Termite bioturbation: Fungal versus non-fungal building strategies lead to different soil sheeting stability

Understanding how soil fauna impact soil aggregate dynamics remains a critical issue in soil science, especially because of the influence on soil aggregate stability on key ecological and environmental processes. This question is even more crucial in tropical countries, where soils are particularly vulnerable to erosion. In many tropical environments, soil bioturbation is mostly carried out by termites. Based on their different building strategies, termites are usually differentiated into two functional groups: the fungus growing (FG) and non-fungus growing termites (non-FG). In this study, we focused on the properties of soil sheeting, i.e., small sized soil aggregates that are built on the ground or on plant materials by termites. Using partial least squares structural equation modeling (PLS-SEM), we showed that the stability of non-FG sheeting was associated with the properties of the surrounding soil, thus suggesting (i) a low ability or need of termites to adapt the stability of their sheeting to their biotic and abiotic environments, (ii) a rapid turnover of the organic matter incorporated by non-FG, which is only superficially incorporated into soil aggregates. The sheeting of FG termites was generally enriched in clay and impoverished in carbon. However, despite changes in soil properties, PLS-SEM did not satisfactorily account for sheeting stability (i.e., no direct or indirect path correlations between the stability of soil sheeting and the other measured variables). Therefore, this study suggested a reorganization of soil aggregates and an adaptation of sheeting properties to the environment with a positive impact of termites on soil sheeting stability restricted to semi-arid to arid environments (mean annual precipitation <500 mm year−1), in agro-ecological biotopes, and when sheeting covered leaves in comparison to wood. Hence building strategies between FG and non-FG termites can have functional consequences in terms of soil aggregate stability in tropical soils.