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Types of Forests. Tropical (Rainforests). Canopy is often closed (little light reaches below) A canopy opening happens when a tree falls Plants competing for the light fill the space Many trees are covered with epiphytes Epiphyte - plants that grow on other plants instead of in the soil
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Tropical (Rainforests) • Canopy is often closed (little light reaches below) • A canopy opening happens when a tree falls • Plants competing for the light fill the space • Many trees are covered with epiphytes • Epiphyte- plants that grow on other plants instead of in the soil • Rainfall determines the vegetation growth rate
Coniferous Forests • Has cone bearing trees (pine, spruce, fir, and hemlock) • Also called temperate rain forests • Warm, moist air from the pacific ocean supports these unique communities • They are usually dominated by one or a few species of trees • The Taiga is the largest terrestrial biome on earth • Receives heavy snowfall but the cone shape of the trees prevents branches from breaking • Currently, they are being heavily logged.
The Northern Coniferous Forest stretches from North America to Eurasia. The southern border of the artic tundra is called the TAIGA. Taiga
Temperate Deciduous • Dense stands of trees • Occur where there is enough moisture to support growth of large trees • More open than rain forests, but not as tall • Has distinct vertical layers • Mammals in these forests hibernate and some migrate to warmer climates • Deciduous- plants that drop their leaves before winter • This is done because temperatures are too low for photosynthesis
Deciduous Trees and Winter Dormancy • Deciduous trees begin to lose their leaves when temperatures begin to get colder and the days become shorter • Circadian Rhythm- a 24 hour cycle that organisms internally live by
What causes leaves to fall? • This happens in 3 steps: • Cells die at the base of each leaf because of forming cork that cuts off the water and nutrients for the leaf • Green chlorophyll turns to other types of chlorophyll that can use sunlight better • Xanthophylls: yellow light • Carotenoids: yellow and orange light • Anthocyanins: scarlet and purple light • Leaves fall to the ground • This prevents trees from being damaged because of freezing temperatures and strong winds • The tree remains dormant in the winter until longer days and warmer weather cause new leaves to grow