Towards a common humus forms classification. The point in Europe: few top soil references as functioning systems. (Humus forms: integration of living ecosystems)

Presentazione grafica della chiave di riconoscimento delle forme di humus concepita dal Gruppo Humus Europeo.- - - - - [ABSTRACT: 1.A European humus group exists and has done some steps into a common classification of the humus forms; 2.The principles of the classification; 3.The future horizons. 1. In Europe as well as in North America a multitude of humus taxonomies exists starting with early approaches in the late 19th century. Due to the variety of sites throughout Europe, different methodological approaches were used, thus resulting in different classification systems. The Canadian (Green et al. 1993) and French (Brêthes et al. 1998) classification systems are frequently used in an international context, but don’t cover all site conditions of European forest ecosystems. Basic concepts of most national European classification systems are similar along general lines. Nevertheless there are differences in parameters used for description and classification of humus forms as well as in scaling these parameters. This results in incompatibility of classifications on the lower levels of the systems. So, i.e. regional humus forms cannot be described and compared as similar designations of humus forms often having differing contents, and similar contents having differing names. In 2003, during a meeting in Trento (Italy), 26 European specialists in humus forms met in Trento (Italy) and of humus forms decided to create set up a “European humus research group” in order to study the process of transformation of the top soil and to find some rules of classification based on a morpho-genetic description and diagnostic horizons, adapted to European ecological conditions. The young born group managed established three commissions named “Vocabulary”, “Classification” and “Diffusion”. These organs of actiongroups produced some common references. and Tthise goal of the presention paper is to illustrates the most important steps in on this way. In July 2004, the commission Classification met in Vienna (Austria) and drew drafted a first schemakey in which to the main terrestrial humus forms have been placed on a plane in based on response to some environmental conditions and specific biological activities. The This draft has beenwas presented in Freiburg (Germany) at the EUROSOIL Congress 2004 (Jabiol et al. 2004) and renewed was worked out furtherly in San Vito (Italy) in 2005 in a well developed taxonomic draft. Protocols for assessment and sampling of ecto- and endorganic layers were set up as well as definitions of specific horizons and the their designation. 2. Taking into account the Canadian (Green et al., 1993) and the French points of view (Brêthes and al. 1998) as well as new national classification systems form Austria, the Netherlands and Germany, it has been possible to individuate four main humus forms (Mull, Moder, Mor and Amphihumus) are classed and each further dividing into many subcategories. Assigning a strong discriminating power to the actions of the pedofauna, which above all modifies the OH and A horizons characters and determines the evolution of the top soil in a given ecosystem, one canit is possible to class both humus form and ecosystem functioning. Mull humus forms are developed due to the mixing activity mainly of anecic and endogeic earthworms, mainly. In unfavourable ecological conditions for earthworms, Moder humus forms are developed by the litter comminuting activity of microarthropods and enchytraeids. Amphihumus corresponds to the activity of both animal groups in different vertical niches strata and, finally, Mor humus forms are found in ecosystems in which soil animal abundance is very low. Some properties are considered as taxonomic differentiae for humus forms: the presence/absence and thickness of diagnostic horizon, type and size of horizons’ structure, presence/quantity of roots, woody debris and rock. Thanks to a Dutch input, the last version of the classification takes into account also the semi-terrestrial ecosystems. Conceived as a dichotomised tree, the first bifurcation of the key divides peat from terrestrial forms. The descriptors for the diagnostic horizons have been conceived in harmony with the FAOWRB-draft (1998) and will be presented in Philadelphia by Broll G. et al. under the title "Topsoil characterization and classifications. New developments and chances for links to WRB. 3. From 2004, a web site is active in Grenoble (France) : http://humusresearchgroup.grenoble.cemagref.fr/. The 40 members of the group are from 10 European countries (Austria, Belgium, Czech Republic, France, Germany, Italy, Netherlands, Rumania, Sweden, Switzerland). The running projects concern nowdeal with better definitions of the Amphi- and Litho- humus forms and all the transitional cases, particularly between Amphihumus - Moder and Moder - Mor. Three meetings are planned in order to look all together at peat (Netherlands, Alterra, 2006), high mountain (France, Grenoble, 2007) and Mediterranean (Italy, Cagliari, 2007) ecosystems. It currently is considered to use the present classification within the BioSoil project of the European Community (repetition of transnational soil condition monitoring)]