Forest Types and Trees

Perception of Forests
Depending where we live and what surrounds us, we might perceive forests as larger green swaths spanning entire landscapes, woodlots within an urban-agricultural matrix, trees shading our streets and cities, riparian forest along streams, planation, hedgerows or some combination of these. Whatever our perception of forests, each serves many ecological and social functions, and provides benefits to society.
In settled landscapes, forests are managed for their traditional values, but are also a component of land use planning, often as part of the municipal green system network (e.g. natural heritage systems, green lands). These green systems link urban areas with the surrounding landscape, protect biodiversity and support many ecological functions and processes necessary to maintain populations of native species. However, they are also part of green infrastructure as they provide a multitude of ecological goods and services. This includes, to name a few, making the urban environment greener, ameliorating urban microclimate, improving air and water quality, reducing storm water runoff, flooding and erosion, and providing recreational and social values to the community.

There are different definitions of forests and many different ways forests can be described.

Forests or Woodlands are terms often used to describe forest fragments within urban-rural landscapes. Characteristics of a woodland depend on the dominant tree species and degree of light penetration to the understory. Understory vegetation consists of mosses, ferns, grasses, sedges, forbs (flowering herbs), shrubs and young trees.

Riparian forests 
Riparian forests are forested areas adjacent to a body of water such as a river, stream, lake, pond, marshland, or reservoir. Quality of riparian vegetation has a significant impact on the quality of water. Riparian vegetation prevents flooding and erosion, filters pollutants, contributes to cooler water, and provides habitat and food sources for aquatic animals.

Forests, by slowing water movement across the landscape and enabling water infiltration into the soil, reduce surface water runoff during rainfall or snow-melt events. This prevents flooding, reduces erosion, recharges aquifers and filters pollutants which otherwise would have been carried directly into waterways. Natural areas play a vital role in this process, especially those that are riparian, wetlands or have steep hillsides.

Riparian forests also provide habitat for terrestrial animals, or can act as wildlife corridors for species moving between habitat patches in fragmented landscapes such as southern Ontario. 

Hedgerows are a linear arrangement of planted trees or shrubs, typically bordering agricultural lands, fields or roads. Hedgerows act as buffers to wind or windbreaks to reduce wind erosion of cropland. Hedgerows may consist of a single species or multiple species intermixed. Historically, Common Buckthorn (Rhamnus cathartica) was used an agricultural hedgerow, but has since invaded North America’s natural areas as an aggressive invasive species.

Southern Ontario from the Air - Eric Boysen

Single trees

At the most basic level, forests are comprised of individual trees. Single trees can be described according to their characteristics such as species name, age, height, diameter at breast height (DBH), carbon content and canopy cover. VSP can be used to measure each of these properties.

Closed and Open Canopy
Forests, depending on the extent of tree canopy cover, can in general have an open canopy or closed canopy. In forests with open canopies tree crowns are widely spaced leaving open areas for light to penetrate. Forests with closed canopies have tree crowns that have grown together to overlap and create a continuous canopy, reducing understory light penetration, which is typically less than 30%.