Ecological Sampling

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Ecological Sampling
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• Measuring biotic components of a system

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Ecological Sampling

• What is a sample?
• A portion, piece, or segment that is
  representative of a whole
• Why do we sample?
• it is usually impossible to measure the whole

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One big assumption

• That the sample is representative of the whole
• It is necessary to take enough samples so that an
  accurate representation is obtained
• It is important to avoid bias when sampling

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Sampling Methods

• Transects and Quadrants
• Plants and Non-motile animals
• Lincoln Index
• Capture Mark- Recapture
• Small animals
• Aerial observations
• Large trees and animals

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Sampling along Transects

• Samples taken at fixed intervals
• Set up along an environmental gradient (e.g. high
  to low on a mountain)

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Line transect method

• A measured line laid across the area in the
  direction of the environmental gradient
• All species touching the line are be recorded
  along the whole length of the line or at specific
  points along the line
• Measures presence or absence of species

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Belt transect method

• Transect line is laid out and a quadrant is
  placed at each survey interval
• Samples are identified and abundance is estimated
• Animals are collected
• For plants an percent coverage is estimated
• Data collection should be completed by an
  individual as estimates can vary person to person

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Quadrats

• Used to measure coverage and abundance of plants
  or animals
• A grid of known size is laid out and all the
  organisms within each square are counted.

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Lincoln Index

• Capture-Mark-Recapture
• Animals are captured, counted, tagged and
  released.
• After a period of time another capture occurs.
• Previously tagged animals are counted and
  unmarked organisms are marked.
• Abundance is calculated using the following
  formula

n1 x n2 n3 n1total marked after catch 1
n1 x n2 n3 n2total marked after catch 2
n1 x n2 n3 n3total caught in catch 2 but marked in catch 1
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Measurements

• Sampling methods measure
• Density
• Coverage
• Frequency
• Biomass
• Diversity

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Density (D)

• The number of individuals per unit area
• Dni/A
• Eg. 10 dandelions/m2
• Relative density i (Rdi)
• The Density of species i, Di, Divided by the sum
  of all the densities of the other species sampled
• RdiDi/S D
• Eg. 10/5816

ninumber of individuals for species i
Athe area sampled (could be the volume V)
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Coverage (C)

• The proportion of ground that is occupied or area
  covered by the plant/species
• Ciai/A
• Relative coverage
• The Coverage of species 1, Ci, divided by the sum
  total of the coverage of the other species sampled

aithe area covered by species i
Athe total area
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Frequency (f)

• The number of times a given event occurs
• Eg. the number of quadrants that contain maple
  trees as a ration of all the quadrants
• fiji/k
• Relative frequency
• The frequency of species i relative to the sum
  total of the frequencies of the other species
  found

jinumber of quadrants with species i
ktotal number of quadrants
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Biomass (B)

• Can be calculated by measuring the mass of the
  individuals per unit area
• B S W/A
• More appropriate measure than density or
  frequency when
• Number of individuals in hard to determine
• Photosynthesis and carbon fixation, energy and
  nutrient transfer are more dependent upon biomass
  than the total number of individuals

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Biomass Measurement methods

• Fresh or wet weight
• Used when organisms are alive
• Dry weight
• Used when the water content varies greatly
• Oven dry at 105oC to remove water
• Ash-Free Weight
• Used when inorganic content varies greatly
• Oxidize at 500oC until only inorganic ash remains

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Diversity

• The measure of variety of an ecosystem
• Consists of 2 components
• The number of different species or the richness
  of species in a specific area
• The relative abundance of the individuals of each
  species in a specific area

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Simpson's Diversity (D)

• Measures species richness
• If D is high the area may be a stable ancient
  site.
• Low D may suggest pollution, recent colonization,
  or agricultural management

DN(N-1) S n(n-1) DDiversity
DN(N-1) S n(n-1) Ntotal number of organisms of all species found
DN(N-1) S n(n-1) nnumber of individuals of a particular species