Biogeography II (Kelt)

Biogeography II (Kelt) - Global Diversity is Very High...

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1 Biogeography II How Climate Dictates the Global Distribution of Biomes and Habitats WFC 10 – D. A. Kelt Global Diversity is Very High What factors make such diversity possible? This is the realm of Ecological Biogeography! Ecological Biogeography To understand ecological biogeography, we need to understand some basics of global climatic patterns. Weather : the condition of the atmosphere at any particular time and place Climate : the accumulation of daily and seasonal weather events over time Thus, the weather on any given day in Ventura may be warm, cold, windy, etc. The climate is defined by the long-term average weather patterns – southern California has a Mediterranean climate. Climate Basics (e.g., “Climate 10”) 1. Seasons The earth is tilted off its axis by 23.5° Winter in the Northern Hemisphere Northern Hemisphere Southern Hemisphere Thus, as the earth rotates around the sun, the sun appears to shift to the north and south. When the northern hemisphere leans towards the sun, it is summer. Leans away . . . winter. Summer in the northern hemisphere corresponds to winter in the southern, and vice versa. When the sun is at it’s polar maximum (north or south), the day/night is longest/shortest; we call this a solstice . During the transition (e.g., spring, autumn) the sun “shifts” from one hemisphere to the other, and on one day each spring and autumn the sun is directly over the equator. These days are called the vernal (spring) and autumnal equinox . 21-22 June (sun at 23.5° N ) 21-22 December (sun at 23.5° S ) 21-22 March 22-23 September At high latitudes the area over which the solar wind impacts is at an angle, and thus is larger, than at tropical latitudes. Moreover, the width of atmosphere that must be passed before reaching the Earth’s surface is also greater than at tropical latitudes Result: At higher latitudes, solar input is distributed over a greater area, and passes through a longer span of atmosphere, before reaching the Earth’s surface. The of solar energy that reaches the top of the atmosphere is subsequently scattered by gases in the atmosphere.
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2 OK – now we are ready to understand the global distribution of some major biomes. At the equator, the sun lies directly overhead.
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Biogeography II (Kelt) - Global Diversity is Very High...

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