Living micro-organisms in the soil, such as bacteria and fungi, break down plant litter in the O horizon. This creates humus and makes the soil more fertile.
Animals, such as earthworms and burrowing animals, break up the soil and allow for the movements of water, humus and air through the soil. When these organisms die, they add nutrients to the soil.
Landscape/relief
Soils in upland areas are generally thin because of mass movement. They are also poorly drained because of heavy rainfall in upland areas.
Soils in lowland areas are deeper, well drained and generally more fertile. They are rich in humus because there is more plant litter and living organisms.
Vegetation Vegetation in the area creates plant litter, which breaks down into humus. Humus makes soil fertile.
Areas with deciduous trees have more plant litter than areas with coniferous trees. That means that areas with deciduous trees have more fertile soils.
Time
It can take up to four hundred years for one centimetre of soil to form because the process is so slow. As soil is a non-renewable resource, we must make sure that we do not overexploit it.
Climate
( Figure 16.8 The interrelated factors that influence the formation of soil
Landscape
organisms
Living
Parent material
Time Vegetation
(i) List the factors that influence soil formation. (ii) Explain what is meant by the term ‘parent material’. (iii) Explain how climate influences soil formation. (iv) Explain why soil is a non-renewable resource.
/ I understand the factors that lead to soil formation. 289
