What Causes Dead Leaves to Break Down?

Chlorophyll Break Down

• Chlorophyll gives leaves their green coloration. The substance breaks down sunlight and nourish the tree. As autumn approaches, the leave's chlorophyll production gradually ceases. Without chlorophyll, the leaves begin to break down and change color. Eventually they fall from the tree. A tree that suffers from considerable drought also will manifest yellow foliage and the leaves will fall to the ground.

Decomposition Rate

• The movements of soil organisms, such as earthworms, through the leaves help to break down the leaf structure. The smaller, broken-down surface area of the leaf is easier for the fungi and bacteria to penetrate. Once within the leaf's cells, the fungi and bacteria further break it down. The rate of decomposition is governed by the temperature. Decomposition accelerates at higher temperatures but continues at a slow and steady pace even during the cold winter months.

Final Decomposition

• Rainwater helps to further break down the leaf particles and wash the nutrients into the soil, where it readily can be taken up by the roots of plants. Earthworms help to mix the leaf fragments into the soil and further break down the pieces. They also ingest fragments and secrete nutrient rich fecal matter. The forest floor annually accumulates approximately 1 lb. of decomposing leaves per square yard, according to the Utah State University.

Nitrogen and Oxygen

• Leaves break down more slowly it they lack adequate nitrogen because fungi and bacteria require that element to produce proteins for their growth, according to the Utah State University. When fungi and bacteria suffer slow growth, the speed of decomposition is reduced. Leaves that fall into water, such as lakes or streams, take longer to breakdown because the bacteria and fungi require oxygen to quickly decompose the leaves.