Trees are connected below the ground by mycorrhizal fungi, which live symbiotically with the roots of the trees. Both the trees and the fungi need each other to survive. But that’s not all. Because the fungi essentially connect the roots of one tree to another, the trees can use the fungi to pass nutrients to one another. So, for example, in winter when aspens are weaker, nearby conifers were found to pass additional nutrients to the aspens to keep them healthy. Similarly, older, more-established trees pass nutrients through the fungi to young seedlings which need to grow larger toward the sun’s light in order to survive. The largest, oldest trees in the forest serve as the hub because they possess and produce large amounts of resources, and their massive roots spread out in all directions.