Helicopter Survey Research Articles

Antarctic ice-shelf meltwater outflows in satellite radar imagery: ground-truthing and basal channel observations

Abstract Ice shelves regulate the flow of the Antarctic ice sheet toward the ocean and its contribution to sea-level rise. Accurately monitoring the basal and surface melting of ice shelves is therefore essential for predicting the ice sheet's response to climatic warming. In this study, we utilize Sentinel-1A synthetic aperture radar satellite imagery combined with shipboard measurements of water temperature and salinity to investigate the presence of surficial meltwater plumes along the Antarctic coastline. Our approach reveals a strong correlation between areas of pronounced low radar backscatter extending from ice shelves and significant decreases in water temperature and salinity, suggesting meltwater-enriched ocean waters. We propose that the low radar backscatter signature of meltwater outflows is caused by stable stratification of the upper water column, driven by density contrasts from buoyant, low-salinity meltwater and surface current shear that reduce Bragg scattering waves. The resulting smooth water surfaces were observed adjacent to the surface expression of deep basal channels, documented in a helicopter survey along part of the Bellingshausen Sea ice edge. We present high-temporal resolution satellite radar as a tool for identifying meltwater release from beneath ice shelves, capable of all-weather, day-and-night imaging.

A trial helicopter survey of crane nesting on floodplains in the Gulf Plains Bioregion, north-western Queensland, and the first record of a three-egg clutch for the Australian Sarus Crane Grus antigone gillae

A trial helicopter survey of crane nesting on floodplains in the Gulf Plains Bioregion, north-western Queensland, and the first record of a three-egg clutch for the Australian Sarus Crane Grus antigone gillae

Comparing contemporary models to traditional indices to estimate abundance of desert bighorn sheep

AbstractAerial surveys for large ungulates produce count data that often underrepresent the number of animals. Errors in count data can lead to erroneous estimates of abundance if they are not addressed. Our objective was to address imperfect detection probability by developing a framework that produces realistic and defensible estimates of bighorn sheep (Ovis canadensis) abundance. We applied our framework to a population of desert bighorn sheep (O. c. nelsoni) in the Great Basin, Nevada, USA. We captured and marked 24 desert bighorn sheep with global positioning system (GPS)‐collars and then conducted helicopter surveys naïve to the locations of collared animals. We developed a Bayesian integrated data model to leverage information from telemetry data, helicopter survey counts, and habitat characteristics to estimate abundance while accounting for availability and perception probability (i.e., detection given availability). Distance to ridgeline, terrain ruggedness, tree cover, and slope influenced perception probability of sheep given they were viewable from the helicopter. There was also annual variation in perception probability (2018: median = 0.64, credible interval [CrI] = 0.37–0.87; 2019: median = 0.81, CrI = 0.49–0.97). The abundance estimates from the integrated data model decreased from 2018 (594; 95% CrI = 537–656) to 2019 (487; 95% CrI = 436–551). In addition, accounting for availability and imperfect perception resulted in greater estimates of abundance compared to traditional directed search methods, which were 340 for 2018 and 320 for 2019. Our modeling framework can be used to generate more defensible population estimates of bighorn sheep and other large mammals that have been surveyed in a similar manner.

Breeding expansion of sandhill cranes in Quebec

AbstractSandhill cranes (Antigone canadensis) were broadly extirpated from much of their historical range in North America at the beginning of the twentieth century. Various conservation‐related legislation, such as the United States Migratory Bird Treaty Act, have assisted with population recovery. The eastern population of sandhill cranes has been growing rapidly since the 1980s and is thought to have expanded its geographic range to Quebec, Canada. Understanding the colonization and habitat use by the species in previously unoccupied breeding areas is necessary to develop and apply management measures. Using a dynamic occupancy modeling approach, we investigated the recent colonization and extirpation patterns of sandhill cranes in Quebec from 2004–2019. We combined data from 3 data sets (helicopter surveys, breeding bird atlas surveys, and eBird) to increase the spatial coverage and the number of species occurrence records while accounting for imperfect detection probability. Detection probability was highest for the helicopter survey (0.70), whereas the 2 other data sets had relatively low detection levels (0.10–0.26). Based on a simulation study, we found that excluding the eBird data from the analysis produced more biased estimates than excluding the atlas and helicopter survey data sets. Throughout the study, sandhill cranes seemed to have completed their colonization of western Quebec and only recently started to nest in eastern areas. Initial occupancy increased with wetland cover and colonization probability increased weakly with the cover of agricultural areas, suggesting that in our study area sandhill cranes rely essentially on natural wetlands during the breeding season.

3D Joint Inversion of Scanning Magnetic Microscopy Data

AbstractScanning magnetic microscopy (SMM) is a modern magnetometry technique that maps the magnetic anomalies resulting from small‐scale variations of remanent magnetization within a sample. This information is vital to understand the origin of rock behavior in laboratory experiments and in larger scale magnetic surveys. To quantify the fine‐scale remanent magnetization, we used 3D magnetic vector inversion to jointly invert SMM data collected both above and below a 5 mm‐thick norite sample from the Bjerkreim‐Sokndal layered intrusion in South Norway. The sample is from an area with a striking remanent aeromagnetic anomaly which shows a minimum of −13,000 nT below background in the high‐resolution helicopter survey. Inversion results confirm bulk remanent magnetization measurements with calculated median magnetization intensities between 79 and 106 A/m and a strong preferred magnetization direction perpendicular to the slab plane. Furthermore, results indicate that the main source of natural remanent magnetization is in the pyroxenes.

Comparison of Aerial Thermal Infrared Imagery and Helicopter Surveys of Bison (Bison bison) in Grand Canyon National Park, USA.

Aerial thermal infrared (TIR) surveys are an attractive option for estimating abundances of large mammals inhabiting extensive and heterogeneous terrain. Compared to standard helicopter or fixed-wing aerial surveys, TIR flights can be conducted at higher altitudes translating into greater spatial coverage and increased observer safety; however, monetary costs are much greater. Further, there is no consensus on whether TIR surveys offer improved detection. Consequently, we performed a study to compare results of a TIR and helicopter survey of bison (Bison bison) on the Powell Plateau in Grand Canyon National Park, USA. We also compared results of both surveys to estimates obtained using a larger dataset of bison helicopter detections along the entire North Rim of the Grand Canyon. Observers in the TIR survey counted fewer individual bison than helicopter observers (101 to 127) and the TIR survey cost was 367% higher. Additionally, the TIR estimate was 18.8% lower than the estimate obtained using a larger dataset, while the comparative helicopter survey was 9.3% lower. Despite our small sample size, we found that helicopter surveys are currently the best method for estimating bison abundances in dense canopy cover sites due to ostensibly more accurate estimates and lower cost compared to TIR surveys. Additional research will be needed to evaluate the efficacy of these methods, as well as very high resolution satellite imagery, for bison populations in more open landscapes.

Variability in the management of agricultural fields spared for conservation

• 30% of landowners doing grassland conservation did not adhere to management guidance. • Land features (e.g., distance-to-road) did not effectively predict field management. • Programmatic-scale evaluation of field management is possible with remote sensing. Private land conservation initiatives are primary channels for wildlife population recovery and management in agricultural ecosystems. Billions of dollars are allocated to these programs in the United States and Europe. Ensuring cost-efficiency is a top priority for funding agencies and substantial resources are dedicated to targeting enrolment to maximize environmental benefits. Landowner management of conservation fields can moderate environmental benefits and may undermine cost efficiency if done incorrectly, therefore it is important to accurately monitor and predict landowner compliance to contract specifications. We investigated landowner compliance to one key wildlife-friendly recommendation (“conformance”) and the amount of woody encroachment in a grassland conservation program, the Kentucky Conservation Reserve Enhancement Program. We used two methods to estimate conformance to wildlife-friendly mowing recommendations and woody encroachment: aerial surveys and supervised classification of satellite imagery. We fit a double observer binomial model to helicopter survey data to estimate impacts of landscape features (e.g., distance to road, field size) on mowing intensity and woody cover. We used the random forest algorithm in Google Earth Engine ( n trees = 1000) to classify vegetation management from SPOT-6 and SPOT-7 satellite images. We surveyed 306 fields in February 2016 via helicopter and classified images from November 2015. At the field scale, estimates of mowed and woody vegetation from image classification were similar to observations from helicopter surveys (<7% difference on average). Approximately 70% of contracts were conformant to wildlife-friendly recommendations. Most variation in mowing intensity and woody encroachment was random. Landscape features were not sufficient predictors of field management and landowners operated independently of one another. Our study is a potent example of how the mis-management of conservation parcels by landowners may diminish efforts to maximize environmental benefits. Resource management agencies that administer private land conservation should dedicate considerable resources to ensuring landowners follow best management practices. Using remote sensing technology is a viable method for surveying compliance at programmatic scales.

Are Composition Surveys for Mule Deer Along Roads or From Helicopters Biased? Lessons from the Field

ABSTRACTMonitoring sex and age ratios (i.e., population composition) is common practice in deer (Odocoileus spp.) management because these estimates are used to determine population vital rates, as well as assess effects of hunting regulations and other management actions. However, there is longstanding recognition of potential biases in sex and age ratios that can arise from differences in deer behavior and sightability, or from methodological issues, such as using roads for sampling. Biologists often use roads for composition surveys because of convenience and roads are often considered to provide coverage of the sampling area and, consequently, unbiased estimates of sex and age ratios. We tested the long‐standing belief that low‐use roads through mule deer (O. hemionus) winter range provided an unbiased sampling scheme by designing and conducting a random‐route survey in conjunction with the road survey through the same winter range in Round Valley, California, USA, during 2015 and 2016. In addition, we conducted a helicopter survey of the same area in 2016. We found adult male:adult female (buck:doe) ratios were 31–45% greater from the random‐route survey compared with the road survey. There was no difference in buck:doe ratios between road and helicopter surveys, but the random‐route survey had 55% greater buck:doe ratios than the helicopter survey. The helicopter survey also had 2.2–4.7 times greater proportions of unclassified bucks than the road or random‐route surveys. There were no differences in fawn:doe ratios among the 3 survey methods. We conducted additional spatial analyses to determine if the buck:doe ratio was greater along random‐routes because bucks were avoiding roads or because the random‐route survey covered different areas. We found that bucks were not avoiding roads; rather, the roads did not adequately cover the winter range area. There were differences between all 3 methods, but our main message is that the assumption that roads provide adequate coverage of winter range and unbiased estimates of population composition should be evaluated. To evaluate that assumption, we recommend conducting ≥1 survey using random routes and comparing composition estimates with road surveys. Further, if information on buck antler‐class is required for management decisions, a ground survey is preferable to a helicopter survey. © 2020 The Wildlife Society.

APPLICABILITY OF AUTONOMOUS UNMANNED HELICOPTER SURVEY OF AIR DOSE RATE IN SUBURBAN AREA.

An autonomous unmanned helicopter (AUH) survey is a useful tool for monitoring the distribution of ambient dose equivalent rates. However, the AUH survey method was developed for plane permeable fields such as agricultural land, and its applicability to urban areas is unclear. In this study, the applicability was investigated by comparing the results of AUH and ground-based surveys conducted in suburban areas, including residential and agricultural lands. The results of both surveys broadly agreed with each other within a factor of 2 in the range independent of land use, and the factor was the same as that reported for plane permeable fields. These results suggest that AUH surveys are applicable in urban areas. The measurement uncertainty of the AUH survey was largely affected by the patchy and local distribution of ambient dose equivalent rates on the ground and differences in the fields of view, rather than land use.

Effects of distance on detectability of Arctic waterfowl using double-observer sampling during helicopter surveys.

Aerial survey is an important, widely employed approach for estimating free‐ranging wildlife over large or inaccessible study areas. We studied how a distance covariate influenced probability of double‐observer detections for birds counted during a helicopter survey in Canada’s central Arctic. Two observers, one behind the other but visually obscured from each other, counted birds in an incompletely shared field of view to a distance of 200 m. Each observer assigned detections to one of five 40‐m distance bins, guided by semi‐transparent marks on aircraft windows. Detections were recorded with distance bin, taxonomic group, wing‐flapping behavior, and group size. We compared two general model‐based estimation approaches pertinent to sampling wildlife under such situations. One was based on double‐observer methods without distance information, that provide sampling analogous to that required for mark–recapture (MR) estimation of detection probability, p^, and group abundance, G^, along a fixed‐width strip transect. The other method incorporated double‐observer MR with a categorical distance covariate (MRD). A priori, we were concerned that estimators from MR models were compromised by heterogeneity in p^ due to un‐modeled distance information; that is, more distant birds are less likely to be detected by both observers, with the predicted effect that p^ would be biased high, and G^ biased low. We found that, despite increased complexity, MRD models (ΔAICc range: 0–16) fit data far better than MR models (ΔAICc range: 204–258). However, contrary to expectation, the more naïve MR estimators of p^ were biased low in all cases, but only by 2%–5% in most cases. We suspect that this apparently anomalous finding was the result of specific limitations to, and trade‐offs in, visibility by observers on the survey platform used. While MR models provided acceptable point estimates of group abundance, their far higher stranded errors (0%–40%) compared to MRD estimates would compromise ability to detect temporal or spatial differences in abundance. Given improved precision of MRD models relative to MR models, and the possibility of bias when using MR methods from other survey platforms, we recommend avian ecologists use MRD protocols and estimation procedures when surveying Arctic bird populations.

Simultaneous modelling of movement, measurement error, and observer dependence in mark-recapture distance sampling: An application to Arctic bird surveys

Mark-recapture distance sampling is a promising method for surveying bird populations from aircraft in open landscapes. However, commonly available distance sampling estimators require that distances to target animals are made without error and that animals are stationary while sampling is being conducted. Motivated by a recent bird survey where these requirements were routinely violated, we describe a marginal likelihood framework for estimating abundance from double-observer data that can accommodate movement and measurement error when observations are made consecutively (as with front and rear observers), when animals are uniformly distributed during detection by the first observer, and when detections consist of both moving and stationary animals. Assuming that all animals are subject to measurement error and that some animals can move between detections, we integrate over unknown animal locations to construct a marginal likelihood for detection, movement, and measurement error parameters. Estimates of animal abundance are then obtained using a modified Horvitz–Thompson-like estimator. In addition, unmodelled heterogeneity in detection probability can be accommodated through observer dependence parameters. Using simulation, we show that our approach yields low bias compared to approaches that ignore movement and/or measurement error, including in cases where there is considerable detection heterogeneity. Applying our approach to data from a double-observer waterfowl helicopter survey in northern Canada, we are able to estimate bird density accounting for movement and measurement error and corrected for observer heterogeneity. Our approach appears promising for generating unbiased estimates of bird abundance necessary for reliable conservation and management.

A comparison of unmanned aerial vehicles (drones) and manned helicopters for monitoring macropod populations

Context Developments in the use of remote aircraft, or unmanned aerial systems (UAS), for ecological study have been rapid. Helicopter surveys have proven to be a reliable, repeatable method for broad-scale monitoring of harvested kangaroo populations in Australia’s rangelands, but the recent availability of long-range UAS may offer improvements in detectability and cost efficiency. Aims We aimed to test the ability of a long-range UAS (Spylite, Bluebird Aero Systems Ltd, Kadima, Israel) to survey macropod populations at a landscape scale, and validate the results against those from the current best-practice helicopter surveys. Methods Four 80-km transects in south-western Queensland were surveyed using a helicopter and UAS. Two observers, occupying the rear seats of the helicopter, recorded animals observed in distance classes perpendicular to either side of the aircraft. Continuous electro-optical (EO) or infrared (IR) video from the UAS were recorded for later processing. Animal densities were calculated using line-transect methods for both techniques. The efficiency and cost effectiveness of each survey technique were also assessed using the flight and data processing times. Key results The encounter rate for macropods during the UAS was significantly lower compared with the helicopter survey, resulting in low estimates of macropod density (3.2 versus 53.8 animals km–2 respectively). The UAS technique recorded between 2.9 and 12.7% of the macropod density observed on each transect during the helicopter survey. The helicopter surveys were less expensive and more efficient and cost effective, requiring less flight and data processing time than the UAS surveys. Conclusions Utilising long-range UAS to detect and count groups of wild animals for landscape-scale wildlife monitoring has potential, but improvements in detection and identification technology are needed to match or exceed the accuracy of the conventional aerial survey technique for kangaroos. Implications Recent advances in camera technology and methodological refinements are encouraging for aerial survey of wildlife using UAS. However, significant improvements are required to survey for kangaroos and new technology should again be tested against current benchmarks.

Geochemical mapping of radioactive elements using helicopter-borne gamma-ray spectrometry (Tiouit, Eastern Anti-Atlas, Morocco): Or occurrence and environmental impact

The spectrometric prospection is a direct geophysical method based on the analysis of the radioactive elements spectra, due to three principal radioactive elements 40K, 238U and 232Th. In order to measure the content of radioactive elements a geophysical helicopter survey was carried out to a flight altitude of 60 m from the subsoil, covering the geological map of Tiouit 1/50000 with an extent of 45.5 × 29 km2. In this paper, we propose an application in the environment and or occurrence by the production of maps concentration in K, U and Th to delimit the areas with purely natural radioactive risk by the calculation of the dose rate in mSv, the found values show a variation of 0,3 to 1.649 mSv with a median value of 0,831 mSv. Moreover, data processing as the horizontal gradient filter which allowed to amplify the spectrometric signatures, this one coupled to the upward continuation, lead us to a better location of the abrupt changes, which materialize by spectrometric lineaments, reflecting the change of the geochemical properties of the basement.

First Report of Phytophthora ramorum Lineage EU1 Infecting Douglas Fir and Grand Fir in Oregon

HomePlant DiseaseVol. 102, No. 2First Report of Phytophthora ramorum Lineage EU1 Infecting Douglas Fir and Grand Fir in Oregon PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Phytophthora ramorum Lineage EU1 Infecting Douglas Fir and Grand Fir in OregonJ. M. LeBoldus, K. L. Sondreli, W. Sutton, P. Reeser, S. Navarro, A. Kanaskie, and N. J. GrünwaldJ. M. LeBoldus†Corresponding author: J. M. LeBoldus; E-mail: E-mail Address: jared.leboldus@science.oregonstate.eduSearch for more papers by this author, K. L. SondreliSearch for more papers by this author, W. SuttonSearch for more papers by this author, P. ReeserSearch for more papers by this author, S. NavarroSearch for more papers by this author, A. KanaskieSearch for more papers by this author, and N. J. Grünwaldhttp://orcid.org/0000-0003-1656-7602Search for more papers by this authorAffiliationsAuthors and Affiliations J. M. LeBoldus † , Oregon State University, Department of Botany and Plant Pathology and Forest Engineering, Resources and Management, Corvallis, OR 97331 K. L. Sondreli W. Sutton P. Reeser , Oregon State University, Department of Botany and Plant Pathology, Corvallis, OR 97331 S. Navarro A. Kanaskie , Oregon Department of Forestry, Private Forests Program, Forest Health Section, Salem, OR 97310 N. J. Grünwald , Horticultural Crops Research Laboratory, USDA Agricultural Research Service, Corvallis, OR 97330. Published Online:21 Nov 2017https://doi.org/10.1094/PDIS-05-17-0681-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Sudden oak death (SOD) is caused by the introduced oomycete pathogen Phytophthora ramorum S. Werres, A. W. A. M. de Cock & W. A. Man in’t Veld. This fungus-like organism has four clonal lineages: NA1, NA2, EU1, and EU2 (Grünwald et al. 2016; Prospero et al. 2007). Until recently, the NA1 lineage was the only clonal lineage of P. ramorum reported in wildland forests in the western United States. In contrast, EU1, NA1, and NA2 have all been found in U.S. nurseries (Grünwald et al. 2012). In the winter of 2015, a symptomatic Notholithocarpus densiflorus Manos, Cannon & S.H.Oh (tanoak) was identified during a SOD helicopter survey in Curry County, OR. P. ramorum was isolated from symptomatic bark tissue. Subsequently, the isolate was determined to be of the EU1 lineage based on 14 microsatellite loci (Grünwald et al. 2016). Continued monitoring of the area in 2016 and 2017 has identified symptomatic Abies grandis (Douglas ex D. Don) Lindl. (grand fir; n = 3) and Pseudotsuga menziesii (Mirb.) Franco (Douglas fir; n = 2) saplings growing near infected tanoak trees in the mixed conifer forest of Curry County, OR. Symptoms with shoot blight for these species were similar to those described in the literature, including wilting and dieback of new shoots, brown discoloration of needles, and needle loss on young shoots. Isolations were made by plating surface-sterilized tip dieback tissue from A. grandis and P. menziesii on a Phytophthora-selective medium. Based on the presence of chlamydospores, characteristic hyphae, and sporangial morphology, the isolates were identified as P. ramorum. DNA was extracted from hyphae, and a portion of the cellulose binding elicitor lectin (CBEL) gene was amplified and sequenced using the CBEL5U and CBEL6L primers (Gagnon et al. 2014). The sequences of the unknown lineage were aligned to sequences of CBEL for NA1, NA2, EU1, and EU2 using the Staden package in GAP version 4.11.2. The lineage of the isolates from A. grandis and P. menziesii (GenBank accession nos. MF918374 and MF918375, respectively) had 100% identity to the EU1 reference sequences (GenBank nos. EU688952 and EF117945). To satisfy Koch’s postulates, three branches of A. grandis and P. menziessii were inoculated with the original EU1 isolates of P. ramorum from those hosts. Ten days after inoculation, the same pathogen was reisolated from symptomatic stem tissue of both tree species. The EU1 lineage is considered more aggressive than the NA1 lineage and is of opposite mating type to NA1, thus potentially resulting in establishment of sexual populations.

Statistical power of replicated helicopter surveys in southern African conservation areas

AbstractUnderstanding the ecology of large ungulates in southern Africa requires accurate and precise measures of population size. Recovery or exploitation of ungulates in reserves is currently instigated when population size changes exceed 15% per annum, but monitoring is usually undertaken with single counts from helicopters, for which precision and the power to detect change are untested. In essence, power being the strength of a monitoring result in showing change over time. Retrospective power analysis is a useful technique to investigate the variability of single‐count aerial surveys. Using replicated helicopter‐based counts of southern African ungulates and post hoc analysis, we investigated the power of currently used single‐count surveys across five common ungulate species and 11 wildlife reserves. We expected high variability in count data and set α = 0.1 and 0.2 (α being the type I error rate), and asked two questions: ‘How much does power vary in replicated aerial counts of southern African wildlife across reserves and species?’ and ‘Can current single‐count aerial surveys detect population changes in response to management actions or are the statistical errors intractable?’ Single counts were mostly unreliable; only one of 42 had sufficient power to detect meaningful changes in population size or their trends at α = 0.1, and only three had sufficient power at α = 0.2. Power varied widely according to species (e.g. warthog, median power at α = 0.1; 0.12–0.37: blue wildebeest, median power at α = 0.1; 0.23–0.74), and, within species, between replicates and reserves. Our retrospective calculations demonstrated insensitivity and ineffectiveness in most currently applied single counts from helicopters. Consequently, it is impossible to interpret the effects of ungulate conservation actions on many southern African reserves. Retrospective power analyses enables determination of which previous aerial surveys were useful for population assessment and adaptive management, and which should be discarded. We recommend that prospective power analyses are undertaken to determine future helicopter survey sample size and replication requirements, especially in small reserves.

Estimating ungulate abundance while accounting for multiple sources of observation error

ABSTRACTWhether a species is rare or overabundant, accurate estimates of population abundance are essential for the development and assessment of conservation plans and management goals. Aerial surveys are commonly used to estimate population abundance and a variety of methods have been used to account for recognized biases associated with imperfect detection. Rarely addressed, however, is the possibility of recording duplicate observations and the influence of duplicate observations on estimates of abundance. Using data provided by Global Positioning System (GPS)‐collared bison (Bison bison) and helicopter survey paths conducted during 2011–2013 in the Henry Mountains, Utah, USA, we determined whether GPS‐collared bison were observed, missed, or observed multiple times. Using these data, covariates hypothesized to influence observation errors, and generalized linear models, we found the probability of detecting a GPS‐collared bison (study‐wide mean of 95%) was consistently greater for individuals in larger groups and less rugged terrain. We also found that the probability of recording a duplicate observation (study‐wide mean of 4.4%) increased with time since the prior survey observation. By incorporating both types of observation error into a modified Horvitz–Thompson estimator, more accurate estimates of bison abundance can be attained, particularly in years when animals segregate into small groups, utilize terrain that makes them difficult to see, or have ample time to move into areas not yet surveyed and be counted again. Our approach of accounting for multiple sources of observation error can easily be applied to aerial surveys for other species in other systems, and has the potential to improve the rigor of wildlife abundance estimation from aerial surveys. © 2016 The Wildlife Society.

Tectonically Controlled Nearshore Deposition: Cozzette Sandstone, Book Cliffs, Colorado, U.S.A

Abstract The Book Cliffs of eastern Utah and western Colorado have been pivotal in the development of outcrop-based sequence stratigraphic concepts for nonmarine to shallow marine siliciclastic depositional settings. Prior studies in this area, and more generally in the Cretaceous western interior foreland basin of North America, have concluded that nearshore accumulation is controlled for the most part by the interaction between oscillatory eustatic change and longer-term regional patterns of flexural subsidence. New outcrop and subsurface evidence reported here from the eastern Book Cliffs suggests that three-dimensional tectonic tilting at length scales of up to ∼ 50 km (31 mi) and timescales of less than ∼ 200 kyr also strongly influenced sedimentation. Continental ice sheets are thought to have been small at the time. Documented patterns of accumulation are inconsistent with those expected from interactions of eustasy and regional flexure alone. The upper Campanian Cozzette Sandstone Member of the Mount Garfield Formation consists of twelve lithofacies arranged into six lithofacies assemblages, inferred to have been deposited in shallow marine, marginal marine, and nonmarine depositional environments. Shallow marine facies are organized into six wedge-shaped units < 40 m thick, bounded by flooding surfaces, and separated into three larger-scale cycles, which display along-strike and time-equivalent aggradational and progradational stacking. These successions are interpreted as shoreface–foreshore–swamp parasequences, and are erosionally overlain by fluvial and estuarine deposits. Both fluvial and estuarine accumulations are underlain by composite erosional surfaces, belonging either to two distinct incised-valley fills or to one composite fill. The proposed interpretation is based on high-resolution correlations made from digital video and continuous photographs acquired during a helicopter survey of the member. This interpretation differs significantly from published cross sections of the Cozzette, in which the sandstone is inferred to consist of at least two sheet-like shallow marine parasequences, truncated by sequence boundaries. Facies variations, stratigraphic thickness trends, and geometrical relationships reveal that three basinward–landward cycles of syndepositional to postdepositional tectonic tilting in the southern Piceance basin controlled accumulation in the Cozzette Sandstone. Differential subsidence to the southeast led to the development of a northeast-trending clinoform rollover. Subsequent tilting to the north resulted in renewed accommodation creation, and reorientation of the rollover to an eastward trend. Following deposition of six shallow marine parasequences, tilting towards the northeast resulted in bypass and the development of a sequence boundary. The main conclusion of our study, that nearshore sedimentation was modulated by local tectonism at timescales of less than hundreds of thousands of years, casts doubt on the generally accepted eustatic paradigm at a location that was among the most important in the development of sequence stratigraphic concepts.

A Denoising Method Based on Kernel Principal Component Analysis for Airborne Time‐Domain Electromagnetic Data

AbstractAirborne time‐domain electromagnetic (ATEM) data usually contain natural and cultural noise, which can lower data quality, influence inversion accuracy or even lead to incorrect interpretation if it is not removed from data using an appropriate filter. To solve this problem, this work suggests a denosing method based on kernel principal component analysis. Firstly, it extracts the principal component from stacked decay curves. Then the useful signals, which are associated with subsurface media, and noise are separated using the energy ratio. Finally, these signals are used to perform reconstruction. This method can not only remove natural noise such as spikes or oscillation caused by sferies, but also effectively suppress cultural noise. Using this method and the AeroTEM software, the real ATEM data from a helicopter survey is processed separately. Comparison of the results shows that the denoising effect of the method suggested by this paper is superior to that of the AeroTEM software.

High performance rotational vibration isolator

We present a new rotational vibration isolator with an extremely low resonant frequency of 0.055 ± 0.002 Hz. The isolator consists of two concentric spheres separated by a layer of water and joined by very soft silicone springs. The isolator reduces rotation noise at all frequencies above its resonance which is very important for airborne mineral detection. We show that more than 40 dB of isolation is achieved in a helicopter survey for rotations at frequencies between 2 Hz and 20 Hz. Issues affecting performance such as translation to rotation coupling and temperature are discussed. The isolator contains almost no metal, making it particularly suitable for electromagnetic sensors.

Long-term impacts of observed and induced climate change on tussock tundra near its southern limit in northern Sweden

Background: Tussock tundra is a main component of the Low Arctic vegetation cover. As it is adapted to underlying permafrost, its marginal sites at its southern distribution limit could be excellent indicators of climate change. There are still some scattered outpost stands of tussock tundra in the subarctic-alpine area of northern Fennoscandia, now showing signs of decline. Aims: The objective was to document changes in community structure of the tussock tundra over a 12-year period in experimentally warmed plots and in non-manipulated controls. In addition, the study included a survey of the present cover of tussock tundra in northern Swedish Lapland and a long-term monitoring of annual flowering intensity in the dominant species, the arctic hare's-tail cottongrass, Eriophorum vaginatum. Methods: The extent of tussock tundra in the region was assessed in a helicopter survey in 2005, followed by ground truthing in 2006. Climate and permafrost have been monitored at Latnjajaure, northern Swedish Lapland, since 1992. An experimental warming study employing open-top chambers (OTCs) was initiated at Latnjajaure for a number of habitats in 1993–1995, and all tussock tundra plots were surveyed in 1995 and 2006. Non-manipulated, permanently marked E. vaginatum tussocks were monitored for flowering frequency annually in 1992–2008. Results: The helicopter survey indicated that tussock tundra covers only few km2 in northernmost Sweden. A stand at the lower end of its altitude range was already in an advanced stage of transition into shrub tundra. In the OTCs at Latnjajaure, evergreen boreal dwarf-shrubs (particularly Vaccinium vitis-idaea) increased in above-ground biomass about eightfold between 1995 and 2006, and almost fourfold in the controls. There has been a significant warming trend in the study area of 0.12 °C per year, likely explaining why the control plots have also changed. The annual monitoring of E. vaginatum flowering indicated a tendency for relaxed synchrony of masting episodes in recent years, probably caused by longer growing seasons. Conclusions: Tussock tundra stands at the southern margin of the ecosystem's range are undergoing rapid changes at present. Increased air temperature and permafrost degradation are likely to be the main drivers of the observed change.