Pasture management and its consequences on the bio-geochemical cycles and on bio-diversity

摘要

Papers of the 4th session of the European Grassland Congress (La Rochelle, 27-30 May 2002) are reviewed and discussed. The three plenary papers in the session dealt with: (1) the amplitude and diversity of effects on grasslands of the present increase in atmospheric carbon dioxide (on grassland production and its distribution, on forage quality, on soil water content and the nitrogen cycle), (2) the key elements of the nitrogen cycle on animal farms (including evaluation of pollution risks; codes of recommended practices), and (3) the main mechanisms explaining the co-existence of species and/or of vegetation dynamics induced by the agricultural practices ('clonal' strategies, interest of the 'functional group' concept). As a whole the papers showed an increased interest in the effects of management on bio-diversity, mainly considered from the botanical point of view; nutrient balances on the farm scale and a larger use of legumes were discussed; and the studies of environmental balances were enlarged to include the climatic change and the greenhouse effect. Three types of problems stand out at the end of this congress: the necessary progress in modelling the bio-geochemical cycles in grasslands; the necessity of integrating approaches to the grassland eco-systems (coupling sward dynamics to the bio-geochemical cycles especially, and reinforcing interface studies; linking together the various approaches); and thirdly the development of the changing of scales in time and space as an investigational tool.