Response of Pyrenean subalpine pastures to continuous warming an annual sporadic variations

The certainty of global warming is leading to the programming of activities and management practices for a future in which conditions will be very different from today. In the case of subalpine mountain pastures (or upland summer grasslands), it is necessary to know the changes that have taken place in the three most important variables: biomass production, forage quality and diversity. This work was carried out in the high-mountain pastures of the Aigüestortes National Park (located above 2000 m a.s.l.) in the Spanish Pyrenees during a period of twenty years, with sampling every five years. The three most abundant types of pasture of the National park, which occupy 60% of its area (Festuca eskia, Nardus and Nardus+Festuca nigrescens) were taken and used to measure aboveground biomass production by means of cuts, forage quality through bromatological analyses of biomass and Pastoral value, and the diversity through transects. Simultaneously, climatic data from three nearby official climatic stations were collected to relate rainfall and temperature variations to vegetation data. The results show that changes in total production are more linked to annual climatology (more temperature in the growth period, less production), whereas general climate warming leads to a decrease in forage quality (more temperature and more rain in the growth period, higher fiber content) and an increase in specific richness (more temperature more diversity). In the future in order to maintain these highly diverse pastures for optimal feeding of the livestock, a downward adjustment of stocking rates will have to be programmed, in accordance with production and quality trends: the pastures will feed fewer animals.

This study was supported by the Forestal Catalana SL and TRAGSEGA SL enterprises.