Mountains are increasingly important islands of nature in our rapidly changing world. They contain some of the most diverse biodiversity hotspots in the world, have a high aesthetic value and their conservation even has a lot of economic importance. There are countless reasons to be happy that we still can rely on this pure and undisturbed nature.
For now, alpine ecosystems are among the better conserved ecosystems in the world. However, we should not be too satisfied with that conclusion. While you are reading this, the countless mountain resources get increasingly exploited. How our beloved mountain ecosystem will react to these changes is hard to predict. Adding to the first steps towards predicting the future reaction of the mountains, that is exactly what our article in PLoS ONE was about (check here the scientific version: Lembrechts, Milbau and Nijs (2014)).
Our main research goal was to study the reaction of the alpine plant world to the building of roads. One lonely road to the top often marks the beginning of an intensive process of disturbance, as it creates access for both tourists and industry. It is well known that roadsides change the ecosystem completely and that they cut the core of the natural vegetation in tiny useless pieces.
Surprisingly, roadsides in the subarctic mountain system allow a HIGHER diversity of plants, as can be seen on this graph. This could sound a bit surprising at first, as we would on first thought expect indeed a negative influence of disturbance.
However, before we all start celebrating this positive outcome, we should have a closer look at the processes that explain this higher species richness. I already highlighted the completely different growing conditions in roadsides. Apparently, these conditions are ideal for a lot of species that normally do not get a chance in the natural system.
In our system, this sudden opportunity for so many species results from the clear negative effect of the roads on the most important plants in the Scandinavian mountains: mosses and crowberries. Together with a limited amount of other berry species, they form an uninterrupted, dense understory. This effectively blocks all germination chances for virtually all other species. The crowberries use an even more vicious trick: they produce chemical compounds that actively limit germination chances of other species. Consequently, the normal, undisturbed ‘climax’ vegetation in the subarctic mountains hosts often not more than a meager ten species, the others are all efficiently outcompeted.
When humans start building roads in these systems, the dense cover of mosses and berries is destroyed. The natural vegetation disappears and the remaining bare soil creates magnificent opportunities for new seedlings of so many species that would otherwise stand no chance at all.
So, the loss of the insuperable bully leaves the playground free for all other plants to flourish. This gives a higher diversity, although it is completely different vegetation than we would expect to find.
But there will be more. It is not only the basic species richness that changes in the roadsides, but the disturbance causes a whole sequence of other effects. More about them in a following post.