Chemical diversity of pyrograms as a discriminating parameter in soil humus and plant residues

The Shannon-Weaver diversity index is applied to pyrograms of different soils and composting plant residues in order to summarize the relative abundance of some pyrolysis products as a simple parameter which permits interpretation and discrimination between humus types. The diversity index reflects the changes in the organic matter during the composting process of plant residues. It reaches a maximum in the intermediate stages of the process, due to the presence of products derived from the original carbohydrates and lignins, together with aromatic compounds typical of mature humus. In the soil samples studied, it adequately discriminates between three anaerobic humus (peat, muck^** ** For a glossary of terms used in this article, see p. 248. A more complete explanation of these and other terms can be found in A Glossary of Soil Science Terms, published by the Soil Science Society) of America, 1979. and anmoor), between some aerobic groups (carbonated mull, forest mull and moder, humus of bioclimatic evolution), and also between the diverse genetic horizons present in well drained soils (A₀, A₁, A₂, B).