共查询到20条相似文献,搜索用时 31 毫秒
1.
John E. Hathaway G. Bruce Schaalje Richard O. Gilbert Brent A. Pulsipher Brett D. Matzke 《Environmental and Ecological Statistics》2008,15(3):313-327
Composite sampling can be more cost effective than simple random sampling. This paper considers how to determine the optimum
number of increments to use in composite sampling. Composite sampling terminology and theory are outlined and a method is
developed which accounts for different sources of variation in compositing and data analysis. This method is used to define
and understand the process of determining the optimum number of increments that should be used in forming a composite. The
blending variance is shown to have a smaller range of possible values than previously reported when estimating the number
of increments in a composite sample. Accounting for differing levels of the blending variance significantly affects the estimated
number of increments.
相似文献
John E. HathawayEmail: |
2.
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: |
3.
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: |
4.
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: |
5.
Griffith DA 《Environmental geochemistry and health》2008,30(6):495-509
Properly sampling soils and mapping soil contamination in urban environments requires that impacts of spatial autocorrelation
be taken into account. As spatial autocorrelation increases in an urban landscape, the amount of duplicate information contained
in georeferenced data also increases, whether an entire population or some type of random sample drawn from that population
is being analyzed, resulting in conventional power and sample size calculation formulae yielding incorrect sample size numbers
vis-à-vis model-based inference. Griffith (in Annals, Association of American Geographers, 95, 740–760, 2005) exploits spatial statistical model specifications to formulate equations for estimating the necessary sample
size needed to obtain some predetermined level of precision for an analysis of georeferenced data when implementing a tessellation
stratified random sampling design, labeling this approach model-informed, since a model of latent spatial autocorrelation
is required. This paper addresses issues of efficiency associated with these model-based results. It summarizes findings from
a data collection exercise (soil samples collected from across Syracuse, NY), as well as from a set of resampling and from
a set of simulation experiments following experimental design principles spelled out by Overton and Stehman (in Communications in Statistics: Theory and Methods, 22, 2641–2660). Guidelines are suggested concerning appropriate sample size (i.e., how many) and sampling network (i.e., where).
相似文献
Daniel A. GriffithEmail: |
6.
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: |
7.
“Protecting coastal zones in the Mediterranean: an economic and regulatory analysis” 总被引:1,自引:1,他引:0
This paper examines existing measures taken to protect the coastal zones of the Mediterranean Sea and assesses their success.
A summary of the main pressures facing this region is given, followed by an analysis of the legislation covering coastal zone
development in ten countries: Algeria, Croatia, Egypt, France, Israel, Italy, Malta, Spain, Tunisia and Turkey. The paper
finds that not all of these States have legislation specifically covering coastal zones, but there is concern in all areas
that existing legislation is not working. The costs and benefits of controlling coastal development are examined. Firstly,
a literature review of valuation studies identifies a range of values placed on the developed and undeveloped coastline for
both users and local property owners. These values were then used in a model to evaluate policy options to control development
of a stretch of coastline. The model indicates that a stricter control regime of coastal development may provide significant
benefits.
相似文献
A. MarkandyaEmail: |
8.
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: |
9.
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: |
10.
Matthew R. Schofield Richard J. Barker Darryl I. MacKenzie 《Environmental and Ecological Statistics》2009,16(3):369-387
Hierarchical mark-recapture models offer three advantages over classical mark-recapture models: (i) they allow expression
of complicated models in terms of simple components; (ii) they provide a convenient way of modeling missing data and latent
variables in a way that allows expression of relationships involving latent variables in the model; (iii) they provide a convenient
way of introducing parsimony into models involving many nuisance parameters. Expressing models using the complete data likelihood
we show how many of the standard mark-recapture models for open populations can be readily fitted using the software WinBUGS.
We include examples that illustrate fitting the Cormack–Jolly–Seber model, multi-state and multi-event models, models including
auxiliary data, and models including density dependence.
相似文献
Darryl I. MacKenzieEmail: |
11.
Glen D. Johnson 《Environmental and Ecological Statistics》2008,15(3):293-311
Infectious disease surveillance has become an international top priority due to the perceived risk of bioterrorism. This is
driving the improvement of real-time geo-spatial surveillance systems for monitoring disease indicators, which is expected
to have many benefits beyond detecting a bioterror event. West Nile Virus surveillance in New York State (USA) is highlighted
as a working system that uses dead American Crows (Corvus brachyrhynchos) to prospectively indicate viral activity prior to human onset. A cross-disciplinary review is then presented to argue that
this system, and infectious disease surveillance in general, can be improved by complementing spatial cluster detection of
an outcome variable with predictive “risk mapping” that incorporates spatiotemporal data on the environment, climate and human
population through the flexible class of generalized linear mixed models.
相似文献
Glen D. JohnsonEmail: |
12.
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: |
13.
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: |
14.
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: |
15.
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: |
16.
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: |
17.
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: |
18.
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: |
19.
We propose a hierarchical modeling approach for explaining a collection of spatially referenced time series of extreme values.
We assume that the observations follow generalized extreme value (GEV) distributions whose locations and scales are jointly
spatially dependent where the dependence is captured using multivariate Markov random field models specified through coregionalization.
In addition, there is temporal dependence in the locations. There are various ways to provide appropriate specifications;
we consider four choices. The models can be fitted using a Markov Chain Monte Carlo (MCMC) algorithm to enable inference for
parameters and to provide spatio–temporal predictions. We fit the models to a set of gridded interpolated precipitation data
collected over a 50-year period for the Cape Floristic Region in South Africa, summarizing results for what appears to be
the best choice of model.
相似文献
Alan E. GelfandEmail: |
20.
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: |