Gamasina

Danra, Dieudonné Djackba, Nukenine, Elias Nchiwan & Koehler, Hartmut, 2018, Soil Gamasina from savanna and ReviTec site of Ngaoundéré (Adamawa, Cameroon): abundance and species diversity, Soil Organisms 90 (3), pp. 187-198 : 195

4.2 Gamasina species composition

More than 50% of the species documented belong to the Rhodacaridae (11 morphospecies) andAscidae (mainly genus Asca , 10 morphospecies). They all are small in size. Being acquainted with the Gamasina fauna of temperate climates (Norther Germany), the absence of Parasitidae is striking.

The Gamasina community documented is indicative for the different plots. As control (ctrl1) mimics degradation, the absence of Afrogamasellus cf. nyinabitabaensis suggests that this species is sensitive to degradation.

The compost amendments seem to have facilitated the dominance of Hypoaspis-Geolaelaps spec. 1 (HYGEOA), Rhodacarus cf. matatlanticae (RHOMAT) and Afrogamasellus cf. nyinabitabaensis (AFRNYI) , the latter particularly where biochar was added.

Hypoaspis-Geolaelaps spec. 1 (HYGEOA), Rhodacarus cf. matatlanticae , 2010 (RHOMAT) and Afrodacarellus spec. 1 (AFROVS) were the omnipresent species as they were recorded in all the investigated plots. Multidentorhodacarus cf. aegypticus -a (MUAEa) is a species from the ReviTec site, which is characterized by being a successional site and by a high vegetation cover, even in ctrl1 by vegetative plant parts, providing an ameliorated microclimate.

Organic amendments with compost in the ReviTec site increased Gamasina abundance and species number considerably when compared to the control (ctrl1) and also to savanna. It is unlikely that Gamasina possibly imported with the substrate and its amendments survive the typical successional conditions. As was shown by a Bremen ReviTec site ( Koehler & Warrelmann 2007), the initial (imported) compost fauna was replaced within half a year by typical successional species. Reactions of Gamasina to organic amendment were reported by Minor & Norton (2004) and Koehler (1997): ephemeral organic materials such as manure or dung initiate colonization by phoretic surface species, e.g. from the families Ascidae , Macrochelidae and Parasitidae .

We found five species in the savanna soil as well as in the compost amended soil, indicating that they prefer organic matter with its associated food source. The biochar amended treatments are colonized by seven exclusive species.

Gamasina clearly preferred the two treatments having biochar as additive: compost + biochar (cpbc) and compost + biochar + bokashi (cpbcbo). Biochar and bokashi could have induced better soil humidity and provided more food and diverse living space which in turn positively affected Gamasina community. Thies & Rillig (2009) reported that pore size variation observed across biochar particles from different feedstocks and pyrolysis conditions is such that the microflora could colonize and be protected from predators and grazers, being a reliable food source for the food web, topped by the predators. The higher porosity of biochar may also retain moisture. According to Bedano et al. (2007) more adequate living space and abundant prey could be another reason for the high species and individual number of Gamasina in these treatments. From a Bremen ReviTec experiment, Oben (2017) reported consistently higher species richness of Gamasina in biochar amended compost substrates. According to Ekebafe et al. (2015) substrate formula containing biochar bokashi supported the development of high soil biodiversity.

Temporal development reveals quite different patterns for the eudominant species, particularly for Afrogamasellus cf. nyinabitabaensis (AFRNYI) , exhibiting a strong increase in August.

Calculations of similarities of the Gamasina communities of the investigated plots confirm the high similarities in the biochar amended treatments, as well as in the compost treatments. The high species identity of the community of savanna with those of the two biochar plots is remarkable: this similarity might be due to the natural pyrogenic carbon in savanna soil from the regular grassland fires. Bedano & Ruf (2007) reported that the choice of similarity measure had a considerable effect on site discrimination. The dominance structure of the Gamasina community was not affected by the habitat differences, due to the prevailing eudominant species.