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Zau Zoura /SD Ayer - Post n°6 : Rocks

The heart of the Zau Zoura is nothing but screes, rocks and cliffs. In this hostile environment mountain forests have developed.

After the last glacial period, the finest sediments deposited on the edges of the valley by the ice accumulated on terraces, creating fertile areas that could be cultivated by men. Steep slopes, where the bedrock is exposed, have given over to the forest. So, the heart of the Zau Zoura is nothing but screes, rocks and countless small cliffs. In this hostile, mineral and dry environment mountain forests have developed, harboring a varied ecosystem and providing timber, an indispensable raw material for villagers.

The rocky outcrop you see here is called amphibolite. It is to be found just about everywhere in the forest along with gneiss, another very hard metamorphic rock. Plant species establish themselves in the smallest cracks of the bedrock and on any flat enough surface, leaving only vertical areas to bare rock or lichens.

In Spring, the blooming of stinking primroses (Primula hirsuta) is a spectacular sight, especially as they remain almost hidden the rest of the year and only their sticky leaves adorning cracks in the rock are noticeable. The roots of the common polypody (Polypodium vulgare) also creep into small crevices. It is best to pick it when it is growing on lush moss as its edible roots are bigger.

Although the three resinous conifers of our forests adapt well to difficult terrains, the Arolla pine (Pinus cembra) is the one that truly thrives in the most unlikely contexts. Its edible seeds look like small hazelnuts and mountaineers compete for them with squirrels (Sciurus vulgaris) and spotted nutcrackers (Nucifraga caryocatactes). These animals stock food for the winter months preferably in hiding places that are difficult to access and where the snow melts early in the year. They also wedge their nuts into cracks in order to shell them.When they forget about them, young Arola pines might grow, sometimes even on the side of a rocky wall. This conifer, whose early development is facilitated by the reserve of food contained in the bean, grows slowly and does not require much light. It can wait till one of its roots meets a richer substrate to finally flourish.

The shallow roots of conifers bind soil particles at the ground surface, reducing their susceptibility to erosion. Tree trunks stop or stall falling stones. To a lesser extent, plant root growth combined with frost shattering can work loose large chunks of stone from rock faces. At the base of crags you can see lighter areas, recently uncovered rocks and screes.

Text : Manu Zufferey, hiking guide
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