Designs for Detecting Trend from Repeated Surveys of Ecological Resources

Urquhart, N. Scott; Kincaid, Thomas M.

doi:10.2307/1400498

Cited by 100 publications

(104 citation statements)

References 6 publications

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“…If site location explains a substantial amount of variation, fixed sites will result in greater power than random sites (Urquhart and Kincaid 1999;Quist et al 2006). Conversely, trends from fixed sites may not be representative of regional trends, even when great care is taken with site selection (Stoddard et al 1998).…”

Section: Discussionmentioning

confidence: 99%

“…While estimating statistical power is fairly straightforward for simple survey designs, estimating power in complex designs requires more sophisticated techniques (Urquhart and Kincaid 1999;Larsen et al 2001). Surveys for larval DHP are hierarchically nested and include samples, subsamples, and sub-subsamples.…”

Section: Introductionmentioning

confidence: 99%

“…Increasing the sample size at levels of sampling with high variance will result in a survey design focused on minimizing variation, thereby maximizing the survey's power to detect changes in the population (Morrissey et al 1992;Larsen et al 2001). As a general rule, increasing the number of samples will result in a greater increase in power than increasing the number of subsamples or sub-subsamples (Urquhart and Kincaid 1999). However, increasing the number of samples is usually more cumbersome and costly than increasing subsamples.…”

Section: Introductionmentioning

confidence: 99%

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Using variance components to estimate power in a hierarchically nested sampling design

Dzul

Dixon

Quist

et al. 2012

Environ Monit Assess

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We used variance components to assess allocation of sampling effort in a hierarchically nested sampling design for ongoing monitoring of early life history stages of the federally endangered Devils Hole pupfish (DHP) (Cyprinodon diabolis). Sampling design for larval DHP included surveys (5 days each spring 2007-2009), events, and plots. Each survey was comprised of three counting events, where DHP larvae on nine plots were counted plot by plot. Statistical analysis of larval abundance included three components: (1) evaluation of power from various sample size combinations, (2) comparison of power in fixed and random plot designs, and (3) assessment of yearly differences in the power of the survey. Results indicated that increasing the sample size at the lowest level of sampling represented the most realistic option to increase the survey's power, fixed plot designs had greater power than random plot designs, and the power of the larval survey varied by year. This study provides an example of how monitoring efforts may benefit from coupling variance components estimation with power analysis to assess sampling design. Abstract We used variance components to assess allocation of sampling effort in a hierarchically nested sampling design for ongoing monitoring of early life history stages of the federally endangered Devils Hole pupfish (DHP) (Cyprinodon diabolis). Sampling design for larval DHP included surveys (5 days each spring 2007-2009), events, and plots. Each survey was comprised of three counting events, where DHP larvae on nine plots were counted plot by plot. Statistical analysis of larval abundance included three components:(1) evaluation of power from various sample size combinations, (2) comparison of power in fixed and random plot designs, and (3) assessment of yearly differences in the power of the survey. Results indicated that increasing the sample size at the lowest level of sampling represented the most realistic option to increase the survey's power, fixed plot designs had greater power than random plot designs, and the power of the larval survey varied by year. This study provides an example of how monitoring efforts may benefit from coupling variance components estimation with power analysis to assess sampling design.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Using variance components to estimate power in a hierarchically nested sampling design

Dzul

Dixon

Quist

et al. 2012

Environ Monit Assess

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“…Each year we sampled the annual panel of transects and one of the five alternating panels. This design allowed for sampling a relatively large overall number of transects over the 5-year sampling cycle (providing better representation of diverse habitats and regions in each park), while providing substantial year-to-year continuity in the dataset by sampling transects in the annual panel every year (Breidt and Fuller, 1999;Urquhart and Kincaid, 1999;McDonald, 2003). Spatially dispersed, random sampling locations were selected as transect starting points using the Generalized Random-Tessellation Stratified (GRTS) sampling method (Stevens and Olsen, 1999, 2003, 2004 with reverse hierarchical ordering.…”

Section: Large Park Sampling Schemementioning

confidence: 99%

Landbird trends in national parks of the North Coast and Cascades Network, 2005-12

Saracco¹,

Holmgren²,

Wilkerson³

et al. 2014

Open-File Report

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For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprodTo order this and other USGS information products, visit http://store.usgs.gov Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.Suggested citation: Saracco, J.F., Holmgren, A.L., Wilkerson, R.L., Siegel, R.B., Kuntz, R.C., II, Jenkins, K.J., Happe, P.J., Boetsch, J.R., and Huff, M.H., 2014, Landbird trends in national parks of the North Coast and Cascades Network, 2005-12 Horizontal coordinate information is referenced to North American Datum of 1983 (NAD 83).Elevation, as used in this report, refers to distance above the vertical datum. Landbird Trends in AbstractNational parks in the North Coast and Cascades Network (NCCN) can fulfill vital roles as refuges for bird species dependent on late-successional forest conditions and as reference sites for assessing the effects of land-use and land-cover changes on bird populations throughout the larger Pacific Northwest region. Additionally, long-term monitoring of landbirds throughout the NCCN provides information that can inform decisions about important management issues in the parks, including visitor impacts, fire management, and the effects of introduced species. In 2005, the NCCN began implementing a network-wide Landbird Monitoring Project as part of the NPS Inventory and Monitoring Program. In this report, we discuss 8-year trends of bird populations in the NCCN, based on a sampling framework of point counts established in three large wilderness parks (Mount Rainier, North Cascades, and Olympic National Parks), 7-year trends at Lewis and Clark National Historical Park (sampled in 2006, 2008), and 5-year trends at San Juan Islands National Historical Park (sampled in 2007. Our analysis encompasses a fairly short time span for this long-term monitoring program. The first 2 years of the time series (2005 and 2006) were implemented as part of a limited pilot study that included only a small subset of the transects. The subsequent 6 years (2007-12) represent just a single cycle through 5 years of alternating panels of transects in the large parks, with the first of five alternating panels revisited for the first time in 2012. Of 204 transects that comprise the six sampling panels in the large parks, only 68 (one-third) have thus been eligible for revisit surveys (34 during every year after 2005, and an additional 34 only in 2012) and can contribute to our current trend estimates. We therefore initiated the current analysis with a primary go...

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“…Although previous studies have compared various partial replacement designs with simpler designs (e.g., Urquhart et al 1993, Urquhart andKincaid 1999), none have incorporated a combination of temporally related factors such as changes in density, distribution, and spatial clustering. Kish and Scott (1971) investigated the ramifications of a changing population among strata over two time periods, but only looked into the specific example of selecting one primary unit per stratum.…”

Section: Plot Selection Across Timementioning

confidence: 99%

Comparison of Three Plot Selection Methods for Estimating Change in Temporally Variable, Spatially Clustered Populations.

Thompson

2001

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Abstract. Monitoring population numbers is important for assessing trends and meeting various legislative mandates. However, sampling across time introduces a temporal aspect to survey design in addition to the spatial one. For instance, a sample that is initially representative may lose this attribute if there is a shift in numbers and/or spatial distribution in the underlying population that is not reflected in later sampled plots. Plot selection methods that account for this temporal variability will produce the best trend estimates. Consequently, I used simulation to compare bias and relative precision of estimates of population change among stratified and unstratified sampling designs based on permanent, temporary, and partial replacement plots under varying levels of spatial clustering, density, and temporal shifting of populations. Permanent plots produced more precise estimates of change than temporary plots across all factors. Further, permanent plots performed better than partial replacement plots except for high density (5 and 10 individuals per plot) and 25% -50% shifts in the population. Stratified designs always produced less precise estimates of population change for all three plot selection methods, and often produced biased change estimates and greatly inflated variance estimates under sampling with partial replacement. Hence, stratification that remains fixed across time should be avoided when monitoring populations that are likely to exhibit large changes in numbers and/or spatial distribution during the study period.

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Designs for Detecting Trend from Repeated Surveys of Ecological Resources

Cited by 100 publications

References 6 publications

Using variance components to estimate power in a hierarchically nested sampling design

Using variance components to estimate power in a hierarchically nested sampling design

Landbird trends in national parks of the North Coast and Cascades Network, 2005-12

Comparison of Three Plot Selection Methods for Estimating Change in Temporally Variable, Spatially Clustered Populations.

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