In my previous blogpost, I highlighted the important effects of local topography on microclimate, and of the latter on species distributions.  I used a man-made structure, a slate quarry, as an extreme example. Now, I’d like to take you to an even more extreme, yet this time fully natural, example: the impressive cave of the ‘Gouffre de Padirac’ in the valley of the Dordogne.

Asplenium scolopendrium, the hart’s tongue fern, growing at the very bottom of cave

This chasm is a big hole in the ground, 35 meters wide and 103 (!) meters deep, and the beginning of a long underground river system. This remarkable landscape element not only provides breathtaking views for those taking the old iron stairs (or elevator) down into its mouth, it also provides unique conditions for plant life.

The staircase that brought us down to the bottom of the ‘Gouffre’

Temperatures down in the grottes are a constant 13°C, which implies a rapid drop in temperatures over the 100 meter gradient. For plants living at the bottom – a surprisingly high variety of ferns, forbs, grasses and even shrubs and trees – it means a life with limited daily and even yearly temperature fluctuations, yet also very little light.

Beautiful stalactite formation in the caves

When wandering off further from the hole in the ground, ultimately the lack of light of course smothers any aspiring plant, but the unique conditions below the hole provide the ideal environment for plant species not very fond of neither high nor low temperatures.

Higher up the slopes of the ‘Gouffre’, for plants it is also a battle for sufficient soil to grab on to, yet many remarkable plants managed even that very well.