Terrestrial Biomes - Forests

Chapter 6

Forests – Coniferous Taiga

Coniferous Forests

• Also called boreal forests or taiga– Also called the spruce-moose forest

• Found across the northern portion of N. America, Europe and Asia – Between the grasslands and the tundra

• No taiga in the Southern Hemisphere

Coniferous Forests

• Long, extremely cold winters with 6-8 hours of sunlight

• Short, cool summers with 19 hours of sunlight

• Annual precipitation (both rain and snow) 14-30”.

Coniferous Forests – Animals

• Populations are scarce, mostly herbivores– Large herbivores

• Reach high into trees or dig into deep snow

– Seed eaters• Pull seeds from cones• Eat fallen seeds on the

ground

• Carnivore size varies– Lynx, wolf

Coniferous Forest - Plants

• Primarily conifers– Also called evergreens

– Stiff needles instead of leaves

– Cones shaped seed cases

• Cones must open to release the seeds

Conifers - Facts

• Adaptations– Needles– Color– Shed their needles slowly– Decrease competition through chemical defense

Temperate Forests Deciduous

Temperate Forests - Facts

• Also called deciduous forests– drop leaves completely every winter

• Found in eastern N. America, western Europe and eastern Asia

• Long, very warm summers

• Cold winters (not severe)

• Forest soil is thick and very fertile

Deciduous Forest - Structure

• Stratified– Canopy

– Understory

– Shrub layer

– Ground cover

– Litter layer

Forest Structure

Deciduous Forest - Animals

• High biodiversity– Includes:

• Birds

• Small and large herbivores

• Small and large carnivores

• High degree of resource partitioning

Deciduous Forest - Plants

• High biodiversity from canopy to ground

• Canopy is primarily deciduous trees – Includes maples,

birches and oaks

Plant Adaptations

• Leaves – broad and flat for maximum photosynthesis

• Excess carbohydrates made during photosynthesis is stored in the sap

Plant Adaptations

• Daylight shortens – Trees prepare to lose their leaves.– Chlorophyll is removed from the

leaves

– Tubes connecting the leaves to the stem close

– Leaves begin to dry

– Leaves fall – leaving only the branches exposed to winter snow, ice and wind

Plant Adaptations - Seeds

• Seeds can’t grow in shadow, so they must be dispersed.

• Done by:– Brightly colored fruit

– Hard shells

– Wings

Forests – Tropical Rainforest

Tropical Rainforests - Facts

• Found along or near the equator– Amazon River (S. America), Indonesia, Africa

and Central America

– Currently covers about 2% of the earth’s land surface

– Believed to be the major source of the world’s fresh air

Tropical Rainforest - Climate

• Hot all year…very little variation in temperature

• No true seasons• Humidity is always high• Rains almost every day,

usually in the afternoon.• Annual precipitation – 80-

160”

Rainforest Structure

Rainforest Structure– Similar structure as

temperate forests plus the emergent layer

– Canopy is very thick. • Only 1% of sunlight

ever reaches the forest floor.

Rainforest Animals

• Highest biodiversity in the world

• Contains at least ½ of the entire world’s plant and animal species

• Species are highly stratified. There is very little competition between species.

• Most animals live in the canopy because of the presence of sunlight.

Rainforest Animals

Rainforest Vegetation

• Trees are very tall (180’) with broad, evergreen leaves.– Mahogany

• Leaf cover is very dense, restricting growth of competing plants

• Roots are shallow to increase absorption of soil nutrients

Vegetation Adaptations

• Shallow tree roots are supported by buttresses.

• Understory plants have huge leaves to maximize sunlight for photosynthesis (elephant ear)

Specialized Rainforest Plants

• Epiphytes– Plants that grow on tree

branches and trunks.

– Roots absorb moisture directly from the air

– Debris collects around their roots forming pockets of organic matter which they use as a nutrient source.

Specialized Rainforest Plants

• Lianas– Climbing vines

– Roots are in the shallow soil, but the main plant is found in the canopy

– Uses the trunks and branches of trees for support to reach the sunlight

Human Impacts on Forests

• Man is clearing the forests faster than the trees can regrow.

• Temperate forests are cleared in N. America, Europe and Asia for timber, cropland and urban development.

• Conifer forests in N. America, Canada and Russia are cleared for timber, mining and hydroelectric dams.

• Tropical rainforests are cleared for timber, domestic cattle and agriculture.

Human Impacts on Forests – Results

• Erosion increases

• Erosion causes suspended solids to increase in rivers and streams, killing aquatic life

• Agriculture in cleared soil rapidly depletes forest soil nutrients

• May lead to global warming

• May lead to overall loss of fresh air