On-Farm Experimentation into Canopy Light Capture, Photosynthesis and Soil Respiration

Read the course reader section 7 before the practical

Location at Camden Campus: Lansdown Farm, 74 Cobbitty Rd, Cobbitty

Background Information

In this practical (which includes the field experimentation at Camden, a computer lab, and the assessment) you will explore basic principles of plant physiology and (agro-) ecosystem function: sunlight capture by the plant’s “solar panel array” (the canopy), photosynthesis in individual leaves, the respiration in ecosystems, and the balance between C (carbon) gain and C loss (the C balance). The ideas underpinning this practical have been introduced in lectures.

The plant species grown for the field practical is a cereal, which is a grass grown for food or feed. The experimental site is Lansdowne farm at Cobbitty. The climate at Cobbitty is temperate and has an average annual precipitation of around 770 mm and an average annual temperature of 16.9 °C.

Aims of the practical

Brief

• Explore the relationships among leaf area, light interception, photosynthesis and the ecosystem C balance

Field

• Measure light interception at different heights in a crop canopy (stratified measurements)
• Measure the leaf area (stratified sampling and measurement) and calculate the leaf area index
• Measure photosynthesis in sun & shade leaves using a licor LI6400 gas exchange systems
• Measure soil respiration using a licor LI8100 soil respiration system

Computer lab

• Verify the description of light interception as given by the Lambert-Beer Law
• Determine the light-response of photosynthesis in sun and shade leaves
• Scale-up from leaf level photosynthesis to canopy scale assuming a “sunny spring-day” at Cobbitty
• Use estimates of leaf respiration and leaf area to calculate respiration of the crop canopy
• Use estimates of soil respiration to estimate heterotrophic respiration
• Determine the C balance of a cereal agro-ecosystem at Cobbitty

Report

• Explore and communicate why light capture and the C balance are important, and the links among light interception, photosynthesis, respiration, growth and the C balance
• Describe and explain the methods and approach used to address the aims of the practical
• Reflect on, and discuss, the results in the context of current big-picture issues

Travel

The travel time to Cobbitty can be up to 90 minutes, which is typical during peak-hours. This means for you to leave at 12:00 pm for the afternoon or at 8:00 am for the morning session.

We recommend car pooling as the most efficient way of travelling there. Please check with fellow students in the first 2-3 weeks of the semester and nominate how you are going to get to Lansdowne farm. You can also use Blackboard to offer, or ask for lifts. Please stick to your nominated travel plans so that we can ensure similar group sizes for all sessions.

Let us know by the end of week 3 if you have difficulties to arrange transport (Contacts: carina.moeller@sydney.edu.au and ivan.desailly@sydney.edu.au).

http://www.facilities.usyd.edu.au/maps/locations.shtml