Topography

For an ecologist interested in where plants are growing, the local climate is crucial. And that microclimate is for a large part influenced by the local topography. Slopes, aspect, elevation, cold air pooling… All the bumps and crevices in the landscape have a profound effect on the climate experienced by what is living there.

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The steep slopes of the slate mines in ‘Les Pans de Travassac’, Limousin

We got to experience a very clear example of these effects on our recent trip to the Limousin in Central France, where we visited one of the last remaining slate quarries in France.

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The artificial cliffs were often too steep for vegetation to cling to, but every rock has its hide-outs

In this magnificent landscape, history had turned an ancient ocean into slates, after which tectonic earth forces positioned these slates vertically. Then, centuries of slate mining cut out vertical holes in the rock with a depth of up to 150 meters (of which over a hundred under water).

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The artificial craters hosted a variety of shade- and cold-loving plant species

The result was a series of deep trenches, overgrown by vegetation wherever sufficient light was available. South facing tops of these artificial cliffs hosted sun-loving species, yet in the depths of the craters, shade- and cold-loving plants ruled.

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Especially ferns love such a cool and dark world, and even in the deepest holes, ferns of over a meter were a common sight.

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Polypodium vulgare, a species of fern that doesn’t mind some sun on its leaves, growing on top of the walls at the slate quarries

Interestingly, recent research has shown that such cool spots, where the microclimate is several degrees lower than in the surrounding environment, could be an ideal hide-out for species in times of climate change: while all around them the climate is heating up, species with an appetite for a cooler world retreat in these so-called ‘microrefugia’, where the remaining population might survive for a very long time.

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In this case, this could mean an unexpected positive effect of the human disturbance of the landscape.

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