4.2 biodiversity

-uses the organisms that are available

-may not be representative

-e.g. walking through a wood and counting the number of birds

-divides the environment or population into pre-agreed subgroups

-samples proportionally from each layer

-e.g. if riverbanks make up 20% of a meadow ecosystem, 20% of the areas sampled should be riverbanks

-carried out at regular intervals

-quadrats can be placed on a grid laid over a map or plan of an area at predetermined points

-alternatively, quadrats can be laid down at regular intervals along a rope or tape stretched across a habitat in a straight line

-proportion of quadrat’s area occupied by the species

-grids can help with estimates

-use a point frame within a quadrat

-include bare ground

-ACFOR scale: abundant, common, frequent, occasional, rare

-species frequency: proportion of quadrats with the species present

-observation

-observation of signs left behind (pellets, droppings, footprints)

-catch or trap animals and estimate number from the trapped sample

-walk through a habitat with a net and sweep the net through the vegetation in wide arcs

-small animals such as insects will be caught and then identified

-works to take samples in water and in low vegetation

-collecting from trees using a sweep net is unlikely to work

-in this case you place a sheet under a branch and knock it with a stout stick

-then quickly identify

-to use a pooter, suck one of the straws on an area containing invertebrates

-the invertebrate will then get sucked through the other straw into the sealed container

-bias by choosing animal to capture

-a pitfall trap is set in the soil to catch small animals

-the rim of the container must be just below the surface. animals moving on the soil surface will fall in

-the trap must contain a little water or scrunched paper to stop the animals escaping

-in wet weather it must be sheltered

-a Tullgren funnel collects animals from leaf litter

-you put the leaf litter in a funnel with a light on it. This drives the animals downwards. they will then fall through the mesh screen

-Put some bait into the trap

-As the animal enters to reach the food the trap closes behind it

-Small hole to release unintended animals

-do not leave too long without checking

-once you have trapped them you can calculate estimates

1. first you capture sample

2. mark each individual in some way that causes no harm. the number captures is C1

3. release the animals and leave the traps for another period of time

4. the number capture this time is C2. the number of already marked animals is C3

-then you can calculate your estimate

total population = C1 x C2/C3

-the estimate can be effected by animals learning about the traps

birds are estimated by a ringing technique and larger mammals can be tagged.

most animal studies require permits

number of species present in the study area

measure the abundance of individuals in each species

measure of biodiversity taking into account species richness and species evenness