Soil is a natural resource that is not renewable at the human time scale and often subjected to a range of alteration events due to human or natural activities. One of the most striking features of soil is its biological complexity, still largely unknown. Soil is indeed the most biological diverse environment on Earth (Dance 2008), and

Istituto di Chimica Agraria ed Ambientale, Universita Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy e-mail: [email protected]

A. Piccolo (ed.), Carbon Sequestration in Agricultural Soils,

DOI 10.1007/978-3-642-23385-2_7, © Springer-Verlag Berlin Heidelberg 2012

its main ecological and productive functions are driven and sustained by the presence and activity of microorganisms (Young and Crawford 2004).

Scientists are still largely debating about the estimations of the size of microbial communities in soils. One of the first estimations, published in 1990, pointed to about 4,000 different bacterial genomes per gram of soil (Torsvik et al. 1990). Later studies have first moved the estimated number of species per gram of soil to 830,000 (Gans et al. 2005) and, then, back down to a number between 20,000 and 50,000 species (Roesch et al. 2007). Of course these estimations are affected by a numbers of factors, starting from the type of soil considered and the methods used for the estimation. Amann et al. (1995) reported that more than 99% of the bacterial species in soils are unculturable, and this has been widely confirmed by recent studies (Handelsman 2004; Deutschbauer et al. 2006). Research is now mining at molecular level into this widely unknown unculturable majority, by taking advantage of new technologies which allow a fine-scale resolution of DNA, RNA and proteins in soils. These approaches will most probably give relevant outcomes at both basic and applied science level in the next years, but at the moment the level of complexity is so high that is difficult to translate the amount of information obtained in, for example, indexes of soil quality and/or alterations due to soil treatments.

Soil scientists have been studying the structure and most importantly the functionality of soil microbial communities for decades, by developing and optimizing methods that are now still applied and widely accepted, even at regulatory levels. We have focused on two of these methods: enzymatic activities and phospholipids fatty acid (PLFA) analyses. Methods and literature evidence are firstly discussed in relation to soil management practices aimed at carbon sequestration, namely amendment with compost and other organic residues, and reduced or no tillage managements. In the second part of the chapter, evidence from MESCOSAGR project is discussed in relation to literature review. Original outcomes about possible effects of the third C sequestration strategy considered in MESCOSAGR (organic matter photo-polymerization under a biomimetic catalyst) on soil PLFAs and enzymes are also presented.

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