Soil Food Webs
Food webs are used to know different energy interactions in a given ecosystem. The soil's food web is very dynamic and the living part of soil and it is very complex and interchanging depending on it's ecosystem. The interactions found in the food web are soil organisms living all or part of their lives in the soil while producing energy and working together with plants to survive. These interactions carried out in the soil by soil organisms and plants are a vital (NRCS)
The organisms found in the soil food web carry out a large amount of microbial processes such as decomposition, mineralization, immobilization, respiration, and fixation along with many others. These processes help support above and below-ground plant growth and their processes make nourishment for plants possible.
The start of all biological interactions within any soil food web would start with organic matter. Organic matter is a key component when it comes to fueling any interaction in the food web such as decomposition and is made up of humus and active organic material. Without any organic matter, microbes will not be present to fuel the plant with essential nutrients. Soil organic matter is the storehouse for the energy and nutrients used by plants and other organisms. Bacteria, fungi, and other soil dwellers transform and release nutrients from organic matter. These microshredders, immature oribatid mites, skeletonize plant leaves. This starts the nutrient cycling of carbon, nitrogen, and other elements. (NRCS) Organic matter is recycled back into the food web when organisms of higher trophic levels die off and are decomposed by the nutrients that were used to create food for them in the very beginning.
There are many different ecosystems in the world and the soil food web is affected by climate, rainfall, management factors, acidity, etc. Soil food webs are found in both terrestrial and freshwater/marine sediment soils. The interactions carried out in the soil food web is highly important in both systems.
Terrestrial soil food webs can consist of but are not limited to many soil microbe/plant interactions. Terrestrial soil food webs are more adaptive to having many plant exudates and very rich organic matter coming from mainly alive primary producers. Given that the primary producers do their role's, terrestrial soils will have a more diverse community of soil microorganisms that can contribute to each different trophic levels in the soil.
Freshwater & Marine Sediment
In more aquatic habitats different composition of soil microorganisms are found. Organic matter and other materials are introduced in a different way and in different concentrations when looking at deep marine sediment and shallow marine sediment.
Interactions among soil microorganisms with each other and also their interactions with primary producers can be very different. Host type and diversity of microbial populations can differentiate these activities. These interactions also affect the makeup of microbial communities and also the makeup of above-ground plant diversity.
Some interactions found in the soil food web that are both positive to the host plant/microorganism and another microorganism can include mutualism, symbiosis, commensalism, and synergism. An example of this would be how the plant gives soil microorganisms nutrients to survive through root exudates, in return the microorganism fix and respire vital nutrients that the plant needs in order to survive.
Interactions can also have a negative effect on either plant/microorganism or a negative effect on both. These would include predation, competition, parasitism, or ammensalism. An example of an interaction having both a negative and positive effect would be parasitism. A microorganism could be attached to a plant's roots and be taking nutrients that are vital to the plants health and the plant could be dying which would be having a positive effect for the microorganism, but a negative one for the plant.
Many processes are conducted within the soil food web in order to keep a proper balance of nutrients available to plants and microbial communities. These processes also contribute to global cycles of carbon and nitrogen and can have ecological effects depending on how much each element is present in a given environment. Each process found in the soil food web is very important when looking at the big picture of global fluxes, and the soil food web and life on Earth would not be possible without each process present.
Respiration & Photosynthesis
Respiration includes both plant and soil microorganisms. Plants need to conduct photosynthesis in order to respire oxygen into the air. Respiration in plants also helps take carbon out of the air and stored in the soil, which is a process that is carried out by soil microorganisms. Other soil microorganisms like algae, lichens, and photosynthetic bacteria are also important in the sequestration of carbon in the soil.
Decomposition is also a vital component of the soil food web. Decomposition of organic matter, both living and dead, helps make nutrients available for plants and other soil microorganisms to carry out other processes to survive. Also, decomposition is one of the last steps to energy transformation in the soil food web.
Fixation of carbon, nitrogen, and other important elements is another important process in the soil food web. Fixation of these minerals can either make them plant-available for uptake and energy use to carry out other processes, or they can make an element immobile in order to not hurt the plant/microorganism or to sequester nutrients for later use.
Many microorganisms are present in soil food webs. Different microorganisms like soil fauna, bacteria, archaea, and fungi carry out all of the processes in soil. Also, these microorganisms differentiate plant-soil interactions and the makeup of microbial communities in the soil.
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Edited by Brian Kirk, a student of Angela Kent at the University of Illinois at Urbana-Champaign.