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1.
Coverage, i.e., the area covered by the target attribute in the study region, is a key parameter in many surveys. Coverage
estimation is usually performed by adopting a replicated protocol based on line-intercept sampling coupled with a suitable
linear homogeneous estimator. Since coverage is a parameter which may be interestingly represented as the integral of a suitable
function, improved Monte Carlo strategies for implementing the replicated protocol are introduced in order to achieve estimators
with small variance rates. In addition, new specific theoretical results on Monte Carlo integration methods are given to deal
with the integrand functions arising in the special coverage estimation setting.
相似文献
Lucio BarabesiEmail: |
2.
Chang Xuan Mao 《Environmental and Ecological Statistics》2007,14(4):473-481
Consider the removal experiment used to estimate population sizes. Statistical methods towards testing the homogeneity of
capture probabilities of animals, including a graphical diagnostic and a formal test, are presented and illustrated by real
biological examples. Simulation is used to assess the test and compare it with the χ2 test.
相似文献
Chang Xuan MaoEmail: |
3.
B. Gail Ivanoff 《Environmental and Ecological Statistics》2009,16(2):153-171
The concept of the renewal property is extended to processes indexed by a multidimensional time parameter. The definition
given includes not only partial sum processes, but also Poisson processes and many other point processes whose jump points
are not totally ordered. Various properties of renewal processes are discussed. Renewal processes are proposed as a basis
for modelling the spread of a forest fire under a prevailing wind.
相似文献
B. Gail IvanoffEmail: |
4.
The influence of multiple anchored fish aggregating devices (FADs) on the spatial behavior of yellowfin (Thunnus albacares) and bigeye tuna (T. obesus) was investigated by equipping all thirteen FADs surrounding the island of Oahu (HI, USA) with automated sonic receivers
(“listening stations”) and intra-peritoneally implanting individually coded acoustic transmitters in 45 yellowfin and 12 bigeye
tuna. Thus, the FAD network became a multi-element passive observatory of the residence and movement characteristics of tuna
within the array. Yellowfin tuna were detected within the FAD array for up to 150 days, while bigeye tuna were only observed
up to a maximum of 10 days after tagging. Only eight yellowfin tuna (out of 45) and one bigeye tuna (out of 12) visited FADs
other than their FAD of release. Those nine fish tended to visit nearest neighboring FADs and, in general, spent more time
at their FAD of release than at the others. Fish visiting the same FAD several times or visiting other FADs tended to stay
longer in the FAD network. A majority of tagged fish exhibited some synchronicity when departing the FADs but not all tagged
fish departed a FAD at the same time: small groups of tagged fish left together while others remained. We hypothesize that
tuna (at an individual or collective level) consider local conditions around any given FAD to be representative of the environment
on a larger scale (e.g., the entire island) and when those conditions become unfavorable the tuna move to a completely different
area. Thus, while the anchored FADs surrounding the island of Oahu might concentrate fish and make them more vulnerable to
fishing, at a meso-scale they might not entrain fish longer than if there were no (or very few) FADs in the area. At the existing
FAD density, the ‘island effect’ is more likely to be responsible for the general presence of fish around the island than
the FADs. We recommend further investigation of this hypothesis.
相似文献
Laurent Dagorn (Corresponding author)Email: |
Kim N. HollandEmail: |
David G. ItanoEmail: |
5.
Lucio Barabesi 《Environmental and Ecological Statistics》2007,14(4):483-494
Line-intersect sampling based on segmented transects is adopted in many forest inventories to quantify important ecological
indicators such as coarse woody debris attributes. By assuming a design-based approach, Affleck, Gregoire and Valentine (2005,
Environ Ecol Stat 12:139–154) have recently proposed a sampling protocol for this line-intersect setting and have suggested
an estimation method based on linear homogeneous estimators. However, their proposal does not encompass the estimation procedure
currently adopted in some national forest inventories. Hence, the present paper aims to introduce a unifying perspective for
both methods. Moreover, it is shown that the two procedures give rise to coincident estimators for almost all the usual field
applications. Finally, some strategies for efficient segmented-transect replications are considered.
相似文献
Lucio BarabesiEmail: |
6.
M. M. Manzano-Sarabia E. A. Aragón-Noriega C. A. Salinas-Zavala D. B. Lluch-Cota 《Marine Biology》2007,152(5):1021-1029
Life histories of penaeid shrimp have been classified according to the preferred habitats of postlarval, juvenile, and adult
stages, ranging from exclusively estuarine to exclusively offshore waters. Brown shrimp Farfantepenaeus californiensis migrate to an offshore habitat at the juvenile stage or even a smaller body size. This paper presents results of monthly
samplings from 24 stations over 1 year in the Agiabampo Lagoon complex, a hypersaline lagoon in northwestern Mexico. Five
species of penaeid shrimp were identified, with brown shrimp the most abundant during the year of sampling. Results suggest
that residency of brown shrimp inside this lagoon is longer than reported in previous studies. An interaction between length
and environmental variables (near-surface temperature, salinity, and rainfall) appear to be cues concerning migration.
相似文献
C. A. Salinas-ZavalaEmail: |
7.
Frederic Paik Schoenberg Jamie Pompa Chien-Hsun Chang 《Environmental and Ecological Statistics》2009,16(2):251-269
This paper explores the use of, and problems that arise in, kernel smoothing and parametric estimation of the relationships
between wildfire incidence and various meteorological variables. Such relationships may be treated as components in separable
point process models for wildfire activity. The resulting models can be used for comparative purposes in order to assess the
predictive performance of the Burning Index.
相似文献
Frederic Paik SchoenbergEmail: |
8.
We present a method for detecting the zones where an irregularly sampled variable changes abruptly in the plane. Such zones
are called Zones of Abrupt Change (ZACs). This method not only allows estimation of ZACs, but also testing of their statistical
significance against the null hypothesis of a stationary correlated random field. The sampling pattern, in particular its
local density, is crucial in the detection of potential ZACs. In this paper, we address the problem of evaluating the sampling
pattern by assessing the power of the local test used for detecting ZACs. It is shown that mapping the power allows us to
identify zones where ZACs may or may not be detected. The methodology is applied to a soil data set sampled at eight different
dates in an agricultural field. Detecting ZACs for the soil water content allowed us to identify permanent structures in the
agricultural field related to the boundaries between different soil types. Mapping the power for various sampling densities
proved to be useful to determine the minimal sampling density necessary for detecting ZACs.
相似文献
Edith GabrielEmail: |
9.
Den Boychuk W. John Braun Reg J. Kulperger Zinovi L. Krougly David A. Stanford 《Environmental and Ecological Statistics》2009,16(2):133-151
We consider a stochastic fire growth model, with the aim of predicting the behaviour of large forest fires. Such a model can
describe not only average growth, but also the variability of the growth. Implementing such a model in a computing environment
allows one to obtain probability contour plots, burn size distributions, and distributions of time to specified events. Such
a model also allows the incorporation of a stochastic spotting mechanism.
相似文献
Reg J. KulpergerEmail: |
10.
James D. McCleave 《Marine Biology》2008,155(3):249-262
This study reviewed literature on spawning times for three north temperate species of anguillid eels estimated by sampling
for small leptocephali (larvae) at sea and for several temperate and tropical species by back-calculating from putative daily
ages derived from otolith increment analysis of glass eels that recruited to coastal waters. Estimates from otoliths of European
eels, Anguilla anguilla, American eels, Anguilla rostrata, and Japanese eels, Anguilla japonica, imply much more protracted spawning seasons than are indicated by sampling at sea during various times of year. European
eels are inferred to spawn year-round from otolith analysis, but the smallest, recently hatched leptocephali are found only
in late winter and spring. From otoliths, the spawning times of these three species are all estimated to occur much later
in the year than when small leptocephali are found at sea, indicating that ages appear to be underestimated. For these and
other temperate and tropical eels, there are inconsistencies in assigned ages among various studies, which are most extreme
for the European eel. This species has the longest larval migration and often has an opaque zone in the glass eels’ otoliths
where it is difficult to discern growth increments. These inconsistencies suggest that interpretation of otolith growth increments
is incorrect at least in some studies, and the apparently consistent mismatch between otolith and sea-sampling studies suggests
that increments may not always be formed at some period during the unusual early life history of anguillids. Because daily
increments may be formed in eels during most of their early life history, future research is needed to determine the cause
of the mismatch of glass eel aging studies and the apparent spawning times of eels offshore.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
James D. McCleaveEmail: |
11.
Rarefaction estimates how many species are expected in a random sample of individuals from a larger collection and allows
meaningful comparisons among collections of different sizes. It assumes random spatial dispersion. However, two common dispersion
patterns, within-species clumping and segregation among species, can cause rarefaction to overestimate the species richness
of a smaller continuous area. We use field studies and computer simulations to determine (1) how robust rarefaction is to
nonrandom spatial dispersion and (2) whether simple measures of spatial autocorrelation can predict the bias in rarefaction
estimates. Rarefaction does not estimate species richness accurately for many communities, especially at small sample sizes.
Measures of spatial autocorrelation of the more abundant species do not reliably predict amount of bias. Survey sites should
be standardized to equal-sized areas before sampling. When sites are of equal area but differ in number of individuals sampled,
rarefaction can standardize collections. When communities are sampled from different-sized areas, the mean and confidence
intervals of species accumulation curves allow more meaningful comparisons among sites.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Daniel SimberloffEmail: |
12.
Geochemical mapping is a technique rooted in mineral exploration but has now found worldwide application in studies of the
urban environment. Such studies, involving multidisciplinary teams including geochemists, have to present their results in
a way that nongeochemists can comprehend. A legislatively driven demand for urban geochemical data in connection with the
need to identify contaminated land and subsequent health risk assessments has given rise to a greater worldwide interest in
the urban geochemical environment. Herein, the aims and objectives of some urban studies are reviewed and commonly used terms
such as baseline and background are defined. Geochemists need to better consider what is meant by the term urban. Whilst the
unique make up of every city precludes a single recommended approach to a geochemical mapping strategy, more should be done
to standardise the sampling and analytical methods. How (from a strategic and presentational point of view) and why we do
geochemical mapping studies is discussed.
相似文献
Christopher C. JohnsonEmail: |
13.
Rudolf Izsák 《Environmental and Ecological Statistics》2008,15(2):143-156
In this paper some properties and analytic expressions regarding the Poisson lognormal distribution such as moments, maximum
likelihood function and related derivatives are discussed. The author provides a sharp approximation of the integrals related
to the Poisson lognormal probabilities and analyzes the choice of the initial values in the fitting procedure. Based on these
he describes a new procedure for carrying out the maximum likelihood fitting of the truncated Poisson lognormal distribution.
The method and results are illustrated on real data. The computer program for calculations is freely available.
相似文献
Rudolf IzsákEmail: |
14.
In this paper we examine the use of data augmentation techniques for simplifying iterative simulation in the context of both
Bayesian and classical statistical inference for survival rate estimation. We examine two distinct model families common in
population ecology to illustrate our ideas, ring-recovery models and capture–recapture models, and we present the computational
advantage of this approach. We discuss also the fact that problems associated with identifiability in the classical framework
can be overcome using data augmentation, but highlight the dangers in doing so under both inferential paradigms.
相似文献
I. C. OlsenEmail: |
15.
Brooke E. Buckley Walter W. Piegorsch R. Webster West 《Environmental and Ecological Statistics》2009,16(1):53-62
In modern environmental risk analysis, inferences are often desired on those low dose levels at which a fixed benchmark risk
is achieved. In this paper, we study the use of confidence limits on parameters from a simple one-stage model of risk historically
popular in benchmark analysis with quantal data. Based on these confidence bounds, we present methods for deriving upper confidence
limits on extra risk and lower bounds on the benchmark dose. The methods are seen to extend automatically to the case where
simultaneous inferences are desired at multiple doses. Monte Carlo evaluations explore characteristics of the parameter estimates
and the confidence limits under this setting.
相似文献
R. Webster WestEmail: |
16.
Hierarchical spatial point process analysis for a plant community with high biodiversity 总被引:1,自引:0,他引:1
Janine B. Illian Jesper Møller Rasmus P. Waagepetersen 《Environmental and Ecological Statistics》2009,16(3):389-405
A complex multivariate spatial point pattern of a plant community with high biodiversity is modelled using a hierarchical
multivariate point process model. In the model, interactions between plants with different post-fire regeneration strategies
are of key interest. We consider initially a maximum likelihood approach to inference where problems arise due to unknown
interaction radii for the plants. We next demonstrate that a Bayesian approach provides a flexible framework for incorporating
prior information concerning the interaction radii. From an ecological perspective, we are able both to confirm existing knowledge
on species’ interactions and to generate new biological questions and hypotheses on species’ interactions.
相似文献
Rasmus P. WaagepetersenEmail: |
17.
When animals die in traps in a mark-recapture study, straightforward likelihood inferences are possible in a class of models.
The class includes M0, Mt, and Mb as reported by White et al. (Los Alamos National Laboratory, LA-8787-NERP, pp 235, 1982), those that do not involve heterogeneity.
We include three Markov chain “persistence” models and show that they provide good fits in a trapping study of deer mice in
the Cascade-Siskiyou National Monument of Southern Oregon where trapping mortality was high.
相似文献
Fred L. RamseyEmail: |
18.
Léa Fortunato Chantal Guihenneuc-Jouyaux Margot Tirmarche Dominique Laurier Denis Hémon 《Environmental and Ecological Statistics》2009,16(3):341-353
Ecological studies enable investigation of geographic variations in exposure to environmental variables, across groups, in
relation to health outcomes measured on a geographic scale. Such studies are subject to ecological biases, including pure
specification bias which arises when a nonlinear individual exposure-risk model is assumed to apply at the area level. Introduction
of the within-area variance of exposure should induce a marked reduction in this source of ecological bias. Assuming several
measurements per area of exposure and no confounding risk factors, we study the model including the within-area exposure variability
when Gaussian within-area exposure distribution is assumed. The robustness is assessed when the within-area exposure distribution
is misspecified. Two underlying exposure distributions are studied: the Gamma distribution and an unimodal mixture of two
Gaussian distributions. In case of strong ecological association, this model can reduce the bias and improve the precision
of the individual parameter estimates when the within-area exposure means and variances are correlated. These different models
are applied to analyze the ecological association between radon concentration and childhood acute leukemia in France.
相似文献
Léa FortunatoEmail: |
19.
The common occurrence of food transfers within human hunter–gatherer and forager–horticulturalist groups presents exciting test cases for evolutionary models of altruism. While kin biases in sharing are consistent with nepotism based on kin selection, there is much debate over the extent to which reciprocal altruism and tolerated scrounging provide useful explanations of observed behavior. This paper presents a model of optimal sharing breadth and depth, based on a general non-tit-for-tat form of risk-reduction based reciprocal altruism, and tests a series of predictions using data from Hiwi and Ache foragers. I show that large, high variance food items are shared more widely than small, easily acquired food items. Giving is conditional upon receiving in pairwise interactions and this correlation is usually stronger when the exchange of value rather than quantities is considered. Larger families and low producing families receive more and give less, consistent with the notion that marginal value may be a more salient currency than quantity.
相似文献
Michael GurvenEmail: Phone: +1-805-8932202 |
20.
The Wadden Sea is an important habitat for harbour seals and grey seals. They regularly haul-out on sandbanks and islands
along the coast. Comparably little is known about the time seals spend at sea and how they use the remainder of the North
Sea. Yet, human activity in offshore waters is increasing and information on seal distribution in the North Sea is crucial
for conservation and management. Aerial line transect surveys were conducted in the German bight from 2002 to 2007 to investigate
the distribution and abundance of marine mammals. Distance sampling methodology was combined with density surface modelling
for a spatially explicit analysis of seal distribution in the German North Sea. Depth and distance to coast were found to
be relevant predictor variables for seal density. Density surface modelling allowed for a depiction of seal distribution in
the study area as well as an abundance estimate. This is the first study to use aerial survey data to develop a density surface
model (DSM) for a spatially explicit distribution estimate of seals at sea.
相似文献
Helena HerrEmail: |