Studied soil biota
Springtails (Collembola) are among the most abundant soil arthropods in the world. They occur at densities between 10,000 and 100,000 per square meter. Measuring only a few millimetres (at most) springtails still are easy to recognize although they are morphologically and ecologically highly variable in almost every trait. But there is no danger of confusion since they carry very unique traits, like the furca, which can be used to propel the animal away and gave this group their common name springtails, and the collembulum, a tubulus structure on the abdomen, which is eponymous for the group.
The distribution of springtail species in the soil is stratified vertically and variable horizontally. Although they occupy all trophic levels they mainly feed on fungal hyphae, bacteria and decaying organic matter. Thereby they play an important role in nutrient cycling as they impact litter decomposition by fragmentation and consuming plant residues. Collembola influence the structure and quality of the soil by depositing millions of faecal pellets which are slowly releasing nutrients available for plant roots.
Collembola ©C. van Capelle
Earthworms (Lumbricidae) presumably are the most commonly known soil invertebrates on our planet. They occur in virtually all soils and are easily recognised by uniform segmentation of their body. Their size ranges from 1 to 110 cm and they can reach densities of about 400 individuals per square meter.
As a classic example of ecosystem engineers earthworms alter the soil more intensively than any other soil invertebrate. By adopting different lifestyles, different species of earthworms provide a broad array of services to the ecosystem and play a key role in maintaining soil fertility. Living in the litter layer or deeper in soil earthworms feed on dead organic matter and integrate it into the soil, while building burrows and depositing casts. This activity is not only making organic matter accessible for other soil biota but also beneficially impacts soil formation and structure, water regulation and pollution remediation.
Earthworm in harvested cereal field ©T. Runge
Potworms (Enchytraeidae) are small representatives of the annelids, which can easily be overseen as they are much smaller than e.g., earthworms. They range from 2 to 50 mm and compensate for the small body size as compared to earthworms by colonizing soils in very large numbers reaching up to 200,000 individuals per square meter. They play an important role in litter degradation, especially if earthworms are absent.
Potworms are living as detritivores by consuming dead organic matter, but also as microbivores feeding on bacteria and fungi, thereby functioning as primary and secondary decomposers. They exhibit a broad spectrum of lifestyles including different reproductive strategies as well as different lifeforms, dwelling in different soil horizons similar to earthworms and springtails. They are able to tolerate a broad range of environmental conditions which in combination with their global distribution makes them very powerful indicators reflecting e.g., soil quality.
Enchytraeidae ©I. Schmook, @ Engell & Schmoock
Mites (Acarina) are colonizing virtually all habitats on earth including the soil. In soil they may reach densities between 50,000 and 400,000 individuals per square meter, thereby often representing the most abundant soil arthropods. Measuring only a few millimetres mites belong to the arachnids and have four pairs of legs. Their body segments typically are fused forming a rather roundish body shape. As arachnids they typically possess pincer-like mouthparts which in the different groups are used for catching prey or fragmenting organic matter.
Within the mites different groups show different food preferences and specialisation. They occupy virtually all trophic levels, occur in different soil depths and play an important role in litter decomposition. Especially moss mites (Oribatida) play an important role in plant litter and wood degradation. They are among the most abundant group of mites and predominantly live as detritivores feeding on decaying organic matter or fungivores feeding on fungal hyphae. By fragmenting organic matter and depositing faeces they contribute to the formation of soils. The remaining groups of mites including Mesostigmata and Prostigmata are mostly predators. They are predominantly feeding on nematodes and springtails and thereby contribute to control e.g., root feeding nematodes.
Acarina © M. Maraun
Investigations on the diversity of these soil biota groups are complemented by assessments of microbial biomass, microbial functional diversity and genetics of earthworms and gastropods.
Studied soil parameters
- Aggregate stability
- Infiltration rates
- Decomposition of organic material
- Pathogen suppression
- Soil suppressiveness