WHAT ARE THE TROPICS?. And, how do they work? 2-10-08. TROPICAL HABITATS . Tropical lowland rainforest (=jungle, hylaea) - >100 inches of rain per year Non-seasonal forest Biodiversity is very high Broad-leaved plants Lianas and epiphytes abundant Abundant and constant rainfall
And, how do they work?2-10-08
As one moves north or south from the tropics, there is a latitudinal change in biomes: tropical rainforest, temperate forests, taiga, tundra, polar ice. As one moves up mountains, one may see the same progression (depending on the height and location of the mountain). Rule-of-thumb: for every 1000m one ascends in elevation, average temperature drops 6ºC.
Each 300 ft ascent up a mountain in the tropics has the same average temperature change as if moving 67 miles toward the pole.
The arrival of cold weather.
Rainfall: wet season vs. dry season.
The Permian World – 225 million years before present (mybp). We call the single continent Pangea. From Strahler. Physical Geography. 4th Ed.
The Late Triassic world – 180 mybp. Note the northern continent – Laurasia, and the southern continent – Gondwana (or Gondawanaland). From Strahler. Physical Geography. 4th Ed.
The Late Jurassic world – 135 mybp. Gondwana has broken up into proto-India and a single land mass that will break into proto-Antarctica and proto-Australia. South America and Africa are beginning to separate. From Strahler. Physical Geography. 4th Ed.
The Late Cretaceous world – 65 mybp. Note proto-India headed toward Asia. When it collides, it will create the Himalayan Mountains. From Strahler. Physical Geography. 4th Ed.
The molten upper mantle oozes out along an undersea rift and the continental crust spreads outward. From E.M.E. Plate Techtonics Slide Series. 1978.
The bottom-line is that continents are constantly being made, recycled via subduction, and certainly always on the move. Understanding these movements helps one understand the present-day distribution of flora & fauna.
EDGE EFFECTIn an ecotone, there is often more species diversity along the “edges” of the two habitats than there is in either habitat. This is because the edge shares aspects of each habitat and thus offers habitat to a greater variety of critters.