Life on Earth Activity for a National 5 Field Trip to TGTF
‘Life on Earth’ Activity for a National 5 Field Trip to TGTF
Using Bochastle car park as a base (NN 607081 or see map below). Bochastle is north of Callander approximately half a mile along A821. This site can be used to study a range of subjects within ‘Life on Earth’ and a ranger can be pre-booked to support outdoor activities.
The site is easy to find and has good parking for a minibus. The site is self-contained (difficult for pupils to get lost!) and safe. Having 3 main habitats within a few 100 metres is ideal for showing how man is influencing the environment.
On- site discussion topics
1)Biodiversity and the distribution of life
- Biotic and abiotic and human influences
Bochastle is an excellent location to tease out these three factors. On one site there is a (semi- natural) broad leaved wood, a planted pine wood (Larch) and open moorland. There is also a small burn which is suitable to study as a fourth habitat type, but only small groups of pupils can study this at one time.
Open moorland Larch forest floor Broad leaf forest
(low growing plants) (limited biodiversity) (Larch trees in background)
- Grazing and predation (biotic factors), pH and temperature (abiotic factors)
The western part of the open moorland is subject to grazing by deer and by cattle, and the eastern part is protected from grazing by a high deer fence.
pH tests of the three sites have been conducted and the results were found to be not as different as would be expected. It would be expected that the open moorland containing peat and heather and the Larch areas would be more acidic (lower pH) than the broad leaf area.
- Biomes
Comparing the three areas can show how the climax community which at this latitude should be a mixed wood is affected by grazing (moor) and by man (Larch plantation). Although not grazed now, the moorland was subject to extensive grazing throughout the 20th Century and sheep were only removed from the land in 2003. Pupils can see the evidence that this grazing has recently stopped by the young rowan and birch trees now becoming established.
- Ecosystem
Conducting some basic measurements e.g. quadrats, light measurements, pH soil testing, temperature and wind speed, pupils can see how biotic and abiotic factors affect each other. Examples from the site are given below.
Pupils can also discuss the many interrelationships between abiotic and biotic factors e.g. although a sapling may not grow until the canopy is opened by the death of a mature tree, having a wall of trees surrounding a sapling protects it from wind damage. Many pine trees can tolerate acidic soil (unlike a number of otherwise competing shrub plants or trees). The slow decomposition of dropped pine needles makes the soil more acidic making the local habitat more suitable to pine trees!
- Niche
The Great Trossachs Forest manages the land to create a mosaic of habitats. This management will improve and support a range of species which are currently in decline. One such species is the black grouse, which needs a mixture of open ground and woodland to be able to feed, breed and rear young. As a result of the returning woodland to this area, there are now an increasing number of black grouse leks across The Great Trossachs Forest.
At Loch Katrine, 12 hectares of non-native pine woodland is being retained in the native woodland corridor, as this patch of woodland supports a small red squirrel population. The non-native pines will only be felled when the surrounding trees have grown to a sufficient height and the red squirrels have moved into the wider area.
‘Green highways’ that link similar habitats are being developed across the area to allow species that exploit a particular niche in one habitat gain access to a wider area which makes the whole ecosystem more robust. An important consideration should long term changes to the climate start to make themselves felt (see climate change fact sheet).
2. Sampling techniques and measurement of abiotic and biotic factors
- Sampling plants and animals using quantitative techniques
Split the pupils into 3 groups with each group working on one of the sites: the broad leafed wood, the Larch wood or the Moor and then collate results. Splitting the groups into the three areas would give sufficient time tosample another site(s) or give each group roughly 20 minutes before rotating the groups.
On site activities
Abiotic Sampling- Temperature
You will need: Temperature Probes
Working in small groups use a temperature probe (not a glass thermometer!) to measure the temperature in each of the three sites. Take readings at chest height, at ground level and a few centimeters into the soil, above and under a rock or log to see if there are any noticeable differences in temperature as although a thermometer is not affected by wind chill there can still be temperature differences.
If the weather is sunny then compare the south aspect temperatures with those recorded to the north.
The purpose of this activity is to show,depending on the size of the organism and where specifically in the habitat that organism lives, micro-habitats will be exposed to different environmental conditions- even at the same site.
Note: Larch drops its needles in winter allowing the energy from winter sun to be reflected off any snowy ground but if average temperatures rise the growth of pine/spruce then trees will be favoured. As they hold onto their needles they continue to absorb sunlight energy in winter heating the surrounding area slightly. This is one of the many ‘positive feedback’ loops thought to play a part in climate change.
Abiotic Sampling- Wind Speed
You will need- Anemometer
Working in small groups,use an anemometer to record the wind speed in each of the three sites at chest height and at ground level.
Although it would be expected wind speed would rise the further from the broad leaved area to the Larch area with the highest speeds being recorded on the moor, further investigation is likely to reveal differences. For example record the wind speed in the open moorland in the lee of heather and just on top of the heather. Is there a difference between the value recorded at chest height?
Note: these wind speed variations can be an important factor governing ‘wind chill’ giving an advantage to animals that do not grow much taller than heather. This is in direct conflict with the basic ‘rule’ that the larger the organism is the smaller it’s surface area to volume ratio and hence the easier it is to keep warm. This is important to bear in mind when considering how animals survive in winter when high calorie food is scarce. Biodiversity within a habitat is therefore in part driven by different organisms finding different ‘solutions’ to maximize their chances of survival and passing on their genes.
Abiotic Sampling- pH
You will need- Soil pH testing kit
Barium Sulphate
Universal indicator
(ideally) de-ionised water + chart
Test tubes + Stoppers
Test tube rack
Take samples of the soil at the three different sites to see whether there are any noticeable differences in the soil pH values.
Fill the test tube to about 2 cm with soil. Keep the soil loosely packed. Add the same volume of Barium Sulphate i.e up to say 4 cm along the length of the tube. Now add roughly the same volume of water i.e. a further 4 cm. Add a few drops of universal indicator. Be careful when stoppering not to force too hard or you may break the test tube! Invert and lightly shake, leave to stand and then read the pH off the pH chart. It is good practice to take a plastic 'waste bottle' rather than pour the contents of the soil tests away on site. If you don't have easy access to de-ionised water you should be able to either buy a small bottle from a garage or use the water from defrosting your freezer BUT the local tap water is almost neutral so just use that if stuck.
Note: When taking samples in the broadleaved woodland, make sure that the sample is taken at some distance from the Larch wood to ensure that the reading truly relates to broadleaved woodland.
Abiotic Sampling- Humus Content
You will need-Plastic containers (and lids) to collect soil samples
Take soil samples whilst out at the three sites in The Great Trossachs Forest and then work out the humus content back in the lab. Care needs to be taken when collecting ‘soil’ at the Larch site. Make sure that your sample is actually soil and not semi-decomposed needles above the soil as this would give an artificially high reading.
In the lab the soil samples need to be dried at a low heat (use an oven/incubator) until they reach constant mass i.e. no loss in mass between two consecutive readings. This removes the mass of water which would otherwise affect the results simply depending on if there had been recent rain or not. Measure out 100g of dry sample into a metal dish before heating with a Bunsen.
Note: Especially with humus rich soil a lot of smoke is produced so use a fume cupboard or at least a well-ventilated lab. Take care not to set off the fire alarm if there are smoke detectors in a nearby corridor.
Loss in mass of dried soil before and after burning
Percentage Humus = ------X 100
Original (dry) mass of soil
Question: If the wet mass of soil figure was used, what difference would this make to the final figure?
Whilst calculating the humus content, you can also calculate the percentage water content:
Loss in mass (as water evaporates off)
Percentage Water = ------X 100
Original (wet) mass of soil
Note– Given the high rainfall in the Trossachs there may only be significant differences in water content if there has been no recent rain.
Abiotic Sampling- Soil Composition
You will need- Test tubes
Take three test tubes and half fill each one with a different soil sample. Fill the test tube with tap water (leave a little air space) and invert/shake. Leave to stand in a test tube rack. Look at the ratio of large/small sediment and organic materials as they will differ across the soil types.
Abiotic Sampling- Soil Moisture
You will need- Soil moisture meter
At all three sites, use a moisture meter to give comparative readings. Try different locations within a site to see whether there are any noticeable differences, such as compare north/south side of a tree or wall. Why do you think these differences occur?
Abiotic Sampling- Mineral content of soil
You will need- Dried soil sample (from activity above)
Back in the lab, using the soil samples which were collected on site and then dried, and use a hand lens or preferably a low powered microscope to look at the grains of crystals that make up the soil.
Abiotic Sampling- Light intensity
You will need- Light meter
Take a light reading in the car park or open moorland and use this as the ‘base’ intensity. Then in one of the wooded sites measure light above a leaf of a shrub (i.e. light that has already been transmitted by or escaped hitting the forest canopy) and then compare the light reading immediately under the leaf. This gives an approximation of the light absorbed by the leaf.
Note: Although you would expect there to be more light reaching the ground under the Larch trees than the broad leaf trees, the pH and richness of Rhizobial fungus (microscopic fungal threads which give the roots of plants a much greater surface area allowing them to absorb water and minerals more efficiently) is poorer in the Larch woodland. The presence of Rhizobial fungi allows great biodiversity. This is a significant factor allowing much greater ground cover/range of plants in the broad leaf forest than the Larch forest despite lower light levels reaching the ground.
Biotic Sampling- Quadrats
You will need- Quadrats
It is impossible to count all the plants in a habitat, so a sample needs to be taken. A technique that is often used to sample plants is a quadrat. It marks off an exact area so that the plants in that area can be counted (and identified).
Working in groups of two or three, randomly throw the quadrat on the ground within the study area and then count how many different plant species are within the quadrat's perimeter and an approximate percentage of ground cover. The quadrat can be secured with pegs at each corner to minimise movement. As a guide look at leaf shape, texture to differentiate between species. Alternatively use identification guides or books to help.
Biotic Sampling- Transect
You will need- 20m measuring tape
Using a 20 metre tape (or pacing) take a series of quadrats as you move from the Larch woodland habitat to the broad leafed habitat. Don’t ignore the forest track as very few plants will grow on the track which shows the human influence on the area.
Biotic Sampling- Pitfall traps
You will need-A Pitfall trap or container (eg yoghurt pot)
At the start of your visit, dig a hole in the ground deep enough for your pitfall trap to fit in at ground level- remember to count how many traps you have set and mark them with a stick so that you can find them later. The purpose of the traps is to collect small animals as the side of the trap will be too tall for them to escape, but they will be unharmed. Come back late in the day or next morning to count how many different kinds of animals you have collected and identify them if possible.
Note: Unless you are sure to return to the site and collect all traps you should not leave pitfall traps. Longworth traps should not be used under any circumstances unless you are expert in small mammal handling and care.
Biotic Sampling- Tullgren funnell
You will need- Soil sample to take back to lab
Take a soil sample back to the lab and set up the funnel. Use filter paper to strain the animals that fall through the sieve. Using a basic soil guide find out which ‘mini-beasts’ found in the soils or if it is not possible to identify them, then count the range of ‘mini-beasts’ that are present.
Biotic Sampling- Tree beating
You will need- A light coloured sheet
Place a light colored sheet under a branch of a tree. Shake the branch/hit the branch to dislodge ‘mini-beasts’. Use a field guide to identify some of the animals found or count the range of animals on the sheet.
Biotic Sampling- Pooters
You will need- A pooter
Use the pooter to ‘suck’ insects into the pooter and then identify them. Make sure that the insect is not too large for the pooter and be careful when approaching the insect as it may move away when it senses you approach.
Biotic Sampling- Pond netting
You will need- A pond net
In small groups at the small burn on site, use the net to see what lives in this aquatic habitat. You are likely to find Caddis fly larvae and water snails.
1 Biology: Field Based Activities
