What is a temperate deciduous forest?

It is a forest of broadleaved trees that lose their leaves each autumn, found where summers are warm, winters are cold and rain falls all year, such as the eastern United States, Europe and East Asia.

Why do leaves change colour in autumn?

Trees stop making green chlorophyll as days shorten, revealing yellow and orange pigments. Some, like maples, also make new red pigments. Sunny days and cool nights give the brightest colours.

Why are the Great Smoky Mountains smoky?

The blue haze comes from water vapour and natural compounds given off by the dense forest, which scatter blue light. Pollution can add to it.

Are there bears in the Great Smoky Mountains?

Yes. Around 1,900 American black bears live in the park. They are wild and should be watched from a distance and never fed.

When is the best time to see autumn colour in the Smokies?

Usually from mid-October to early November, starting on the high ridges and moving down into the valleys.

Red maples, golden beeches and oaks in the oldest mountains of eastern America

Deciduous forest in autumn

3D landscape · Great Smoky Mountains, USA, in October

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Deciduous forests of broadleaved trees cover much of the eastern United States, Europe and eastern Asia. They are forests of four seasons: bare in winter, bright green in spring, shady in summer and blazing with colour in autumn before the leaves fall. In this app you can land in the Great Smoky Mountains on the border of Tennessee and North Carolina in October and explore it in interactive 3D: sugar maples turned scarlet and orange, red oaks and American beeches in rust and gold, rhododendron thickets, ferns and fallen logs, with blue ridges fading into the famous haze.

White-tailed deer browse at the forest edge, black bears forage for acorns before winter, wild turkeys scratch through the leaf litter and red foxes hunt along the clearings. The Smokies are one of the most biodiverse temperate regions in the world and the most visited national park in the United States.

Key facts

Model setting: Great Smoky Mountains, USAA forested mountain range in Tennessee and North Carolina, part of the Appalachians
National park: Established 1934A UNESCO World Heritage Site since 1983 and an International Biosphere Reserve
Highest point: Kuwohi, 2,025 mFormerly called Clingmans Dome; renamed in 2024
Tree species: Over 100 native kindsMore than in any other US national park, according to the park service
Black bears: Roughly 1,900The park estimates about two bears per square mile
Salamanders: About 30 speciesThe Smokies are often called the salamander capital of the world
Peak autumn colour: Mid-October to early NovemberEarlier on the high ridges, later in the valleys
The 'smoke': Natural hazeVolatile organic compounds given off by the forest scatter blue light, adding to moisture in the air

Where deciduous forests grow

Temperate deciduous forest is found in regions with a long, warm growing season, a cold winter and rain spread through the year. The largest areas are in the eastern United States and southeastern Canada, western and central Europe, and eastern Asia, including China, Korea and Japan. Smaller patches occur in South America, New Zealand and elsewhere. Much of this forest was cleared for farming and towns long ago, so large, old forests are now precious.

The Great Smoky Mountains are part of the Appalachian Mountains, which run for some 3,000 km from Alabama to Newfoundland. Their rocks were folded and lifted in mountain-building events that ended roughly 270 million years ago, when the continents joined into Pangaea, making them some of the oldest mountains on Earth, worn down since then into long, rounded ridges.

Why leaves turn colour and fall

Leaves are green because of chlorophyll, which captures sunlight for photosynthesis. As days shorten and nights cool in autumn, deciduous trees stop making chlorophyll and break down what is there to recover its nutrients. Yellow and orange carotenoid pigments that were present all along become visible. Many trees, including red and sugar maples, also make new red and purple pigments called anthocyanins in autumn, which is why bright, sunny days and cool (but not freezing) nights give the best colour.

The tree then grows a layer of cells at the base of each leaf stalk that seals it off, and the leaf falls. Dropping leaves lets the tree avoid losing water through them in winter, when the ground may be frozen, and avoid damage from snow and ice. Fallen leaves rot into a rich soil that feeds the next year's growth.

Maples, oaks, beeches and more

Smoky Mountains forests include sugar maple, red maple, red and white oaks, American beech, tulip tree, hickories, yellow birch and buckeye, with eastern hemlock along streams. Sugar maples turn orange to scarlet, red maples crimson, beeches golden and then copper, and oaks deep red and brown, often holding their leaves late into autumn.

Beneath them grow dense thickets of rhododendron and mountain laurel, which stay green all winter, along with ferns, mosses and hundreds of kinds of wildflowers in spring. Some valleys hold old-growth cove forests that were never logged, with trees well over a metre across.

Lost giants

The American chestnut was once one of the most common trees in these forests. A fungal disease introduced in the early 1900s killed almost all of them. Today hemlocks are under similar threat from an introduced insect, the hemlock woolly adelgid.

Bears, deer and turkeys

The American black bear is the symbol of the Smokies. In autumn bears eat almost constantly, fattening on acorns, hickory nuts, beechnuts and berries before denning for winter, often in hollow trees. White-tailed deer are common in open valleys such as Cades Cove, where wild turkeys also gather in flocks. Red and grey foxes, bobcats, raccoons and coyotes hunt through the forest, and elk, reintroduced in 2001, graze in the Cataloochee valley.

The park's greatest biodiversity is small and hidden: around 30 species of salamanders, thousands of kinds of fungi and insects, and synchronous fireflies that flash together on early summer nights.

A forest of four seasons

Winter in the Smokies brings bare trees, frost and snow on the high ridges. Spring arrives as a wave of wildflowers on the forest floor before the trees leaf out and shade the ground. Summer is warm, humid and green, with frequent afternoon thunderstorms. Autumn colour spreads downhill from the high peaks in early October to the valleys in early November.

Because the mountains rise from about 250 m to over 2,000 m, the high ridges have a climate more like southern Canada, with spruce and fir forests, while the valleys are much warmer.

Pressures on the forest

Air pollution once seriously reduced visibility across the Smokies and acidified some high-elevation soils and streams; it has improved since stricter rules on power plants. Invasive insects and diseases are an ongoing challenge, from chestnut blight to the hemlock woolly adelgid and beech bark disease.

A warming climate is expected to shift species upslope and could threaten the cool spruce–fir forests on the highest peaks, which have nowhere higher to go.

Surprising facts about Deciduous forest in autumn

The yellow and orange of autumn leaves are in the leaves all summer; they only show once the green chlorophyll is broken down.
The blue haze that gave the Smoky Mountains their name partly comes from natural chemicals released by the trees themselves.
The Appalachians were once probably as high as the Alps, before hundreds of millions of years of erosion.
The Smokies have more tree species than almost anywhere else in temperate North America.
Around 30 kinds of salamanders live in the park, some of them found nowhere else.
American chestnuts once made up a large share of the trees in Appalachian forests before an introduced disease nearly wiped them out.

Frequently asked questions

What is a temperate deciduous forest?: It is a forest of broadleaved trees that lose their leaves each autumn, found where summers are warm, winters are cold and rain falls all year, such as the eastern United States, Europe and East Asia.
Why do leaves change colour in autumn?: Trees stop making green chlorophyll as days shorten, revealing yellow and orange pigments. Some, like maples, also make new red pigments. Sunny days and cool nights give the brightest colours.
Why are the Great Smoky Mountains smoky?: The blue haze comes from water vapour and natural compounds given off by the dense forest, which scatter blue light. Pollution can add to it.
Are there bears in the Great Smoky Mountains?: Yes. Around 1,900 American black bears live in the park. They are wild and should be watched from a distance and never fed.
When is the best time to see autumn colour in the Smokies?: Usually from mid-October to early November, starting on the high ridges and moving down into the valleys.

Keep exploring

The landscapes in Ember’s Universe are procedural 3D scenes modelled on real places. The landforms, plants and light follow the real thing, but the details are generated, not mapped.

Sources