Dead, rotting logs on the forest floor provide the habitat for a small mammal, the red-backed vole, which subsists almost entirely on the portion of certain specialized fungi which grows aboveground. The fungi-spores are deposited on the forest floor by the voles. Some of the fungi that develop from these spores form underground sheaths around the fine roots of growing trees, and assist the trees by processing and sharing nutrients and producing an antibiotic which protects the trees from disease.
The presence of rotting logs on a forest floor can have beneficial effects on the trees around them is the conclusion that is supported by the information above.