
Wiegert’s Method?
 Pick the quadrat size or shape that minimizes the product of relative cost and
 relative variance

What size quadrat?
 want norm dist
 min edge effect
 different species different values per size quad
 easy to read
 costperson min/quadrat
 stat precision high

Hendrick's assumptions?
 1)
 Assumes that the slope of the line is between 0 and 1.
 •This
 is a very restrictive assumption, and if the slope is not within this range,
 the method can not be used
 2)
 Assumes that the amount of time to read a quadrat is directly proportional to
 size (i.e. 2m2 is twice as costly as 1m2).

What's different about Hedrick's Method?
 Pointed
 out that variance usually decreased with larger quadrat size.
 The
 log of variance will fall linearly with the log of the quadrat size.

Two approaches for picking size and shape quadrate?
Go to lit, do same as everyone else.
Better, do pilot study

Sampling design?
Method of placement
 Number of samples
 ..also think about gear (2 practical components)
 decided before hand

Best sampling design..
maximizes...
best...
smallest possible...
at lowest...
 efficiency
 statistical estimates
 confidence intervals
 cost

To determine a sampling design...
specify...
decide on...
select a...
 statistical pop
 sampling/experimental units
 sample and adopt a variety of sample plans

Simple random sampling?
2 things
 N sampling unit pop
 every one has equal chance
note: sampling with replacement better

Stratified random sampling?
 divided in subpops that don't overlap
 randomly sample within each sub pop

Strata?
 a subpop in a stratified random sample
 together make up entire pop

random versus simple random sampling?
 random=every indiv has equal chance
 simple random=every possible group has an equal chance

Benefits of Stratification?
get estimates of means and confidence intervals for each subpop
sampling problems can be addressed at each level
RESULTS IN GAIN OF PRECISE ESTIMATES FOR WHOLE
maybe more than one lab studying same..admin convenience

Systematic sampling?
regular or systematic placement of samples
simple and even, hopefully objective

problems with systematic sampling?
 periodic variation, not common though in ecology
 still good if looking for gradients, or if you need cheap and easy

centric systematic sample?
equal strata, sample in middle

Adaptive sampling? Why?
Take advantage of spatial pattern to get a better estimate of abundance.

Multistage sampling?
two or more levels of sample selection; 7 lakes primary, benthic areas of 10m2 is element

Cover? how is it expressed?
area of ground covered by plants, rock, litter, bare ground
percent

Four types of cover?
basal, canopy, foliar, ground

cover, indicator of 2 things...
 ecological processes
 (dominance)
managementerosion etc

cover is a good substitute for....
biomass; too hard and too much disruption.

Three general approaches to measuring cover?
Points, lines, plots/quadrats

3 Spatial patterns in nature?
 Aggregated (clumped)
 Uniform (regular or spaced)
 Random

poisson distributions resemble what kind of habitat distribution?
uniform

Negative k binomial distributions are like what in nature?
synonymous with aggregation

3 measures from Line Transect Sampling?
 sighting distance
 sighting angle
 perpendicular distance

Problems with Line transect sampling?
 detectability falls with distance
 undercount bias

Detection function?
estimate the zone of detectability, falls with distance

distance methods, 2 general approaches?
 random organism to nearest neighbor
 random point to nearest organism
 (object to object, or point to object)

problems with object to object and point to object approach in distance methods?
hard to pick a random organism
point to organism is biased towards isolated individuals

distance methods for plants?
n,n,p,r
 nearest neighbor
 pointcentered quarter
 nearest individual
 random pairs
there's more

