Populations & Sampling

Population The number of individuals of a 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 Sampling To 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 species located within a habitat

Random Sampling It 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

Quadrat Typically 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 Transect Used 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 Transect Similar 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 abundance Cover 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 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 cover

YOUR TASK Determine the density and number of plant species as well as the presence and absence of plant species using a quadrat simulation online Do the first one together