High altitude vegetation

An archipelago of green islands among the rocks

Berardia, plant growing on limestone scree | APAM Archive, G. Pallavicini

High altitude reliefs are often harsh and rocky. The continuous carpet of grass in the subalpine belt, makes way for an archipelago of islands and green peninsulas, connected by passages and interrupted by cones of debris and rock walls. The thickness of the soil varies according to the slope; the steeper a slope is, the thinner the substratum will be. This means that plants that vegetate in the most inaccessible places must be able to make do with very little soil. In addition, the type of rock that generates the substrate has a significant influence on the vegetation. The pastures on calcareous substrates such as those found in the Marguareis Nature Park are home to the most beautiful flowers: the colours vary from white to purple, blue to golden yellow. Higher still, the richness of colours gives way to groups of sedges (Cyperacee) and grasses (Poaceae), often structured in more or less compact tufts, with inconspicuous flowers reduced to the bare essentials.

The highest peaks of the Ligurian Alps are surrounded by moraines and scree cones at the base of the rock walls. The landscape is enchanting and the silence is broken only by the noise caused by the occasional falling rocks, or by the calls of the choughs that watch hikers from above. The downward movement of rocks caused by atmospheric and biological factors disturbs plant colonization. They try to counter this phenomenon with anchoring and consolidation strategies, in other words, plants adapted to live on debris have formidable roots.

In the Park these environments are characterized by the imposing calcareous screes of Marguareis and, to a lesser extent, of the Cima delle Saline, but there is no lack of siliceous rock debris. The species that inhabit these areas have a relevant phytogeographic importance. In the most stable calcareous scree, we find Berardia subacaulis, a species endemic to the southwestern Alps of very ancient origin, probably present in these regions even before the formation of the Alps. In addition, we find Campanula alpestris and Allium narcissiflorum, endemic to the southwestern Alps, the Sulphur highlights of Papaver rhaeticum, the infrequent Galium megalospermum and pusillum, as well as Valerian saliunca and the more widespread Noccaea rotundifolia, Doronicum grandiflorum, Cerastium latifolium, Adenostyles alpina and Linaria alpina.

Across the siliceous debris, generally less mobile, we find Oxyria digyna, the small fern Cryptogramma crispa and also Achillea erba-rotta and Adenostyles leucophylla, both endemic to the western Alps.
At the bottom of the scree falls, but in other environments as well, we find basins and hollows where the snow persists until late summer. In such sites unusual dwarf willows can be observed.

Also on the hostile rocky walls of the highest peaks of the Park, apparently inhospitable and barren, a vegetation, rich in rare or endemic species, has adapted to live in extreme ecological conditions. The climatic conditions in this rocky habitat are extremely harsh, the daily and seasonal temperature range is considerable, frost and wind are always intense. As if that were not enough, there is a lack of soil for the plants to take root and the very nature of the rocks, at times, contrasts their colonization. The same atmospheric agents, however, eroding the rocks, cause the formation of cracks where the casmophytes, the plants growing in cracks, can penetrate with their very developed roots. But even where every plant form seems to be missing and life seems to surrender due to force majeure, in reality there are lower plants that resist, such as mosses and lichens which, with particular adaptations, manage to colonize even the most compact rocks.

Clearly, these limestone massifs, offering stretches of dolomitic scenery to the Alpine landscape of the Park, are the predominant features of the protected area. Here, in addition to the endemic species already mentioned, you can find species of considerable value such as, the pretty Saxifraga caesia and the very rare Saxifraga diapensioides; the minute Sedum fragrans endemic to the southwestern Alps. Then Potentilla caulescens, Petrocallis pyrenaica, the espaliers of Rhamnus pumila, the rare Erigeron atticus and the genepì group. The aromatic Artemisia umbelliformis subsp. eriantha and subsp. umbelliformis. Also recurrent in the subalpine belt we have the endemic Phyteuma charmelii and Globularia repens, together with the rare Asplenium fissum and very rare Erinus alpinus, on the cliffs near Carnino.

The siliceous rock populations are no less important since they can count on species such as Saxifraga pedemontana or Jovibarba allionii, endemic to the Western Alps.
On the crests, rare entities such as Astragalus depressus and Oxytropis helvetica accompany the rock flora.