Soil Mesofauna

─ The soil-litter system is the natural habitat for a wide variety of organisms, microorganisms and invertebrates, with differences in size and metabolism, which are responsible for numerous functions. The soil mesofauna is composed of animals of body diameter between 100 μm and 2 mm, consisting of the groups Araneida, Acari, Collembola, Hymenoptera, Diptera, Protura, Diplura, Symphyla, Enchytraeidae (Oligochaeta), Isoptera, Chilopoda, Diplopoda and Mollusca. These animals, extremely dependent on humidity, move in the pores of the soil and at the interface between the litter and the soil. The edaphic fauna, besides having a great functional diversity, presents a rich diversity of species. As a result, these organisms affect the physical, chemical and, consequently, the biological factors of the soil. Therefore, the edaphic fauna and its activities are of extreme importance so that the soil is fertile and can vigorously support the vegetation found there, being spontaneous or cultivated. The composition, distribution and density of the edaphic acarofauna varies according to the soil depth, mites size, location and the season of the year. Edaphic mites are generally found in greater quantities in the organic matter layer than in the soil mineral. The subclass Acari is divided in seven orders being the Mesostigmata, Trombidiformes, Endeostigmata and Sarcoptiformes those that frequently occur in the soil. In the order Sarcoptiformes the suborder Oribatida (formerly Cryptostigmata) is one of the more numerous groups of soil arthropods, both in number of species and specimens. Considering the above facts, it was the objective of this work to know the acarofauna of the soil in a coffee plantation and rank the taxa in a decreasing way, by the use of faunistic analysis. The soil samples were taken in coffee plantation in the Experimental Station of EPAMIG, in São Sebastião do Paraíso, MG, Brazil, in two periods, end of dry and end of rainy season of the year 2013, and the extraction of edaphic mites of the soil mesofauna was done at the Laboratory of Acarology of EPAMIG Sul/EcoCentro, in Lavras, as well as other activities related to the study. The result show that edaphic mites of the cohort Astigmatina and suborder Oribatid are dominant in both periods studied, and can be worked to be an indicative of soil quality.

Soil fauna (macrofauna and mesofauna) were sampled in 13 beech forest stands of the Ardenne mountains (Belgium) covering a wide range of acidic humus forms. The composition of soil fauna was well correlated not only with humus form, but also with elevation, phytosociological type, tree growth, mineral content of leaf litter, and a few soil parameters such as pH and C/N ratio. The nature of the mechanisms that can explain these relationships is discussed in light of existing knowledge.

Decomposition is a key process for rain forest nutrient cycling, and this may be altered by the increasing rate of deposition of reactive nitrogen on rain forests. Tropical heath forests are characterised by slow litter decom- position rates due to low quality litter, along with acidic soil pH and low availability of soil nitrogen (N). To investigate whether soil N or pH is most important in regulating tropical heath forest organic matter decom- position, we used a factorial N and CaCO3 addition experiment, and measured wood and leaf litter decom- position rates and mesofaunal activity (using bait-lamina sticks and numbers of worm casts). Our heath forest site in the Kabili-Sepilok Forest Reserve (Sabah, Malaysia) had a decomposition rate (calculated using standard tea material) comparable to that of temperate forest soils. Overall, the experimental modification of both soil pH and available N had weak effects on decomposition rates, although different materials responded differently to the experimental treatments. There was a clear, but transient, increase in number of worm casts in the CaCO3 and N + CaCO3 treatment. Although we obtained some evidence that low soil acidity reduced decomposer activity, it may take longer than one year for the decomposer community, and associated processes, to be influenced by the experimentally altered edaphic conditions.

The fauna inhabiting a small area (ca. 5 cm x 5 cm) were investigated in a Scots pine stand. After microstratification of the litter layers in the field and fixation in 95% ethyl alcohol, invertebrates, mainly mesofauna, were sorted under a dissecting microscope and mounted or dissected in order to study their intestinal guts. Faeces were mounted or sectioned to obtain information about the activity of other invertebrate groups not represented in the sample and to follow the fate of plant and microbial material after defaecation occurred. Plant material, mainly from moss, bracken, pine needles and bark, was extensively consumed by enchytraeid and lumbricid worms, sciarid larvae and phthiracarid mites. Fungal material was ingested by all groups, either in combination with plant material or alone (camisiid and oppiid mites, some species of Collembola, sciarid and chironomid larvae). Isotomid springtails and chironomid larvae appeared to consume faecal material. The choice and the degree of comminution and digestion of the material differed greatly from one group to another, but without any indication of resource sharing.