Macrofauna and Mesofauna
Macrofauna are defined as being larger than 2mm in size. This group includes larger animals such as badgers, rabbits and gophers, which all spend a part of their life in the soil, as well as moles, snails, slugs, earthworms, ants, termites, millipedes, woodlice, which all spend most of their life in the soil. Burrowing animals such as earthworms, ants and millipedes create their own living space by burrowing into the soil. Creatures such as mites and collembola live in the existing air spaces in the soil.
Earthworms are very helpful creatures to have in the soil. They eat plant remains and injest soil organic matter in various stages of decomposition, together with microorganisms associated with this material. They also ingest mineral particles from the soil and the material they excrete after it has been digested in their bodies is often well aggregrated and nutrient rich. They help to produce a good soil structure through their burrowing and casting. They also help to release nutrients and make them available to growing plants. There are several thousand species of earthworms worldwide. There are also several thousand species of ants that inhabit the soil. Some feed on dead organic remains, some are herbivores and a few are predators on other soil organisms. Like earthworms, ants tend to aerate and mix the soil, thereby increasing soil drainage.
Mesofauna are 0.1 to 2mm in size. They include arthropods, such as mites, collembola and enchytraeids. In some soils these are very abundant. For example, over 200,000 arthropods have been recorded in just a square metre of old grassland soils. Some mesofauna feed on bacteria, fungi and algae, others scavenge on degraded organic matter. They all contribute to the breakdown of organic matter, stimulation of microorganisms and deposition of faeces which increase soil fertility.