Explain Temperate Deciduous Forests-Taiga and tundra?

Temperate deciduous forests are typified by the type of forests predominantly found in the eastern and northeastern United States, southeast Canada, and northern and central Europe and Scandinavia. These types of forests can also be found in other parts of the world such as Russia, Asia, parts of Australia, Brazil, Africa, and much of New Zealand. The term "temperate" refers to the relatively non-extreme, or moderate temperatures that characterize the region's climate, although winters can be dramatic. The term "deciduous" refers to trees that lose their leaves in the winter, and grow new leaves in the spring. Although water is frozen and largely unavailable in winter, rainfall is not restricted to any one season, and amounts range between 75 to 250 cm per year.

Temperatures range from -30 degrees C to +30 degrees C, and rainfall is relatively evenly distributed over the course of a year. This type of biome typically experiences warm summers with rain and cold winters. These conditions support the growth of large deciduous trees and the building of a deep, organically rich soil structure. Species that are typically found in deciduous forests are oak, maple, birch, beech, and hickory. Temperate deciduous forests have a characteristic vertical structure consisting of a top canopy, understories, shrub layer, and herbaceous ground cover. Light conditions at each level often determine the vertical makeup of the forest.

Taiga : Taiga is also refered to as northern coniferous forest, and is found below the arctic in Europe and North America. The vegetation that makes up this biome is very distinctive, characterized by stands of pine, fir, hemlock, and spruce that cover vast expanses. The very cold dry winter season lasts for long periods and the summers are short and wet. The winter days are extremely short in duration (6-8 hours), as opposed to summer days, which are very long, and can last up to 16 hours. As a result, the plants that live in the taiga grow very rapidly when sunlight conditions are favorable.

The taiga gets covered by a thick layer of snow in the winter, providing an insulating blanket that keeps the ground from freezing. This allows the forest to grow, and supports a community of small animals like rodents beneath. The snow pack also reduces the predation from animals such as lynx, wolves and wolverines. The taiga is also home to large animals such as moose, elk, deer, and bear. In the summer, the snow melt forms bogs and marshes, ponds and lakes. Plants like willows and birches, usually found around water, grow here in the taiga as well as other non-coniferous trees such as polar and alder.

Tundra :  The biome known as the tundra is found north of the taiga, and extends to just below the permanently frozen Arctic ice. The vegetation that characterizes the tundra consists of patches of low grasses, lichens, small shrubs, and short, dwarf forms of trees. In general, these are perrenial plants with underground stoage organs that undergo quick bursts of growth in the summer. During the the summer season, which is very short in duration, the snow melts and the top two feet of frozen ground thaw, producing a bog situation. Since the water can't percolate down through the remaining frozen ground layers, conditions are roughly equivalent to a saturated sponge. The frozen layers below are called permafrost.

Rainfall is relatively low, averaging under 25 cm. per year. But because the ground is frozen, water is for the most part not usable by the plants for much of the year, except during the short summer season, which averages 6 to 8 weeks. The sun's angle at these high latitudes does not provide very much energy for photosynthesis either, so the growth is relatively limited.

Standing water allows fertile breeding grounds for insects like flies and mosquitos. Snowshoe hares and lemmings are also fairly typical inhabitants of the tundra. Lemmings go through cyclical population explosions, which, in turn, influences the populations of their predators like foxes, lynx, weasels, snowy owls, and the arctic wolf. Large mammals, such as musk-ox, caribou, and reindeer also browse (graze) the tundra.

At the edge of its northern range, tundra ends in barren windswept rocks and ice, where plants are few and far between. Glaciers and ice flows occupy the rest of the land masses north of the tundra.