Agriculture Reference
In-Depth Information
4.2.4
OTHER SOIL MESOFAUNA
Acari and Collembola are generally the major taxa in mesofauna communities. Nonetheless,
four minor groups, Protura, Diplura, Pauropoda and Symphyla may be locally important
because of their relative abundances and the unique roles they play in soils.
Protura, Diplura
Protura and Diplura are Apterygota Insecta which are found consistently in soils, although
at low densities.
Protura are minute insects characterised by the absence of wings, antennae and eyes
which live in humid organic environments. They are panphytophages with highly
aggregated patterns of distribution. The highest density, 28,000-50,900 ind. was
recorded in a spruce mor with a moss cover in Norway. Figures of a few hundred to few
thousands of individuals are commonly cited for a variety of ecosystems namely,
temperate forests (Nosek, 1973), temperate grasslands and crops (Persson and Lohm,
1977; Axelsson
et al.,
1984; Lagerlöf, 1987) and African moist savannas (Athias, 1974).
As these insects are very small (0.4 to 8 µ g individual dry weight) biomass does not
exceed a few mg in most environments.
Diplura are another consistent though minor component of the soil mesofauna.
Their lengths range from a few tenths to several millimetres. They may be panphytophages
(
Campodeidae
) or predators of other microarthropods (Fox, 1957). They are concentrated
in the upper part of the profile and have highly aggregated distributions. Density estimates
range from
nil
to several thousands with highest values reported from such different
habitats as a
Liriodendron
forest in Tennessee (McBrayer
et al.,
1977) or
the moist African savannas at Lamto in the Côte d'Ivoire (700-1,000 ind.
) (Athias,
1974). Maximum biomass estimates do not exceed a few mg dw
Micromyriapoda
Three diverse groups of the Myriapoda may be classified as mesofauna
i.e.,
Pauropoda,
Symphyla and Polyxenida. Pauropoda are small (less than 1 mm), blind and pale pan-
phytophagous invertebrates which live in decomposing litter and organic horizons and
feed on fungi and decomposing leaves (McBrayer
et al.,
1977). They have patchy dis-
tributions and their densities generally range from a few hundred to 2000 ind.
biomasses are limited to a few mg dw in both temperate and tropical soils. The largest
populations recorded are of 6,200 ind. in a West African pastures (Belfield, 1956)
and 17,900 ind. in a Californian
Pinus ponderosa
forest (Price, 1973). They do not
seem to occur in extreme tundra and desert environments.
Symphyla are unique in that their small size and slender body shape allows them to
move readily through the larger soil pores and colonise soils to one metre in depth
(Belfield, 1956). They are polyhumic endogeics (euedaphic), and feed mainly on dead
and living roots and on micro-organisms. Some of them may become serious pests of
a wide range of plants (Anglade, 1967). Densities are generally a few hundreds ind.
although they may exceptionally reach maximum values of 1.2 to
ind.
in
cultivated temperate soils and 10,800 ind.
in West African pastures (Belfield, 1956).
