SvS Biology 2000 - more than a food web

Measuring abiotic factors:

1. Salinity:

• Take 5mL water sample in test tube
• Add 3 drops AgNO3 (Silver Nitrate)
• Shake test tube
• Record amount of precipitation formed
• Develop a modified scale to reflect this quantitatively

2. pH:

• Take 5mL water sample in test tube
• Add 3 drops Universal indicator
• Shake test tube
• Compare colour with Universal Indicator colour chart
• Record pH (1-14)

    n.b.:  acids are lower range values, neutral = 7, bases are higher range values
            reds, oranges, yellows = acids
            green = neutral
            green-blue, blue = bases

3. Wind speed and direction:

• Using a modified Beaufort scale, assess the characteristics on a quantitative scale
• windsock, smoke, paper taper can be used to determine strength and speed of wind
• the angle of the windsock will be directly proportional to the wind strength
• the windsock will also show the direction the wind is travelling

4. Water content of soil:

• Dig out a soil sample from the ground
• Place onto plastic sheeting
• Weigh the mass of the soil
• Evaporate the water by spreading out the sample or placing in low heat convection oven
• Re-weigh the mass of the soil
• Subtract final weight from initial weight
• Record difference as soil water content (expressed as amount of water per initial soil weight)

Eg:     Initial weight: 3 kg
          Final weight: 2.4 kg
         Weight change: 0.6 kg
         Water weight in soil 0.6kg in 3.0kg soil&water [25% water content]

This will reflect the drainage of the soil, as well as elude to the soil particle size and type.

5. Water availability by precipitation:

• Use an open necked bottle
• tape a funnel securely to the bottle
• record the surface area over which the funnel will collect rain (pr²)
• leave for designated length of time
• measure amount of water collected in mL for the recorded time interval
• multiply the mL/area by the area of ecological study to determine total rainfall on that area

6. Light availability:

• measured using a photometer (what else?!?!?)
• units: usually kilolux

7. Temperature range:

• using a thermometer that sets at lowest and highest obtained values

8. Aspect:

• using a compass

9. Inclination:

• using plum-bob method with a protractor:
• extend protractor by attaching a longer, straight pole
• obtain string with weight at the end
• affix string to the midline of protractor
• hang vertically - gravity will therefore provide the mean position
• record angle produced where string bisects the protractor
• subtract this angle from 90 degrees to determine angle of incline

(alternately use a builder's spirit level)

BACK TO MODULE 8.2

Email me at: svs@radford.com.au to post questions

S. van Strien