Examples of symbiosis in a deciduous forests include the relationship between mistletoe and trees, foxes and wolves, and lichen. These relationships between organisms are specifically defined as, in order, Parasitic, Commensalisitc, and Mutualistic.
Symbiotic relations are interactions between species in which at least one benefits. In the first example, mistletoe uses its roots to burrow into the bark of the trees and extract nutrients. This is harmful to the tree, causing death of limbs or the tree itself, which makes mistletoe a parasite of the tree.
Foxes do not always hunt their own food; they often scavenge the remains of kills from other predators, such as wolves. The fox simply waits for wolves and bears to eat their fill and leave before moving in on the carcass. The wolf is not harmed by this interaction and the fox gets a free meal, making this a commensalistic relationship.
Lichen is a moss-like growth that appears on rocks and trees in the forest. Despite it's simple appearance, it is actually a complex community of algae and fungi, each incapable of living without the other. The fungi provide structural filaments and water, while the algae provides food from sunlight. There is some contention in the biological sciences that the term "symbiosis" ought to be restricted to these mutualistic relationships.