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The effects of fire and fragmentation on occurrence and flowering of a rare perennial plant

PLANT ECOLOGY 2011年第6期212卷 1057-1067页

作者： Barrios, Beyte Arellano, Gabriel Koptur, Suzanne Florida Int Univ Dept Biol Sci Miami FL 33199 USA Consejo Super Invest Cient Real Jardin Bot Madrid Spain

The pine rocklands of southern Florida are a fire-dependent forest associated with outcroppings of limestone. Pine rockland plants have several adaptations to fire, and for many species burns increase plant growth, flowering, and seedling establishment. The pine rockland forest has been reduced and fragmented in recent decades. Outside of Everglades National Park, only two percent of the original pine rocklands remain, and are in the form of small fragments. Habitat fragmentation may have a negative effect on the biology of plants;we investigated the effects of both fire and fragmentation on Angadenia berteroi (***.) Miers, a threatened species of the southern Florida pine rockland. We estimated the density and flowering of A. berteroi using adaptive cluster sampling in six study sites with different fire and disturbance histories. A. berteroi is more abundant in the largest fragments, and those having experienced fire most recently. However, fragmentation and lack of fire did not appear to have a great impact on flowering or fruit production. Insights from this threatened species may provide impetus not only to conserve, but to properly manage remaining pine rocklands in south Florida.

关键词： Angadenia berteroi Apocynaceae adaptive cluster sampling Reproductive phenology Pine rocklands

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adaptive and unequal probability survey designs for environmental management

Adaptive and unequal probability survey designs for environm...

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MSSANZ 19th Biennial Congress on Modelling and Simulation (MODSIM)

作者： Brown, Jennifer A. Salehi, Mohammad M. Moradi, Mohammad Panahbehagh, Bardia Smith, David R. Univ Canterbury Dept Math & Stat Christchurch 1 New Zealand

ISBN: (纸本)9780987214317

Designing an efficient large-area survey is a challenge, especially in environmental science when many populations are rare and clustered. adaptive and unequal probability sampling designs are appealing when populations are rare and clustered because survey effort can be targeted to subareas of high interest. For example, higher density subareas are usually of more interest than lower density areas. adaptive and unequal probability sampling offer flexibility for designing a long term survey because they can accommodate changes in survey objectives, changes in underlying environmental habitat, and changes in species-habitat models.

关键词： adaptive cluster sampling Two-phase sampling Stratified sampling adaptive two-stage sequential sampling Complete allocation stratified sampling

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adaptive Probability-Based Latin Hypercube Designs

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JOURNAL OF THE AMERICAN STATISTICAL ASSOCIATION 2011年第493期106卷 213-219页

作者： Hung, Ying Rutgers State Univ Dept Stat & Biostat Piscataway NJ 08854 USA

adaptive sampling is an effective method developed mainly for regular regions. However, experimental regions in irregular shapes are commonly observed in practice. Motivated by a data center thermal management study, a new class of adaptive designs is proposed to accommodate a specific type of irregular region. Because the adaptive procedure introduces biases into conventional estimators, several design-unbiased estimators are given for estimating the population mean. Efficient and easy-to-compute unbiased estimators are also introduced. The proposed method is applied to obtain an adaptive sensor placement plan to monitor and study the thermal distribution in a data center. All of the supplemental materials used in this work are available online.

关键词： adaptive cluster sampling Computer experiment Latin hypercube design Rao-Blackwell method Sequential design Space-filling design

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Effect of imperfect detectability on adaptive and conventional sampling: simulated sampling of freshwater mussels in the upper Mississippi River

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ENVIRONMENTAL MONITORING AND ASSESSMENT 2010年第1-4期170卷 499-507页

作者： Smith, David R. Gray, Brian R. Newton, Teresa J. Nichols, Doug USGS Leetown Sci Ctr Kearneysville WV 25430 USA USGS Upper Midwest Environm Sci Ctr La Crosse WI 54603 USA

adaptive sampling designs are recommended where, as is typical with freshwater mussels, the outcome of interest is rare and clustered. However, the performance of adaptive designs has not been investigated when outcomes are not only rare and clustered but also imperfectly detected. We address this combination of challenges using data simulated to mimic properties of freshwater mussels from a reach of the upper Mississippi River. Simulations were conducted under a range of sample sizes and detection probabilities. Under perfect detection, efficiency of the adaptive sampling design increased relative to the conventional design as sample size increased and as density decreased. Also, the probability of sampling occupied habitat was four times higher for adaptive than conventional sampling of the lowest density population examined. However, imperfect detection resulted in substantial biases in sample means and variances under both adaptive sampling and conventional designs. The efficiency of adaptive sampling declined with decreasing detectability. Also, the probability of encountering an occupied unit during adaptive sampling, relative to conventional sampling declined with decreasing detectability. Thus, the potential gains in the application of adaptive sampling to rare and clustered populations relative to conventional sampling are reduced when detection is imperfect. The results highlight the need to increase or estimate detection to improve performance of conventional and adaptive sampling designs.

关键词： adaptive cluster sampling Detection errors Freshwater mussels

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Estimating population size and habitat associations of two federally endangered mussels in the St. Croix River, Minnesota and Wisconsin, USA

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AQUATIC CONSERVATION-MARINE AND FRESHWATER ECOSYSTEMS 2010年第3期20卷 250-260页

作者： Hornbach, Daniel J. Hove, Mark C. Dickinson, Benjamin D. Macgregor, Kelly R. Medland, Jill R. Macalester Coll Dept Environm Studies St Paul MN 55015 USA Macalester Coll Dept Biol St Paul MN 55015 USA Macalester Coll Dept Geol St Paul MN 55015 USA Natl Pk Serv St Croix Natl Scen Riverway St Croix Falls WI 54024 USA

1. North America is a globally important centre of freshwater mussel biodiversity. Accurate population estimates and descriptions of critical habitat for endangered species of mussels are needed but are hindered by their patchy distribution and the dynamic nature of their habitat. adaptive cluster sampling (ACS) was used to estimate population size and habitat associations of two federally endangered species, Higgins eye (Lampsilis higginsii) and winged mapleleaf (Quadrula fragosa), in the St. Croix River. 2. This river holds the largest known winged mapleleaf population in the upper Mississippi River and contains Essential Habitat Areas for Higgins eye. Winged mapleleaf density ranged from 0.008-0.020 individuals m(-2) (coefficient of variation = 50-66%), yielding an estimate of 13 000 winged mapleleaf in this reach of the river. Higgins eye density varied from 0.008-0.015 individuals m(-2) (coefficient of variation = 66-167%) giving an estimate of 14 400 individuals in this area. 3. Higgins eye and winged mapleleaf were associated with areas of the overall highest mussel density and species richness, suggesting these endangered species occur in 'premier' mussel habitat. There were no differences in many microhabitat factors for sites with and without either endangered species. Select hydraulic measures (such as shear velocity and shear stress) showed significant differences in areas with and without the winged mapleleaf but not for Higgins eye. Areas that are less depositional support dense and diverse mussel assemblages that include both endangered species, with winged mapleleaf having a narrower habitat range than Higgins eye. 4. This study suggests that ACS can provide statistically robust estimates of density with 2-3 times more efficiency than simple random sampling. ACS, however, was quite time consuming. This work confirmed that of others demonstrating that larger-scale hydraulic parameters might be better predictors of prime mussel habitat than fine-scaled

关键词： endangered mussels adaptive cluster sampling mussel habitat population estimates

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Inventory of sparse forest populations using adaptive cluster sampling

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SILVA FENNICA 2006年第1期40卷 101-108页

作者： Talvitie, M Leino, I Holopainen, M Univ Helsinki Dept Forest Resource Management FI-00014 Helsinki Finland

In many studies, adaptive cluster sampling (ACS) proved to be a powerful too] for assessing rare clustered populations that are difficult to estimate by means of conventional sampling methods. During 2002 and 2003, severe drought-caused damage was observed in the park forests of the City of Helsinki, Finland, especially in barren site pine and spruce stands. The aim of the present study was to examine sampling and measurement methods for assessing drought damage by analysing the effectiveness of ACS compared with simple random sampling (SRS). Horvitz-Thompson and Hansen-Hurwitz estimators of the ACS method were used for estimating the population mean and variance of the variable of interest. ACS was considerably more effective than SRS in assessing rare clustered populations such as those resulting from drought damage. The variances in the ACS methods were significantly smaller and the inventory efficiency in the field better than in SRS.

关键词： adaptive cluster sampling simple random sampling drought damage coarse woody debris efficiency

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Efficiency of adaptive cluster and random sampling in detecting terrestrial herpetofauna in a tropical rainforest

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WILDLIFE SOCIETY BULLETIN 2006年第1期34卷 59-68页

作者： Noon, BR Ishwar, NM Vasudevan, K Colorado State Univ Dept Fishery & Wildlife Biol Ft Collins CO 80521 USA Wildlife Inst India Dehra Dun 248001 Uttar Pradesh India

We sampled forest floor herpetofaunal communities in a monsoonal rainforest in South India for three consecutive years to evaluate the use of cluster sampling in estimating species composition and density, Our initial experimental design consisted of comprehensive random searches of multiple 25m(2) quadrats (SRS) for animals. After our initial season we found that most quadrats had zero animals detected and, when encountered, animals were spatially aggregated. To increase sampling efficiency and derive more precise density estimates, we shifted to adaptive cluster sampling (ACS). We compared the relative sampling efficiencies of ACS to SRS and the ability of the 2 methods to detect rare species. adaptive cluster sampling failed to yield the more precise density estimates as predicted by statistical theory. However, ACS yielded more individual and rare species detections. Our results suggest the ACS assumptions should be carefully evaluated prior to use because it may not be appropriate for all rare, spatially aggregated populations.

关键词： adaptive cluster sampling amphibians India rainforest reptiles sampling efficiency simple random sampling species richness rainforest

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ASSESSING THE PERFORMANCE OF sampling DESIGNS FOR MEASURING ABUNDANCE OF UNDERSTORY PLANTS AFTER FOREST RESTORATION

ASSESSING THE PERFORMANCE OF SAMPLING DESIGNS FOR MEASURING ...

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作者： ILANA LAVINIA ABRAHAMSON University of Montana

学位级别：硕士

Accurate estimation of the responses of understory plants to natural and anthropogenic disturbance is essential for understanding efficacy and non-target effects of management and restoration activities. However, ability to assess changes in abundance of understory plants that result from disturbance may be hampered by inappropriate sampling methodologies. Conventional methods for sampling understory plants may be robust for common, well- distributed species, but may fail to adequately characterize the abundance of less-common species, which are often the taxa of management concern. I tested conventional and novel approaches to sampling understory plants to determine their efficacy (in terms of number of replicates and time required) for quantifying abundance of plants of varying frequency and spatial heterogeneity on three control and three thinned-and-burned treatment units located within the western Montana block of the Fire and Fire Surrogates Project (FFS) - a large- scale investigation of the effects of fuel-hazard reduction treatments on a variety of ecosystem components. In each treatment unit, I used four sampling methods (modified Whittaker plots, Daubenmire transects, point line intercept transects, and strip adaptive cluster sampling) to estimate the cover of 24 understory species that vary in abundance. Compared to Daubenmire and point line intercept transects, modified Whittaker plots estimated cover with the lowest variances and, consequently, for the majority (67%) of species required the smallest sample sizes to accurately measure cover. However, this greater sampling efficiency was offset by increased time required to sample. For species grouped by growth-form and for common species, all three conventional sampling designs (i. e. Daubenmire transects, modified Whittaker plots, and point line intercept transects) were capable of estimating cover with a 50% relative margin of error with reasonable sample sizes (3-36 plots or transects for growth- for

关键词： adaptive cluster sampling sampling design understory vegetation

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adaptive cluster sampling for estimation of abundances within local populations of low-abundance plants

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ECOLOGY 2005年第5期86卷 1091-1100页

作者： Philippi, T Florida Int Univ Dept Biol Sci Miami FL 33199 USA Florida Int Univ Coastal Everglades LTER Miami FL 33199 USA

Quantitative estimates of abundance for rare plants can be difficult, as the most widely used sampling techniques are ill-suited for rarity. adaptive cluster sampling (ACS) can take advantage of the spatial clustering common in rare plant populations to provide more efficient unbiased estimates of population sizes than simple random sampling. When plants are found in a quadrat, all adjacent quadrats are adaptively added to the sample. Despite this biased sampling, the Horvitz-Thompson estimator for adaptive cluster sampling provides unbiased estimates of population means or totals, and variances of those estimates. Because ACS disproportionately samples quadrats with plants, it can provide additional efficiency whenever further attributes of rare individuals need to be assessed, such as demographic parameters or genotypes. adaptive cluster sampling was performed on a population of Aletris bracteata, a moderately visible herbaceous species, in a savanna near Chekika, Everglades National Park, Florida. Both 1-m(2) and 4-m(2) quadrats provided reasonable estimates of the population size. The 1-m(2) sampling included 30-36% of the estimated total plants while sampling only 5% of the total area. The 4-m(2) sampling captured 78% of the estimated total population while sampling only 21% of the area.

关键词： adaptive cluster sampling Aletris bracteata Chekika population abundance rare plant sampling

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Two-stage adaptive cluster sampling

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Statistical Methods and Applications 2005年第1期14卷 3-10页

作者： Naddeo, Stefania Pisani, Caterina Università di Siena Dipartimento di Metodi Quantitativi Italy

adaptive cluster sampling is usually applied when estimating the abundance of elusive, clustered biological populations. It is commonly supposed that all individuals in the selected area units are detected by the observer, but in many actual situations this assumption may be highly unrealistic and some individuals may be missed. This paper deals with the problem of handling imperfect detectability in adaptive cluster sampling by using a pure design-based approach. A two-stage adaptive procedure is proposed where the abundance in the selected units is estimated by replicated counts. © Springer-Verlag 2005.

关键词： adaptive cluster sampling Imperfect detectability Replicated counts Two-stage estimation

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