Saturday, May 14, 2011

Needleleaf biome



              Needleleaf forest is composed largely of straight trunked, conical tress with relatively short branches, and small, narrow, needlelike leaves. These tress are conifers. Where evergreen, the needleleaf forest provides continues and deep shade to the ground so that lower layers of vegetation are sparse or absent except for a thick carpet of mosses in many places. Species are few and large tracts of forest consist almost entirely of but one or two species.

              Needleleaf evergreen forest extends into lower latitudes wherever mountain range and high plateaus exist. Thus in western North America this formation class extends southward into the United States on the Cascade, Sierra Nevada, and Rocky Mountain ranges and over parts of the higher plateaus of the southwestern states. In Europe, needleleaf evergreen forests flourish on all of the higher mountain ranges, and well into Scandinavia.

Taiga

            The taiga is the biome of the needleleaf forest. Living in the taiga is cold and lonely. Coldness and food shortages make things very difficult, mostly in the winter. Some of the animals in the taiga hibernate in the winter, some fly south if they can, while some just cooperate with the environment, which is very difficult.

           Temperature range in the summer gets as low as -7° C (20° F). The high in summer can be 21° C (70° F). The summers are mostly warm, rainy and humid. They are also very short with about 50 to 100 frost free days. The total precipitation in a year is 30 - 85 cm (12 - 33 in) . The forms the precipitation comes in are rain, snow and dew. Most of the precipitation in the taiga falls as rain in the summer.

          The main seasons in the taiga are winter and summer. The spring and autumn are so short, you hardly know they exist. It is either hot and humid or very cold in the taiga.

          There are not a lot of species of plants in the taiga because of the harsh conditions. Not many plants can survive the extreme cold of the taiga winter. There are some lichens and mosses, but most plants are coniferous trees like pine, white spruce, hemlock and douglas fir.

         Evergreens in the taiga tend to be thin and grow close together. This gives them protection from the cold and wind. Evergreens also are usually shaped like an upside down cone to protects the branches from breaking under the weight of all that snow. The snow slides right off the slanted branches.

         The taiga is susceptible to many wildfires. Trees have adapted by growing thick bark. The fires will burn away the upper canopy of the trees and let sunlight reach the ground. New plants will grow and provide food for animals that once could not live there because there were only evergreen trees.

Temperate coniferous forest

         Temperate coniferous forest is a terrestrial biome found in temperate regions of the world with warm summers and cool winters and adequate rainfall to sustain a forest. In most temperate coniferous forests, evergreen conifers predominate, while some are a mix of conifers and broadleaf evergreen trees and/or broadleaf deciduous trees. Temperate evergreen forests are common in the coastal areas of regions that have mild winters and heavy rainfall, or inland in drier climates or mountain areas. Many species of trees inhabit these forests including cedar, cypress, douglas-fir, fir, juniper, kauri, pine, podocarpus, spruce, redwood and yew. The understory also contains a wide variety of herbaceous and shrub species.


           Coniferous trees are also known as evergreens. They have long, thin waxy needles. The wax gives them some protection from freezing temperatures and from drying out. Evergreens don't loose their leaves in the winter like deciduous trees. They keep their needles all year long. This is so they can start photosynthesis as soon as the weather gets warm. The dark color of evergreen needles allows them to absorb heat from the sun and also helps them start photosynthesis early.

A pine forest is an example of a temperate coniferous forest

          Structurally, these forests are rather simple, generally consisting of two layers: an overstory and understory. Some forests may support an intermediate layer of shrubs. Pine forests support an herbaceous understory that is generally dominated by grasses and herbaceous perennials, and are often subject to ecologically important wildfires.