Savannah Grassland

Savannah Grassland
ntroduction: ? A savannah is hot, seasonally dry grassland with scattered trees. ? This environment is intermediate between grassland and a forest. ? Savannahs are located in the dry tropics and the subtropics, often bordering a rainforest. ? Savannahs are located in Africa, Madagascar (an island off the East Coast of Africa), Australia, South America, India, and the Myanmar-Thailand region of Southeast Asia. Location: ? Located between the latitudes of 5? and 15? north and south of the Equator. ? Some savannah grassland is found within central parts of continents e.g. Brazilian Highlands. Climate: ? Temperatures are high throughout the year but it is slightly cooler when the sun is overhead at the tropic in the opposite hemisphere. ? Annual range may be slightly higher as a result of the sun?s slightly reduced angle in the sky for part of the year.
Temperatures may drop on the onset of the rainy season. ? Wet and dry season?s alternate. ? Wet season occurs when the sun moves overhead bringing with it the heat of the Equator. ? Heavy convectional rainfall may give up to 80% of the annual rainfall in four or five months. ? Dry season occurs when the Sun moves on and with it the heat of the Equator due to strong and steady trade winds. Humidity is low during this season. ? Places near to the desert margins tend to experience dry, stable conditions. Vegetation: ? Estimated to have a mean npp of 900 g/m2/yr. ? Less than the rainforest due to the smaller number of trees, species and layers and a reduced rate of decomposition during the winter leaving considerable amounts left stored in leaf litter. ? Closed savannah = deciduous trees with areas of grasses. ? Open savannah = vegetated only by scattered tufts of grass. ? The trees lose their leaves to reduce transpiration due to winter drought. When there are leaves they are small and waxy and sometimes thorn like. ? Roots are long and extend to tap any underground water. ? Trunks are gnarled and the bark is usually thick to reduce moisture loss. E.g. the baobab tree. ? Savannah trees reach 6 to 12m in height. Many have Y-shaped, branching trunks. ? The number of trees increases near to rivers and waterholes. Animals: ? Over 40 different species of large herbivore graze on the grassland including wildebeest, zebra and antelope. ? Home to several carnivores (predators) such as lions and hyenas (scavengers). ? Termites and microbes are major decomposers. Problems: ? Fire ? either set deliberately by farmers or electrical storms. ? Desertification. ? Deforestation due to the demand for fuel. ? Overgrazing which reduces the productivity of the grassland. [image] [image] Savannah Soils: ? When the grasses die back in the dry season the decomposed organic matter provides a thin, dark brown layer of humus. ? During the wet season rapid leaching and a relatively high pH removes silica from the soil composition leaving the red coloured oxides of iron and aluminium. ? Seasonal changes between leaching and capillary action produces cement layer ? laterite, restricting drainage, root penetration and ploughing. ? Parent material weathers into clay ? sticky and plastic in the wet season. ? Few nutrients. ? Not really suited to agriculture. ? Better suited to pastoral rather than arable farming.

Savannah Grassland 6.9 of 10 on the basis of 879 Review.