MadSci Network: Botany

Re: Which tree produces more oxygen? A young vigorous growing tree or

Date: Sun Jul 30 11:30:47 2000
Posted By: Richard Kingsley, Science teacher
Area of science: Botany
ID: 962046256.Bt

Which produces more oxygen?

When I was young, I read that the Amazon rainforest produced a seventh of the world's oxygen supply. Now I do not know whether this is accurate, but it led me to believe that we should not cut down rainforests because our oxygen supply would run out. This is a common misconception that I have found in many of my students.

Mature trees due to their size are able to capture more of the sun's energy and photosynthesise at a faster rate. Mature trees therefore produce more oxygen.

But now let's consider the equation for photosynthesis:

Carbon Dioxide + Water + Energy (sunlight)® Carbohydrate + Oxygen

When a plant carries out photosynthesis, it fixes carbon from the atmosphere (in the form of CO2) and stores it in its tissues (initially, in the form of carbohydrate). In the process, it releases oxygen to the atmosphere. Thus, it is only possible for a tree to produce a net amount of oxygen when it is accumulating carbon.

Young vigorous trees are accumulating carbon as they grow while mature trees are not. Mature trees lose the carbon they accumulate to consumers, to environmental damage and to respiration, which eats up oxygen. All organisms respire including plants. Larger mature plants respire more and use up oxygen at a faster rate than young vigorous plants. Mature trees are also limited in their ability to accumulate carbon by available resources. While it is true that mature trees in general produce more oxygen than young trees, it is also true that they use up more oxygen for maintenance. Therefore, young trees produce a larger net amount of oxygen than mature trees.

So the answer to your question depends on whether you were considering total oxygen or net oxygen production. As a mature ecosystem, the amazon rainforest (for the same reasons as listed above) would use up roughly the same of amount of oxygen as it produced. There are many good ecological reasons for conserving mature trees and mature forests, but oxygen production is not one of them.

Richard Kingsley 

Current Queue | Current Queue for Botany | Botany archives

Try the links in the MadSci Library for more information on Botany.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network,
© 1995-2000. All rights reserved.