Forests, Rainforests, Trees

Forests

A forest is an area with a high density of trees (or, historically, a wooded area set aside for hunting). Actually, many definitions of a forest exist. These plant communities cover large areas of the globe and function as carbon dioxide sinks, animal habitats, hydrologic flow modulators, and soil conservers, constituting one of the most important aspects of the Earth's biosphere.

Forests can be found in all regions capable of sustaining tree growth, at altitudes up to the tree-line, except where natural fire frequency is too high, or where the environment has been impaired by natural processes or by human activities.

As a general rule, forests dominated by angiosperms (broadleaf forests) are more species-rich than those dominated by gymnosperms (conifer or needleleaf forests), although exceptions exist (for example, species-poor aspen and birch stands in northern latitudes).

Forests sometimes contain many tree species within a small area (as in tropical rain and temperate deciduous forests), or relatively few species over large areas (e.g., taiga and arid montane coniferous forests).

Forests are often home to many animal and plant species, and biomass per unit area is high compared to other vegetation communities. Much of this biomass occurs below-ground in the root systems and as partially decomposed plant detritus. The woody component of a forest contains lignin, which is relatively slow to decompose compared with other organic materials such as cellulose or carbohydrate.

Forests are differentiated from woodlands by the extent of canopy coverage: in a forest the branches and foliage of separate trees often meet or interlock, although there can be gaps of varying sizes within an area referred to as forest. A woodland has a more continuously open canopy, with trees spaced further apart, which allows more sunlight to penetrate to the ground between them.

Among the major forested biomes are:

Classification

Forests can be classified in different ways and to different degrees of specificity. One such way is in terms of the biome in which they exist combined with leaf longevity of the dominant species (whether they are evergreen or deciduous). Another distinction is whether the forests composed predominantly of broadleaf trees, coniferous (needle-leaved) trees, or mixed.

Boreal forests occupy the subarctic zone and are generally evergreen and coniferous.
Temperate zones support both broadleaf deciduous forests (e.g., temperate deciduous forest) and evergreen coniferous forests (e.g., Temperate coniferous forests and Temperate rainforests). Warm temperate zones support broadleaf evergreen forests, including laurel forests.
Tropical and subtropical forests include tropical rainforests, tropical and subtropical moist forests, tropical and subtropical dry forests, and tropical and subtropical coniferous forests.
Physiognomy classifies forests based on their overall physical structure or developmental stage (e.g. old growth vs. second growth).
Forests can also be classified more specifically based on the dominant tree species present, resulting in numerous different forest types (e.g., ponderosa pine/Douglas-fir forest).

Forest management

The scientific study of forests is referred to as forest ecology, while the management of forests is often referred to as forestry, often with the goal of sustainable resource extraction.

Forest ecologists concentrate on forest patterns and processes, usually with the aim of elucidating cause and effect relationships. Foresters often focus on wood extraction and silviculture, including tree regeneration and growth processes.

Forests can be altered when logging, forest fires, acid rain, herbivores, or diseases, among other things, cause damage to trees. In the United States, most forests have historically been affected by humans to some degree, though in recent years improved forestry practices has helped regulate or moderate large scale or severe impacts. However the United States Forest Service estimates that every year about 1.5 million acres (6,000 kmž) of the nation's 750 million acres (3,000,000 kmž) of forestland is lost to urban sprawl and development. It is expected that the South alone will lose 20 to 25 million acres (80,000 to 100,000 kmž) to development.

Facts About Forests Wikipedia

In the News ...

Oldest Living Tree Found in Sweden - 9,550 years old National Geographic - April 14, 2008

California wildfires of October 2007 Wikipedia

Singapore's "Magic Monkey" Trees Inspire Cult, Cynics September 27, 2007

Monkey Tree Phenomenon Wikipedia

Texas: Mysterious 'Fairyland' Spider Web Found Live Science - August 30, 2007

Ancient forest found in Hungary BBC - August 12, 2007

Giant Fossil Rain Forest Discovered in Illinois National Geographic - April 25, 2007
A giant fossilized rain forest has been unearthed in an Illinois coal mine. Preserved by a major ancient earthquake, the forest covers four square miles (a thousand hectares) and features an abundance of huge leaf impressions, large trunks of extinct trees, and tree-size horsetail plants, the researchers said.
Ancient Rainforest Revealed in Coal Mine Live Science - April 23, 2007
Scientists exploring a mine have uncovered a natural Sistine chapel showing not religious paintings, but incredibly well preserved images of sprawling tree trunks and fallen leaves that once breathed life into an ancient rainforest. Replete with a diverse mix of extinct plants, the 300-million-year-old fossilized forest is revealing clues about the ecology of Earthšs first rainforests.
Earth's First Rainforest Unearthed PhysOrg - April 23, 2007

Oldest Tree, Forest Fossil

Newfound Fossils Reveal Secrets of World's Oldest Forest National Geographic - April 18, 2007

Until now, however, scientists could only speculate what type of tree the Gilboa stumps, designated Eospermatopteris, represented. "What we found in the last couple of years was evidence of what the top of these things looked like," Stein said. The new fossils indicate that the fossil trees belong to a previously known plant group called cladoxylopsids, Stein said. Scientists suspected the fernlike cladoxylopsids were large, but experts never had more than the branches to work with, Stein added. "What we got here is like a double whammy," he said. "On the one hand, we know Eospermatopteris is these great stumps. On the other hand we have real evidence for how big the cladoxylopsids actually were."

Brigitte Meyer-Berthaud is a paleobotanist with the National Center for Scientific Research in Montpellier, France. She said the new fossils are surprising because they indicate Earth's first trees evolved without the aid of leaves and horizontal branches. "It was probably so advantageous to be bigger than the others that they achieved [height] even if they didn't have the proper organs," she said. Meyer-Berthaud, who co-authored an accompanying article on the new research, identified in 1999 a different type of tree called Archaeopteris as the earliest modern tree.

These trees, which date to around 385 million to 359 million years ago, had horizontal branches, leaves, and an extensive root system. Such structures are considered important to achieve treelike stature and are common to most trees in temperate and tropical areas today. The Gilboa forest dates to 385 million years ago, and the group of cladoxylopsids that includes the Gilboa trees was widespread around the world from about 385 million to 400 million years ago. Stein noted that these early trees played a major role in establishing Earth's first terrestrial ecosystems. "Trees really dominate those kinds of environments they're found in. They really are the entire fabric in which an entire ecology fits in a terrestrial realm," he said.

How Ancient Forests Looked -- Understanding the full appearance of the Gilboa trees allows scientists to infer what the entire forest ecosystem was like. For example, since the Gilboa trees lacked leaves, sunlight would have filtered down to the forest floor. And the trees, like modern palms, likely dropped their branches on a yearly or seasonal cycle, filling the forest floor with woody litter suitable for arthropods such as spiders and insects. The trees also would have removed carbon dioxide from the atmosphere, causing global temperatures to drop, Stein added. The traits of the Gilboa trees are found in many tree types throughout history, he noted. "The traits cannot all be traced back to the same common ancestor, so it's clearly a recurrent evolved form," he said. "The reason for that is probably ecology, probably something to do with a way of being a large tree or a large plant. It's one way to do it, and it is now clearly the oldest way," he added.

World's First Tree Reconstructed Live Science - April 18, 2007

In 2004, scientists unearthed a 400-pound fossilized top or crown of the same genus a few miles away. The following summer, the same team discovered fragments of a 28-foot trunk. Piecing together stump, trunk and crown now reveals what the full tree looked like for the first time.

Species belonged to a group of early fern-like plants called Wattieza.

Worldšs first tree reconstructed MSNBC - April 18, 2007

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