The plant biodiversity of the Pyrenees in the face of global change

In a cross-border project, POCTEFA Florapyr Avance, botanists from very diverse centers around the Pyrenees, from IRBio-UB Dr. Estela Illa, Dr. Josep Ninot and Dr. Ignasi Soriano, have carried out a series of actions that contribute to the Pyrenean Climate Change Observatory (OPCC) through the analysis of aspects of the flora and vegetation relevant in strategies for adaptation to change. Among these actions, the valued publication of the red list of Pyrenean flora, the creation of a cross-border network of seed banks for ex-situ conservation of species at risk, the formation of a monitoring network for invasive plants, and the monitoring of snowfield communities in the Pyrenean alpine landscape.

The snowfields represent emblematic habitats, on the one hand because of their Pyrenean location on its southern limit on a European scale, and on the other because, as depending on the seasonal duration of the snow cover, they are sensitive to climate change. The trend towards diminishing snow accumulations and warmer summers means that generalist alpine meadow plants are becoming increasingly important in the snowfields, to the detriment of species adapted to short summers. These snowfield plants are capable of become active suddenly when they are free of snow, between mid-July and mid-August, and close their annual cycle quickly.

For this reason, in two actions co-led by Estela Illa, a phenological monitoring of the snowfield plant communities has been carried out in 14 locations distributed throughout the mountain range, during nine consecutive summers. In addition, in five of these localities a small-scale environmental manipulation experiment has been carried out since 2018. It consists of the establishment of four pairs of plots in each locality, in which one plot of each pair experienced a slight warming (between 1 and 2 °C on average) in the soil surface and in the vegetation through Open Top Chambers, small greenhouses open at the top. The response of the vegetation has been evaluated mainly through Salix herbacea, a species of dwarf willow emblematic of these habitats. After four summers, the plants of this willow subjected to heating have significantly modified several foliar parameters and, in general, have regressed slightly in their ground cover.