Such factors may include temperature, pH, chemical milieu, nutrient supply, presence of symbionts or solid substrates, gaseous atmosphere (aerobic or anaerobic) etc.
This type of microecosystem can adjust rapidly to changes in the nutrition or health of the host animal (usually a ruminant such as cow, sheep, goat etc.
A typical soil microecosystem may be restricted to less than a millimeter in its total depth range owing to steep variation in humidity and/or atmospheric gas composition.
Because of the predominant solid phase in these systems they are notoriously difficult to study microscopically without simultaneously disrupting the fine spatial distribution of their components.
Along the path of terrestrial water flow the resulting temperature gradient continuum alone may provide many different minute microecosystems, starting with thermophilic bacteria such as Archaea "Archaebacteria" (100 °C (212 °F) or more), followed by conventional thermophiles (60–100 °C (140–212 °F)), cyanobacteria (blue-green algae) such as the motile filaments of Oscillatoria (30–60 °C (86–140 °F)), protozoa such as Amoeba, rotifers, then green algae (0–30 °C (32–86 °F)) etc.