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USGS2021

Determination of burn severity models ranging from regional to continental scales for the conterminous United States

Identifying meaningful measures of ecological change over large areas is dependent on the quantification of robust relationships between ecological metrics and remote sensing products. Over the past several decades, ground observations of wildfire and prescribed fire severity have been acquired across hundreds of wildland fires in the United States, primarily utilizing the Composite Burn Index (CBI) plot protocol. These observations have been coupled to spaceborne passive spectral reflectance indices (e.g. Landsat-derived variations of the Normalized Burn Ratio [NBR]) to produce regression models describing their relationship. Here we develop regression models by vegetation type for multiple vegetation classification systems representing a range of spatial scales, and a decision tree framework for evaluating these regression models. Our overall goals were to determine which scale of ecological classifications provided the best estimate of burn severity from Landsat data and how to choose the best regression model. We aggregated a total of 6280 CBI plots for 234 wildland fires that burned between 1994 and 2017 and produced Landsat-derived NBR and differenced NBR (dNBR) values for each plot. We then calculated best fit linear or higher order regression equations between CBI and NBR/dNBR for each landcover classification system from smallest to largest scale: LANDFIRE Biophysical Settings (BPS), National Vegetation Classification macrogroup (NVC) landcover classifications, Omernick III, II, and I ecoregions, LANDFIRE Fire Regime Groups (FRG), and the entire conterminous United States (CONUS) dataset. The CONUS regression model goodness of fit was moderate (R 2 = 0.55, P < 0.001) for dNBR and poor (R 2 = 0.30, P < 0.001) for NBR. Within landcover classifications, CBI was better fit by dNBR than NBR. Finer scale regional regression models including BPS (dNBR R 2 ¯ "> R2¯ = 0.56 and 0.00–0.83 R 2 range; NBR R 2 ¯ "> R(bar) 2 = 0.43 and 0.00–0.82 R 2 range) and NVC (dNBR R 2 ¯ "> R(bar) 2 = 0.55 and 0.15–0.78 R 2 range; NBR R 2 ¯ "> R(bar) 2 = 0.41 and 0.00–0.79 R 2 range) were on average the same or better than the CONUS models for dNBR and NBR, with the strongest fit models exhibiting R 2 ≥ 0.70, whereas larger scale regional models R 2 ¯ "> R(bar) 2 ranged from 0.28 to 0.5. However, variation in accuracy among landcover types indicate that dNBR and NBR regression models could be used to effectively estimate CBI for future fires in certain regions, while for other regions models may require additional field observations or alternative spectral transformations. Our decision tree schema can be used to help users determine which scale is likely to produce the most accurate results using our models. The CBI regression models developed here, paired with the decision tree, provide users with a simple method to estimate burn severity in units of CBI for any fire within CONUS with moderate to high levels of confidence and provide a template for further development of models with new data going forward.

Conterminous United States↗

USGS2023

Reconstructing missing data by comparing interpolation techniques: Applications for long-term water quality data

Missing data are typical yet must be addressed for proper inferences or expanding datasets to guide our limnological understanding and management of aquatic systems. Interpolation methods (i.e., estimating missing values using known values within the dataset) can alleviate data gaps and common problems. We compared seven popular interpolation methods for predicting substantial missingness in a long-term water quality dataset from the Upper Mississippi River, U.S.A. The dataset included 80,000 sampling sites collected over 30 yr that had substantial missingness for total nitrogen (TN), total phosphorus (TP), and water velocity. For all three interpolated water quality variables, random forests had very high prediction accuracy and outperformed the methods of ordinary kriging, polynomial regressions, regression trees, and inverse distance weighting. TP had a mean absolute error (MAE) of 0.03 mg (L-TP) −1 , TN had a MAE of 0.39 mg (L-TN) −1 , and water velocity had a MAE of 0.10 m s −1 . The random forests' error rates were mapped and showed low spatiotemporal variability across the riverscape, indicating high model performance across many habitat types and large spatial scales. In the current era of “big data,” interpolation becomes an imperative step prior to ecological analyses yet remains unfamiliar and underutilized. Our research briefly describes the importance of addressing missingness and provides a roadmap to conduct model intercomparisons of other big datasets. We also share adaptable data analysis scripts, which allows others to readily conduct interpolation comparisons for many limnology applications and contexts.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗

USGS2008

Mapping the information landscape: Discerning peaks and valleys for ecological monitoring

We investigate previously unreported phenomena that have a potentially significant impact on the design of surveillance monitoring programs for ecological systems. Ecological monitoring practitioners have long recognized that different species are differentially informative of a system's dynamics, as codified in the well-known concepts of indicator or keystone species. Using a novel combination of analysis techniques from nonlinear dynamics, we describe marked variation among spatial sites in information content with respect to system dynamics in the entire region. We first observed these phenomena in a spatially extended predator-prey model, but we observed strikingly similar features in verified water-level data from a NOAA/NOS Great Lakes monitoring program. We suggest that these features may be widespread and the design of surveillance monitoring programs should reflect knowledge of their existence.

Journal of Biological Physics↗

USGS2013

Diatom evidence for the onset of Pliocene cooling from AND-1B, McMurdo Sound, Antarctica

The late Pliocene, ~ 3.3–3.0 Ma, is the most recent interval of sustained global warmth in the geologic past. This window is the focus of climate reconstruction efforts by the U.S. Geological Survey's Pliocene Research, Interpretation, and Synoptic Mapping (PRISM) Data/Model Cooperative, and may provide a useful climate analog for the coming century. Reconstructions of past surface ocean conditions proximal to the Antarctic continent are essential to understanding the sensitivity of the cryosphere to this key interval in Earth's climate evolution. An exceptional marine sediment core collected from the southwestern Ross Sea (78° S), Antarctica, during ANDRILL's McMurdo Ice Shelf Project preserves evidence of dramatic fluctuations between grounded ice and productive, open ocean conditions during the late Pliocene, reflecting orbitally-paced glacial/interglacial cycling. In this near-shore record, diatom-rich sediments are recovered from interglacial intervals; two of these diatomites, from ~ 3.2 Ma and 3.03 Ma, are within the PRISM chronologic window. The diatom assemblages identified in PRISM-age late Pliocene diatom-rich sediments are distinct from those in mid-Pliocene and later Pliocene/Pleistocene intervals recovered from AND-1B, and comprise both extant taxa with well-constrained ecological preferences and a diverse extinct flora, some members of which are previously undescribed from Antarctic sediments. Both units are dominated by Chaetoceros resting spores, an indicator of high productivity and stratification that is present at much lower abundance in materials both older and younger than the PRISM-age sediments. Newly described species of the genus Fragilariopsis , which first appear in the AND-1B record at 3.2 Ma, are the most abundant extinct members of the PRISM-age assemblages. Other extant species with established environmental affinities, such as Fragilariopsis sublinearis , F . curta , Stellarima microtrias , and Thalassiothrix antarctica , are present at lower abundances. Environmental inferences drawn from extant diatom assemblages are in good agreement with those from Chaetoceros resting spores and the Fragilariopsis radiation. All three lines of evidence indicate the onset of late Pliocene cooling in the Ross Sea near-shore environment at 3.2 Ma, with intensification and possible regional persistence of summer sea ice by 3.03 Ma. An important implication of this research is the indication that the Ross Ice Shelf fluctuated dramatically on orbital timescales at a time when nearshore Antarctic conditions were only modestly warmer than present.

Palaeogeography, Palaeoclimatology, Palaeoecology↗

USGS2020

Spatial distribution of heavy metals in the West Dongting Lake floodplain, China

The protection of Dongting Lake is important because it is an overwintering and migration route for many rare and endangered birds of East Asia and Australasia, but an assessment of heavy metal contamination in West Dongting Lake is lacking. A total of 75 sediment samples (five sites x three sediment depths x five repeats) were collected in West Dongting Lake in January 2017 to assess the spatial distribution and ecological risk of heavy metal in West Dongting Lake. Heavy metal values varied by sediment depth including As, Cd, Zn, and Cu, with depth giving an indication of recent vs. historical deposition. The major input of Hg, Cu, Ni may come from continued anthropogenic activities related to regional industrial activities within Yuan River and Li River whereas, the major sources of spread Cd pollution may be from agricultural fertilizers.

West Dongting Lake floodplain↗

USGS2008

Abrupt climate change and collapse of deep-sea ecosystems

We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically driven oceanographic changes. Species diversity as measured by the Shannon-Wiener index falls from 3 to as low as 1.6 during these events. Major disruptions in the benthic communities commenced with Heinrich Event 1, the Inter-Aller??d Cold Period (IACP: 13.1 ka), the Younger Dryas (YD: 12.9-11.5 ka), and several Holocene Bond events when changes in deep-water circulation occurred. The largest collapse is associated with the YD/IACP and is characterized by an abrupt two-step decrease in both the upper North Atlantic Deep Water assemblage and species diversity at 13.1 ka and at 12.2 ka. The ostracode fauna at this site did not fully recover until ???8 ka, with the establishment of Labrador Sea Water ventilation. Ecologically opportunistic slope species prospered during this community collapse. Other abrupt community collapses during the past 20 ka generally correspond to millennial climate events. These results indicate that deep-sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less. ?? 2008 by The National Academy of Sciences of the USA.

Proceedings of the National Academy of Sciences of↗

USGS1974

Flood profiles and inundated areas along the White River, Chelan County, Washington

Flood profiles covering the main stem to river mile 11.0 (kilometer 17.7) of the White River in Chelan County, Wash., were developed in a 3-year field study (1970-72) in cooperation with the State of Washington Department of Ecology. Flood-frequency curves based on an average of a regional computation and a Log-Pearson Type III analysis of 18 years of record indicate that the 100-year flood will have a discharge of about 6,600 cubic feet per second, or about 186 cubic meters per second,at river mile 6.4.or kilometer 10.3. Discharge of a 50-year flood was computed to be about 6,300 cubic feet per second, or about 178 cubic meters per second. The greatest flood discharge during the study period occurred on June 10, 1972, and was 5,310 cubic feet per second, or about 150 cubic meters per second; such a discharge has a recurrence interval of 4 years. Most of the flood plain of the White River probably is inundated during a 100-year flood.

Washington↗

USGS2021

Cloud water interception in Hawai‘i: Developing capacity to characterize the spatial patterns and effects on water and ecological processes responses in Hawai‘i

Cloud-water interception (CWI) is the process by which fog or cloud water droplets are captured and accumulate on the leaves and branches of plants, some of which drips to the ground. Prior studies in Hawai'i indicate that CWI is highly variable and can contribute substantially to total precipitation. In this study, we monitored CWI and other processes at five mountain field sites on the Islands of Oʻahu, Maui, and Hawaiʻi to explore how CWI (1) varies with different climate and vegetation characteristics, (2) affects plant water use and growth, and (3) contributes to water resources. Results show that annual CWI varied from 158 to 910 mm, accounting for 3-34% of total water input at individual sites. This large variation was caused by differences in the quantity of cloud water, wind speed, and vegetation structure between sites. We developed a model to predict CWI using both climatic and forest canopy characteristics. On average, the model underestimated annual CWI by 18%, but reproduced the site differences relatively well. Plant water use decreased during periods of fog events mainly because of associated higher humidity. This new CWI model can be used to assess impacts of climate and land cover change on CWI and provide valuable information for resource management in Hawai‘i, which was not previously possible. At one field site, we explored the impacts of fog water on hydrological and ecological processes. Fog effects on native plant growth were indirect, primarily buffering effects of solar radiation. Removal of grass allowed natural regeneration of seedlings but did not alter soil moisture values. A soil data-collection program was initiated to help evaluate the role CWI has in providing moisture for plants, reducing wildfire risk within the fog zone, and contributing to groundwater recharge to aquifers that supply drinking water and groundwater discharge to streams.

Hawaii↗

USGS2016

Assessing models of speciation under different biogeographic scenarios; An empirical study using multi-locus and RNA-seq analyses

Evolutionary biology often seeks to decipher the drivers of speciation, and much debate persists over the relative importance of isolation and gene flow in the formation of new species. Genetic studies of closely related species can assess if gene flow was present during speciation, because signatures of past introgression often persist in the genome. We test hypotheses on which mechanisms of speciation drove diversity among three distinct lineages of desert tortoise in the genus Gopherus . These lineages offer a powerful system to study speciation, because different biogeographic patterns (physical vs. ecological segregation) are observed at opposing ends of their distributions. We use 82 samples collected from 38 sites, representing the entire species' distribution and generate sequence data for mtDNA and four nuclear loci. A multilocus phylogenetic analysis in *BEAST estimates the species tree. RNA‐seq data yield 20,126 synonymous variants from 7665 contigs from two individuals of each of the three lineages. Analyses of these data using the demographic inference package ∂a∂i serve to test the null hypothesis of no gene flow during divergence. The best‐fit demographic model for the three taxa is concordant with the *BEAST species tree, and the ∂a∂i analysis does not indicate gene flow among any of the three lineages during their divergence. These analyses suggest that divergence among the lineages occurred in the absence of gene flow and in this scenario the genetic signature of ecological isolation (parapatric model) cannot be differentiated from geographic isolation (allopatric model).

Ecology and Evolution↗

USGS2013

Worldwide phylogenetic relationship of avian poxviruses

Poxvirus infections have been found in 230 species of wild and domestic birds worldwide in both terrestrial and marine environments. This ubiquity raises the question of how infection has been transmitted and globally dispersed. We present a comprehensive global phylogeny of 111 novel poxvirus isolates in addition to all available sequences from GenBank. Phylogenetic analysis of the Avipoxvirus genus has traditionally relied on one gene region (4b core protein). In this study we expanded the analyses to include a second locus (DNA polymerase gene), allowing for a more robust phylogenetic framework, finer genetic resolution within specific groups, and the detection of potential recombination. Our phylogenetic results reveal several major features of avipoxvirus evolution and ecology and propose an updated avipoxvirus taxonomy, including three novel subclades. The characterization of poxviruses from 57 species of birds in this study extends the current knowledge of their host range and provides the first evidence of the phylogenetic effect of genetic recombination of avipoxviruses. The repeated occurrence of avian family or order-specific grouping within certain clades (e.g., starling poxvirus, falcon poxvirus, raptor poxvirus, etc.) indicates a marked role of host adaptation, while the sharing of poxvirus species within prey-predator systems emphasizes the capacity for cross-species infection and limited host adaptation. Our study provides a broad and comprehensive phylogenetic analysis of the Avipoxvirus genus, an ecologically and environmentally important viral group, to formulate a genome sequencing strategy that will clarify avipoxvirus taxonomy.

Journal of Virology↗

USGS2019

Discoveries and novel insights in ecology using structural equation modeling

As we enter the era of data science (Lortie 2018), quantitative analysis methodologies are proliferating rapidly, leaving ecologists with the task of choosing among many alternatives. The use of structural equation modeling (SEM) by ecologists has increased in recent years, prompting us to ask users a number of questions about their experience with the methodology. Responses indicate an enthusiastic endorsement of SEM. Two major elements of respondent’s experiences seem to contribute to their positive response, (1) a sense that they are obtaining more accurate explanatory understanding through the use of SEM and (2) excitement generated by the discovery of novel insights into their systems. We elaborate here on the detection of indirect effects, offsetting effects, and suppressed effects, and demonstrate how discovering these effects can advance ecology.

Ecology and Evolution↗

USGS2006

Regional processes in mangrove ecosystems: Spatial scaling relationships, biomass, and turnover rates following catastrophic disturbance

Physiological processes and local-scale structural dynamics of mangroves are relatively well studied. Regional-scale processes, however, are not as well understood. Here we provide long-term data on trends in structure and forest turnover at a large scale, following hurricane damage in mangrove ecosystems of South Florida, U.S.A. Twelve mangrove vegetation plots were monitored at periodic intervals, between October 1992 and March 2005. Mangrove forests of this region are defined by a -1.5 scaling relationship between mean stem diameter and stem density, mirroring self-thinning theory for mono-specific stands. This relationship is reflected in tree size frequency scaling exponents which, through time, have exhibited trends toward a community average that is indicative of full spatial resource utilization. These trends, together with an asymptotic standing biomass accumulation, indicate that coastal mangrove ecosystems do adhere to size-structured organizing principles as described for upland tree communities. Regenerative dynamics are different between areas inside and outside of the primary wind-path of Hurricane Andrew which occurred in 1992. Forest dynamic turnover rates, however, are steady through time. This suggests that ecological, more-so than structural factors, control forest productivity. In agreement, the relative mean rate of biomass growth exhibits an inverse relationship with the seasonal range of porewater salinities. The ecosystem average in forest scaling relationships may provide a useful investigative tool of mangrove community biomass relationships, as well as offer a robust indicator of general ecosystem health for use in mangrove forest ecosystem management and restoration. ?? Springer 2006.

Hydrobiologia↗

USGS2007

Mercury at the Oat Hill Extension Mine and James Creek, Napa County, California: Tailings, sediment, water, and biota, 2003-2004

The Oat Hill Extension (OHE) Mine is one of several mercury mines located in the James Creek/Pope Creek watershed that produced mercury from the 1870's until 1944 (U.S. Bureau of Mines, 1965). The OHE Mine developed veins and mineralized fault zones hosted in sandstone that extended eastward from the Oat Hill Mine. Waste material from the Oat Hill Mine was reprocessed at the OHE Mine using gravity separation methods to obtain cinnabar concentrates that were processed in a retort. The U.S. Bureau of Land Management requested that the U.S. Geological Survey measure and characterize mercury and other chemical constituents that are potentially relevant to ecological impairment of biota in tailings, sediment, and water at the OHE Mine and in the tributaries of James Creek that drain the mine area (termed Drainage A and B ) (Figs. 1 and 2). This report summarizes such data obtained from sampling of tailings and sediments at the OHE on October 17, 2003; water, sediment, and biota from James Creek on May 20, 2004; and biota on October 29, 2004. These data are interpreted to provide a preliminary assessment of the potential ecological impact of the mine on the James Creek watershed. The mine tailings are unusual in that they have not been roasted and contain relatively high concentrations of mercury (400 to 1200 ppm) compared to unroasted waste rock at other mines. These tailings have contaminated a tributary to James Creek with mercury primarily by erosion, on the basis of higher concentration of mercury (780 ng/L) measured in unfiltered (total mercury, Hg T ) spring water flowing from the OHE to James Creek compared to 5 to 14 ng/L Hg T measured in James Creek itself. Tailing piles (presumably from past Oat Hill mine dumping) near the USBLM property boundary and upstream of the main OHE mine drainage channel ( Drainage A ; Fig. 2) also likely emit mercury, on the basis of their mercury composition (930 to 1200 ppm). The OHE spring water is likely an appreciable source of sulfate and carbonate to James Creek, because the spring water was enriched in sulfate (130 mg/L) and carbonate (430 mg/L as CaCO 3 ) compared to James Creek water (70 to 100 mg/L SO 4 2- and 110 to 170 mg/L as CaCO 3 ) at the time of sampling. Concentrations of mercury in active channel sediment from James Creek are variable and potentially high, on the basis of chemical analysis (2.5 to 17 _g/g-wet sediment) and easily visible cinnabar grains in panned concentrates. Average (geometric mean) organic mercury (presumably monomethyl mercury (MMHg); §2.3.3) concentrations in several invertebrate taxa collected from the James Creek watershed locations were higher than invertebrates taken from a Northern California location lacking a known point source of mercury. The mean proportion of MMHg to total mercury in James Creek predatory insect samples was 40 percent (1 standard deviation = 30 percent); only 40 percent of all insect samples had a MMHg/Hg T proportion greater than 0.5. The low proportions of MMHg measured in invertebrates in James Creek and the presence of cinnabar in the creek suggest that some invertebrates may have anomolously high Hg concentrations as a result of the injestion or adhesion of extremely fine-grained cinnabar particles. Interpretation of Hg T in frogs and fish as an indicator of mercury reactivity, biouptake, or trophic transfer is limited, pending MMHg measuremens, by the possibility of these whole-body samples having contained cinnabar particles at the time of analysis. To minimize this limitation, the gastrointestinal tracts and external surfaces of all amphibians, where cinnabar most likely resides, were carefully flushed to remove any visible particles. However, extremely fine-grained, invisible, adhesive cinnabar particles likely exist in the amphibians' habitats. Hg T in foothill yellow-legged frogs collected from the James Creek study area, ranging from 0.1 to 0.6 μg/g Hg, was on average twice that of an extensive database compiled from Hg T in frogs studied throughout Northern California. Average concentrations of Hg T in frogs from James Creek were similar upstream (0.18 μg/g) and downstream (0.15 μg/g) of the confluence with Tributary 1 and at the lower Corona Mine adit drainage (0.14 μg/g). Frogs may be susceptible to trophic transfer of MMHg from invertebrates, but further study is required to rule out cinnabar ‘contamination.’ Hg T concentrations in rainbow trout collected from James Creek upstream and downstream of Tributary 1 averaged 0.10 μg/g and 0.13 μg/g, respectively. Compared to invertebrates, trout Hg T was less variable, suggesting that trout were less contaminated with cinnabar. California roach had significantly higher Hg T on average than trout (0.16 vs. 0.12 μg/g), and can be considered moderately contaminated compared to the same species from other sites in Northern California, which average 0.12 μg/g Hg. While limited measurements of mercury in water, sediment, and fish exceed, in some samples, predefined ecologically protective criteria for mine-impacted California systems, they do not clearly demonstrate that the biota residing in James Creek in the vicinity of the OHE are ecologically impaired. The potential for ecological impairment is clearly evident from invertebrate methyl mercury results and may manifest in other biological ecosystem residents that have yet to be studied (e.g., piscivorous birds). Methyl mercury concentrations in flowing water and sediment from James Creek and the tributary that drains the OHE are relatively low, ranging from 0.04 to 0.08 ng/L, although these data should be cautiously interpreted (see §3.2). While the results of this investigation suggest that the OHE contributes inorganic mercury to James Creek, they do not indicate the extent to which the OHE site is ecologically impairing biota relative to other sources of mercury. Improved sampling and analytical methods are recommended for future study.

California↗

USGS2020

The abundance of Greater Sage-Grouse as a proxy for the abundance of sagebrush-associated songbirds in Wyoming, USA

Surrogate-species concepts are prevalent in animal conservation. Such strategies advocate for conservation by proxy, wherein one species is used to represent other taxa to obtain a conservation objective. The efficacy of such approaches has been rarely assessed empirically, but is predicated on concordance between the surrogate and sympatric taxa in distribution, abundance, and ecological requirements. Our objective was to identify whether the abundance of a high-profile umbrella species (Greater Sage-Grouse, Centrocercus urophasianus , hereafter sage-grouse) was associated with the abundance of six other members of the avian community for which it is presumed to be a surrogate, including three sagebrush-obligate and three sagebrush-associated songbird species. We predicted that sage-grouse abundance would align most closely with the breeding abundance of other sagebrush-obligate birds. We used two different indices of sage-grouse abundance for comparisons: field-collected counts of fecal pellets (primarily indexing abundance in the nonbreeding season) and a spatially explicit index of breeding population size. Neither index of sage-grouse abundance was consistently predictive of co-occurring songbird abundance, with one species more abundant (Horned Lark [ Eremophila alpestris ]) and one species less abundant (Vesper Sparrow [ Pooecetes gramineus ]) where sage-grouse pellet counts were higher, and no relationship evident between songbird abundance and the spatially explicit sage-grouse population index. Ours is one of few assessments of the efficacy of sage-grouse as a surrogate species to consider abundance, and not habitat overlap alone. We suggest that the utility of sage-grouse as a surrogate species likely varies across spatial scales. Within the scale examined here (10–15 ha sites), however, indices of sage-grouse abundance were unreliable proxies for the abundance of six declining songbird species.

Wyoming↗

USGS2020

Movement ecology and habitat use differences in Black Scoters wintering along the Atlantic coast

For migratory species such as Black Scoters ( Melanitta americana ) whose range encompasses a variety of habitats, it is especially important to obtain habitat use information across the species’ range to better understand anthropogenic threats, e.g., marine development and climate change. The objective of our study was to investigate the winter movement patterns and habitat use of Black Scoters in the Atlantic Ocean by quantifying the following key movement indices: number of wintering sites, arrival and departure dates to and from the wintering grounds, days at a wintering site, area of a wintering site, distance between wintering sites, and differences in habitat features of wintering sites. We also tested if winter movement patterns varied by sex or along a latitudinal gradient. To quantify winter movement patterns of Black Scoters, we used satellite telemetry data from 2009 to 2012 (n = 29 tagged females and 15 males for a total of 66 winter seasons, 38 female winter seasons, 28 male winter seasons). Our results indicated that the average wintering site area and distance between wintering sites varied with latitude. Wintering sites located at southern latitudes were larger and further apart than wintering sites located at more northern latitudes. Additionally, wintering sites varied in bathymetry, distance to shore, and the slope of the ocean floor at different latitudes; northern wintering sites were in deeper waters, closer to shore, and on steeper slopes than southern wintering sites. Our results suggest that habitat use may differ by latitude, indicating that habitats used in northern locations may not be representative of habitats used in more southern wintering areas. Understanding variation of habitat use along a latitudinal gradient will enable managers to focus sampling effort for Black Scoter abundance and distribution along the Atlantic coast and provide insight on the wintering ecology and movement of Black Scoters.

Connecticut, Delaware, Florida, Georgia, Maryland,↗

USGS2015

Response of Schoenoplectus acutus and Schoenoplectus californicus at different life-history stages to hydrologic regime

For wetland restoration success to be maximized, restoration managers need better information regarding how the frequency, depth, and duration of flooding affect soil chemistry and the survival, growth, and morphology of targeted plant species. In a greenhouse study we investigated the impact of four different flooding durations (0 %, 40 %, 60 %, and 100 %) on soil physicochemistry and the responses of seedlings and adults of two species of emergent wetland macrophytes commonly used in restoration efforts ( Schoenoplectus acutus and Schoenoplectus californicus ). The longest flooding duration, which created more reducing soil conditions, resulted in significantly reduced survival of S. acutus adults (34 ± 21 % survival) and complete mortality of seedlings of both species. Schoenoplectus californicus adults exhibited higher flooding tolerance, showing little impact of flooding on morphology and physiology. A companion field study indicated that S. californicus maintained stem strength regardless of flooding duration or depth, supporting the greenhouse study results. This information serves to improve our understanding of the ecological differences between these species as well as provide restoration managers with better guidelines for targeted elevation and hydrologic regimes for these species in order to enhance the success of restoration plantings and better predict restoration site development.

Wetlands↗

USGS2006

Effects of sample survey design on the accuracy of classification tree models in species distribution models

We evaluated the effects of probabilistic (hereafter DESIGN) and non-probabilistic (PURPOSIVE) sample surveys on resultant classification tree models for predicting the presence of four lichen species in the Pacific Northwest, USA. Models derived from both survey forms were assessed using an independent data set (EVALUATION). Measures of accuracy as gauged by resubstitution rates were similar for each lichen species irrespective of the underlying sample survey form. Cross-validation estimates of prediction accuracies were lower than resubstitution accuracies for all species and both design types, and in all cases were closer to the true prediction accuracies based on the EVALUATION data set. We argue that greater emphasis should be placed on calculating and reporting cross-validation accuracy rates rather than simple resubstitution accuracy rates. Evaluation of the DESIGN and PURPOSIVE tree models on the EVALUATION data set shows significantly lower prediction accuracy for the PURPOSIVE tree models relative to the DESIGN models, indicating that non-probabilistic sample surveys may generate models with limited predictive capability. These differences were consistent across all four lichen species, with 11 of the 12 possible species and sample survey type comparisons having significantly lower accuracy rates. Some differences in accuracy were as large as 50%. The classification tree structures also differed considerably both among and within the modelled species, depending on the sample survey form. Overlap in the predictor variables selected by the DESIGN and PURPOSIVE tree models ranged from only 20% to 38%, indicating the classification trees fit the two evaluated survey forms on different sets of predictor variables. The magnitude of these differences in predictor variables throws doubt on ecological interpretation derived from prediction models based on non-probabilistic sample surveys. ?? 2006 Elsevier B.V. All rights reserved.

Ecological Modelling↗

USGS2024

Comparing risk of chronic wasting disease occurrence using Bayesian hierarchical spatial models and different surveillance types

Spatial modeling of wildlife diseases can be used to describe patterns of disease risk, understand biological mechanisms of disease occurrence, and for spatial prediction. Risk of wildlife disease occurrence in relation to environmental variables is often modeled and predicted using Markov chain Monte Carlo (MCMC) methods, which are unsuitable for large datasets and those covering large spatial extents. Integrated nested Laplace approximation (INLA) and INLA using the stochastic partial differential equation (INLA-SPDE) approach have become popular alternatives to MCMC for Bayesian inference because of their fast computational time and ability to process large datasets. Studies investigating risk of disease occurrence in wildlife, to our knowledge, have not yet compared Bayesian hierarchical spatial models over large spatial extents using real world data. Using chronic wasting disease (CWD) surveillance data from white-tailed deer ( Odocoileus virginianus ) collected in Pennsylvania, United States, as a case study, we first demonstrate how parameter estimates compare among MCMC, INLA, and INLA-SPDE modeling frameworks. We then model CWD (detected/non-detected) using INLA-SPDE over a much larger spatial extent than has been conducted previously for this disease to determine how surveillance type (e.g., hunter harvest, roadkill, or all surveillance) influences model parameters and predicted risk of CWD occurrence at locations not sampled. Fixed effects considered in the models included deer age and sex, elevation, slope, distance to streams, percent clay, and proportion of two habitat classes (forest and open) known to influence deer movements. We found INLA to produce comparable estimates to MCMC and permit modeling large datasets covering expansive spatial extents much faster and more efficiently than MCMC. We identified potential biases in surveillance types, indicating the value of including all surveillance in models rather than only a single type. Comparing modeling tools available for mapping diseases of wildlife in relation to ecological variables at large spatial extents will guide future modeling efforts for CWD and other wildlife diseases. Understanding spatial patterns of CWD using different surveillance types can help improve understanding of CWD disease outbreaks, assist with control of CWD through geographical targeting, and inform future CWD surveillance efforts.

Ecological Modeling↗