Environmental Science Ch 9. Forest Biomes
Types of Forests The term forest is actually used to describe 3 different types of sub-biomes that are made up predominantly of trees They are: Coniferous forest: primarily contain trees that bear seeds in cones Decidous forests: primarily contains trees that lose their leaves during a particular season of the year Rain forest: primarily contains broadleaf evergreens
Coniferous Forest **Sometimes called the temperate rainforest The moist conditions of temperate rain forests generally support an understory of mosses and are notable for trees of massive proportions, including Giant Sequoia (Sequoiadendron gigantea). These forests are quite rare, occurring in small areas of North America, southwestern South America and northern New Zealand. One example of temperate coniferous forest, the Klamath-Siskiyou forests of northwestern California and southwestern Oregon, is known particularly for its rich variety of plant and animal species
Conifers Coniferous trees are usually called conifers These are trees that produce seeds that are held within dynamic structures called cones Conifers also contain a specialized leaf, called a needle which is covered in a waxy substance to help prevent damage and water loss Conifer needles also prevent large amounts of snow and wind to get trapped on them reducing damage during winter and storms Most Conifers are also evergreens.
A Hard Life for a Pine Tree The growing season in most coniferous forests is very short with long cold winters This makes pine trees specialized to grow rapidly during the brief summers and utilize slower growth during the cold, long winters Much of the year, moisture is trapped in snow and ice and only can be utilized by plant life during the brief spring and summer months It is also a hard life for the many organisms that live in this biome
Deciduous Forests A deciduous tree is a tree that loses its leaves during a particular season. A deciduous forest is predominantly made up of deciduous trees These forests are common in areas where the climate shows a cold season where the suns energy is too low for photosynthesis It is also common to areas that get seasonal snow storms, but usually less frequent than the subarctic These forests usually receive around 50 300 cm of rainfall
Temperate Forests Often times a deciduous forest is referred to as a temperate forest because it is well adapted to the temperate zones Temperate zones are areas of the Earth with large temperature variability (warm summers and cold winters) Deciduous forests have a higher level of diversity than a coniferous forest because they have longer growing seasons Longer growing seasons = more energy = more bio mass = more food = more organisms
3 Layers of the Deciduous Forest A deciduous forest has three layers, each with their own unique niches and species: The highest level is the canopy and is made of the upper branches and leaves of the forest The middle level is call the understory and is made up of the are under the canopy containing younger trees and tall bushes The lowest level is called forest floor and is made up of anything lying on the forest ground. It is also composed of things living within the leaf litter
Rain Forest Tropical zones are dominated by large hardwood (usually broad leaf) tree that never lose their leaves (evergreen) These areas are warm year round, see little seasonal change, and have a the largest biomass of any biome These areas are called Tropical Rainforests or Jungles These fragile environments make up only about 3% of the Earth s lithosphere but contain 50-70% of all species on Earth
Rain, Rain, Everyday (almost) The rainforest is a biome with a dense canopy of leaves that allows little light to protrude to the forest floor On average they receive a minimum of 200cm of rain fall each year Because of the warm, wet climate, dead organic matter is cycled back into the ecosystem very rapidly This makes the soil surprisingly low in nutrients Rainforest trees have shallow roots to take advantage of the thin layer of rich soil and large thick bases to help anchor the tall trees
HUGE DIVERSITY The rainforest is known for its unmatched diversity of species, both in plants and animals The large amount of available energy and water, without the threat of freezing temperatures are ideal for species There may be several hundred tree species in just a few acres of land There may be over a hundred different species living in and on a single tree
Going, going, GONE In the last 60 years we have lost about 50% of the total rainforest biome to deforestation This is considered to be the number one priority to most environmentalists because rainforests house most of the worlds species Losing a single acre may cause 1,000 species or more to go extinct Most rainforests occur in economically poor countries who readily sell the logging rights for needed economic gain The elevated concern for these areas make them environmental red zones
The Disappearing Forest Few biomes have been more drastically changed than the deciduous forest At one time in the recent past deciduous forests stretched across Europe and Asia and covered most of the Eastern half of the United States Now, most forests have been destroyed do to human deforestation for lumber and colonization Today, most forests are small fragments of what they used to be
The EDGE Effect Environmentalists for years have been concerned about the effects of fractioning forest biomes Aside from having vertical layers that allow for different niches and biomes, many forests also have horizontal layers These layers consist of an edge, a semi-edge, and a forest heart Many organisms can only survive in the heart of the forest which is the inner most area As a forest habitat is fragmented, the amount of forest heart area is dramatically reduced and the edge and semi edge dramatically increase