For example, protozoa are abundant where bacteria are plentiful. Where bacteria dominate over fungi, nematodes that eat bacteria are more numerous than nematodes that eat fungi. Management practices change food webs . For example, in reduced tillage agricultural systems, the ratio of fungi to bacteria increases over time, and earthworms and arthropods become more plentiful. Direct counts counting individual organisms with the naked eye or with a microscope.
Plate counts counting the number of bacterial or fungal colonies that grow from a soil sample.
Measuring activity levels . Activity is determined by measuring the amount of by-products, such as CO2, generated in the soil, or the disappearance of substances, such as plant residue or methane used by a large portion of the community or by specific groups of organisms. These measurements reflect the total work the community can do. Total biological activity is the sum of activities of all organisms, though only a portion are active at a particular time. Respiration measuring CO2 production.