Formiguer Soils The Mediterranean analogue to terra preta de Indio in the humid tropics?

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Soils heavily influenced by human action are increasingly gaining in importance because of unsolved global issues such as global warming, soil degradation, increasing world population and related food security. As shown by the example of terra preta de Índio in the humid tropics, Anthrosols can contain tremendous nutrient and soil organic matter stocks after several hundred years. However, only few Anthrosols are comparably intensive investigated than terra preta. An interesting example is the formiguer fertilization technique in the Mediterranean Catalonia (Spain) aiming an increasing soil fertility. The method is based on carbonization of piles of biomass under a thick soil cover. After burning, the heated soil cover, ash, charcoal and highly probable also dung were distributed and incorporated into the soil. The resulted soils still contain high amounts macroscopically visible charcoal particles, are dark in soil colour, having a good soil moisture and active soil fauna, which is in contrast to surrounding non-treated soils. In how far the input materials and properties of the formiguer soils are comparable to terra preta de Índio and thus its Mediterranean analogue and model for sustainable land use in Mediterranean regions, is a key question of the project. The project focuses three main issues using state-of-the-art methods. First, land use history will be reconstructed using radiocarbon dating (14C), phosphorous and nitrogen isotope (d15N) analysis combined with molecular markers for identification and quantification of charcoal (black carbon) and faecal matter (stanols and bile acids). The impact of formiguer fertilization on soil properties will be determined by soil basic characterisation of formiguer soils compared with non-treated adjacent soils. Changes of charcoal properties in the long-term under intensive soil cultivation are still poorly understood. Thus, the second subject addresses the chemical properties of fresh and aged charcoals in formiguer soils and possible stabilization mechanisms, which may lead, beside chemical recalcitrance, to its long-term stabilization in soils. Elemental composition of charcoal (C, N, O, H and O) as well as the quality and quantity of black carbon will provide deeper insights in charcoal formations process (fire intensity) and recalcitrance of charcoals. Changes of chemical properties of charcoals exposed in soil will be determined by combining microscope and spectroscope techniques such as SEM-EDS, FTIM, XPS and thin sections. The third subject of the project focusses on the impact of the formiguer fertilization technique on microbial biomass and microbial community structure. Amino sugars, muramic acid and PLFA will be used as marker for fungi and bacteria.