Trees and watertables

Focus

This activity provides opportunities for students to analyse the importance of tree in the landscape, the long-term effects of overclearing, and how science can contribute to community understanding of problems and land management practices. Students investigate the effects of a rising watertable on the soil and plants in an area.

Science

Life and Living

5.3 Students evaluate consequences of interactions which occur between the living and non-living parts of environments.

Materials

Per group:

Teaching considerations

Watertables

This activity starts with some simple activities that illustrate two aspects of watertable management. The first activity shows how trees can lower the level of watertables by transpiration. The second activity shows how salt below the earth can be brought to the surface by a rising watertable. Both activities encourage students to consider the consequences of management strategies. Teacher guidance will be required to enable students to make the link between the activity and its implications for watertables (see Current scientific conceptions in the 'Background' section).

Plants

A number of different plants would be suitable for this activity. It is important that the seedlings are healthy, well grown and about the same size. Students will need to be encouraged to carefully preserve as many roots as possible when removing the soil from around them.

Open-ended investigations

Strategies for approaching experimental design are discussed in the sourcebook. A planning session is required to allow students to choose a problem, to design an initial experiment and to list the equipment required. Sufficient time should be given to laboratory assistants to prepare the equipment. If time allows, it is helpful for students to evaluate their initial experiments and to improve upon their original design.

Working scientifically

Time: 30 minutes in one lesson; 30 minutes in a follow-up lesson. Open-ended investigations can take up to a week.

Guided by the teacher, students brainstorm ideas about the effects that trees can have in a valley, and about land use practices. Questions could include:

Students then carry out experiments to develop a better understanding of the causes of soil salinity.

First, they set up five beakers, each containing 250 mL of water. They place one tomato seedling in each of four beakers. After 3 days (or an appropriate time for the conditions), the students remove the tomato seedlings and measure the amounts of water left in the beakers. Students calculate the difference between the remaining amounts of water in each beaker and explain the difference.

In the second experiment, students place about a millimetre of salt in the bottom of a 250 mL beaker and two-thirds fill the beaker with soil. They then fill the beaker with water to the level of the soil and leave it to evaporate. After an appropriate period of time, they make observations about the location of the salt in the beaker and draw conclusions about the role that this phenomenon may play in a catchment.

Working in groups, students discuss the questions at the end of Resource Sheet 5. Different groups can be selected to provide feedback to the whole class on particular questions.

Additional learning

Groups of students design experiments to test the effects of salty water on plants. Ideas for experiments could include:

Gathering information about student learning

Sources of information could include:

* Requires Adobe Reader

Last updated 2 August 2010

Catchment management