian taxa than previously thought and, although the underlying migration strategies of temperate ungulates and birds are quite different, stopover use is important to both. 5. Exploring the role of stopovers in land migrants broadens the scope of stopover ecology and recognizes that the applied and theoretical benefits of stopover ecology need not be limited to avian taxa.

Journal of Animal Ecology↗
USGS2017

Do you hear what I see? Vocalization relative to visual detection rates of Hawaiian hoary bats (Lasiurus cinereus semotus)

B ats vocalize during flight as part of the sensory modality called echolocation, but very little is known about whether flying bats consistently call. Occasional vocal silence during flight when bats approach prey or conspecifics has been documented for relatively few species and situations. Bats flying alone in clutter-free airspace are not known to forgo vocalization, yet prior observations suggested possible silent behavior in certain, unexpected situations. Determining when, why, and where silent behavior occurs in bats will help evaluate major assumptions of a primary monitoring method for bats used in ecological research, management, and conservation. In this study, we recorded flight activity of Hawaiian hoary bats ( Lasiurus cinereus semotus ) under seminatural conditions using both thermal video cameras and acoustic detectors. Simultaneous video and audio recordings from 20 nights of observation at 10 sites were analyzed for correspondence between detection methods, with a focus on video observations in three distance categories for which accompanying vocalizations were detected. Comparison of video and audio detections revealed that a high proportion of Hawaiian hoary bats “seen” on video were not simultaneously “heard.” On average, only about one in three visual detections within a night had an accompanying call detection, but this varied greatly among nights. Bats flying on curved flight paths and individuals nearer the cameras were more likely to be detected by both methods. Feeding and social calls were detected, but no clear pattern emerged from the small number of observations involving closely interacting bats. These results may indicate that flying Hawaiian hoary bats often forgo echolocation, or do not always vocalize in a way that is detectable with common sampling and monitoring methods. Possible reasons for the low correspondence between visual and acoustic detections range from methodological to biological and include a number of biases associated with the propagation and detection of sound, cryptic foraging strategies, or conspecific presence. Silent flight behavior may be more prevalent in echolocating bats than previously appreciated, has profound implications for ecological research, and deserves further characterization and study.

Hawai'i↗
USGS2025

Interspecific effects of invasive wild pigs (Sus scrofa) on native nine-banded armadillos (Dasypus novemcinctus)

Biological invasions pose significant risks to ecosystems and native species. Wild pigs ( Sus scrofa ) are a highly detrimental invasive species in North America, directly and indirectly affecting native species. Co-occurrence of wild pigs and native species may lead to interspecific interactions that alter ecological communities. Accordingly, we investigated spatial and temporal factors influencing detection and occupancy of Eurasian Wild Pig and Nine-banded Armadillo ( Dasypus novemcinctus ) before examining interspecific effects. We analyzed camera-trap data collected from August to September 2021 using a hierarchical modeling framework to estimate detection and occupancy of both species individually (single-species analyses) and concurrently (conditional co-occurrence analyses). We observed higher Wild Pig detection rates and space use in late summer and in areas with greater riparian cover, respectively. Armadillo detection increased linearly throughout our sampling season and in response to precipitation. Moreover, armadillo detection was 3.5 to 5.1× higher at sites used by wild pigs, regardless of whether wild pigs were detected during a survey period. Occupancy of armadillo was best explained by a quadratic trend in site elevation but did not depend on the presence of wild pigs. Our results indicate that wild pigs may influence armadillo detection (or site-use intensity), but not occupancy, therefore revealing nuanced interspecific interactions. Between species, we observed high overlap in diel activity but significantly different activity peaks, with armadillos being strictly nocturnal and wild pigs being crepuscular but with more cathemeral activity, suggesting that fine-scale temporal partitioning may have occurred. Our results provide insights into the influence of a large-bodied and destructive invasive species (Wild Pig) on a smaller, ecologically important native species (Nine-banded Armadillo).

Oklahoma↗
USGS2026

Expansion trends and impacts of Phragmites australis on the Louisiana Gulf Coast

Invasive plant species pose substantial threats to ecosystem integrity by disrupting ecosystem processes, reducing biodiversity, and complicating restoration and management efforts. Non-native lineages of Phragmites australis are invasive in wetlands across parts of North America, causing declines in the diversity of native wetland plants and disrupting biogeochemical cycles. Despite recognition of these effects, important knowledge gaps remain regarding the spatiotemporal dynamics, environmental drivers, and consequences of Phragmites expansion for native communities. Here, we examined long-term data from the Louisiana Coastwide Reference Monitoring System (CRMS), collected from 2006 to 2023 and spanning 390 sites across nine basins, to quantify basin-specific Phragmites cover trajectories and evaluate their associations with co-occurring native plant cover and soil properties. Louisiana supports both long-established noninvasive and (since ~2000) invasive European P. australis lineages, but CRMS cannot distinguish them; thus, our basin-level trajectories reflect species-level cover dynamics that may integrate lineage-specific turnover. Phragmites dynamics varied markedly among basins over the study period: Phragmites cover decreased in the Mississippi River Delta (initially >25%), whereas the Calcasieu-Sabine, Mermentau, Teche-Vermilion, and Terrebonne basins, each starting with <5%, exhibited positive expansion trends. The remaining four basins maintained low and stable Phragmites cover (<5%) over the study period. These distinct basin-level trajectories may reflect basin-to-basin differences in a hydrogeomorphic setting and associated sediment and nutrient inputs. In basins with positive expansion trends, Phragmites cover was associated with decreases in native plant cover. Overall, Phragmites expansion was positively associated with higher soil nutrients, lower pH, and higher salinity, highlighting key environmental factors that could inform targeted management to prevent or mitigate its expansion. Although Phragmites cover remains low in most basins (<10%), expansion in several basins suggests the value of basin-specific early-warning monitoring to maintain native plant cover and associated ecosystem functions. Our two-step framework offers a transferable monitoring template that integrates Phragmites cover trends (expanding/stable/declining), concurrently measured native plant cover, and key soil and pore-water indicators to flag emerging hotspots and prioritize adaptive management in other estuarine and deltaic systems.

Louisiana↗
USGS2008

A double-observer method for reducing bias in faecal pellet surveys of forest ungulates

1. Faecal surveys are used widely to study variations in abundance and distribution of forest-dwelling mammals when direct enumeration is not feasible. The utility of faecal indices of abundance is limited, however, by observational bias and variation in faecal disappearance rates that obscure their relationship to population size. We developed methods to reduce variability in faecal surveys and improve reliability of faecal indices. 2. We used double-observer transect sampling to estimate observational bias of faecal surveys of Roosevelt elk Cervus elaphus roosevelti and Columbian black-tailed deer Odocoileus hemionus columbianus in Olympic National Park, Washington, USA. We also modelled differences in counts of faecal groups obtained from paired cleared and uncleared transect segments as a means to adjust standing crop faecal counts for a standard accumulation interval and to reduce bias resulting from variable decay rates. 3. Estimated detection probabilities of faecal groups ranged from < 0.2-1.0 depending upon the observer, whether the faecal group was from elk or deer, faecal group size, distance of the faecal group from the sampling transect, ground vegetation cover, and the interaction between faecal group size and distance from the transect. 4. Models of plot-clearing effects indicated that standing crop counts of deer faecal groups required 34% reduction on flat terrain and 53% reduction on sloping terrain to represent faeces accumulated over a standard 100-day interval, whereas counts of elk faecal groups required 0% and 46% reductions on flat and sloping terrain, respectively. 5. Synthesis and applications. Double-observer transect sampling provides a cost-effective means of reducing observational bias and variation in faecal decay rates that obscure the interpretation of faecal indices of large mammal abundance. Given the variation we observed in observational bias of faecal surveys and persistence of faeces, we emphasize the need for future researchers to account for these comparatively manageable sources of bias before comparing faecal indices spatially or temporally. Double-observer sampling methods are readily adaptable to study variations in faecal indices of large mammals at the scale of the large forest reserve, natural area, or other forested regions when direct estimation of populations is problematic. ?? 2008 The Authors.

Journal of Applied Ecology↗