During your hike, have you noticed the dead trees - a few still standing, many scattered on the ground - in various states of decay?  They may give a bit of an untidy appearance to the forest, but there are good reasons to leave the downed timber just where it falls (unless, of course, it lands on the trail).  As many as half of the species in a forest use old, dead timber for their homes and/or their food source, including moss, mushrooms, ants, spiders, and owls!