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Originally appears in the Spring 2023 issue.

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By Darren Sleep, Ph.D

What is a forest? It’s so much more than a bunch of trees: forests are critical ecosystems. If we think of forests as ecosystems, it’s easier to see how trees and forests influence their environment and how the environment influences trees and forests. 

Students learn in school that everything is connected, from birds, insects, fish, dirt, and trees to our pets, our food, and ourselves. But to really understand how absolutely interconnected all life forms in an ecosystem are, it helps to experience those webs of life first-hand, inside and outside the classroom. 

That’s why a forest is a great place for students to continue learning about ecosystems and how we are all part of larger nature-based systems. Many students live within easy reach of forests, especially if we consider urban forests in our communities.

Using forests to understand concepts like nature-based systems helps boost fundamental comprehension of the relationship between forests and humans, and how forests make a difference in our lives. If we can help students make these important connections, they are more likely to form personal connections with nature and become stewards of the natural environment. ^[1]  Because we all know that people only value what they understand, and it starts with students.

As a scientist who supports educators, I know how important it is to understand basic ecological principles and concepts like ecosystems and how they apply to forests. I was excited to help the Project Learning Tree Canada (PLT Canada) team produce the Forest Literacy Framework: A Guide to Teaching and Learning About Forests (plt.org/forestliteracy). It’s a great resource for educators who want to help students answer the question: What is a forest?

Defining what makes up a forest is the first step in connecting with forests 

Forests are ecosystems characterized by a higher density tree cover and may include a wide range of different species, structures, or ages of trees. They also include myriad other plants, a range of wildlife, and commonly include waterbodies like streams, rivers, ponds, and lakes. Forests may be classified by the dominant tree species or combination of tree species present. Forests range in size from under an acre to thousands of acres. (See sidebar: Plant types explained)

The nature of a forest is affected by living (biotic) things such as plants, animals, humans, and their interactions. Forests are also subject to non-living (abiotic) factors, including, for example, soils, nutrients, moisture, sunlight, and climate. Forest health is affected by many other factors, too, including natural competition and availability of space, light, water, and nutrients, as well as the frequency and intensity of natural disturbance, human interventions, pests, and disease.

Forests can be public resources or private, but the benefits of forests — like the clean air they produce or the water they purify — are almost always public and don’t have boundaries. We can find forests in rural, suburban, and urban areas. An urban forest is defined as all trees within a defined urban core boundary. Forests may be sustainably managed for a particular resource like carbon or timber, managed purely for recreation or conservation, or in a few cases unmanaged. Many forests are managed for multiple values all at once.

Forests as ecosystems 

Organisms within forest ecosystems play a variety of roles, such as primary producers, consumers, and decomposers. Abiotic components — things like sunlight, soil, minerals, and water — also can have a dramatic role to play in a forest ecosystem. (See sidebar: Producers, consumers, and decomposers in an ecosystem)

Forests interconnect with other terrestrial and aquatic ecosystems to form biospheres. Grasslands, rivers and lakes are common ecosystems that border on forests, and either slowly transition with forests like at a forest edge next to a field or lake, or more gradually, as tiny ephemeral streams in forests lead to larger and larger streams, rivers and lakes. 

Forest ecosystems are complex and dynamic and continuously undergo natural change and adaptation. Gradual change includes succession or replacement of existing trees by newly growing ones and climate adaptation. More abrupt changes are brought on by wildfire, pests, and disease. These changes — both gradual and abrupt — are mediated by chemical and nutrient processes that involve energy transfers and chemical cycling. In a forest there is an exchange of nutrient elements like oxygen, nitrogen, and hydrogen among the soil, plants, and animals that live there. 

Sustainable forest harvesting is often adapted to mimic these natural disturbances whenever possible. As the forest is adapted over millennia to natural disturbances, adapting forest practices to mimic them reduces the long-term effects of management on forests. Natural events like wildfires, storms, ice damage, insects, disease, and volcanic activity help us understand how forests react to change, allowing us to adapt human-caused activities like forest management and road construction in a way that is compatible with natural forest dynamics. 

Forests grow through natural regeneration or may be assisted through silviculture — or the science of growing and cultivating trees. In Canada and the United States, strict laws and regulations, augmented by voluntary certification standards, ensure that harvested trees must be replanted. 

Appreciating the trees that make up a forest 

Of course, most students understand that the key defining characteristic of any forest is the trees within it. But to really advance how students learn about and perceive forests, appreciating the uniqueness of tree species and comprehending how individual trees function and interact in a forest ecosystem can go a long way. (See sidebar: Plant types explained)

A tree is a woody perennial plant usually 12 feet or greater in height at maturity, often with a single main stem, and a distinct crown of leaves, needles, or scales. Trees can be identified by these distinct features and others like their seeds, leaves, flowers, bark, and shape. They can be classified into family, genus, and species groups. Trees are broadly classified into two botanical groups: conifer and broadleaf. Trees within each group are then divided again into deciduous and evergreen depending on their leaves.

Deciduous trees have leaves or needles that die and drop after one growing season. Coniferous trees retain their green leaves, needles, or scales for two or more growing seasons.

Trees experience primary and secondary growth. Primary growth results in an increase in root length and tree height. Secondary growth results in the increasing diameter of roots, branches, and stems. Like all plants, trees have life stages that include germination, growth, maturity, reproduction, decline, and death.

Trees play various important roles as part of the forest ecosystem. These roles include supplying oxygen, producing food, providing habitat for wildlife, stabilizing soil, moderating temperature, capturing and storing carbon, and cycling water and nutrients. After their death, trees often provide habitat for other creatures to live on or in and provide nutrients and soil as they decay.

Classifying and differentiating forests 

Classifying and differentiating forests into biomes and types helps people understand the forests in their community, in their country, and around the world. Different forest biomes exist around the world. Examples include tropical forests, temperate forests, and boreal forests. In North America, major forest biomes include boreal, temperate deciduous, tropical deciduous, temperate coniferous, and temperate rainforest. 

Many different forest types exist within a biome, typically distinguished by their dominant tree species. For example, there are oak-hickory forests, spruce-fir forests, and many others. Forest types can be further broken down into more distinct natural communities that recur on the landscape, characterized by finer-scale descriptions of vegetation, including shrubs and ground cover. (See sidebar: Natural communities)

Around the world, forests live in places with considerable variation in soil types, elevation, temperature, wind, and precipitation patterns. These variations create the different forest types and associated plants and animals (flora and fauna) that, together with disturbance history and patterns, contribute to a region’s biodiversity. 

Humans are part of the forest ecosystem. They depend on and influence forest ecosystems and are also influenced by them. 

Helping students to answer the question: What is a forest?

To help students deepen their understanding of forests, consider these kinds of activities from the Forest Literacy Framework: A Guide to Teaching and Learning About Forests. These activities and concepts from the Forest Literacy Framework have direct connections to Next Generation Science Standards (NGSS) in the United States and to social studies standards. Many concepts also support English language arts and mathematics standards as well.

Grades K-2:

Read Welcome to the Neighborwood by Shawn Sheehy or another book that introduces children to forests and forest organisms. 

Gather students by a tree and invite them to act out the different stages of a tree’s life. 

Grades 3-5: 

Challenge students to identify the names of trees in the schoolyard, in a park, or along a street. 

Lead an investigation of biotic (living) and abiotic (nonliving) components of ecosystems through a plot study comparing shady and sunny locations in the schoolyard or a nearby park. 

Grades 6-8: 

Guide students to select a tree native to their region and write a research report about it. 

Lead students on a field study of three different environments, such as a lawn, a stand of trees, and a pond or creek. 

Grades 9-12:

Lead students in conducting a tree survey of the school grounds, identifying the genus of each tree and measuring the height of each tree and the diameter at chest height. 

Ask students to conduct an opinion survey to determine the community’s view on forests and forest management issues. 

Forest literacy helps students understand what a forest is and so much more

Helping students understand what a forest is can be a great chance to make connections between science, social studies, mathematics, health, economics, and many other subjects. Learning about forests opens the door to understanding the importance of forest ecosystems to meeting sustainability challenges today and tomorrow. Preparing students to meet these challenges can help them become better learners and help them help forests.

Project Learning Tree has many resources to help answer questions students have about forests. PLT is committed to advancing environmental education, forest literacy, and green career pathways, using trees and forests as windows on the world. PLT’s award-winning resources offer a lifetime of learning, from early childhood through adulthood, and its wide and diverse network provides professional development for educators and opportunities for young adults to explore forests and green careers. PLT is an initiative of the Sustainable Forestry Initiative (forests.org). SFI is a nonprofit charitable organization with the mission of advancing sustainability through forest-focused collaboration.

Darren Sleep, Ph.D is Lead Scientist at the Sustainable Forestry Initiative. He ensures that SFI’s work is grounded in thoughtful, science-based knowledge and communications, and that SFI standards and education programs reflect the latest in scientific understanding.

Endnote:

[1]Environmental Education Encourages Environmental Stewardship, 2023, The National Environmental Education Foundation, https://www.neefusa.org/education/benefits#encourages