Kindling Neighborly Connections between People and Nature.

Monday, April 5, 2021

Sacrificial Lichens Fertilize Forest

I walked our property and was struck by the amount of lichens that littered the forest floor. We own roughly two acres of spruce-fir forest in the northern reaches of New York's Adirondack Park. One of the things that quickly captures the attention of most visitors is the abundance of lichens that drape the horizontal branches of the balsam fir and red spruce trees that adorn the landscape here. One of the things I noticed in late winter is that an abundance of lichens had fallen off of the tree's branches and now littered the forest floor.

Winter was cold and there were some windy days, but nothing that seemed out of the ordinary weather-wise. However, it seemed about every four feet was another lichen that had gotten displaced from it's perch in the trees and was now doomed to decay into the soil of the forest floor. As is so often the case in nature, death brings life. In this case, death brings life in the form of nitrogen cycling through the forest ecosystem.

Plants need nitrogen to build their plant bodies like people need calcium to build strong bones. This is why farmers will often fertilize crop fields with the nutrient nitrogen. It turns out that the trees in our forest feel the same way.

This late-winter cascade of lichens upon the forest floor offered me a good look into the nitrogen cycle of the spruce-fir forest.  Many lichens contain cyannobacteria which are one of the few organisms that can gather nitrogen from the air making it usable for its fungal partner. When these lichens are broken down into soil, the nitrogen once taken from the air to become part of their bodies provides the plants and trees of the forest with a much needed boost of usable nitrogen. 

The lichens that drape the trees, and even the lichens that hug the trees (and are a little less obvious) in hardwood forests throughout New York and Pennsylvania act as middlemen in the nitrogen cycle. Cyannobacteria gathers nitrogen from the air bringing it into the body of the lichen. When some lichens fall to the forest floor and get decomposed, the limited resource of nitrogen can then be used by plants and trees.

In life and in death, lichens contribute to forest health in some very important ways.

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