Flit's sampling_effort [23 articles]

Abstract

Species distribution models should provide conservation practioners with estimates of the spatial distributions of species requiring attention. These species are often rare and have limited known occurrences, posing challenges for creating accurate species distribution models. We tested four modeling methods (Bioclim, Domain, GARP, and Maxent) across 18 species with different levels of ecological specialization using six different sample size treatments and three different evaluation measures. Our assessment revealed that Maxent was the most capable of the four modeling methods in producing useful results with sample sizes as small ...

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Abstract

FAO never used its remote sensing survey to make estimates at the national scale, such as Bolivia. Rather, FAO used detailed forest inventory data supplied by each of 217 nations. Unfortunately, these national data include inherent limitations for multi-national and global assessments (FAO 2001, Stokstad 2001). Each nation optimises their own national forest inventory within their own funding constraints to address their own national issues, and the importance of international compatibility is rarely an important design criterion. Few tropical nations regularly ...

Abstract

Improved sampling designs are needed to detect, monitor, and predict plant migrations and plant diversity changes caused by climate change and other human activities. We propose a methodology based on multi-scale vegetation plots established across forest ecotones which provide baseline data on patterns of plant diversity, invasions of exotic plant species, and plant migrations at landscape scales in Rocky Mountain National Park, Colorado, USA. We established forty two 1000-m(2) plots in relatively homogeneous forest types and the ecotones between them on ...

Abstract

The size of a sampling unit has a critical effect on our perception of ecological phenomena; it influences the variance and correlation structure estimates of the data. Classical statistical theory works well to predict the changes in variance when there is no autocorrelation structure, but it is not applicable when the data are spatially autocorrelated. Geostatistical theory, on the other hand, uses analytical relationships to predict the variance and autocorrelation structure that would be observed if a survey was conducted using ...

Abstract

Landscape- and ecoregion-based conservation efforts increasingly use a spatial component to organize data for analysis and interpretation. A challenge particular to remotely sensed cover maps generated from these efforts is how best to assess the accuracy of the cover maps, especially when they can exceed 1000 s/km(2) in size. Here we develop and describe a methodological approach for assessing the accuracy of large-area cover maps, using as a test case the 21.9 million ha cover map developed for Utah Gap Analysis. ...

Abstract

To assess conservation priorities, a means of measuring the distribution of a much larger part of overall biodiversity is needed that will at the same time reduce the colossal sampling problems of exhaustive surveys. One possibility is a 'top-down' taxonomic approach, in which the biodiversity of different areas may be compared using measures based on the number of higher taxa present in each. The advantage of this approach is that survey costs should be greatly reduced because identification to species level, ...

Abstract

Oxford monographs on biogeography ; 3 ...

Abstract

We used a probabilistic approach to address the influence of sampling artifacts on the form of species?area relationships (SARs). We developed a model in which the increase in observed species richness is a function of sampling effort exclusively. We assumed that effort depends on area sampled, and we generated species?area curves under that model. These curves can be realistic looking. We then generated SARs from avian data, comparing SARs based on counts with those based on richness estimates. We used an ...

Abstract

The recognition of geographic patterns in biodiversity is of considerable interest to biologists and natural resource managers. A key component is the mapping of biodiversity, which combines cartographic procedures for vegetation mapping with biological models to predict biodiversity. An important example is the gap analysis project of the National Biological Service (Scott et al., 1993), which seeks to map the spatial distribution of vertebrate species richness and to identify gaps in the protection of species richness. This paper describes cartographic and ...

Abstract

In field measurement programmes, stratified sampling can optimize sampling efficiency, but stratification is often undertaken classification schemes such as those used for vegetation maps. In order to avoid the problems associated with a priori subjective schemes, we explore here an objective procedure, Regression Tree Analysis (RTA). RTA has previously been used in local-scale studies, but here we apply it to a very large study domain, namely the entire humid tropical zone of South America. The aim of the study was to ...

Abstract

This paper studies the problem of modelling fruit dispersal of anemochorous forest trees by the statistical analysis of fruit collections in traps. The statistical model of fruit dispersion and the choice of trap positions turn out to be very important. It is shown that the lognormal distribution of 'fruit-tree' distance seems to be of great practical interest. The trap positions have considerable influence on the precision of the estimates, particularly on the total number of fruits per tree ...

Abstract

Maps of wholesale species richness (numbers) are urgently required to guide the conservation of biodiversity. The problem is that complete counts of organisms are impractical at present. Indirect solutions are needed that will be both cheap and quick. One approach is to re-deploy sampling effort higher up the taxonomic scale, to measure richness among genera, tribes or families. Data for numbers of higher taxa have the advantage over data for species that they are usually not only more complete, but also ...

Abstract

10.1126/science.1070656 ...

Abstract

Given increasing access to large amounts of biodiversity information, a powerful capability is that of modeling ecological niches and predicting geographic distributions. Because, sampling species' distributions is costly, we explored sample size needs for accurate modeling for three predictive modeling methods via re-sampling of data for well-sampled species, and developed curves of model improvement with increasing sample size. In general, under a coarse surrogate model, and machine-learning methods, average success rate at predicting occurrence of a species at a location, or ...