Essay About Underlying Soil And Zonal Soil

Latosol Soil
Latosol soils[pic 1]        In an undisturbed biome the underlying soil that has developed over time, is in balance with its environment and is known as zonal soil.                                                                                               This is mature soil and its characteristics reflect the climate, the zonal soil type of a tropical rainforest is a latosol. Characteristics: Over 40m deep.Latosols are nutrient poor, as soon as leaf litter is broken down into humus; it is absorbed by the growing vegetation.Constant hot wet climate encourages chemical weathering of bedrock. Ferrallitisation is the process where bedrock is chemically weathered into clay minerals and sesquioxides which are used by the soil.The latosol soils are red in appearance due to the presence of iron & aluminium minerals (created by fertilisation). Rainfall exceeds evapotranspiration causing a soil water surplus. This means water percolates down which washes soluble silica minerals down from the top A horizon by leaching or eluviation. Iron and aluminium compounds are less soluble so do not get leached & so are left behind which is why the soil is ‘reddish’[pic 2]Since the latosols are loose they are easily eroded into gullies which reduce the productivity of farmland. Once the trees are removed the soils further lose fertility which is why farmers constantly need to move cultivation (farming) elsewhere.How vegetation has adapted to the soil:Rainforests have a shallow layer of fertile soil, so trees only need shallow roots to reach the nutrients therefore the roots spread over a wide area. However, shallow roots cant support huge rainforest trees; so many tropical trees have developed huge buttress roots. These stretch from the ground to two metres or more up the trunk and help to anchor the tree to the ground.Many leaves are waxy and have drip tips which allow water to run off them and into the soil where it can be taken up by roots. (This also prevents leaves rotting).