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1.
Spatial pattern and persistence of historical fire boundaries in southern interior British Columbia 总被引:2,自引:0,他引:2
Geraldine J. Jordan Marie-Josée Fortin Kenneth P. Lertzman 《Environmental and Ecological Statistics》2008,15(4):523-535
Recent ecosystem and fire management research aims to quantify, model and understand historical fire disturbances focusing
on their frequency, size and distribution. Less attention, however, has been paid to fire boundaries and their location on
the landscape. Our study presents a spatial method to quantify the location, pattern and persistence of historical fire boundaries
using tree ring fire scar data in the lower Stein watershed (British Columbia). Data from Pinus ponderosa and Pseudotsuga menziesii collected in 35 one-hectare plots over a 412-hectare study area were analyzed for the period between 1879 and 1947 using
local spatial statistics and boundary detection techniques. Results of the analysis using local spatial statistic Moran’s
I showed significant clustering of boundaries near topographic breaks. To determine and test whether fire boundaries between
plots were persistent, we used boundary detection methods and developed a spatially restricted randomization test. The results
revealed that out of 86 possible boundary links, 8 were significantly persistent (P < 0.025) while another 8 were significantly rare (P < 0.025). These spatial methods can help determine the historical spatial configuration of persistent boundaries and can
be used to maintain natural forest dynamics.
相似文献
Geraldine J. JordanEmail: |
2.
Fiat boundaries: some implications for interpretation,decision-support,and multi-temporal analysis 总被引:1,自引:0,他引:1
Kim Lowell 《Environmental and Ecological Statistics》2008,15(4):369-383
Polygon-based thematic maps can be composed of boundaries that exist by definition—i.e., bona fide boundaries—or those that
exist relative to a specific interpretation of a spatial phenomenon—i.e., fiat boundaries. The construction of maps composed
of fiat boundaries is usually based on a subjective interpretive methodology that is affected by the data used to construct
the map and the minimum mapping unit employed. That fiat boundaries are not the same as bona fide boundaries affects their
use in computer-based spatial decision support tools. This is discussed both in terms of an analysis conducted at one specific
moment, and in respect to increasingly common multi-temporal analysis.
相似文献
Kim LowellEmail: |
3.
Spatial structure effects on the detection of patches boundaries using local operators 总被引:1,自引:0,他引:1
Mathieu D. Philibert Marie-Josée Fortin Ferenc Csillag 《Environmental and Ecological Statistics》2008,15(4):447-467
Landscapes exhibit various degrees of spatial heterogeneity according to the differential intensity and interactions among
processes and disturbances that they are subjected to. The management of these spatially dynamical landscapes requires that
we can accurately map them and monitor the evolution of their spatial arrangement through time. Such a mapping requires first
the delineation of various spatial features present in the landscape such as patches and their boundaries. However, there
are several environmental (spatial variability) as well as technical (spatial resolution) factors that impair our ability
to accurately delineate patches and their boundaries as polygons. Here, we investigate how the spatial structure and spatial
resolution of the data affect the accuracy of detecting patches and their boundaries over simulated landscapes and real data.
Simulated landscapes consisted of two patches with parameterized spatial properties (patches’ level of spatial autocorrelation,
mean value and variance) separated by a boundary of known location. Real data allowed the investigation of a more complex
landscape where there is a known transition between two forest domains with unknown spatial properties. Boundary locations
are defined using the lattice-wombling edge detector at various aggregation levels and the degree of patch homogeneity is
determined using Getis-Ord’s G*. Results show that boundary detection using a local edge detector is greatly affected by the spatial conditions of the data,
namely variance, abruptness of the spatial gradient between two patches and patches’ level of spatial autocorrelation. They
also suggest that data aggregation is not a panacea for bringing out the ecological process creating the patches and that
indicators derived from local measures of spatial association can be complementary tools for analysing spatial structures
affecting boundary delineation.
相似文献
Marie-Josée FortinEmail: |
4.
5.
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: |
6.
7.
Andrew O. Finley Sudipto Banerjee Ronald E. McRoberts 《Environmental and Ecological Statistics》2008,15(2):241-258
In efforts such as land use change monitoring, carbon budgeting, and forecasting ecological conditions and timber supply,
there is increasing demand for regional and national data layers depicting forest cover. These data layers must permit small
area estimates of forest area and, most importantly, provide associated error estimates. This paper presents a model-based
approach for coupling mid-resolution satellite imagery with plot-based forest inventory data to produce estimates of probability
of forest and associated error at the pixel-level. The proposed Bayesian hierarchical model provides access to each pixel’s
posterior predictive distribution allowing for a highly flexible analysis of pixel and multi-pixel areas of interest. The
paper presents a trial using multiple dates of Landsat imagery and USDA Forest Service Forest Inventory and Analysis plot
data. The results describe the spatial dependence structure within the trial site, provide pixel and multi-pixel summaries
of probability of forest land use, and explore discretization schemes of the posterior predictive distributions to forest
and non-forest classes. Model prediction results of a holdout set analysis suggest the proposed model provides high classification
accuracy, 88%, for the trial site.
相似文献
Ronald E. McRobertsEmail: |
8.
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: |
9.
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: |
10.
B. Mike Wotton 《Environmental and Ecological Statistics》2009,16(2):107-131
Understanding and being able to predict forest fire occurrence, fire growth and fire intensity are important aspects of forest
fire management. In Canada fire management agencies use the Canadian Forest Fire Danger Rating System (CFFDRS) to help predict
these elements of forest fire activity. In this paper a review of the CFFDRS is presented with the main focus on understanding
and interpreting Canadian Fire Weather Index (FWI) System outputs. The need to interpret the outputs of the FWI System with
consideration to regional differences is emphasized and examples are shown of how the relationship between actual fuel moisture
and the FWI System’s moisture codes vary from region to region. Examples are then shown of the relationship between fuel moisture
and fire occurrence for both human- and lightning-caused fire for regions with different forest composition. The relationship
between rate of spread, fuel consumption and the relative fire behaviour indices of the FWI System for different forest types
is also discussed. The outputs of the CFFDRS are used every day across Canada by fire managers in every district, regional
and provincial fire management office. The purpose of this review is to provide modellers with an understanding of this system
and how its outputs can be interpreted. It is hoped that this review will expose statistical modellers and other researchers
to some of the models used currently in forest fire management and encourage further research and development of models useful
for understanding and managing forest fire activity.
相似文献
B. Mike WottonEmail: |
11.
Vertical movement and habitat of opah (Lampris guttatus) in the central North Pacific recorded with pop-up archival tags 总被引:1,自引:0,他引:1
Data from 11 pop-up archival transmitting tags attached to opah (Lampris guttatus, F. Lampridae) in the central North Pacific between November 2003 and March 2005 were used to describe their vertical movement
and habitat. In the subtropical gyre northwest of the Hawaiian Islands, opah generally inhabited a 50–400 m depth range and
8–22°C temperatures. They were frequently found in depths of 50–150 m at night and in greater depths (100–400 m) during the
day, but were constantly moving vertically within this broad range. At night, excursions below 200 m were not uncommon and
during the day they were very likely to spend some time at depths <175 m. Their vertical speeds were generally <25 cm s−1 but on one occasion an opah descended at a burst speed of 4 m s−1. Vertical habitat use by individual opah apparently varied with local oceanographic conditions, but over a 24-h period the
average temperature experienced was always in the narrow range of 14.7 to 16.5°C.
相似文献
Jeffrey J. PolovinaEmail: |
12.
Modeling and analysis of nest-site selection by honeybee swarms: the speed and accuracy trade-off 总被引:5,自引:2,他引:3
Nest-site selection in honeybees is a process of social decision making in which the scout bees in a swarm locate several
potential nest sites, evaluate them, and select the best one by means of competitive signaling. We develop a model of this
process and validate that the model possesses the key features of the bees' decision-making process, as revealed by prior
empirical studies. Next, we use the model to study the “design” of the nest-site selection process, with a focus on how certain
behavioral parameters have been tuned by natural selection to achieve a balance between speed and accuracy. First, we study
the effects of the quorum threshold and the dance decay rate. We show that evolution seems to have settled on values for these
two parameters that seek a balance between speed and accuracy of decision making by minimizing the time needed to achieve
a consensus and maximizing the probability that the best site is chosen. Second, we study the adaptive tuning of the tendency
of bees to explore for vs be recruited to a site. We show that this tendency appears to be tuned to regulate the positive
feedback process of recruitment to ensure both a reasonably rapid choice and a low probability of a poor choice. Finally we
show that the probability of choosing the best site is proportional to its quality, but that this proportionality depends
on its quality relative to other discovered sites.
相似文献
Thomas D. SeeleyEmail: |
13.
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: |
14.
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: |
15.
16.
Amanda S. Hering Cynthia L. Bell Marc G. Genton 《Environmental and Ecological Statistics》2009,16(2):225-250
We analyze and model the structure of spatio-temporal wildfire ignitions in the St. Johns River Water Management District
in northeastern Florida. Previous studies, based on the K-function and an assumption of homogeneity, have shown that wildfire events occur in clusters. We revisit this analysis based
on an inhomogeneous K-function and argue that clustering is less important than initially thought. We also use K-cross functions to study multitype point patterns, both under homogeneity and inhomogeneity assumptions, and reach similar
conclusions as above regarding the amount of clustering. Of particular interest is our finding that prescribed burns seem
not to reduce significantly the occurrence of wildfires in the current or subsequent year over this large geographical region.
Finally, we describe various point pattern models for the location of wildfires and investigate their adequacy by means of
recent residual diagnostics.
相似文献
Marc G. Genton (Corresponding author)Email: Email: |
17.
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: |
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 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: |
20.
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: |