Oribatid mite (Acari: Oribatida) contribution to decomposition dynamic of leaf litter in primary forest, second growth, and polyculture in the Central Amazon

Abstract

We studied the contribution of oribatid mites in the dynamics of litter decomposition in an experiment using litterbags of three different mesh sizes (20 microns, 250 microns, and 1 cm). The experiment was carried out at a primary forest (FLO), a secondary forest (SEC), and at two polyculture systems (POA and POC). We compared the weight loss of the leaves of Vismia guianensis and the changes of the oribatid mite species community. We processed the samples after 26, 58, 111, 174, 278, and 350 days from the beginning of the experiment by using the Berlese-Tullgren to extract the animals. We hypothesized that: 1. the abundance and diversity of oribatid mites would exert an influence in the decomposition process; 2. there would be a successional changing of the species during decomposition; and 3. there would be differences in the colonization of species in relation to the mesh size of the litterbags. A total of 95 species of oribatid mites was found. The biomass data was the first registered for the Amazon region. The great dominance of oribatid mites did not exert an influence in the decomposition process. There was not a successional changing of the species during the course of the decomposition process, unlike those shown by results obtained in the temperate forest, because we found neither early colonizers nor species that prefer advanced decomposition stages. The oribatid mite community, which developed in the litterbags under tropical conditions, was atypical of the normal stages of leaf litter breakdown and decomposition. There were differences in the colonization of species in relation to the mesh size of the litterbags. These differences were very closely related to the specific habits and habitat of the dominant species.

Microenvironmental preferences of oribatid mite species on the floor of a tropical rainforest

“…This great dominance of S. mochlosimilaris agrees with the findings of Franklin et al (2004), who recorded high dominance of a related Scheloribates species in decomposing leaf litter in the Central Amazon. Woas (2000) has also reported that species of Scheloribatidae are also dominant in steppes, prairies or savannas.…”

Oribatid mites as a major dietary source for alkaloids in poison frogs

“…Oribatid mites are well known to be among the most abundant and diverse arthropods in soil and leaf-litter, in both temperate and tropical regions (28)(29)(30). Their food generally consists of decaying higher plant material and saprophytic fungi (31,32), although stable isotope studies indicate that necrophagy or predation on small invertebrates is common, especially in tropical soils (32,33).…”

Edaphic and arboricolous oribatid mites (Acari; Oribatida) in tropical environments: changes in the distribution of higher level taxonomic groups in the communities of species

“…Therefore, we did not register the same tendency for the other secondary forest (sf25), probably because the rather thinner litter layer was mostly composed of leaves of Vismia sp. ("Lacre"), that are smaller and less palatable compared to the leaves of Clitoria racemosa (Franklin et al, 2004). Therefore, the dominance of Lower Oribatida over Oppioidea increased to the ratio of 3.4 on average.…”

“…The Oppioidea are dominant in environments with great concentrations of decaying plant material and a non-compacted soil structure (Woas, 2002;Franklin et al, 1997b;Franklin et al, 2004) and they can invade more open terrain, tending to live in a thick layer of decaying plant material in savannah, steppe, salt marsh and related biomes (Beck et al, 1997). In tropical rainforests they may reach a higher number of species and a higher population density if the input of decaying plant material on the soil is increased (Woas, 2002).…”

“…Others factors, not tested here, would be the humidity and the fungi community colonizing the leaves. According to Franklin et al (2004), the bags represent a very artificial and humid environment and their oribatid mite community is different from the normal fauna found in natural conditions in the tropics.…”