Search results for "Transect"
showing 10 items of 102 documents
A Random Field Approach to Transect Counts of Wildlife Populations
1991
Line transect counting of a wildlife population is considered a sampling from a planar marked point process, where the marks describe the detectability of the animals. Sampling properties of transect counts and a new density estimator are derived from a counting process, which is a shot-noise field induced by the marked point process. A general formula for the sampling variance of a transect is derived and applied to compare five common types of transects. Some stereological connections of transect sampling and density estimators are shown.
Evaluation of Landsat-8 TIRS data recalibrations and land surface temperature split-window algorithms over a homogeneous crop area with different phe…
2021
Abstract Successive re-calibrations were implemented in Landsat-8 TIRS data since launch. This paper evaluates the performances of both: (1) these re-calibrations, up to the last calibration update announced for TIRS data in the next Landsat Collection 2; and (2) single-channel (SC) corrections and split-window (SW) algorithms to retrieve land surface temperature (LST) from TIRS data. A robust and accurate multi-year (2014–2019) set of reference ground data were used, which included thermal infrared (TIR) radiance measurements taken along transects in a uniform and thermally homogeneous rice paddy area, but also emissivity measurements for the different ground covers at the site through the…
Impacts of oak deforestation and rainfed cultivation on soil redistribution processes across hillslopes using 137Cs techniques
2021
Abstract Background As one of the main components of land-use change, deforestation is considered the greatest threat to global environmental diversity with possible irreversible environmental consequences. Specifically, one example could be the impacts of land-use changes from oak forests into agricultural ecosystems, which may have detrimental impacts on soil mobilization across hillslopes. However, to date, scarce studies are assessing these impacts at different slope positions and soil depths, shedding light on key geomorphological processes. Methods In this research, the Caesium-137 (137Cs) technique was applied to evaluate soil redistribution and soil erosion rates due to the effects …
Influence of artificial reefs on the surrounding infauna: Analysis of meiofauna
2002
We adopted a bottom-up approach in studying the effect of two artificial reefs in contrasting environmental conditions (sandy-mud and meso-eutrophic in the Adriatic Sea versus coarse sands and oligotrophic in the Tyrrhenian Sea) on the surrounding environment by assessing changes in the meiofauna. The spatial distribution of meiofaunal assemblages was established along a transect running from within each reef to well outside its direct sphere of influence, along with information on the trophic conditions of sediments (chloropigments, proteins, carbohydrates and total organic matter). Although total densities were significantly higher in the Adriatic than in the Tyrrhenian, the meiofauna dis…
Spatial models for monitoring the spatio-temporal evolution of ashes after fire-a case study of a burnt grassland in Lithuania
2013
Ash thickness is a key variable in the protection of soil against erosion agents after planned and unplanned fires. Ash thickness measurements were conducted along two transects (flat and sloping areas) following a grided experimental design. In order to interpolate data with accuracy and identify the techniques with the least bias, several interpolation methods were tested in the grided plot. Overall, the fire had a low severity. However, the fire significantly reduced the ground cover, especially on sloping areas, owing to the higher fire severity and/or less biomass previous to the fire. Ash thickness depended on fire severity and was thin where fire severity was higher and thicker in lo…
Recent changes in measured wind in the NE Atlantic and variability of correlation with NAO
2010
The paper deals with wind measurements, recorded since the 1950s, at twelve meteorological stations along a transect near the westernmost European border, between 64° and 44° N. Extreme wind speed tends to decrease sharply near the northern boundary (at Reykjavick), near the middle of the study area (at Shannon and Valentia) and near the southern boundary (at Brest and Cap Ferret), to increase at Thorshavn, with less significant trends at the other stations. Average wind speeds confirm the above tendencies, with an additional increasing speed at Lerwick, Kirkwall, Malin Head, Belle-Ile and Cap Ferret. To compare changes in wind activity, the data have been subdivided into three periods: unt…
Millennial-scale terrestrial ecosystem responses to Upper Pleistocene climatic changes: 4D-reconstruction of the Schwalbenberg Loess-Palaeosol-Sequen…
2021
Abstract Loess-Palaeosol-Sequences (LPS) in the Central European region provide outstanding terrestrial polygenetic and multiphase archives responding to past climate and environments over various spatial and temporal scales. As yet, however, the geomorphological and pedogenic processes involved in LPS formation, and their interplay with changes in ecological conditions, impede robust correlation with other palaeoenvironmental archives. The Schwalbenberg LPS, which drape a hillslope in the Middle Rhine Valley in western Central Europe, provide unique high-resolution records highly suitable for investigating the processes involved in their formation and the relationship to climatic influence…
Stand structure and spatial pattern of regeneration of Pinus sylvestris in a natural treed mire in Latvia
2009
We examined the regeneration patterns of Pinus sylvestris L. in a natural treed mire in the hemiboreal zone in Latvia. Data on tree stem age and size was collected in 207 fine-scale plots (10 m) and 4 medium-scale plots (400 m). Size structure of living and dead trees was also estimated on transects 180-m and 250-m length and 10-m width. In addition, the vegetation was described in 1-m plots to determine preferred microsites for P. sylvestris establishment. Pinus sylvestris showed continuous regeneration by an inverse J-shaped age and size structure. Pulses of mortality induced by fire were also evident. Regeneration of P. sylvestris was mostly on Sphagnum magellanicam Brid. hummocks free o…
Activity and body orientation of Gallotia galloti in different habitats and daily times
2011
Abstract In lizards, site selection is related to the acquisition of resources such as refuges, mates or prey, but also to the exploitation of sites suitable for thermoregulation. The latter process may be affected by lizard posture and body axis orientation in relation to the sun as a way to optimize heat exchange throughout the day. Specific postures and body orientations could also contribute to more efficient signal transmission in social contexts. In this paper we analyze activity and body axis orientation of adult males and females of the lacertid Gallotia galloti in two localities of Tenerife with different structural habitats. We performed transects at both sampling localities in t…
Mercury Speciation in Floodplain Soils and Sediments along a Contaminated River Transect
1998
A novel mercury-specific sequential extraction procedure (SEP) for the assessment of mercury (Hg) speciation in soils and sediments, with emphasis on studying the interaction between Hg and organic matter (OM), was developed and tested. It was applied to determine Hg speciation in floodplain topsoils and surface sediments along the Hg-contaminated part of the river Elbe, and to simultaneously derive some information on the (re)mobilization potentials for Hg from these matrices. The majority of the total Hg in the ecosystem today is bound in the floodplains, which also still geographically reflect the historic emission record. Most of the Hg in both matrices is bound strongly to OM, suggesti…