Transcript Designing investigations

© Amy Rogers
© Amy Rogers
© Amy Rogers
Heathlands
Designing Investigations
© Amy Rogers
• Investigations can be classroom based ‘thought’
experiments or could be designed to be carried out
in the field.
© Amy Rogers
• Pupils could come up with their own investigation
topics after observing a site. Alternatively, the
following slides provides activity ideas. Click on the
investigation that interests you to find further
suggestions.
© Carl Corbidge
• Heathlands are excellent habitats to use for
designing and carrying out experiments. Plants are
often relatively easy to identify when compared
with other habitats and invertebrate communities
are usually diverse.
Key words for pupils
Encourage pupils to think about:
• Predictions, accuracy, reliability, dependent and
independent variables, random and systematic
errors, fair test/avoiding bias, validity;
• Presenting data, graphs, tables,
continuous/discontinuous variables;
• Data and experimental design limitations;
• Drawing conclusions, and the implications of the
findings.
Possible investigations – heathland plants
• Effect of trampling
• Effect of grazing
• Effect of different management techniques
• Effect of abiotic factors e.g., slope, soil pH, soil temperature, light,
soil water content
• Edge effects (the effect of distance from the heathland edge)
• Adaptations of heathland plants
• Competition between plant species
Click here for invertebrate activity suggestions
Possible investigations - invertebrates
• Which plants support the highest diversity of invertebrates
• Herbivore damage to plants
• Distribution of spider webs
• Pollinator visits to plants
• Invertebrate distributions - sweep netting
• Invertebrate distributions - quadrats
Click here for plant activity suggestions
• Effect of trampling on the abundance and diversity of heathland
plants
Procedure:
Human trampling may effect vegetation. The intensity of trampling is expected to decrease with
distance from a footpath. If there is a suitable footpath at the site, a transect could be run away
(perpendicular) from the footpath. Every metre along the transect a quadrat could be placed
and the % ground cover and average height of different plant species recorded.
Equipment:
Tape measure, quadrat (0.5 m x 0.5 m), plant identification key.
Notes:
Trampling may make it difficult for plant seedlings to become established. Some species may
be more susceptible to trampling then others. If grazing is taking place at the site trampling by
livestock may effect the results observed. The intermediate disturbance hypothesis states that
local species diversity should be greatest at intermediate disturbance levels.
Click to return to plant activity list
• Effect of grazing on the abundance and diversity of heathland plants
Procedure:
Livestock grazing is a common management technique on heathland sites. You may have a site
that has some areas that have been grazed and others that have been fenced off from livestock
and un-grazed. The vegetation of the two sites could be compared by sampling the same
number of quadrats at each site. Quadrats would need to be randomly placed. The % ground
cover and height of different plant species in each quadrat sample could be recorded.
Equipment:
Quadrat (0.5 m x 0.5 m), plant identification key, random number generator, tape measures.
Notes
Used appropriately, grazing is thought to increase species diversity and structural diversity of
vegetation at heathland sites. However, overgrazing or inappropriate stocking could result in
unexpected results.
Click to return to plant activity list
• Effect of different management techniques on the abundance and
diversity of heathland plants
Procedure:
Heathlands need to be actively managed to prevent succession. Common management
techniques include: controlled burning, grazing, turf removal, bracken bruising, chemical control
of bracken, mowing/cutting, tree removal. You may have a site, or nearby sites that have been
subjected to different management techniques. The vegetation of the two sites could be
compared by sampling the same number of quadrats at each site. Quadrats would need to be
randomly placed. The % ground cover and height of different plant species in each quadrat
sample could be recorded.
Equipment:
Quadrat (0.5 m x 0.5 m), plant identification key, random number generator, tape measures.
Notes:
Landowners should be able to inform you of current and past management practices at the site.
Click to return to plant activity list
• Effect of abiotic factors e.g. slope, soil pH, soil temperature, light, soil
water content on the abundance and diversity of heathland plants
Procedure:
A transect could be run along a known gradient e.g. down a slope, away from a tree with shading
branches. Quadrats could be taken at regular intervals along the transect and % ground cover and
height of vegetation recorded. Abiotic measurements could also be recorded for each quadrat
location, or soil samples collected for later analysis.
Equipment:
Ranging pole, optical clinometer, pH probe, thermometer, light meter, trowel for collecting soil sample
for later moisture analysis, tape measure, quadrat (0.5 m x 0.5 m), plant identification key.
Notes:
Students should be aware that it could be very difficult to distinguish between cause and effects of
some abiotic factors. For example, a change in pH could result in a change in vegetation composition
or, alternatively, some other factor may effect vegetation composition and the plants themselves may
then effect the soil pH e.g. by altering the composition of the leaf litter.
If you are carrying out soil chemistry tests or are planning to remove soil samples for later
testing you will need to obtain permission from the land owners.
Click to return to plant activity list
• How abundance and diversity of heathland plants varies with
distance from the edge of a heathland
Procedure:
A transect could be run from the edge of the heathland site towards the centre of the site.
Quadrats could be collected at regular intervals along the transect and the % ground cover and
height of vegetation recorded. Abiotic measures e.g. soil pH, soil nitrate level, light intensity,
could also be taken for each quadrat location.
Equipment:
Tape measure, quadrat (0.5 m x 0.5 m), plant identification key.
Notes:
Heathlands often display significant edge effects, this is particularly true of smaller sites. For
more details see:
http://www.biw.kuleuven.be/lbh/lbnl/ecology/pdf-files/pdf-art/katrien/AEEdef.pdf
Click to return to plant activity list
• Adaptations of heathland plants
Procedure:
Many plants inhabiting heathland sites are xerophytes and provide a good opportunity to investigate
adaptations to water loss. Sloping sites may provide a particularly interesting opportunity as at the top
of a slope drainage is more efficient and the soil moisture content will be lower than at the bottom of
the slope. The effect will be more pronounced on south facing slopes. Species composition and
morphological characteristics e.g. leaf surface area could be compared along a moisture gradient.
The leaves of bilberry plants show morphological differences depending on whether they occupy the
shade or sunny side of heather bushes and could be a good topic of investigation if they are present
at your site.
Notes:
Drier soil will be dominated by heather and bell heather, gorse (with needle-like leaves) and invading
bracken. Wet heath at the bottom of slopes will be dominated by cross leaf heath (as opposed to bell
heather) and mosses, particularly Spaghnum mosses, will be more abundant. NB: In addition to it
being drier at the top of slopes, nutrient levels will be lower at the top of a slope as nutrients are
leached away with draining water.
Click to return to plant activity list
• Competition between plant species
Procedure:
Some species that are characteristic of heathlands, e.g. heather, are relatively slow growing
and particularly susceptible to interspecific competition with faster growing species such as
bracken. If the site has areas with different densities of bracken, pupils could see if there was a
relationship between the average distance between bracken plants (i.e. bracken density) and
the amount of heather present. Alternatively, students could see if there is a relationship
between the size of heather bushes and the distance separating them from the nearest bracken
plant.
Equipment:
Tape measure, pegs/tape to mark out large quadrats.
Notes:
Bracken is known to produce and release allelopathic chemicals which inhibit the growth of
other plants.
Click to return to plant activity list
• Which plants support the highest diversity of invertebrates
Procedure:
Students could investigate particular plants e.g. heather vs bracken to determine which plant
species supports a more diverse range of invertebrates. Plants could be searched for a similar
amount of time and any invertebrates found identified and recorded in a table.
Equipment:
Pooter, dustpan and brush, paintbrush, sweep net, collecting pots, stopwatch, invertebrate
identification guide.
Notes:
Encourage students to control for as many variables as possible e.g. to choose plants of similar
size/surface area when making comparisons between species.
Click to return to invertebrate activity list
• Herbivore damage to plants
Procedure:
Students could look for evidence of insect herbivory in order to compare the amount of damage to different
plant species or the amount of damage to the same species in different locations (e.g. damage to heather
plants in the centre vs the edge of the site).
The following resource provides information about the different categories of invertebrate herbivores e.g.
cutters, grazers, miners, skeletonisers, galls with examples of the type of invertebrate that were probably
responsible for the damage observed:
http://australianmuseum.net.au/Uploads/Documents/16435/H2D%20field%20guide.pdf
This website provides a useful way to record the extent of herbivore damage to leaves
http://australianmuseum.net.au/document/Herbivore2Damage
Equipment:
Hand lens, invertebrate guide, leaf damage score sheet.
Notes:
The most important herbivores of heather, in terms of biomass, are the larvae of moths and butterflies. More
than 100 UK species of moth caterpillars have been recorded feeding on heather e.g. ling pug, common
heath, and northern eggar. The most damaging invertebrate herbivore found on heather is the heather
beetle. Outbreaks can lead to the death of large areas of heather.
Click to return to invertebrate activity list
• Distribution of spider webs
Procedure:
Pupils can investigate the distribution of spider webs within and between different plant species.
They could investigate a single plant species (for example, heather) and try and correlate
factors (e.g. height above ground, aspect, surrounding vegetation type) with the abundance of
spiders webs. Alternatively they could compare different plant species to see if spiders favoured
different species when constructing webs or whether different species of spider/types of web
were associated with different plants.
Equipment:
Fine misting water spray to see webs more clearly, plant identification guide, spider
identification guide, hand lens, tape measure.
Notes:
More species of spiders are found living on lowland heathland than any other habitat, including
the ladybird spider, one of the rarest spiders in Britain.
Click to return to invertebrate activity list
• Pollinator visits to plants
Procedure:
Students can investigate pollinator visits to heathland flowers (e.g. heather). In particular
students could compare different flower species, shapes, colours, sizes and/or arrangements
(i.e., clumped flowers vs. isolated flowers) to see if there is a difference in the species of
pollinator the flowers receive, how often the flowers are visited by likely pollinators, and how
long the pollinators stay on different flowers.
Equipment:
Stopwatch, invertebrate identification guide.
Notes:
The most effective pollinators of heather are honey bees and bumblebees. Other insects such
as wasps, flies, butterflies and moths also act as pollinators.
Click to return to invertebrate activity list
•
Invertebrate distributions - sweep netting
Procedure:
Pupils could sample invertebrates using sweep nets. Comparisons could be made between
different areas within the same site or along transects e.g. from the centre to the edge of a site.
Pupils will need to ensure they put the same amount of effort into sampling if they are
comparing different sites e.g. same number of sweeps, same amount of time in different
locations. Pupils should also measure abiotic factors for each sample. Abiotic factors, such as
light intensity, could be an important factor in the abundance and diversity of invertebrates
found.
Equipment:
Sweep nets, invertebrate collecting pots, invertebrate guide, stop watch, tape measure, light
meter.
Notes:
This sampling method is likely to favour collection of the invertebrate orders Homoptera (true
bugs), Orthoptera (grasshoppers and crickets) and Araneae (spiders).
Click to return to invertebrate activity list
• Invertebrate distributions – quadrats
Procedure:
Pupils could sample invertebrates using quadrats. Quadrats could be randomly placed within a
site, used to compare two different areas within a site, or used to sample along a transect (e.g.
from the centre to the edge of a site, along a slope, or away from a footpath).
Equipment:
Quadrat, invertebrate collecting pots, invertebrate guide, random number generator, tape
measures, white tray for leaf litter sampling.
Notes:
This method of sampling is likely to miss quicker flying invertebrate species.
Click to return to invertebrate activity list