Forestry

A forest is an area where tree species are the dominant type of vegetation present on the site. Forests can be vast areas of several thousands of acres of land comprised of many different stands, or they could be smaller individual woodlots. Forests are dynamic and always changing as they age and are affected by natural and human disturbance. The term succession refers to the ecological process by which forests pass from one stage to another. Early succession forests, also called “young forests", are thick with many small trees present and are typically established after a disturbance such as a large wind event or a clear cut type of timber harvest. Over time, these young forests then grow into mid-successional forests characterized by small to medium diameter trees that are easy to walk through and provide a canopy overhead.  Foresters would refer to this as the pole timber stage.  As the forest continues to age, the trees become taller, increase in diameter and shrubs and small trees begin to establish under the tree canopies. Finally, a forest will exhibit late successional characteristics over time to include large diameter trees, high diversity of tree species, significant amounts of dead wood (standing dead trees and trees that have fallen on the forest floor), and gaps in the canopy allowing for varied vertical structure. All these different characteristics of different successional stage forests make them important areas to harbor and propagate many wildlife species. 

Forests provide vital resources such as food, water, cover, and space for many wildlife species to survive. These four key components together are considered an animal's habitat. When managing for particular wildlife species, it is important to remember that all of these elements must be present for them to call an area their home. The different forest successional stages described above typically contain different types of food and cover. As such, different wildlife species utilize these different areas as their habitat. This is why it is important to have representation of the different forest successional stages on the landscape which will help to ensure use by the greatest number of wildlife species.​

Food and Cover

The two most critical elements of wildlife habitat are food and cover. Forested areas excel at providing these elements and provide them throughout the different seasons of the year. Each forest successional stage will offer different types of food and cover for wildlife to utilize. Young forests often provide thick lush growth of vegetation desirable for many species to eat and also promote many of the soft mast shrubs like blackberry and raspberry. The thick nature of these areas also makes them ideal for nesting and brooding cover as well as escape cover and allow wildlife to hide themselves and their young from predators. Pole timber forests begin to provide vertical structure, start to contribute dead wood, and also start to contribute hard and soft mast from trees.  As pole timber ages to more mature timber, the vertical structure grows, more dead wood is available and other shrubs and small trees provide nesting cover for bird and mammal species alike.  Late successional forests provide nesting and feeding cover for canopy nesting birds and mammals. Coniferous, evergreen tree species provide valuable cover in harsh weather conditions such as snow, rain, and wind. 

Water

Forests provide many different types of water sources for wildlife. They often harbor important perennial and intermittent streams and protect the quality of these areas. This protection allows for the establishment of insect, fish, and amphibian species which can be important food sources for wildlife. Spring seeps are another water source found in forests and are often areas with high herbaceous plant and insect diversity. These areas are also typically open during the winter time and available to wildlife even when there is a persistent snow pack in the surrounding forest. This water source being available at such a critical time in the life cycle of many wildlife species makes them worth protecting and promoting when possible. Vernal pools are another water feature found in the forest. These are areas that fill up with water in late winter and spring, another critical part of most wildlife's life cycle. These pools are often teeming with insect and amphibian life.  Over the course of the year, they can then dry out in the summer and fall timeframes.

Space

This is also referred to as a species home range. A home range for a particular species needs to have all of the food, cover, and water requirements present. As you can imagine a cottontail rabbit's home range would be very different from a white-tailed deer or black bear home range. Where a rabbit would call a particular forest stand or woodlot and associated edge habitat home, a white-tailed deer or black bear would require several square miles of associated habitats to call an area their home. Also, migratory song birds have extensive home ranges sometimes spanning across North America or even into South America. In this case, Pennsylvania forests provide that niche habitat they need for nesting and brood rearing.

Dead wood

Both standing dead trees and dead wood lying on the forest floor are very important features for many species of wildlife.  Standing dead trees often have cavities that can be used by birds or mammals for cover and nesting areas. They also typically attract many insect species that bore into the wood creating a smorgasbord for birds. Dead limbs free of leaves and branches also serve as perches for birds of prey so that they can see clearly through the forest to hunt. Dead wood on the ground provides similar attributes in the attraction of insects and potential for cavities. Different wildlife species will utilize the downed wood versus the standing dead wood, so it is important to have both present and represented in the forest. The size of standing dead wood or downed wood also matters in addition to the species of trees. Some tree species will decay faster than others. For example hemlock trees will decay much faster than oak or hickory trees due to the properties of their wood. Moisture level also matters as more wet sites will promote rot and decay much quicker than dry sites.​

Pennsylvania has many different forest types based on several factors such as location in the state, climate, soil type, and elevation. The most common types found are oak/hickory, northern hardwoods, and conifer types. ​The northern hardwood and oak/hickory types are both deciduous forest types meaning the trees lose their leaves in the fall and grow new ones in the spring. The conifer types are dominated by evergreen trees that keep their needles on all year long.

Oak/ Hickory – These forests are dominated by mixed oak species of trees and typically grow on upland sites.  They are important for production of hard mast food sources such as acorns and hickory nuts.

Northern Hardwoods – These forests are dominated by maple/beech/cherry/birch species of trees and are important for the production of soft mast food sources such as black cherries and hard mast such as beech nuts.

Conifer – These forests are dominated by hemlocks, white pines, or red spruce and are important for their thermal cover they provide in the winter time and for their hard mast production of pine nuts and other seeds.

Aging forests​

In Pennsylvania, many of the forests are in the 80 to 120 year age class due to extensive logging in the early part of the 1900's. During this time period vast acreages were clearcut for building materials and for fuelwood. Forest fires were also prevalent in many areas.  Because of this large disturbance happening in a relatively short amount of time, the distribution of age classes is now skewed with an under representation of young forests and very old forests (should insert some sort of diagram here). As discussed above, varied ages and structures of forest are desired to provide the maximum benefit to wildlife. Action is needed to help bring the age class distribution into a more balanced state on the landscape. This concept can also be applied to smaller land ownerships where younger patches of forest can be created to help fill the role of providing varied age and structure.

Regeneration

Due to the age classes of the majority of forests in Pennsylvania being very similar, the forests are essentially middle aged and are often in a stagnant state with high tree densities and closed canopies creating an abundance of shade on the forest floor. This is causing some tree species like oaks to have trouble regenerating. Remember that oak trees are important sources of hard mast and are desirable to have on the landscape for their drought tolerance. Oaks need some sunlight reaching the forest floor to become established and grow to a point where they would successfully start a new young forest. Also, white tailed deer in many cases prefer to eat oak seedlings and saplings versus other tree species as a part of their diet. This preferential browsing does not allow oak to be competitive against other tree species that are not as preferred by deer. Competing vegetation that is more tolerant of shade such as red maple and black birch, are also compounding the problem by crowding out oaks and taking up valuable growing space on the forest floor.
Invasive Species

Invasive species can be a serious threat to the health of a forested area and to the quality of wildlife habitat on the site.  They typically spread prolifically and can overtake, crowd out, and discourage the establishment of desired herbaceous plants, shrubs, and trees. This can cause serious disruptions in the food chain and limit dispersal of desirable vegetation in an area.  Invasive species can be both non-native and native plants. Non-native plants are those that were introduced to the North American landscape from another area or continent. For the most up to date list of invasive plants found in Pennsylvania click here

• Some examples of non-native invasive species found in Pennsylvania forests are: Japanese stiltgrass, mile-a-minute vine, multiflora rose, autumn olive, non-native honeysuckles, glossy buckthorn, tree-of-heaven, and royal paulownia. These species all should be removed from an area to ensure native species have the best chance at establishment and survival over time.
  
• Some examples of native vegetation that can become invasive in Pennsylvania forests are: hay-scented fern and striped maple. These plants can also become very thick and choke out other desirable native species, particularly oak regeneration.​