|A moist maple forest with rich soil.|
The reason the maple is so very picky is because of its roots. Just like branches of deciduous trees shed their leaves annually, larger roots also shed tiny roots annually and with dry weather. Maples produce an abundance of these fine roots at very shallow depths, right where the nutrients are highest. It has been estimated that 60 percent of annual productivity of maples is actually contained within these roots. This is quite amazing when you consider the great density of leaves maple trees produce annually. The fact that so much of the tree is in-fact these very sensitive tiny roots makes the whole tree very sensitive to whatever happens on or in the most shallow layers of soil. Trampling by foot traffic, vehicles, or cattle can damage these roots as well as cause the soil to dry out, killing the roots and potentially killing the whole tree. If fire burns across the ground, the surface soil will be significantly dried out also potentially killing the roots. The heat of the fire can also kill the roots very easily. Pollution, such as acid rain, can change the chemistry of the soil, also killing fine roots and damaging the overall tree.
Fortunately, the maple tree does have some adaptations that help make it at least a little less sensitive to changes in the surface soil. For one, the overall root system of maples is capable of hydraulically redistributing moisture from deep within the soil to more shallow soils. The thick shade of maples also helps to prevent evaporation of moisture from the soil. Also, the fact that maples transpire, or "exhale", large amounts of water vapor while photosynthesizing helps cool the environment and increase humidity. Fallen leaves are very absorbent and are a very effective mulch that help hold moisture in the soil. All of this helps moisture to be retained within the soil where it can be utilized by the tree and prevents moisture from evaporating into the environment. All around, the maple works to keep its environment as moist as possible.
|Sugar Maple tree in fall.|