Project: Clay minerals and pedogenic oxides: key components of soil organic matter storage and stabilization in highly weathered tropical soils

Highly weathered soils in tropical Africa are largely affected by land use changes from forests to arable lands. The uncertainty about losses of soil organic matter (SOM) and the responsible mechanisms have a huge impact because functioning of these tropical soils highly depends on SOM. Therefore, the main objective of the project is to identify and quantify important soil components and mechanisms for SOM storage and stabilization in highly weathered tropical soils in the East Usambara Mountains, Tanzania (Fig. 1). Pedogenic iron oxides and clay minerals should play a vital role for SOM by the formation of mineral-organic associations and soil aggregates. However, there is a knowledge gap about how changes in both soil components may influence stored amounts of SOM and the responsible stabilization mechanisms, and which are more important under certain soil conditions.We selected soils representing a natural gradient in both components, i.e. pedogenic iron oxides and clay. Soils have been sampled and will be analyzed by advanced approaches to characterize soil minerals and aggregates and their interactions with SOM. Our project will deliver an improved mechanistic understanding of SOM storage and stabilization in these highly vulnerable tropical soils. Based on our fundamental research, management strategies can be developed for sustainable land-use planning and good agricultural practice.

Fig. 1: Project concept

Land-use change