Transcript Biomes
The Biosphere Climate and Biomes • You’ve probably heard a lot about Global Climate Change (sometimes called Global Warming). • What is climate? • What effects can a changing climate have on living organisms? • Suppose your region has an especially hot summer, followed by a very cold winter that includes a snowstorm. Does this support, disprove, or have little to do with Global Climate Change? D A I L Y W O R K Climate • Climate is not the same thing as weather! • Climate consists of the prevailing weather patterns in a region over longs periods of time. • Climate is caused by many factors, including location on the globe, nearness to an ocean, wind direction, geography. The sun drives climate as well as the seasons. North Pole Summer in the Northern Hemisphere 90° N 23.5° tilt 0° 0° 23.5° tilt South Pole June 21st : northern summer solstice; southern winter solstice Summer in the Southern Hemisphere 90° S December 21st : northern winter solstice; southern summer solstice • Average temperature at any part of the globe is affected not by how close we are to the sun (a common misconception) but by the angle of incidence of the sun’s rays. Less direct rays = less solar energy = cooler region More direct rays = more solar energy = warmer region cold, dry air falls • Global air circulation influences local climates. • Rising air cools and drops moisture. • Descending air tends to be dry. Polar 90 N Easterlies polar cap 60 N Westerlies cool, moist air rises (rain/snow) warm, dry air falls 30 N desert N.E. Tradewinds rotation 0 hot, moist air rises (rain) rain forest S.E. Tradewinds 30 S Westerlies rain forest 60 S Polar polar cap Easterlies 90 S cold, dry air falls desert warm, dry air falls cool, moist air rises (rain/snow) • According to this diagram, where on the planet should we find: • Deserts? B. Warm, dry, falling air • Tropical rain forests? • Permanent snowfields? C. Warm, moist, rising air A. Cool, moist, rising air D A I L Y W O R K • Ocean current also affect climate. • Water tends to absorb and retain heat, and lose it slowly. • Ocean water near the equator tends to be warm, so currents from the equator are warm. • Water near the poles is much cooler. • The Gulf Stream carries warm water from the equator northward, warming the coast of Europe. • There is evidence that the Greenland ice is melting, due to Global Climate Change, and pouring cold water into the North Atlantic. If this happens what will happen to the climate of Northern Europe? Water is carried from ocean by prevailing winds. Water is released as air rises and cools. moist climate Dry air sinks, warms and absorbs water from the land. dry climate in rain shadow high rock, snow, ice tundra altitude coniferous forest deciduous forest tropical forest low equator (0°) latitude poles (90°) Biomes • The concept of “biome” is controversial. • What “biomes” an ecology text describes depends on how fine-grained the divisions are. • At the broadest view, there are six major biomes. Major Biomes • Hot, dry = hot desert • Hot, wet = tropical rain forest • Warm, dry = grasslands • Warm, wet = temperate deciduous forest • Cold, dry = tundra, cold desert • Cold, wet = northern boreal forests (taiga) low Temperature tundra coniferous forest (taiga) cool desert high warm desert low cool grassland temperate deciduous forest warm grassland temperate rain forest savanna Rainfall tropical deciduous forest tropical rain forest high Desert • Deserts may be hot or cold, though hot deserts have a different structure than cold deserts. • Deserts are characterized by low rainfall. • When rain does fall, it often falls “all at once,” and runs off. Sagebrush Desert, Utah Mojave Desert, California Sahara Desert, Northern Africa Where is this? A dry valley in Antarctica! Not all deserts are hot! And even “hot” deserts aren’t always hot. Snow in the Mojave Tropical Rain Forest • Characterized by a warm climate and high rainfall. • Very high biodiversity. • Forest structure may include multiple layers: floor, understory, canopy, and emergent layers. • Soil layer is thin, because organic material decays quickly and is taken up by plants. Tropical Rain Forests Mists over a tropical rain forest Grassland • Grasslands, shrublands, and dry woodlands are characterized by: • Low to moderate rainfall (semi-arid) • Warm to hot summers, cold winters • Prairies may have deep, rich soil Shortgrass prairie, South Dakota Zhongdian Steppe, Tibet Prairie habitats are fire-based ecosystems. Temperate Deciduous Forest • Deciduous forests grow in temperate regions with moderate rainfall that also tend to have wet summers. • Trees drop their leaves before the cold winters. • The open spring canopy allows a flush of spring wildflowers before the trees leaf out again. Mohican State Memorial Forest, Ohio Oak-Hickory forest, Missouri Northern Boreal Forest • Coniferous forests are favored where there are either dry seasons or harsh winters, or both. • Needle-shaped leaves with waxy coats can endure harsh, cold winds in northern climates and on mountains. • Needle-leaved conifers are also found near oceans, where harsh salt spray can dry out plants. High winter rainfall can create temperate rainforests in this biome, such as the Hoh Rainforest in Washington. Where there is less rainfall, the trees are more sparse, as in this taiga forest in Alaska. Tundra • Arctic tundra is characterized by permafrost, shrubby vegetation, and sometimes bogs. • Alpine tundra usually does not have permafrost, but does feature alpine meadows or shrubby vegetation, and no trees. Arctic tundra in the Arctic National Wildlife Refuge Alpine tundra on Mt. Rainier Ocean Biomes • Oceans are often divided into zones just as the land is, including: • Estuary • Intertidal zone • Continental shelf • Open ocean • Hydrothermal vents intertidal zone near-shore zone open ocean plankton photic zone 200 m aphotic zone Estuary Intertidal zone: Rocky Intertidal zone: sandy Continental Shelf Reef Open Ocean Deep Ocean Hydrothermal Vents