Soil ecology; deals with primary production in soil, soil fauna and flora, litter decomposition, nutrient cycle, soil food web, soil biodiversity, and interrelations with soil processes. Organisms living in soil have vital importance on these processes, however, estimation of the impact of each organism is too difficult. Soil ecologists who are specially working on these processes separate the organisms in two simple units as “guild” and “functional groups” according to their roles on ecosystem processes such as food resource, dietary specializations, reproductive rates and defense strategies against predators or distribution in soil profile. Communities within functional groups connected each other’s with the relations such as competition and hunting. Soil food web studies try to figure out the relations among these functional groups connected with each other’s.