A forest isn’t just a bunch of trees; it's a dynamic, living web where trees, plants, animals, fungi, me, and microorganisms coexist with nonliving elements like soil, water, air, and landforms.
Together, these components create an intricate ecosystem, constantly interacting in ways that support and sustain life; by mirroring their processes on a smaller scale, we can build flourishing, self-sustaining, food-producing ecosystems in our urban and suburban yards.
The Forest as a System
These interactions move essential resources—energy, water, carbon, air, and nutrients—through food chains and webs.
To recreate these systems on a smaller scale, we first have to understand what they are and how they work.
To begin with, the very heart of all the systems in the forest is the food system. The food system is made up of three categories: producers, consumers, and decomposers. Each playing a vital role in nutrient movement.
Producers
Producers are organisms like plants, algae, and some bacteria that can produce their food through photosynthesis. In this process, they convert sunlight, carbon dioxide (CO₂), and water into glucose (sugar) and oxygen.
This energy-rich glucose is the food for plants and forms the base of the food chain. Young native trees, shrubs, and grasses are the producers in a brand-new forest or meadow.
These plants support the ecosystem by providing energy for other organisms and play a key role in regulating the Earth's atmosphere by absorbing CO₂ and releasing oxygen.
Consumers
Consumers are organisms that rely on other organisms for their energy and nutrients. The types of consumers are categorized by what they eat.
Herbivores: These animals feed directly on producers. For instance, a deer feeds on grasses, shrubs, and tree leaves, gaining energy from the plant material it consumes. In a new forest, a bird that eats the seeds of the new grasses would be a consumer.
Carnivores: These animals eat other consumers, typically herbivores. A wolf, for example, may hunt and feed on deer, obtaining its energy from the animals it consumes.
Omnivores: These organisms consume both plants and animals. Humans, raccoons, and bears are examples of omnivores eating various foods, including fruits, vegetables, and meat.
Consumers play a crucial role in maintaining ecosystem balance by controlling plant and animal populations and recycling nutrients within the food web.
Decomposers
Decomposers are organisms that break down dead organic matter into simpler substances, such as fallen leaves, dead animals, and decaying plants. This group includes fungi, bacteria, and detritivores like worms and beetles.
Decomposers release nutrients such as nitrogen, phosphorus, and carbon into the soil by breaking down dead material. Plants then take up these nutrients, enabling the life cycle to continue.
Decomposers are essential in nutrient cycling, enriching the soil, helping sustain plant life, and supporting consumers. Without decomposers, dead organic material would pile up, and ecosystem nutrient flow would be disrupted.
Wood chips in new forests support decomposers and enhance soil health. As the chips break down, they provide an ideal environment for mycelium, forming a nutrient-rich foundation. We then add rich soil, logs, and seeds, replicating the structure of a natural forest floor.
The Food Web
The balance between producers, consumers, and decomposers is vital in every ecosystem. Producers, such as grasses and plants, capture energy from the sun. Consumers, like deer, rely on these plants for sustenance, while decomposers, such as worms, break down organic matter, returning nutrients to the soil to fuel new growth.
This process accelerates what would take years in a natural forest, giving our plants and seeds the best possible start in a thriving, regenerative environment.
The Cycles of Life in a Forest
Forests thrive on four key natural cycles—oxygen, carbon, water, and nitrogen—and keep the continuous flow of essential elements coming.
The Oxygen Cycle: Plants absorb carbon dioxide and release oxygen through photosynthesis, providing the air we breathe. In turn, plants and animals respire oxygen and release carbon dioxide into the atmosphere.
The Carbon Cycle: Trees act as carbon sinks, storing carbon absorbed from the atmosphere. When trees die and decompose or burn in a fire, this carbon is released back into the environment, continuing the cycle.
The Water Cycle: Water moves through the forest as precipitation, runoff, groundwater, and evaporation. Forests are critical in regulating water flow and maintaining clean water supplies.
The Nitrogen Cycle: Nitrogen is essential for plant growth and cycles between the soil, plants, and atmosphere. Decomposers, such as bacteria, break down organic matter to release nitrogen into forms that plants can absorb.
Layers of the Forest
When designing and installing a new urban forest, it’s important to consider the different layers of a natural forest. Each layer has a unique role in the ecosystem, and when we replicate these layers in an urban setting, we create a more resilient, self-sustaining environment.
The Canopy
The highest layer consists of mature trees whose leaves form a dense cover. This layer captures sunlight, enabling photosynthesis, and is home to species like eagles, bats, and insects. Some of the major trees that make up a Pacific Northwest Forest Canopy are:
Douglas-fir (Pseudotsuga menziesii): Provides habitat and food for wildlife, stabilizes soil, and improves air quality. Supports bark beetles, Douglas-fir tussock moths, and over 100 bird species like woodpeckers and nuthatches. Mammals include squirrels, deer, and black bears. Max Height: 200-300 feet.
Urban Planting Tips: It needs well-draining soil and plenty of space for its roots and canopy. Plant in parks or large open spaces, and avoid areas near power lines.
Oregon White Oak (Quercus garryana) supports diverse wildlife, improves soil with leaf litter, and provides shade. It hosts hundreds of insect species, such as moths and beetles, and mammals like woodpeckers, deer, and western gray squirrels rely on its acorns.
Max Height: 60-90 feet.
Urban Planting Tips: Prefers full sun and well-drained soils. Avoid overwatering. It is ideal for larger yards, parks, or naturalized areas.
Bigleaf Maple (Acer macrophyllum): Produces abundant leaf litter that enriches soil and provides shade and water retention. Supports pollinators like bees and butterflies. Seeds feed birds like grosbeaks and mammals like chipmunks.
Max Height: 50-100 feet.
Urban Planting Tips: Thrives in moist, well-draining soils and can tolerate some urban pollution.
Western Redcedar (Thuja plicata): Provides bird shelter and nesting sites, stabilizes soil, and regulates water flow. Supports cedar waxwings, owls, and deer species. Its foliage is a food source for moth larvae.
Max Height: 150-200 feet.
Urban Planting Tips: Plant in moist, shaded areas with good drainage. Avoid planting near concrete to prevent root damage.
Western Hemlock (Tsuga heterophylla): Creates dense canopy cover that moderates soil temperature, reduces erosion, and retains moisture. Its needles enrich the soil with acidic organic matter as they decompose. Supports caterpillars of various moth and butterfly species, bark beetles, and sap-feeding insects. Provides critical nesting and roosting habitat for owls, woodpeckers, chickadees, and kinglets.
Max Height: Up to 200 feet
Urban Planting Tips: Prefers partial to full shade, especially as a young tree, and moist, well-drained, acidic soil with decomposing wood. It thrives in cool, damp environments.
Urban Tree Planting Tip: Groves
Planting native trees in groves is beneficial because it mimics the natural structure and function of forests, creating a more resilient and self-sustaining ecosystem. In a natural forest, trees grow in communities where they support one another through interconnected root systems, shared mycorrhizal networks, and wind protection.
Planting trees in groves mimics natural forests by fostering ecological relationships that enhance soil health, regulate temperature, and provide habitat for wildlife. For example, a grove of bigleaf maples and doug firs will naturally enrich the soil with organic matter, create shade that benefits understory plants, and help the trees withstand storms, drought, and pests more effectively than lone trees.
By replicating these natural patterns in urban and restored landscapes, we create thriving ecosystems that require less maintenance and provide long-term benefits for people and wildlife. Native tree groves improve air and water quality, prevent soil erosion, and support pollinators, birds, and other wildlife, helping to rebuild the interconnected web of life that defines a healthy forest.
The Understory
The understory of a Pacific Northwest forest is the layer of smaller trees that grow beneath the canopy of Douglas fir, western red cedar, and hemlock. This layer consists of shade-tolerant species like vine maple, Pacific dogwood, and cascara, which thrive in the dappled light that filters through the upper branches.
These trees provide essential habitat for birds, insects, and small mammals, offering shelter and food through seeds, berries, and nectar. Many understory trees, such as vine maple, have multi-stemmed growth patterns that create dense thickets, offering protection for wildlife and adding to the structural diversity of the forest. Some of the major trees that make up the understory of an Oregon native plant forest are:
Pacific Dogwood (Cornus nuttallii): Provides food for pollinators, birds, and mammals; enhances soil health with its leaf litter. It supports butterflies, moths (like the spring azure), and birds such as robins and cedar waxwings. Mammals like deer eat berries and twigs.
Max Height: 15-30 feet.
Urban Planting Tips: Prefers partial shade and well-draining, acidic soil. Avoid compacted areas and overwatering.
Vine Maple (Acer circinatum):
It stabilizes soil, provides cover and nesting sites, and supports pollinators. It hosts moths, butterflies, and sap-feeding insects. Birds like grosbeaks and mammals like chipmunks and deer consume seeds and twigs.
Max Height: 15-25 feet.
Urban Planting Tips: Thrives in partial shade and moist, well-draining soil. Great for small yards or as part of a multi-layered planting.
Cascara (Rhamnus purshiana):
Provides nectar for pollinators, berries for birds, and shade for soil health. Attracts bees, butterflies, and birds like waxwings and thrushes. Bears and other mammals feed on its berries.
Max Height: 20-40 feet.
Urban Planting Tips: It does well in sun or partial shade and in moist, well-drained soils. Avoid planting near sidewalks, as roots can lift concrete.
Beaked Hazelnut (Corylus cornuta): Beaked hazelnut stabilizes soil and provides dense cover and forage for wildlife. Its nuts are a critical food source for many species, enhancing biodiversity in understory habitats. It attracts pollinators like native bees and supports the larvae of moths and butterflies. Squirrels, chipmunks, deer, and bears rely on their nuts, while birds like jays and woodpeckers feed on them.
Max Height: Typically grows 10-15 feet, forming a dense, bushy habit.
Urban Planting Tips: Thrives in partial to full shade but can tolerate sun. Prefers moist, well-drained soils but is adaptable to various conditions.
The Shrub Layer
Made up of saplings and woody plants like ossoberry and blue elderberry, this layer supports browsers like deer and insects, including mosquitoes. Some of the major plants that make up the shrub layer of a forest are:
Snowberry (Symphoricarpos albus): Offers shelter for birds and small mammals; stabilizes soil and prevents erosion. Attracts pollinators like bees and moths. Birds like towhees and thrushes eat its berries; small mammals use it for cover.
Max Height: 3-6 feet.
Urban Planting Tips: Grows in various soil types and tolerates shade, making it great for urban rain gardens or under canopy trees.
Salal (Gaultheria shallon): Excellent ground cover for preventing erosion; provides food and shelter for wildlife. Bees pollinate its flowers, and birds (such as thrushes and jays) and mammals like deer eat its berries.
Max Height: 3-7 feet.
Urban Planting Tips: Thrives in partial to full shade and acidic soils. Ideal for woodland gardens and under taller trees.
Produces Food: Yes, sweet berries are edible for humans and wildlife.
Osoberry (Oemleria cerasiformis): One of the first shrubs to bloom in spring, providing essential early-season nectar for pollinators and food for wildlife. Supports native bees and butterflies. Birds like robins and cedar waxwings eat the berries. Deer browse the foliage.
Max Height: 6-16 feet.
Urban Planting Tips: Prefers partial to full sun and moist, well-drained soil. Works well in naturalized areas or mixed hedgerows.
Salmonberry (Rubus spectabilis): Stabilizes streambanks and moist soils while providing food and cover for wildlife. Flowers attract bees, bumblebees, and hummingbirds. Berries are a favorite for bears, deer, squirrels, and birds like robins and cedar waxwings.
Max Height:Typically grows 3-10 feet, forming dense thickets.
Urban Planting Tips: Prefers moist, rich soils in partial to full sun but can tolerate some shade.
It is best planted near rain gardens or alongside water features to replicate natural conditions. If necessary, prune to manage the spread.
Produces Food: edible orange-red berries enjoyed by both wildlife and humans. The berries are tart and can be eaten fresh or made into preserves.
Thimbleberry (Rubus parviflorus): Provides erosion control on slopes and streambanks while offering habitat and food for wildlife. Flowers attract native bees and butterflies, supporting pollinator populations. Berries feed bears, deer, small mammals, and birds like wrens and grosbeaks. The foliage also provides cover for small wildlife.
Max Height: Grows 3-8 feet, with broad, soft leaves creating a lush appearance.
Urban Planting Tips: Thrives in partial to full shade with moist, well-draining soils. Its tolerance for dappled light makes it perfect for planting under taller trees.
Produces Food: Produces sweet, edible red berries for humans and wildlife. These soft and flavorful berries can be eaten raw or used in jams and desserts.
Pacific Rhododendron (Rhododendron macrophyllum): Known for its stunning flowers and evergreen foliage, the Pacific Rhododendron plays a critical role in stabilizing soil and preventing erosion, especially on slopes and near streambanks. Its flowers attract a range of pollinators, including bees and butterflies, while its dense foliage provides shelter and cover for wildlife.
Max Height: Reaches heights of 6-10 feet, with large, leathery leaves that add structure and richness to the landscape.
Urban Planting Tips: Prefers partial to full shade and thrives in moist, well-draining soils. It is particularly suited for planting in shaded woodland gardens, under taller trees, or along the edges of wooded areas in urban environments.
Western Azalea (Rhododendron occidentale): The Western Azalea brings beauty and biodiversity to urban gardens. It supports pollinators like bees and butterflies with its fragrant, showy blooms and offers habitat for birds and small mammals. This plant plays a role in maintaining ecosystem health by attracting beneficial species and providing food and shelter for wildlife.
Max Height: Grows up to 6-8 feet, with delicate, fragrant flowers and deciduous leaves that add seasonal interest to landscapes.
Urban Planting Tips: Prefers partially shaded areas with moist, acidic soils. This azalea thrives under the canopy of taller trees or in spots with dappled sunlight, making it an excellent addition to woodland gardens and shaded urban yards.
The Herbaceous Layer
Grasses, wildflowers, ferns, and other nonwoody plants dominate this layer. It provides food and shelter for snakes, mice, and other small creatures.
This list focuses on herbaceous plants adapted to the shaded conditions of Oregon's forest understories.
Inside-Out Flower (Vancouveria hexandra): Provides ground cover to stabilize soil, retains moisture, and suppresses weeds. Attracts native bees and supports pollinating insects. Small mammals use it for cover.
Urban Planting Tips: Thrives in partial to full shade and moist, well-drained soil. Great for shaded borders or under trees.
Western Trillium (Trillium ovatum): Provides early-season nectar and pollen for pollinators; helps stabilize forest soil. Attracts bees and ants, which disperse seeds. Deer and rodents may browse on foliage.
Urban Planting Tips: Plant in deep shade with rich, moist soil. Avoid areas with heavy foot traffic, as they are sensitive to disturbance.
Vanilla Leaf (Achlys triphylla): Acts as a ground cover, prevents erosion, and deters pests with its aromatic leaves. Provides shelter for insects. Deer avoid eating it due to its strong scent.
Urban Planting Tips: Prefers full to partial shade and moist, well-drained soils. Excellent for naturalizing shady areas.
Piggyback Plant (Tolmiea menziesii): Provides dense ground cover to retain soil moisture and control erosion. Attracts small insects and provides cover for amphibians and small mammals.
Urban Planting Tips: Thrives in shady, moist areas. Great for container planting or as a ground cover under trees.
Wild Ginger (Asarum caudatum): Offers ground cover, prevents soil erosion, and supports soil organisms. Flowers attract flies for pollination. Small mammals and amphibians use it for cover.
Urban Planting Tips: Thrives in deep shade with moist, rich soils. Ideal for under trees or shaded perennial beds.
Sword Fern (Polystichum munitum): Sword fern is a robust, elegant groundcover that helps control soil erosion while fostering a healthy, diverse soil ecosystem. Its lush fronds shelter small mammals, insects, and amphibians, supporting local wildlife.
Urban Planting Tips: Sword fern flourishes in partial to full shade and moist, well-drained soils. It's perfect for planting in shaded woodland areas, under trees, or along the edges of perennial beds, where it creates a rich, verdant backdrop.
Forest Succession: A Cycle of Renewal
Forests are ever-changing, cycling through growth, death, and regeneration stages. This process, known as succession, is influenced by natural and human-caused disturbances. For example:
Natural Disturbances: Events like wildfires, storms, and insect outbreaks create opportunities for establishing new plant and animal communities.
Human-Caused Disturbances: Logging, urbanization, and farming can alter forest composition and structure.
Succession begins with hardy pioneer species, such as grasses and sun-loving trees, which pave the way for intermediate species and eventually mature forest communities.
When a forest is newly forming or recovering from a disturbance, it follows a natural process called succession. Initially, the area was dominated by fast-growing plants like grasses and wildflowers, which took advantage of the open sunlight and bare soil.
Over time, shrubs and pioneer trees, such as douglas firs and big leaf maples, begin to establish, providing shade and enriching the soil with nutrients. As these trees mature, they create conditions that favor more shade-tolerant species like hemlocks and cedars, gradually shifting the composition of the plant community.
Eventually, the ecosystem reaches a stable climax community, where long-lived trees dominate, and the forest supports diverse plants and animals. This cycle continues as natural disturbances reset the process, allowing the forest to evolve and regenerate.
When we install a new forest, it mimics the natural process of succession, starting much like a newly disturbed area. Initially, the landscape is dominated by fast-growing grasses and wildflowers, which help stabilize the soil and attract pollinators.
As the ecosystem develops, shrubs and pioneer trees like douglas firs, big leaf maples and Oregon White Oaks take root, enriching the soil with organic matter and providing shade. Over time, these early species create the conditions for more shade-tolerant trees, such as vine maple and cascara, to establish and gradually create the understory.
Eventually, the forest matures into a stable, self-sustaining ecosystem that supports diverse plant and animal life. By intentionally planting forests this way, we accelerate natural regeneration and create thriving habitats that will evolve and sustain themselves for generations.
How Can Rewilding Benefit Portland?
Rewilding Portland, Oregon, with a focus on forests, can profoundly impact the city by restoring critical habitats and natural systems that are essential for the environment and its residents. By reintroducing native trees, shrubs, and plant species, we can help balance the urban ecosystem, mitigate the urban heat island effect, and improve air and water quality.
Forests, in particular, act as natural sponges, absorbing rainfall, reducing flood risks, and stabilizing soil. They also provide homes for wildlife, support pollinators, and enhance biodiversity, creating healthier ecosystems within the city. Additionally, forested areas help filter carbon from the air, improving local climate conditions.
Beyond the environmental benefits, urban forests offer tranquil recreational spaces, encourage physical activity, and boost mental health by connecting residents to nature. Portland can revitalize its natural landscape by focusing on rewilding efforts that include forests and creating a more resilient, vibrant city for future generations.
A Web of Life
Rewilding Portland with a focus on forests can transform the city by restoring critical habitats and natural systems that support the environment and its residents.
By reintroducing native trees, shrubs, and understory plants, we can rebalance the urban ecosystem, cool the city, and improve air and water quality. Forests act as natural sponges, absorbing rainfall, reducing flood risks, and stabilizing soil while providing wildlife shelter, supporting pollinators, and increasing biodiversity.
They are crucial in filtering carbon, improving climate conditions, and creating a thriving urban environment. Beyond these benefits, urban forests offer peaceful spaces for recreation, inspire physical activity, and enhance mental well-being by reconnecting people with nature. Prioritizing forested rewilding efforts will restore Portland’s natural landscape and ensure a healthier, more vibrant city for future generations.
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