C1.3.8 Carbon Dioxide Enrichment Experiments as a means of predicting future rates of photosynthesis and plant growth

What is the purpose of carbon dioxide enrichment experiments?

understand how atmospheric increase in CO2 concentrations will..

• affect photosynthesis rates and plant growth

• whether carbon lock up by increased biomass will moderate its rise

What are the 2 main kinds of carbon dioxide enrichment experiments?

• enclosed greenhouse experiments

• free-air carbon dioxide enrichment experiments (FACE)

describe the enclosed greenhouse experiments (variables, findings, application)

• variables: CO2 concentrion (IV), temp and light intensity are both controlled (CV)

• Findings: inc CO2 -> inc rate of photosynthesis and plant growth

• Application: growing tomatoes

describe how FACE is carried out and its two series

Series 1: plant growth in agricultural crops and young tree plantation

Series 2: natural or semi-natural forests

 

Circles of towers

• Release either CO2 (exp) or air (control condition)

• CO2 con. is monitored. When too low, CO2 is released on upwind side to it blows into the circle

distinguish between controlled variables and control experiments

Control experiment ("just control"): any obj or system used as a standard of comparison in an experiment, to allow the experimenter to assess significance of a variable

Controlled var. : any factor that can vary but which is kept the same in all parts, so X impacts outcomes

Give an example of a control experiment / just control

Use of a denatured enzyme in an enzyme experiment to show catalysis is involved

FACE: condition where towers release air, not CO2

contrast lab and field experiments

• lab - better control, but only in the lab

• field - lower control, more ecological validity, X causation. some experiments can only be done in field (ethical issues, ecology, structured observations)