Caractérisation de la diversité fonctionnelle des prairies à flore complexe : vers la construction d’outils de gestion

Characterizing the functional diversity of grasslands with a complex flora : towards the creation of tools for management

This paper has a twofold aim : first, to characterize the functions of natural grasslands regarding both their level of vegetation and their utilization ; second, to show how such a characterization may be helpful in the creation of tools for the diagnosis and for the management of complex swards. Two sets of data were utilized : 1) a network of 87 natural pastures in the Pyrénées, characterized by their botanical composition and by agricultural practices (levels of nitrogen and phosphate nutrition, types of pasture management) ; 2) a collection of species grown under semi-controlled conditions on which a number of agri-ecological measurements were taken (traits, agricultural characteristics…). The second set was used to illustrate the relationships between traits and agricultural characteristics and also to define at which level the data from the network of 87 pastures would be interpreted. The levels at which diversity was characterized (specific, life forms, functional types of the grasses) are presented. The variations in nutritional levels and in types of management within the network of 87 pastures contributes to the existence of a considerable diversity of vegetational types. Lastly, the diversity of grasslands, expressed as a function of the proportions of the various functional types of the grasses, was correlated to the utilization value, which expresses the functions of pastures that are expected by the farmers. This approach supplies new prospects of investigation ; moreover, we propose to adapt a table for the characterization of the types of pasture management according to the dominant grass type.