One fifth of the Earth's land surface is grassland - a biome found on every continent except Antarctica Sources: Earth Observatory; Grassland biomes can be found in the middle latitudes, in the interiors of continents Most of the world's natural grasslands have been converted to wheat or corn fields Environmental Science10/27/08 Mrs. RosenMrs. Waldinger Do Now: Use the textbook to describe the difference between a savanna and a grassland. Aim: How is a grassland different than the tropical rainforest and deserts that we have studied? Homework Packet #9 is due next Monday.

THEMATIC SLIDES

GRASSLAND

Conversion of grasslands into agriculture Narok, Kenya 1975: The agricultural expansion is just beginning 2000: This image shows the degree to which farmlands have expanded

Farmlands abandoned for savannas Peanut Basin, Senegal Shows growing patchwork of savannas (greenish patches) 1979: Image shows farmland before being abandoned 1999: Hundreds of villages are scattered throughout the region to enjoy fallow and grazing lands

Impact of drought and over-grazing Revane, Senegal 1965: Ancient valleys cutting through gravelly plateaus, with extensive bushland vegetation 1999: The badland phenomenon spread extensively along the shallow valley slopes

Fire – a regular occurrence in Wyperfeld National Park, Australia 1973: Vegetation in the Wyperfeld National Park is mostly a rich green in the image 2000: The dark green areas are now mottled with light patches, areas where the ground is bare after a burn 2004: Significant additional burned areas

Changing landscape of Upper Green River, United States The landscape in 1989 Over 3000 wells (black/white dots) Have been approved in the basin, and development is occurring at a rapid rate

-found near the equator -temperature varies little from approximately 23°C -the length of daylight varies from 12 hours by less than one hour -rainforest>2000mm Tropical Rain Forest

-canopy trees up to 55 m tall -largest biome, on an area basis -soils are generally unfertile -nutrients and carbon stored in plant biomass, not soils

Tropical Savanna/Seasonal Forest

-found in the tropics (but > 10° latitude) -pronounced dry season with <5 cm rainfall in some months Tropical Savanna/Seasonal Forest

-scattered trees and grass -fire & grazing by animals also contribute to predominance of grasses

Temperate Grassland/Shrubland

-similar to tropical savanna, but with cold winter -relatively hot summer -potential evapotranspiration > ppt

Temperate Grassland/Shrubland -scattered trees and shrubs -trees are short statured -fire & grazing by animals also contribute to predominance of grasses, but that depends on climate

Summary Tropical Rainforests Deserts Hot Warm Cold Savanna Grasslands Latitude and Climate Biotic/Abiotic Factors  Living organisms  Food Chain