Tree – Part 2: Nutrients and Trees

In Part 2 of our discussion about how trees use nutrients, we take a look at the role of oxygen in trees. Oxygen is one of the high concentration nutrients, meaning that oxygen is required in a concentration of at least 1000 parts per million.

Plants use oxygen the same way that we or animals do – a process called respiration. Respiration is the burning of photosynthates (sugars) to produce usable forms of energy for all living cells to operate. In trees, the amount of oxygen they use for respiration is less than the amount of oxygen that they produce during photosynthesis. It is for this reason that we will always rely on plants for the oxygen that we breathe.

Photosynthesis is different than respiration in that photosynthesis only occurs when sunlight is present. Respiration occurs 24 hours a day. When the sun is shining and photosynthesis is occurring, the oxygen that is needed for respiration is supplied as a by-product of photosynthesis. At night, the needed oxygen is acquired through plant roots, stomata in the leaves, and in some species through the bark.

The following table is from the Colorado State University Extension, and shows a simplified breakdown of the differences between photosynthesis and respiration.

The availability of oxygen is just as essential to plants as it is to people and animals. Without oxygen, plants would be able to produce sugars, but would not be able to convert those same sugars to the energy needed to make its cells function and grow. One of the easiest ways to kill a tree is to drown it with too much water. When excessive water pushes all of the oxygen out of the soil, there is nothing left for the roots to absorb to supply the process of respiration. Caring for trees means to care for every part of the tree and the soil that supports them.