Lesson 3: Nutrient Cycling

Carbon, hydrogen, and oxygen are obtained from carbon dioxide and water. The other 13 nutrients are provided by the soil and absorbed by tree roots, as we investigated earlier in this course.

These soil nutrients originate mainly from the breakdown of mineral-bearing rocks and from organic material (which comes from the gradual decomposition of plants and animals).

The nutrients absorbed by the tree become incorporated into the various parts of the tree as it grows, including the leaves, wood, bark, and roots. These nutrients will eventually be returned to the soil when the tree dies and decomposes. This will ensure that the nutrients are used again and again and again.

Of course, if trees are logged and hauled out of the forest for timber, then this cycle is broken. This is because the tree will no longer have the opportunity to decompose in the forest once it is dead.

Commercial logging operations, by removing trees,  take large amounts of organic matter out of nature's nutrient cycle.