Fragmentation
Fragmentation is the bio-physical process by which organic material such as crop residues are broken down into smaller bits. Soil meso- and macro-fauna are the main facilitators of this process. Herbivorous acari (mites), earthworms, enchytraeids, isopods and millipedes depend on organic material as their food source. While feeding, they ingest parts of the organic material and leave other fragments behind in the soil. Fragmentation results in a higher surface area of the ingested organic material making it more available for mineralisation by microbes.
Fragmentation occurs in three of the four soil function models. It is an important step in the cycling of carbon and nutrients in soil covered in the Carbon and climate regulation and Nutrient cycling models. The fragmented and partially digested organic material are more accessible to microorganisms, which may feed on it and further decompose it releasing CO2 and nutrients available for plant uptake. Fragmentation also supports the Water regulation and purification function because these smaller fragments of organic matter can improve soil structural stability and thereby enhance the capacity of a soil to store water.
Methods for measuring fragmentation include the use of litterbags[1] through which one can monitor changes in litter weight and size over time as well as insertion of strips with mini-baits[2] into the soil to measure faunal feeding activity over short time periods.
[1] Lecerf A. 2017. Methods for estimating the effect of litterbag mesh size on decomposition. Ecological Modelling 362: 65–68.
[2] Kratz W. 1998. The bait-lamina test. Environmental Science and Pollution Research 5: 94–96.