We’re all familiar with the dramatic changes in our deciduous trees during the fall. First, the leaves turn a bright red, orange, or yellow. Then they brown and fall to the ground.
Another process is taking place during this fall transition. It’s called resorption, and it happens when the tree draws nutrients like nitrogen and phosphorus out of the dying leaves before they fall. During the winter, these nutrients are stored in the tree’s woody tissue. When spring arrives, they are remobilized to produce new leaves.
It’s nature’s way of recycling. Just as we take good stuff out of our trash and send it to recycling centers for reuse, the tree takes good nutrients out of leaves that are getting ready to fall. As a result of this process, a dead leaf on the ground may have only 40 percent of the nitrogen it contained during its heyday in the summertime.
Gary Lovett, a forest ecologist at the Cary Institute of Ecosystem Studies, says that nutrients in leaves are actually recycled in two different ways…
“The first way is that, as a neat trick that plants do, they can take back the important nutrients in the leaves, such as nitrogen and phosphorous, they bring them back into the plant for the winter, and in the spring they can use those nutrients to grow new leaves.”
“The second way is for the nutrients that are left in the leaf materials that fall to the ground, these leaves decompose on the ground and then those nutrients are liberated in the soil. But those nutrients are subject to competition. Microbes can take them up, other plants can take them up, and they can also be washed away in drainage water. So that method of recycling is risky or less certain for the plant.”
As always, nature makes efficient use of her resources. We should too.
Photo, taken on October 6, 2007, courtesy of Flickr.