WHAT IS UNDERGROUND IN A FOREST. I wondered how the size of a large tree underground compares to the size of the tree above ground. This article on the Arnold Arboretum website by Thomas O. Perry notes at the outset that weighing or counting each root tip or leaf is a “heroic if not impossible task” so that sampling is used. However, I am satisfied with his statement that: “A tree possesses thousands of leaves and hundreds of kilometers of roots with hundreds of thousands of root tips….the surface of the root system concealed in the soil can be greater than the surface of the leaves! I take it that as a rough approximation, the part of the tree above ground is comparable to the amount of the tree that is underground.
Perry adds: “Amazingly, this conclusion does not take into account the fact that nearly all tree roots are associated with symbiotic fungi(mycorrhizae), which functionally amplify the effective absorptive surface of the finer roots a hundred times or more.”