1. Measuring biotic components of a system
Ecological Sampling
Measuring biotic components of a system

2. 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

3. 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

4. Sampling Methods Transects and Quadrants Lincoln Index
Plants and Non-motile animals
Lincoln Index
Capture –Mark- Recapture
Small animals
Aerial observations
Large trees and animals

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

6. 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

7. 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

8. 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.

9. Lincoln Index Capture-Mark-Recapture n1 x n2 n3
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
n1=total marked after catch 1
n2=total marked after catch 2
n3=total caught in catch 2 but marked in catch 1

10. Measurements Sampling methods measure Density Coverage Frequency
Biomass
Diversity

11. Density (D) The number of individuals per unit area
D=ni/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
Rdi=Di/S D
Eg. 10/5+8+16
ni=number of individuals for species i
A=the area sampled (could be the volume V)

12. Coverage (C)
The proportion of ground that is occupied or area covered by the plant/species
Ci=ai/A
Relative coverage
The Coverage of species 1, Ci, divided by the sum total of the coverage of the other species sampled
ai=the area covered by species i
A=the total area

13. 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
fi=ji/k
Relative frequency
The frequency of species i relative to the sum total of the frequencies of the other species found
ji=number of quadrants with species i
k=total number of quadrants

14. 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

15. 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

16. 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

17. 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
D=N(N-1)
S n(n-1)
D=Diversity
N=total number of organisms of all species found
n=number of individuals of a particular species