Tropical rain forest is the most productive

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Tropical Rain Forests (cont.) Tropical rain forest is the most productive, structurally complex, and species-rich biome Photosynthesis occurs year-round; but trees often form a closed canopy that blocks light from the forest floor Deforestation is an ongoing threat to tropical rain forests in developing countries with fast-growing human populations
Tropical Rain Forests (cont.) Decomposition and mineral cycling happen fast in the warm, moist environment Soils are highly weathered, heavily leached, and are very poor nutrient reservoirs
Coniferous Forests Conifers withstand harsher conditions than broadleaf trees, so they grow farther north and at higher altitudes The coniferous forest that extends across northern Asia, Europe, and North America – known as boreal forest or taiga – is the most extensive land biome boreal forest Extensive high-latitude forest of the Northern Hemisphere; conifers are the predominant vegetation
Coniferous Forests (cont.) Conifers (evergreen trees with seed-bearing cones) such as pine, fir, and spruce are the main plants in coniferous forests Conifers are adapted to conserve water during drought or times when the ground is frozen – winters are long, cold, and dry; and most rain falls in the cool summer Moose are the dominant grazers
Other Coniferous Forests Montane coniferous forests of spruce, fir, and pine extend southward through great mountain ranges Spruce and fir dominate highest elevations Firs and pines occupy lower elevations Coniferous forests in temperate lowlands along the Pacific coast from Alaska into northern California hold the world’s tallest trees: Sitka spruce to the north Coast redwoods to the south
Other Coniferous Forests (cont.) New Jersey pine barrens are a mixed forest of pitch pines and scrub oaks that grow in sandy, acidic soil Southeastern pine forests hold fast-growing loblolly pines that survive periodic fires that kill most hardwood species – these pines are a major source of lumber and wood pulp
Tundra Low-growing, cold-tolerant plants have only a brief growing season on two types of tundra arctic tundra Highest-latitude Northern biome, where low, cold-tolerant plants survive with only a brief growing season alpine tundra Biome of low-growing, wind-tolerant plants adapted to high-altitude conditions
Arctic Tundra Arctic tundra forms between the polar ice cap and belts of boreal forests in the Northern Hemisphere Snow covers arctic tundra up to nine months of the year; lichens and shallow-rooted plants grow quickly during a brief summer under nearly continuous sunlight Food webs include voles, arctic hares, caribou, arctic foxes, wolves, and brown bears; many migratory birds nest here in the summer
Arctic Tundra (cont.) Only the surface layer of soil thaws during summer – below that lies permafrost up to 500 meters (1,600 feet) thick Permafrost prevents drainage; and cool, anaerobic conditions slow decay, so organic remains build up permafrost Continually frozen soil layer that lies beneath arctic tundra and prevents water from draining
Tundra Life is apparent in short summer Grasses & sedges
Alpine Tundra

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