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Sampling Methods
You will be visiting Rotokare Scenic Reserve to collect your data from a lowland forest habitat- keep this in mind as you learn about the different sampling methods. Go back to the assessment information for more information on what you are investigating and Rotokare Scenic Reserve. You will need to select the appropriate sampling method to enable you to gather both abiotic and biotic data.
BIOTIC DATA
It is usually difficult to count all the members of a population (census), so instead a sample is taken. The sample needs to be representative (typical) of the whole population.
Sample areas must be chosen randomly. Either by dividing the habitat into a grid, or using random numbers to obtain grid coordinates. Or by using random numbers to determine the distance into the habitat to survey. This will avoid BIAS
Mark, Recaputre
Mark, Recaputre
Quadrats
Quadrats
Transects
Transects
When carrying out a transect in the forest, collecting data to determine tree height and diameter is possible - see below for more information.
Measuring Heights
Using a clinometer look through the site and aim it with the top of the tree. Press the triger and record the angle.
You also need to measure the distance in meters from where you stand to the tree you are measuring.
Finally you will need to know the eye height of the person recording the angle.
With these three pieces of data the height of the tree can be calculated.
ANSWER
ANSWER
ANSWER
ANSWER
Measuring Tree Diameter
ABIOTIC DATA
You will take a range of abiotic measurements while on the field trip, think about why you are taking these measurements, and how they relate to the pattern you are looking for. How many measurements should you take?
Light Intensity: The unit used for light intensity is lux
Think about how light intensity would be an important factor for plants in a forest community. How might different levels of light be limiting? Refer back to plant adaptations to help develop your ideas of what you might see in a forest ecosystem.
Temperature: The unit used for temperature is °C
is linked with other abiotic factors in the forest such as light intensity and humidity. Think about what you know about photosynthesis, how could this effect the temperature also.
Temperature changes could influence the plants living in a forest ecosystem, and the adaptations those plants may have
Humidity: this is measured as a %
Relative humidity is a measure of how much moisture is in the air, and is usually measured as a % (saturation of water: air). Again think about the process of photosynthesis - why would we see variable humidity rates in a forest ecosystem
PROCESSING THE DATA
Depending on the sampling method presenting the data can be done either by a profile or kite diagram
A profile diagram is a visual representation of data - in this case, it aids in detecting an ecological pattern. It is particularly useful for determining forest stratification
A profile diagram doesn't require a lot of artistic ability, you will need to differentiate between the different tree and plant species, the shape of the foliage is a simple way to differentiate (ovals, triangles, etc). You can create a key or if room label each one. On the Y axis will be the heights you measured or calculated from your clinometer data and the x-axis will represent your transect. At every meter, you will draw in a plant or tree.
PROFILE DIAGRAM PRACTISE
- You are required to use the scientific names for the species, these are a mix of common European and Maori names
- You will need to add other details to the diagram, such as the climbing and perching species (epiphytes and lianes)
- Remember that some of these individuals are juveniles - for example, Nikau is a sub-canopy species, however, at the 20m mark a juvenile plant was measured at just 1m.
A kite diagram is a good choice if you are wanting to compare how often a certain organism occurs along a transect. It is a great choice when looking at the pattern of zonation.
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