Diagnostic agro-écologique de la végétation des alpages laitiers des Alpes du Nord humides : établissement et utilisation d'une typologie simplifiée

Abstract

Summary — Agro-ecological diagnosis of the vegetation on dairy cow mountain pastures in the French northern Alps: development and utilization of a simplified typology. Ensuring perennial growth of dairy cow mountain pastures in the French northern Alps is particularly dependent upon good exploitation of mountain resources. A good knowledge of these resources is essential for appropriate management. A typology of vegetation on such pastures has been developed aiming at an agro-ecological diagnosis. It is based upon 220 linear surveys, sampled from 7 summer pastures representative of the area under study. Multivariate analysis of these data, including correspondence analysis followed by hierarchical clustering resulted in the selection of 11 types and 25 subtypes of vegetation. This typology serves various purposes. It is a guide for a simplified identification of pastoral resources which is simple enough to be used by individuals with no specific expertise in flora. The key for identification of vegetation types is based upon a joint assessment of different criteria: morphology (ie plant height), dominant or characteristic species (25 for the 11-type simplified typology), environmental conditions, or grazing and fertilizing practices. This classification can be extended to all mountain pastures in the northern part of the French Alps. It is a tool for pastoral diagnosis, since each vegetation type is defined by its grazing capacity, in terms of productivity, nutritive value, growing rate and stocking rate. Recommendations have been made to maintain or improve native pasture vegetation, and evolutionary hypotheses have been put forward. Establishment of this typology is an essential step for future research on vegetation dynamics analysis and also for vegetation mapping via remote sensing techniques, in view of rangeland managment in mountainous areas.