Leaves are part of an amazingly fine-tuned cycle, the nutrient cycle. Let’s take a look at how this cycle works in the woods:
1. Let’s start with Decomposed material supplies nutrients to trees. The soil in which the decomposed material exists is ideal for the survival of small feeder roots from trees and certain beneficial bacteria (rhizobia) and fungi (mycorrhizal).
There are amazing symbiotic (beneficial) relationships between these different living organisms. These beneficial bacteria and fungi promote nutrient mineralization (so nutrients are accessible to plants). They produce plant growth hormones and help protect trees from plant pests, parasites, and diseases. They also help supply water to feeder roots to take up the nutrients trees need.
- Tree roots take up 16 different nutrients or elements
- Primary ones: Hydrogen and Oxygen (H2O), Nitrogen, Phosphorous, and Potassium
- Secondary ones: Calcium, Magnesium, Sulphur and 8 other micro-nutrients
2. Trees use nutrients to grow leaves. The nutrients taken up by the roots are now available for trees to process so they can be utilized in different ways. Trees use photosynthesis (sunlight) to break down carbon dioxide (CO2) from the air and water (H2O) and make sugar which the tree can use to store energy. Buds are little packages of next year’s leaves and twigs created from sugars and other nutrients and controlled by a growth hormone. When the temperatures warm enough in the spring the buds begin to grow and create new twigs and leaves.
3. Leaves fall to the ground. In the fall as the days grow shorter and cooler, trees produce hormones that form an abscission layer at the base of the leaf stem. This shuts down transport of life-giving materials and causes leaves to break off and fall to the ground.
4. Fallen leaves are decomposed. Through different critters, fungi, and bacteria decomposing these leaves, their nutrients are made available again to be taken up by tree roots. So, the cycle repeats itself year after year.
Each step in this nutrient cycle is dependent on the step before it. No decomposers… the cycle won’t work. It is an amazingly fine-tuned system!
Something to appreciate when you are raking your leaves, walking through the leaves in the forest, enjoying the fall colors, or seeing the new leaves as the buds open up.
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