Soil Formation:- Living Organisms
Plants, animals and micro-organisms (fungi and bacteria) all affect soil formation by producing or contributing to humus production.
The amount of humus in a soil is a result of how much plant material has been incorporated into it. If vegetation is sparse a soil will be low in humus and less fertile.
Grasses have fibrous root systems that spread throughout the tiny pores of the soil - as the roots die and decay the soil becomes well supplied with humus.
Living Organisms-Litter Layer:
Tree roots, being much larger than grass roots, do not invade pores of the topsoil as completely, so the humus content of soils under forests is usually lower.
Instructions: click on the diagram ("click here for Key", or Magnification label) for below ground organism diagrams.
Instructions: click on the diagram ("click here for Key", or Magnification label) for forest floor organism diagrams.