Abundance of biogenic structures of earthworms and termites in a mango orchard

A comparative study of the spatial distributions and the quantity of biogenic structures produced by earthworms and termites (Odontotermes nilensis and Ancistrotermes guineensis) has been conducted in a mango orchard at Thiès (Senegal).This study showed that surface biogenic structures may represent a large amount of modified soil (up to 536.5 g m−2) which vary depending upon the seasons and the species. Whilst the quantity of casts was independent on the season (178.6 g m−2), O. nilensis sheetings fluctuated with the seasons. In addition, we show that the spatial organisation of surface biogenic structures fluctuates with seasons. It displays patches ranging from 5 to 15 m. There is a link between the distribution of earthworm casts and the vegetation. In addition, spatial distribution was also linked to the biology of constructing species. We observed that the A. guineensis’ filling structures were mainly located under the mango trees during the dry season where the stems and the brushwoods were abundant. It appears that the spatio-temporal distribution of the biogenic structures under study depended upon two main factors: season and vegetation. However, depending upon the biology of the engineer, these two factors influenced the spatial distribution of structures in different ways.