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Soil Mesofauna are invertebrates between 0.1mm and 2mm in size, which live in the soil or in a leaf litter layer on the soil surface. Members of this group include nematodes, mites, springtails (collembola), proturans, pauropods, rotifers, tardigrades, small araneidae(spiders), pseudoscorpions, opiliones(harvestmen), enchytraeidae such as potworms, insect larvae, small isopods and myriapods.  They play an important part in the carbon cycle and are likely to be adversely affected by climate change.
Soil mesofauna feed on a wide range of materials including other soil animals, microorganisms, animal material, live or decaying plant material, fungi, algae, lichen, spores, and pollen. Species that feed on decaying plant material open drainage and aeration channels in the soil by removing roots. Fecal material of soil mesofauna remains in channels which can be broken down by smaller animals.
Soil mesofauna do not have the ability to reshape the soil and, therefore, are forced to use the existing pore spaces, cavities, or channels for locomotion within soil. Soil organisms (e.g. earthworms, termites, ants, some insects’ larvae) can make the pore spaces and hence can change the soil shape. Mesofauna contribute to habitable pore spaces and account for a small portion of total pore spaces (Hassink et al. 1993).
In agricultural soils, most of the biological activity occurs in the top 20 centimetres (7.9 in) (which is referred as the plow layer) while in non-cultivated soils, the most biological activity occurs in top 5 centimetres (2.0 in) of soil. Among different horizons of soil, the organic horizon (O) is the area of accumulation of animal residues (low carbon-to-nitrogen (C/N) ratio) and recognizable plant material (high C/N ratio) (House et al. 1984). Microorganisms use the amino acids and sugar that are exuded by the plant roots, as a food source (Curl and Truelove 1986). Swift et al. (1979) described that macro- and mesofauna contribute to ecosystem processes such as decomposition of plant residues (Badejo et al. 1995; Gobat et al. 2010) and nutrient cycling in complex and interactive ways. Approximately 30% of nitrogen mineralization is contributed by soil fauna in agriculture and natural ecosystem (Elliott et al. 1988).
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