How is carbon dioxide recycled in a terrarium?

Answer 1

A closed terrarium is a closed ecosystem just on a much smaller scale. The

supply of carbon dioxide in the terrarium air is very small because of the

limited volume of air. Therefore, unless the terrarium contains animals

to provide carbon dioxide or microbes break down large amounts of organic

matter in the soil and release carbon dioxide, the plants in a sealed

terrarium cannot gain significant dry weight. They would basically refix

the same carbon dioxide over and over. The carbon dioxide the plants

release during cellular respiration would be refixed via photosynthesis,

then respired, refixed, respired, refixed, etc.

Most terrariums are not completely sealed so carbon dioxide can enter and

plants can gain dry matter via photosynthesis. The inventor of the

terrarium, Nathaniel Bagshaw Ward (1791-1868), supposedly had a "sealed

terrarium" that survived four years but it is questionable if it was

completely sealed because of the substantial plant growth he observed.

Another attempt at a closed terrarium on a larger scale was the big

Arizona greenhouse called Biosphere Two . It was

originally supposed to be a sealed terrarium for two years containing

several people, many animals and all sorts of plants. However, it got out

of balance, and they had to add more oxygen because the amount of

photosynthesis was less than required to supply adequate oxygen to all the

animals.

References:

Hershey, D.R. 1996. Doctor Ward's accidental terrarium. American Biology

Teacher. 58:276-281.