Accuracy

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Accuracy Precision Efficiency
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Plant Sampling Issues

• Target
• Single species, Target species, Whole community
• Issues
• Spatial pattern, underlying gradients (affecting
  density).
• Extent Patches and patch boundaries.
• Differential size of individuals
• Clonal Growth
• Seasonal phenology, cryptic populations
• Strategies for estimation
• Plots 1 m2 10m2, 0.1 ha etc.
• Transects Gradsect
• Intercepts----grasses, cryptic species
• Distances point center, random distances
• What to measure
• Density, frequency, biomass (IV 300)
• Number of individuals

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Estimating Density through Counts
Confidence Interval 95 CI 1.96 x SE SE
SD / Sqrt(n)
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EDGE ISSUES When is a plant in, when is it
out? Reducing bias.
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How big should the plot be?
A nested plot sample can help determine an
appropriate sized plot (when surveying multiple
species).
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Clumping ADDS UNCERTAINTY
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Environmental Gradients add further uncertainty.
Solutions Stratified random sampling to make
sure that you capture samples from all
regions. Transects perpendicular to obvious
environmental gradients in order to sample across
the gradient (Gradsect sampling).
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DISTANCE MEASURES
Nearest Individual Density 10,000/ 2(Ave
distance (m))2
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DISTANCE MEASURES
Wandering Quadrat method Efficiency ease
allows sampling large areas
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Cover
Estimating cover
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Line Intercept Measuring cover
Measures cover, or a form of abundance by
measuring the distance along a transect line of
contact with that line. Cover distance abc /
total distance
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Point Intercept Measuring Cover
Variants 100 point pin frame
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Universally accepted protocol Diameter at Breast
Height 4.5 ft (1.37 m)
MEASURES OF SIZE, BIOMASS
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Diameter at Breast Height----- DBH----4.5 feet
above ground, but
Problems
International Society of Arboriculture
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Modified Whittaker Plot Design
Sampling multiple species with very different
sizes For example a forest with plants ranging
from canopy trees to mosses on the ground.
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Quail Ridge
Monday.
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