Populations &Populations &SamplingSampling

PopulationPopulation

The number of species living in a particular place and a particular time

Population ecology looks at knowing the dynamics of species population and how they interact with the environment

Why is studying populations important?

Population SamplingPopulation SamplingTo obtain information on the abundance and distribution of a certain organism in a certain place and time

Can find out how dense a population is

How dispersed a population is within a habitat

Types of populations located within a habitat

Random SamplingRandom SamplingIt is almost impossible to count every individual organism

Random sampling is a way of obtaining an accurate representation of some spatial characteristics of the population without counting every organism

To ensue an adequate representation is obtained and eliminate bias

Typically undertaken in areas where the population is relatively uniform, large and limited time for data collection is available

QuadratQuadratTypically a square frame that allows comparable samples to be obtained from areas of constant type and shape

Allows you to sample percentage cover and abundance

Can be used in large and small sample areas

What are some advantages disadvantages?

Line TransectLine TransectUsed to illustrate a particular gradient or linear pattern along which a population change

Provides information on species present or absent in a habitat

Undertaken by unrolling a transect line along an identified gradient

Species touching the line can be recorded the whole length of the line

What are some advantages/disadvantages of this method?

Belt TransectBelt TransectSimilar to line transect but provides you with information on population abundance not just presence or absence

It can be considered as a widening of the line transect in a continuous belt with the aid of quadrate

Transect line is laid out with a quadrate placed at a marked point on the line. The species within the quadrate are identified and their abundance estimated

Whats an advantage/disadvantage of this?

Cover abundanceCover abundanceCover abundance is the measure of plant cover. Often based on percentages at the end but uses abundance estimates for species with a low cover plant cover

Cover abundanceCover abundance• Specht developed a system which has become

widely used both in Australia and overseas.• It is based on three elements:–First, identify the lifeform of the tallest stratum (or layer) of plants in an area (e.g., trees, shrubs, hummock grasses or other herbs). –Second, determine the height and/or type of vegetation in the tallest stratum (e.g., ‘trees over 30m’, or ‘shrubs, non-sclerophyllous’, etc.). –Third, determine the projective foliage cover of the tallest

stratum. This is the percentage of area which is covered by that foliage (leaves).

Closed > 70% < 10%

Open 30-70%

Open 10-30%

Foliage coverFoliage cover

YOUR TASKYOUR TASK

Determine the density and number of plant species as well as the presence and absence of plant species using a quadrate simulation online

Do the first one together

http://www-saps.plantsci.cam.ac.uk/ecology/siteA/