Tree roots are the essential framework for preventing soil erosion. Without roots to hold the soil in place, forest slopes simply wash away. Tree roots can extend great distances, and in some cases, roots from separate trees (of the same species) can "graft" themselves together. Roots from many trees can grow together into a single enormous network that supports many individual trees. Thus, when nutrients from a healthy tree are brought down into the roots, they may be "stolen" by a different individual tree that gets very little sunlight. Stumps connected to this network of roots can remain alive by receiving nutrients from the other trees.