3.7 Biogeography and soils of the world notes

1. 3.7.1Soil formation: factors, processes and the soil profile

   Soil forms slowly from weathered rock as climate and living things work on it over time; its layers (horizons) record these processes, and its five controlling factors are parent material, relief, climate, organisms and time.

   Standard · 8 min · Full course
2. 3.7.2Major soil types of the world and their distribution

   World soils follow world climates and vegetation: leached red laterites in the wet tropics, ash-grey podzols under northern conifers, rich black chernozems under mid-latitude grasslands, and thin salty soils in deserts.

   Standard · 8 min · Full course
3. 3.7.3World forests: equatorial, monsoon, Mediterranean, temperate and coniferous

   The world's forests change with climate from the dense, layered evergreen rainforests of the equator, through monsoon forests that shed leaves in the dry season and drought-adapted Mediterranean woodland, to temperate broadleaf forests and the vast needle-leaved taiga of the north.

   Standard · 9 min · Full course
4. 3.7.4World grasslands: savanna, prairie, steppe, pampas, veld and downs

   Grasslands grow where rain is too little or too seasonal for forests: tall grass with scattered trees (savanna) in the tropics, and short, treeless grassland in the interiors of mid-latitude continents, which carries a different name on each continent.

   Standard · 7 min · Full course
5. 3.7.5Deserts of the world: hot and cold deserts and polar regions

   Deserts are places of very low rainfall — hot deserts on the western sides of continents in the subtropics, cold deserts in mid-latitude interiors and rain shadows, and the polar deserts and tundra where cold, not heat, limits life.

   Standard · 9 min · Full course

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