The soil layers and the living organisms
The soil is composed of three layers , They are the top soil layers , the lower soil layers and the rocky layers , The soil horizon is the layer that parallel to the soil crust and its physical characteristics differ from the layers above and beneath Each soil type .
The top soil layers
The top soil layers contain the roots of the plants , the leaves of the plants , the humus , the small pieces of the rocks may be found , the organisms as the earthworms , the ants , the spiders and the insects , So , a lot of the creatures exist in the top layers .
The roots of the plants extend deeply in the top soil layers , And they are very important to the plants , The roots take the water and the nutrients from the soil , and they fix the plant in the soil .
The roots are very important to the soil as they help the soil to be cohesive , they provide the soil with the nutrients as they are converted into the humus after death , and they prevent the soil erosion from happening quickly .
The leaves of the plants are the parts of the plants exist in the top soil layers , And when these parts fall in the soil , they decay forming the humus .
The ants and other insects are the organisms existing in the top soil layers , they dig the tunnels in the soil to make the nests and lay the eggs , And when these organisms die , their bodies decay forming the humus .
The earthworms and some spiders are the organisms existing in the top soil layers , And the soil is very important to them . It is considered the shelter for the earthworms and some spiders , because they make their home underground by digging the tunnels .
The earthworms and some spiders are very important to the plants as they help in the growth of the plant roots , as the tunnels that are formed by them allow the air , the water and the nutrients to pass easily through the soil , then to the plant roots .
The lower soil layers
The lower soil layers lie beneath the top soil layers , and the do not have much humus .
The rocky layers
The upper layers of the rocky layers contain pieces of the rocks , but their lower layers contain the solid rocks .