8. Soil biota in Terra Preta soils
While soil physical and chemical properties of Terra Preta are fairly well known, soil biology is lagging behind. We hypothesize that soil biota play a crucial role in Terra Preta functioning, as Terra Preta soils have been characterised as ‘living soils’. The ways in which previous and present-day management practices affect soil biota and how this affects their agronomic potential are not known, either. The following groups of soil organisms will be studied: root mutualistic micro-organisms (rhizobia, arbuscular mycorrhizal fungi), saprotrophic micro-organisms that can attack recalcitrant (pyrogenic) materials; ecosystem engineers such as earthworms. More specifically the project will test the following hypotheses: (1) Terra Preta food webs could be characterized by differently co-evolved mutualists (rhizobia, AMF); (2) high P levels could positively affect rhizobia and negatively affect mycorrhizal functioning, making their combined effect difficult to predict; (3) the composition of saprotrophic micro-organisms that decompose fresh organic inputs differs between Terra Preta and oxisols; (4) Terra Preta soils contain micro-organisms with enhanced capabilities to decompose substances with high recalcitrance; (5) Terra Preta and oxisols differ in species composition, abundance and functional groups of earthworms; (6) earthworm species adapt to (or even co-evolve with) Terra Preta; (7) ecosystem engineers (earthworms) play a causal role in the origin or maintenance of Terra Preta. Finally the project will study local knowledge of these organisms and the way(s) in which local people use soil biological activity as indicator for Terra Preta.