Bioturbation
The larger and more mobile soil organisms, such as ants, enchytraeids and earthworms, mix and move soil from one place to another and create belowground tunnels (burrows) and nests. The result of their activity is called bioturbation. Anecic earthworms, for example, create burrows that come to the surface of the soil to allow them to collect and drag plant remains from the surface deeper into the soil profile. While endogeic earthworms create horizontal burrows at 5-40 cm depth where they eat the soil material and excrete it out again as they pass through. These two forms of bioturbation thoroughly mix soil and organic matter, it also helps to break-up dense and compacted soil layers.
Bioturbation influences the structure of the soil and therefore directly impacts the soils’ capacity for water infiltration, percolation (flow through) and storage in the Water regulation and purification function. Mixing of the soil and soil organic matter also determines how and where carbon and nutrients are available for plants and soil biota. In that way, bioturbation also supports the Carbon and climate regulation and Nutrient cycling functions.
Methods to measure bioturbation involve studying how the activity of ants enchytraeids and earthworms change the morphology of the soil by building burrows (tunnels) or producing cast (faeces)[1],[2],[3].
[1] Evans AC. 1947. LVII - A method of studying the burrowing activities of earthworms. Annals and Magazine of Natural History 14: 643–650.
[2] Arnone III JA & Zaller JG. 1997. Activity of surface-casting earthworms in a calcareous grassland under elevated atmospheric CO2. Oecologia 111: 249–254.
[3] Shipitalo MJ & Protz R. 1987. Comparison of morphology and porosity of a soil under conventional and zero tillage. Canadian Journal of Soil Science 67: 445–456.