Sampling is a set of ways in which scientists try to accurately estimate the total population in community based upon a limited number of individuals

This is done because in most real life scenarios it is not possible to capture, collect or view every organism at once or over a period of time. Look at a gram of healthy soil. One teaspoon of topsoil contains 5 billion bacteria in addition to all other organisms.

Sampling is an estimate. It gives a solid approximation but…there is still a margin of error.

D= n/s(area) Number ÷ Space = Population Density

Take a number of samples from around the sampling site so as to be reasonably sure that the samples represent the site in general

the samples represent the whole… It is necessary to take enough samples so that an accurate representation is obtained It is necessary to avoid bias when sampling

Type determined by the organisms and the physical nature of the habitat being sampled Area of ground surface Volume of air, water or soil Standard units enable comparison of results

Raw Mark Recapture Systematic Stratified Random

Raw Sampling Raw sampling assumes all individuals are evenly spaced throughout the habitat. No adjustment or allowances is made for differences in distribution. Count the individuals in a small area, the project to the entire area

Presence-absence Identify the presence or absence of a designated species This is the simplest method. And the least precise. It is only used in a an initial study to determine what species are there. It does not estimate population

Mark-recapture Mark-recapture allows for differences in distribution to be accounted for in a statistically significant method: (total number captured) X (number marked)/ total number marked recaptured

Often used when the area being studied is varied, not very large, or when time is available Samples are taken at fixed intervals

Systematic samples are usually taken along a transect line marked by a tape measure Transect- a line laid across an area

Transect Line A measured line is laid across the area in the direction of the environmental gradient The species touching the line can be recorded along the whole length of the line (continuous sampling) or at specific points along the line (systematic sampling)

Transect line is more accurate then raw sampling, and more appropriate then mark recapture for plants and slow moving organisms. It requires standard counting procedure, how far from the transect line individuals will be counted, abiotic conditions, and accurate mapping

Transect Line

Similar to line transect but widens the sampling area Transect line is laid out

Samples are taken by determining abundance or % cover in an area that is a defined distance from the line Samples can be taken all the way along the line, at specific intervals or even randomly

4. Beltline Transect A belt line transect is similar to a transect line except that it used alternating squares along a transect line to collect data from

4. Beltline Transect Gives good randomization of data Has a specific fixed area to collect data from It is time consuming to measure correctly and set up.

belt transects measure the quantities of vegetation (within a quadrate frame placed along the transect line) and a line transect used to record the vegetation at different points (useful in succession) So basically... belt = quantities of all vegetation in a % i.e ground coverage Line = species of vegetation present

Often used when there are small areas within a larger habitat that are clearly different Strata- major differences within communities recognized before sampling begins

Often used when the area being studied is fairly uniform, very large, or when there is a limited amount of time available Random = chosen by chance rather than according to a plan; all outcomes are equally likely Samples are taken from different positions within a habitat and those positions are chosen randomly

Choose individuals or Place “sampling units” haphazardly This is rarely completely random OR… Assign numbers to the areas or individuals to be sampled Use a random number table to select which areas or individuals will be sampled