Test of Observer Variability in Measuring Riparian Shrub Twig Length

Hall, Frederick C.; Max, Timothy A.

doi:10.2307/4003634

Cited by 13 publications

(11 citation statements)

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“…Percentage of browsed stems was determined for each plant by estimating the number of browsed leaders or stems and dividing by the total number of stems. The number of observers was limited to reduce the variability in observer measurement of browse (Hall and Max, 1999). Crown area was calculated by multiplying the two crown widths.…”

Section: Study Areamentioning

confidence: 99%

INFLUENCE OF HERBIVORY ON REGROWTH OF RIPARIAN SHRUBS FOLLOWING A WILDLAND FIRE¹

Dwire

Ryan

Shirley

et al. 2006

J American Water Resour Assoc

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Streamside vegetation frequently regenerates faster than upland vegetation following wildland fire and contributes to the recovery of riparian and stream ecosystems. Limited data are available, however, on the post‐fire growth of riparian species and the influence of herbivory on regeneration. To determine post‐fire regrowth of riparian vegetation, height, crown area, crown volume, and browse levels were measured for key riparian shrub species in streamside burned and unburned plots along second‐order streams in western Wyoming. Shrubs in the burned plots were subject to high levels of browse ‐ up to 84 percent of the leaders were browsed ‐ by native ungulates in 2002, the second post‐fire year (September 2001 to September 2002). In summer 2003, the burned watershed was also grazed by livestock, resulting in increased browse levels and decreased shrub heights for several species. In the third post‐fire year, September 2002 to September 2003, four of the six most common species showed no increase in crown area or crown volume, indicating that the combination of native ungulate and cattle browsing suppressed their growth. Potential impacts of grazing on post‐fire recovery of stream and riparian ecosystems are discussed.

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Section: Study Areamentioning

confidence: 99%

INFLUENCE OF HERBIVORY ON REGROWTH OF RIPARIAN SHRUBS FOLLOWING A WILDLAND FIRE¹

Dwire

Ryan

Shirley

et al. 2006

J American Water Resour Assoc

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“…Recent studies have shown that it is extremely difficult and time consuming to accurately measure utilization (browsing) impacts on many riparian shrubs (Hall 1999 There generally is a reduction in seed production on those plants that have utilization values above 55 percent. There can be a reduction in the overall health of plants, including size and root strength, when heavy and severe utilization levels are sustained over time.…”

Section: Deathmentioning

confidence: 99%

Monitoring the vegetation resources in riparian areas

Winward¹

2000

123

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___________________________________________This document provides information on three sampling methods used to inventory and monitor the vegetation resources in riparian areas. The vegetation cross-section method evaluates the health of vegetation across the valley floor. The greenline method provides a measurement of the streamside vegetation. The woody species regeneration method measures the density and age class structure of any shrub or tree species that may be present in the sampling area. Together these three sampling procedures can provide an evaluation of the health of all the vegetation in a given riparian area.

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“…Hall and Max (1999) studied the differences among 15 observers who assessed utilization by measuring twig length and found that observer variability was twice the size of variability among shrubs. Thorne and others (2002) found statistically significant differences among observers for a shrub canopy volume method, although estimates from a single observer were not statistically different.…”

Section: Woody Species Regeneration Methodsmentioning

confidence: 99%

“…A study of twig length measurement found that 20 percent of the total variation was due to the observer, leading the researchers to "seriously question the feasibility of measuring riparian shrub utilization" (Hall and Max 1999). A study of precision in estimating willow canopy volume found an average CV of 25 percent, indicating large differences among observers, although variability was lower for a single observer (Thorne and others 2002).…”

Section: Introduction ____________________mentioning

confidence: 99%

An Assessment of Metrics to Measure Seasonal Variation in and Grazing Effects on Riparian Plant Communities

Laine

Kettenring

Roper³

2015

Western North American Naturalist

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______________________________________Tests were conducted to evaluate variability among observers for riparian vegetation data collection methods and data reduction techniques. The methods are used as part of a largescale monitoring program designed to detect changes in riparian resource conditions on Federal lands. Methods were evaluated using agreement matrices, the Bray-Curtis dissimilarity metric, the coefficient of variation, the percentage of total variability attributed to observers, and estimates of the number of sites needed to detect change.Community type (CT) cover data differed substantially among the six to seven observers that sampled the same sites. The mean within-site similarity in the vegetation data ranged from 40 to 65 percent. Converting CT data to ratings (bank stability, successional, and wetlands ratings) resulted in better repeatability, with coefficients of variation ranging from 6 to 13 percent and a percentage of variability attributed to observers of 16 to 44 percent. Sample size estimates for the ratings generated from CT cover data ranged from 56 to 224 sites to detect a change of 10 percent between two populations. The woody species regeneration method was imprecise. The effective ground cover method was quite precise with a coefficient of variation of two, but had so little variability among sites that statistically significant change in this attribute would not be expected. In general, reducing the CTs to ratings increased precision because of the elimination of differences among observers that were not important from the perspective of the rating.Studies that seek to detect change at a single site would need to take into account the observer variability described here. Studies that seek to detect differences between populations of sites could detect relatively large changes with these methods and ratings. Small differences among populations would be difficult to detect with a high degree of confidence, unless hundreds of sites were sampled.

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Test of Observer Variability in Measuring Riparian Shrub Twig Length

Cited by 13 publications

References 0 publications

INFLUENCE OF HERBIVORY ON REGROWTH OF RIPARIAN SHRUBS FOLLOWING A WILDLAND FIRE¹

INFLUENCE OF HERBIVORY ON REGROWTH OF RIPARIAN SHRUBS FOLLOWING A WILDLAND FIRE¹

Monitoring the vegetation resources in riparian areas

An Assessment of Metrics to Measure Seasonal Variation in and Grazing Effects on Riparian Plant Communities

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Test of Observer Variability in Measuring Riparian Shrub Twig Length

Cited by 13 publications

References 0 publications

INFLUENCE OF HERBIVORY ON REGROWTH OF RIPARIAN SHRUBS FOLLOWING A WILDLAND FIRE1

INFLUENCE OF HERBIVORY ON REGROWTH OF RIPARIAN SHRUBS FOLLOWING A WILDLAND FIRE1

Monitoring the vegetation resources in riparian areas

An Assessment of Metrics to Measure Seasonal Variation in and Grazing Effects on Riparian Plant Communities

Contact Info

Product

Resources

About

INFLUENCE OF HERBIVORY ON REGROWTH OF RIPARIAN SHRUBS FOLLOWING A WILDLAND FIRE¹

INFLUENCE OF HERBIVORY ON REGROWTH OF RIPARIAN SHRUBS FOLLOWING A WILDLAND FIRE¹