Estimating Density From Surveys Employing Unequal-Area Belt Transects

Stehman, Stephen V.; Salzer, Daniel

doi:10.1672/0277-5212(2000)020<0512:edfseu>2.0.co;2

Cited by 19 publications

(8 citation statements)

References 3 publications

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“…For smaller samples, normal confidence intervals underestimate true intervals by no more than 8% (Stehman & Salzer, 2000). In our trend analysis, small strata had few elephants and, therefore, contributed little to trend estimates (see below).…”

Section: Methodsmentioning

confidence: 99%

Continent-wide survey reveals massive decline in African savannah elephants

Chase¹,

Schlossberg²,

Griffin

et al. 2016

PeerJ

262

243

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African elephants (Loxodonta africana) are imperiled by poaching and habitat loss. Despite global attention to the plight of elephants, their population sizes and trends are uncertain or unknown over much of Africa. To conserve this iconic species, conservationists need timely, accurate data on elephant populations. Here, we report the results of the Great Elephant Census (GEC), the first continent-wide, standardized survey of African savannah elephants. We also provide the first quantitative model of elephant population trends across Africa. We estimated a population of 352,271 savannah elephants on study sites in 18 countries, representing approximately 93% of all savannah elephants in those countries. Elephant populations in survey areas with historical data decreased by an estimated 144,000 from 2007 to 2014, and populations are currently shrinking by 8% per year continent-wide, primarily due to poaching. Though 84% of elephants occurred in protected areas, many protected areas had carcass ratios that indicated high levels of elephant mortality. Results of the GEC show the necessity of action to end the African elephants’ downward trajectory by preventing poaching and protecting habitat.

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Section: Methodsmentioning

confidence: 99%

Continent-wide survey reveals massive decline in African savannah elephants

Chase¹,

Schlossberg²,

Griffin

et al. 2016

PeerJ

262

243

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“…Belt line transects are very commonly used in studies on the population biology of plants [17,18] and they result in more precise estimates of population size, even for rare organisms, compared with square meter quadrats [19]. Following the procedures described by Praptosuwiryo et al [5,20], the belt line transects were 20 × 250 m 2 in size with 20 × 25 m 2 subplots.…”

Section: Methodsmentioning

confidence: 99%

Population Study of the Golden Chicken Fern (Cibotium barometz (L.) J. Sm. in Riau Province, Sumatra

Praptosuwiryo

Puspitaningtyas

Pribadi

et al. 2017

JTLS

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Cibotium barometz (L.) J.Sm. (Cibotiaceae) is an important export commodity for both traditional and modern medicine. Populations of this species in several countries have decreased rapidly due to the uncontrolled collection of the rhizome parts for medicinal purposes. Since 1976, this species has been included in Appendix II of the Convention on International Trade in Endangered Species (CITES). This means that no export is allowed without a prior permit issued by the CITES committee. In order to utilize an endangered species sustainably, the global NDF (Non-Detriments Finding) system is applied for determining annual quotas. Therefore, monitoring and updating the inventory of C. barometz in its natural habitat should be carried out annually. A population study of C. barometz carried out in 2011 in Riau Province, Sumatra, is reported here. The aims of the study were: 1) to inventory C. barometz and determine its variation in Riau Province, Sumatra, 2) to study the distribution and ecology of C. barometz, and 3) to assess the population size of this species by using random search methodology incorporating belt line transects. Two variants of C. barometz are recognized; they are the golden yellow and golden brown variants. C. barometz is distributed in eight locations of Kampar District of Riau Province, in the secondary forest and rubber agroforest between 80 m and 600 m above sea level (asl). This species grows well in open to partially opened areas of secondary forest and rubber plantation in hills with a range of slope between 30° and 90°, with a relatively high humidity, 60 -90%, in acid to nearly neutral soil, with a range of soil fertility from very poor to very humus rich soil. The average population density determined in our study was 20 plants per 100 square meter. The highest population size was in the secondary forest of Bukit Kuda Beban at 590 -600 m asl., viz. 9405 plants with a population density of 47 plants per 100 square meter.

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“…For sampling with strips in an irregular-shaped area, the study area can typically be divided into M non-overlapping strips perpendicular to a baseline, having fixed width but unequal length. For estimation of population totals the above given expressions apply, but a ratio estimator considering the area of each strip might perform better (Stehman and Salzer, 2000).…”

Section: P Subsamplingmentioning

confidence: 99%

Sampling of Sparse Species with Probability Proportional to Prediction

Ringvall

Kruys

2005

Environ Monit Assess

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In this article, a 3P sampling (Probability Proportional to Prediction) approach is presented for surveying sparse species connected to certain types of substrates. The method uses the surveyor's judgement of the probability of finding the species on a substrate as the base for selection of substrates for species inventories. The method is presented together with estimators, variances and variance estimators. The method is first presented for sampling based on all substrates in a study area and then as a subsampling technique in a two-stage design in which plots or strips are selected in a first stage. The presented approach was evaluated as a subsampling technique in a strip survey of calicioid lichen species associated with coarse broadleaf trees. In comparison with a simple random subsampling without replacement, 3P subsampling was in one study area found to be an improvement with 30-55% in terms of standard errors. The improvement was more modest in the other study area, only between 10-16%. The strip survey with 3P subsampling was more cost-efficient than a strip survey without subsampling except in one case. Based on the results in the test, 3P sampling seems to have a potential for sampling sparse species.

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Estimating Density From Surveys Employing Unequal-Area Belt Transects

Cited by 19 publications

References 3 publications

Continent-wide survey reveals massive decline in African savannah elephants

Continent-wide survey reveals massive decline in African savannah elephants

Population Study of the Golden Chicken Fern (Cibotium barometz (L.) J. Sm. in Riau Province, Sumatra

Sampling of Sparse Species with Probability Proportional to Prediction

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