A EUROPEAN NETWORK OF LONG-TERM SITES FOR STUDIES ON SOIL ORGANIC-MATTER

In this paper we describe the GCTE global Soil Organic Matter Network (SOMNET) before focusing on the European network of long-term sites. W e then select two examples from the European site network and demonstr ate how such data can be used to (a) track long-term changes in soil o rganic matter, (b) evaluate and compare soil organic matter models, an d (c) make rough estimates of the potential for carbon (C) sequestrati on in soils at the regional (European) level. Our simple calculations based on only two long-term experiments suggest that amendment of arab le soils with 10 Mg ha(-1) of organic manure could lead to an increase in current total European soil C stock to 30 cm of about 4.8% over 90 yr, a scenario with limited potential for sequestering C, Similarly, afforestation through natural woodland regeneration of 30% of current arable land (surplus to requirements by 2010) could lead to an increas e in current total European soil C stock of 12.4% over 100 yr. This is equivalent to 43 Tg C yr(-1) or 3.8% of anthropogenic CO2-C emissions from Europe. If temporary C storage in standing woody biomass is incl uded in the estimate, the amount of C sequestered is quadrupled and co uld account for 15.28% of Europe's annual CO2-C emissions. This is equ ivalent to 2.8% of annual global anthropogenic CO2-C emissions. These calculations are presented to demonstrate a simple technique for estim ating rough C sequestration potentials but they do suggest some potent ial to sequester C in European agricultural soils. As a result, a more sophisticated approach using statistical relationships derived from a large number of long-term experiments was developed. The need for bal ancing the effects of these scenarios on soil C against other environm ental considerations is discussed. Methods for improving estimates of the potential for soil C sequestration using the European site network are also discussed. (C) 1998 Elsevier Science B.V. All rights reserve d.