Soil Ecology, Biology tutorial


Soil is the collection of individual soils, each with distinguishing profile characteristics. Soils are vital to life on earth due to a great degree; the quality of soil decides the nature of plant ecosystems and the ability of land to support animal life and society.

Factors Determining Soil Formation:

Based on observation and cautious field and laboratory research, five main factors which control the formations of soils have been recognized. These factors are climate, parent materials, topography, biota and time. Though, in certain situations one of the factors could have had dominant influence in determining difference among the set of soils, such a set of soils are referred to as climosequence, lithosequence, toposequence, biosequence, or chronosequence as the case may be. That is to say the dominating influence is by parent material (lithosequence), biota (biosequence), climate (climosequence), topography (toposequence) or time (chronosequence).

Parent Materials:

The nature of the parent materials intensely influences soil characteristics. For instance a soil might inherit the sandy texture that is coarse-grained, quartz-rich parent materials like granite or sandstone. In addition, the chemical and mineralogical compositions of parent material also manipulate characteristics of soil formed.


The most important factor acting on parent material is possibly climate. It determines nature and intensity of the weathering which takes place over large geographic areas. Precipitation and temperature both have an effect on rate of chemical, physical and biological processes.


Activities of living organisms (flora and fauna) potentially improve nutrient cycling, organic matter and aggregate stability. For instance, leading of soil mineral and erosion of surface soil could be slowed down by natural vegetative cover. Furthermore, animals play important role in change animals like bush rates, soil - formation processes, moles and smaller ones like earthworms bone tunnels in soil, thus improving movement of water and air in subsurface layers.


The elevation, slope and landscape position may either speed up or retard work climate forces. For instance, steep slopes usually encourage rapid soil loss by erosion and permit less rainfall to enter soil before running off.


Soil forming processes take time to illustrate their effects as time interacts with order factors of soil formation.

Weathering Processes:

Weathering is the biochemical process which involves both destructs and synthesis. Without noticeably affecting soil composition, physical disintegration breaks down rock in smaller rocks and finally in sand and silt particles. Also, minerals decompose chemically, releasing soluble materials and synthesizing new minerals. During chemical changes, particle size continues to reduce, and constituents continue to dissolve in aqueous weathering solution.

Physical Weathering (Bio-Integration):

Temperature, abrasion by water, ice and wind, and living organisms (flora and fauna) all operate together brining, about physical weathering. For example, rocks heat up in day and cool down at might, causing alternate expansion and contraction of the rocks. In addition, water has wonderful cutting power particularly when loaded with sediments.

Physical weathering is also improved by plant roots that at times enter cracks in rocks resulting in further breakdown of rocks.

Biochemical Weathering:

Water, oxygen, microbes and plant - root exudates are different agents acting in concert to convert primary minerals (like feldspars and micas) to secondary minerals (like clays and carbonates) and release plant nutrient elements in soluble forms. Chemical weathering is governed by six basic kinds of reactions:

  • hydration
  • hydrolysis
  • dissolution
  • carbonation and order acid reactions
  • oxidation - reduction (redox)
  • chelation

Soil Formation Processes:

During formation (genesis) of the soil from parent material, the regolith (loose earth materials above solid rock) suffers several profound changes. These changes are brought about by variations in four broad soil forming processes.


This takes place when soil constitutions are chemically or physically altered or destroyed and others are synthesized from precursor materials.


Translocations involve of movement of in organic and organic materials laterally within the horizon or vertically from one horizon up or down to another.


Inputs of materials to the developing soil profiled from outside sources are considered additions.


Materials are lost from soil profile from outside source are considered additions.

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