That damn snow again

During last year’s field trip to Sweden, at the very end of August, an early autumn snowstorm threw us of the mountain. You can (re)read the account of that humbling hike here. We were beaten. Defeated. Nature’s powers were too strong. We managed to hike up, yes, but trying to identify plants under a growing pile of snow turned out close to impossible.

Last year’s snow storm covering the landscape in grey and white.

This year we came earlier to that damned valley, determined to win and find back the sensors we had hidden there when days were better and slopes uncovered.  But again, the valley would only reluctantly reveal its secrets. Oh yes, the weather was great, we made sure we waited for the best day of our whole trip. But there was snow. Again. Tons of it.


Turned out the valley was holding on to every inch of snow it accumulated over that surprisingly long Arctic winter. And thus, even now, the 20th of July, two weeks later than we usually manage to reach the top, we found massive snowpacks on our path.

Low in the valley, the shadowy sides of the river were still covered with snow.

Too early for spring!? Yes, this is the subarctic, where spring has to hurry up as soon as winter finally releases it, before autumn catches up with it again only a few weeks later. This is the subarctic, where the summer suns are plentifull, yet life is living on the edge.

Early spring at the edge of a snowpack gives for beautiful flowers of Arctic willows

The snow started low enough to make us worry about getting anywhere at all, as we had to rely on a ‘summer bridge’, which only gets installed when snow is melted. Yet we were lucky in that regard, and we could continue our conquest of this amazingly wild valley.

Tiny flowers of Rhododendron lapponicum at the edge of a snowpatch

Unlike last year, luck now stayed at our side for most of the hike. While a few plots were buried under a thick pack of white softness, most of our plots balanced on the edge of the snowpacks. A bit of digging, a bit of luck, and in all but one plots at least one of the two sensors could be dug up.

The trail marks appearing above the snow pack, helping us finding back our plots

That damn snow, yes, but it ensured the most beautiful views ever. We felt like true explorers, fighting the rough elements, and being rewarded with the best what nature has to offer.

Reindeers enjoying the snow, and reluctantly accepting us in the tough world of their Arctic valley
Reindeer in the middle of a frozen world

On a hunt for mountain plants

Valerian flower in a Norwegian valley

We are at the height of our 2017 resurvey of the vegetation along Norwegian mountain roads, and the fieldwork has been highly successfull. It has been great revisiting the plots and discovering the changes – and often the highly interesting lack of it – in the last 5 years.

Harebell flowers on the side of a fjord

The fieldwork brought some annoying bits of rain, yet mostly plenty of sun. It included beautiful flowers and breathtaking views, but also tons of sample bags and hours bending over in roadsides. We climbed rocks, jumped rivers and swam in an Arctic fjord, yet also spent hours in the lab, weighing leaves and sifting roots. An intense ten days, collecting data that can easily keep us busy for a few more years.

Cottongrass in a species-poor mountain marsh

And the first results indeed look very promising, even though a lot of data still has to come in before we can get to any conclusions. Luckily, I can again count on an awesome fieldwork team, this year with three highly dedicated master students who use this extremely interesting study system for their master theses. With their help, the data will soon reveal all its secrets.


Aliens and their way to the top

5 years later, we are getting ready for a re-survey of our longterm observational plots along the roads in the Norwegian mountains. The perfect moment to summarize in a series of posts what we learned from our first trip.

Remember my story about how lowland roadsides are flooded with species that do not  belong in the natural system? Remember how these new species could profit from the lower competition when the natural vegetation got destroyed by the process of road building? A lot of these species are well known to Northern Scandinavia, but some of them are not. And this last group deserves our special attention.

A group of true culture-followers. The real roadside species. The ultimate weeds. They followed human development up to the north at one point in time, some decennia or centuries ago. We call them aliens: visitors (and sometimes invaders) from another ‘world’. (But do not let them fool you, because they are just species like our regular white clover!)

Trifolium repens

What is really curious is how almost all these aliens share the same story. Their invasion always starts in the lowlands, where they got introduced, after which they closely follow roads and human structures up into the mountains. Not too many of them really reach the top, however. We see a progressive drop-out of species on the way, victims to the cold alpine climate (but keep in mind this is a dynamic process, they could still be on their way!). This progressive loss of alien species with elevation got the fancy term ‘directional ecological filtering’ and it also seems to be happening in our subarctic ecosystem. The mountain acts as a filter, only allowing a select group of aliens to the highest elevations, while the weaker ones are filtered out (check the clear decrease in roadside alien richness with elevation as visualized by the black line on the graph).

Alien species richness with increasing elevation in the roadsides (black) and the natural vegetation (grey).

The question is which skills are needed to sneak through this filter to reach the highest elevations in the mountains. It turns out that all winners of the race to the top follow a similar strategy: they are all generalists, which means they can thrive in a wide range of environments. That makes them different from the vast majority of plants that got adapted for one particular situation. It also makes them incredibly suited for mountain invasion. Mountain invaders have to overcome both lowland and alpine conditions. Strong competitors loom in the lowlands, where conditions are good and fast and efficient growing are the keys. In the highlands, the harsh climate demands stress-tolerant traits to survive the cold: growing slow, staying close to the ground and using resources to fight the harsh conditions.

Summer snow

That is the reason why pure competitive alien species are stuck in the lowlands, while the generalists can follow the road all the way up to the alpine zone. While both know how to handle the intense competition in the lowlands, only the generalists can change their strategy to deal with the totally different alpine conditions from the highlands. And as soon as these generalists reach the top, they might become problematic and start escaping the roadsides, yet that’s a story for another post to tell.

Clear view on the vegetation gradient

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Road effects

5 years later, we are getting ready for a re-survey of our longterm observational plots along the roads in the Norwegian mountains. The perfect moment to summarize for a second what we learned from our first trip.

Roadsides host more plant species than the natural vegetation. That is the conclusion I drew in my previous post. While this difference is clear on low elevations, it vanishes as we get higher in the mountains, ending in similar species richness in the alpine zone above the tree line. Surprisingly, as can be seen on the graph, this pattern is the result of a higher diversity of alpine species (dashed grey line, white dots, versus the black line and dots representing the roadside) in the natural vegetation.

Graph native species richness

The alpine zone is a rocky, barren place without trees. That sounds as a bad thing for plants, but it also results in a higher availability of open places. The dominance of mosses and dwarf shrubs (like the crowberries mentioned in the previous post), is less intense here. More open spots, less competition, more diverse habitats, all kinds of factors that could explain the higher plant diversity as revealed by the graph. All of this explains the higher species richness on high elevations. But why don’t we have the additional higher species richness in roadsides here as well, as we saw in the lowland roadsides?

Alpine vegetation

Here is why: the higher amount of species in lowland roadsides comes from a bunch of typical roadside species, mostly highly competitive weeds (e.g. willowweed, Epilobium angustifolium, see picture). They do not belong in such numbers in the ‘traditional’ undisturbed subarctic mountain vegetation, but typically follow humans, agriculture and the availability of rich soils and mild conditions. Such culture followers form an important part of the lowland roadside vegetation. These species are added on top of the baseline species richness of typical subarctic mountain vegetation. Therefore: higher roadside diversity.

Hairy willowweed, a typical competitive weed

These competitive weeds are rare in the roadsides on high elevations, where conditions are a lot harsher. The roadsides there serve more as a refuge for stress-tolerant alpine species, because the difference in environmental conditions with the surrounding undisturbed areas is much smaller: both contain open, low vegetation, with a lot of bare rock, exposed to the harsh climate. Ideal circumstances for stress-tolerant plants (like Saxifraga stellaris, see picture), yet a disaster for the competitive kind.

Saxifraga, a typical stress-tolerant alpine species

Conclusion: the subarctic mountain road has a much smaller effect on native plants than its lowland counterpart. Lowland roadsides suffer from the invading pressure of competitive weeds, while they serve on high elevations more as a refuge for a wide diversity of alpine species.

Roadside vegetation

You want to know the exact scientific story? Here it is!

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What is hiding in mountain roadsides?

5 years later, we are getting ready for a re-survey of our longterm observational plots along the roads in the Norwegian mountains. The perfect moment to summarize for a second what we learned from our first trip.

View on the valley of the Abiskojokka
Autumn in the Arctic mountains, the setting for our research. All pictures from the previous campaign in 2012.

Mountains are increasingly important islands of pristine 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 is important even from an economic viewpoint.


For now, alpine ecosystems are among the least disturbed ecosystems in the world. However, climate change and increasing levels of human influence are rapidly changing the face of our mountain nature. A clear example of this human influence is given by the building of roads in mountains, which does not only physically disturb the alpine vegetation, yet also initiates an avalanche of consecutive effects on the mountain ecosystem.

View on Abisko village

With our long-term observational project, we study the reaction of the alpine vegetation to such mountain 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 in all its facets and that they cut the core of undisturbed vegetation in smaller, devaluated pieces.


Perhaps surprisingly, roadsides in the subarctic mountain system host a HIGHER plant diversity, as can be seen on the following graph. A counter-intuitive result, at first sight, as you might not have expected any positive effect of such a radical disturbance on nature.

 Graph native richness

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 plant species in the Scandinavian mountains: mosses and crowberries. Together with a few other berry species, they create an  uninterrupted, dense understory. This dense mattress 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 their competitors for space. Consequently, the normal, undisturbed ‘climax’ vegetation in the subarctic mountains often hosts only a meager ten species, the others are all efficiently outcompeted.

Crowberry - Empetrum nigrum


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.

Road in the autumn

So, the loss of the insuperable bully leaves the playground free for all other plants to flourish. This gives a higher diversity, although the resulting vegetation is completely different from the one occurring naturally in the mountains.

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 those in a next post.

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5 years later

Summer 2012. I was a young masters student, spending my first month of many above the polar circle. I joined a global consortium called MIREN, the Mountain Invasion Research Network, that surveyed plant invasions along roads in mountain regions scattered across the globe.

Eriophorum vaginatum – pictures from our 2012 campaign

With 3 roads in the north of Norway, close to Narvik, we added the northernmost sample sites to this expanding network. With its short summers, freezing winters, yet surprisingly versatile plant species, the Northern Scandes promised to be very interesting.

One of our Norwegian roads in early summer

The unfortunately cold Nordic summer of 2012 was spent surveying these roads, monitoring all plant species that grew in the roadside or the adjacent natural vegetation, with the aim to initiate a long-term monitoring project of the movement of the plant species.

The study area in northern Norway

We are now in the year 2017, five years after this memorable first survey. Time to bring a new team together, with one ambitious goal: return to exactly the same plots that were first surveyed in the summer of 2012, and investigate in detail what happens to the species on the move. A challenge made possible thanks to the INTERACT Transnational Access program.

Midnight sun above lake Torneträsk, Sweden

In a series of posts, we will first cover what came out of the first survey, followed by the fieldwork adventures we encounter on our new mission. Stay tuned, because this will be our most exciting summer of the century (or, well, at least the last 5 years of it…).


More on this and many other topics covered in my PhD on my personal website.

The Anti-Arctic

When the arctic is covered in snow, we turn our scientific interests to the other side of the world: the (sub)antarctic. Our goal is to see if the patterns in the vegetation we observe at one part of the globe – the subarctic world of Lapland – hold true at the completely opposite side as well.

Local Nothofagus forest in the snow
Subantarctic Nothofagus forest in the snow

With this idea in mind, we go to the city of Punta Arenas, on the absolute southernmost point of the American continent. There we study the possibilities of exotic plant invasion in extreme environments. With these trips to the south we hope to come up with a comparison of the limits for common Western European weeds on this far away location with what we know and learn in Northern Scandinavia.

Flowers of invading red clover in South America
Flowers of invading red clover in South America

Our last field trip has been in April, when summer on the southern hemisphere disappeared and made way for snowy autumn storms. This intermediate season presented us with true roller-coaster weather, with freezing lows and icy storms right before the clearest blue skies.

Our high elevation plots covered in unexpected early autumn snow
Our high elevation plots covered in unexpected early autumn snow

The results of this last trip to the south look very promising at first sight. The climatic gradient in the mountains around the city of Punta Arenas turns out to be a pretty drastic one. In the city itself, the ocean buffers temperatures and weather is cold but mild, in fact more a borderline temperate climate than a true subantarctic one.

Huge invasive red clover after harvest
Huge invasive red clover after harvest

The nonnative European species, like the well-known dandelion and white and red clover, profit from these mild circumstances and flourish sometimes even more than in their native range!

Large clover leave
Large clover leave

Several hundred meters above the city, however, you arrive in a different place. The howling winds that already torture the city of Punta Arenas all year round, can blow even more freely up here, and temperatures drop to zero almost every night during the whole summer season. This environment feels much more like Antarctica, the icy continent that is so close-by.

Antarctic feel on top of the mountain
Antarctic feel on top of the mountain

Plants see their growing season reduced to less than half of the months they have at sea level. The negative effects on plant performance are inevitable. Where the nonnative species seemed to be unimpressed by the climate within the safe boundaries of the city, their survival and growth is reduced to virtually zero on the highest elevations.

A little mouse that did not seem to mind the extreme circumstances
A little mouse that does not seem to mind the extreme climatic circumstances on top of the mountains

Interestingly, the interactions of our invaders with the established vegetation seem to change as fast as the weather. However, we have to dig in the data first to get those patterns clear. Hopefully soon more news about that!


And afterwards, it is back to the Arctic, where summer is finally on its way again!

Click here for more information about my research on top of the world.

Flying a helicopter

This post was originally posted on ‘On top of the world‘.

Our most remote plots involve hours of climbing on steep mountain slopes, through dense willow shrubs and over dry rocky areas.


But not this time. This time we had to walk for 20 minutes to Abisko’s helicopter base and do the full hourlong walk in less than 5 minutes.


The helicopter was a nice, big red insect that we had seen zooming around through the mountains before. But now, it was us who had to put our luggage in its trunk, put on the huge headset and communicate like true professionals through the microphone.


The flight itself was as exciting as it was short. The helicopter was really stable, so you almost could not feel the lift-off. It sheered closely over the mountains, right past the famous Lapporten gate, and in no-time we reached the top.


There, the helicopter quickly dropped us off – landing on the open Arctic tundra was no problem – and we ran away of its swirling propellers.


We were up on the mountain top at 8:50 in the morning, the earliest we have ever been. Of course, the rest of the day, working and walking downhill, were as easy as can be, so we managed to do a lot more than expected.


If it was not for the money, I would not mind more of this way of travelling in the future!  DSC_0031

Please do not disturb

On top of the world

If you leave your experiment behind in the Scandinavian mountains, you will have to deal with the wildlife up there.

Reindeer and Lapporten

We learned that lesson the hard way. It turns out that the high north houses a high density of reindeer, a fact we immediately noticed in our plots: labels destroyed, large footprints everywhere, flowers eaten, even some dung piles… The reindeer seemed to be attracted to our research!

Sassy rein

The first few days, we only saw their tracks, obvious as they were. It only took us some time to finally see one in real life.

Reindeer and Torneträsk

We thought they might have been hiding from us far away in the mountains, on the highest and less-visited peaks, but in the end our first sighting was right next to the chairlift, on the most touristical location in the whole northern mountain range.

Reindeer and chairlift

The next day, we saw some more disturbers, with impressive antlers and a fierce look.

Majestic reindeer bull

They were too majestic…

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