Catching the Arctic summer

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When summer treats you kindly in the Arctic, there is no better place to be. Summers are short up in the north, however, so you’ll need to be lucky to catch them.

The midnight sky in northern Sweden, end of July

We were very lucky this year, and were offered countless beautiful summer days up in the north. Some of the most memorable ones were offered when surveying our field sites on mount Nuolja, close to Abisko, which we got to experience in the best possible light.

The author, enjoying an evening on mount Nuolja after a long day of satisfactory fieldwork

Such an opportunity for summer weather needs to be taken with both hands, so we decided to spend the night on the mountain, greatly reducing the time effort needed to hike up and down.

Pyrola minor, one of the countless botanical beauties this summer brought

That decision resulted in two unforgettable fieldwork days, in which we managed to get so many plots done, while still enjoying one of the most crucial reasons why we were there in the first place: the Swedish mountains are just so beautiful!

The trail to the top of mount Nuolja, one of the stars of this summer’s fieldwork

When I am writing this, September is already in full swing again, bringing another great fieldwork season to an end. The outdoor life is mostly behind us, and lab and computer work is again on the horizon. But with fieldwork days like these in our memories, how can I lack the necessary energy to tackle that?

An alpine meadow (with a.o. Taraxacum officinale, Bistorta vivipare, Anthoxanthum odoratum and a leaf of Trollius europaeus) in the evening sun

SoilTemp: towards a global map and database of soil temperature and climate

Short: we are looking for soil temperature data from the Arctic and all over the world for inclusion in our global database. This post was published first on

Many questions in ecology revolve around climate: what climatic requirements do organisms have, how do they survive in extreme climatic conditions, and – increasingly relevant – how do they deal with the rapid changes in climate we are experiencing?

Despite climate thus being a crucial component of today’s ecological research, we are still very much limited in the climatic data we have to our disposal to actually answer these questions, especially at the global scale. Most of the data we do have comes from weather stations (or interpolations based on those): coarse-grained data measured at two meter above the ground.

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Climate and temperatures are and have always been a crucial factor in ecological research

For many organisms, however, these free-air climatic averages are far from relevant: many species operate at much smaller spatial or temporal scales, for example. Free-air temperature and climate patterns also differ significantly from what happens at the soil surface, or a few centimeters below it. For many organisms in the soil and close to the surface (soil micro-organisms, ground beetles, herbs, forbs, mosses or tree seedlings, for example) there is thus a large mismatch between the climatic data we have, and the climate they actually experience.

Soil temperature forest understory
For forest understory species, free-air temperature is meaningless, as temperatures at the forest floor will differ several degrees from what happens above the forest canopy

However, while the quality and resolution of free-air and surface temperature data at the global scale is rapidly improving thanks to elaborated networks of weather stations and satellite data, the availability of soil temperature datasets is still largely limited. That is the rationale behind our launch of SoilTemp, a global effort to develop a database of soil temperature data and build global maps of soil climate that answer to the pressing needs of modern ecologists.

For alpine species, temperatures close to the surface are what matters, especially in winter, when they can hide from the frost under a protective snow cover

Yet for such a global effort, we will need your help! If you feel one or more of the following statements apply to you, please e-mail jonas.lembrechts [at] for more information:

1) You have georeferenced soil temperature data (0 till 10 cm below the surface) for a period of at least 1 year with maximum a 4-hour interval, and would like it to be part of this open access global database/map.
2) You have associated species (plants or other taxa) composition or trait data from the same location.
3) You know other possible partners with interesting soil temperature datasets, or working on similar topics, who might be interested in collaborating.
4) You are interested to be involved in this project in any other way.
Small and cheap temperature loggers (like these iButtons) have recently made such a global-scale endeavour as ‘SoilTemp’ possible

Trail adventures

Interested to join our MIREN Trail Survey? Find all the details here. The story below gives you a feel of how it works, and originally occurred on The story itself plays in the Alps, but gathering more data like this from the Arctic would be of great interest to us, which is why we post it here as well.

The 20th of June, Davos, Swiss Alps. The day before the longest day of the year, and amazing weather is predicted. Also the day on which I decided to kill several birds with one stone.

I had to be in Davos for the Polar2018-conference, which brought together scientists studying the Arctic, Antarctic and high mountains. And this visit to Davos provided the perfect opportunity to collect data for our MIREN Trail Survey (all details on it here). With this global survey, we study some globally distributed plant species along mountain trails; and everybody can help. This summer, we are launching the project in full, with athe help of a great app – Survey123 – that makes joining very easy. By now, we already collected up to 3000 data points, and have engaged scientists in 13 different countries; and summer only just started!

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A hiking trail in the Swiss Alps with Alpine’s bird foot’s trifoil (Lotus alpinus)

So I added a nice Swiss trail to the growing list of sites. A local mountain trail ecologist suggested me the ideal one: hiking up in the Flüelapass from Tschuggen to the top of the Pischahorn. A nice hike with some ideal features for the survey: it started above treeline, which increased the chance that I would pass the upper limit of our study species’ distribution rather quickly. It also crossed 1000 meters in elevation, which promised a nice climate gradient, and it was rather touristic. The latter fact is interesting, as we are focussing on species that are following humans up in the mountains. This trail would allow us to check if they do that in Switzerland as well.

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Red clover – one of our study species – in grassy trailside vegetation in the Swiss alps

I decided to focus on all 4 of our study species: white clover (Trifolium repens), red clover (Trifolium pratense), common yarrow (Achillea millefolium) and narrowleaf plantain (Plantago lanceolata). A brave plan, as searching all of them would slow me down a bit, especially in their native range, where they can be common. The Survey123-app allows you to mark the first and last occurrence when a species occurs continuously, but even then you have to keep a close eye on the trailside to make sure the species is still there. If you are new to the project, or have limited time, I thus recommend focussing on one species only. In that case, it’s even easier, as you can save your answers as favourites in the app, and copy-paste them for each observation.

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White clover along my study trail

As predicted, the first meters of the survey went rather slow. The two clover species and common yarrow were very common in the grassy trailside vegetation, and I had to walk slowly to find them all. Especially common yarrow turns out rather hard to find this early in the summer, before the flowering period. Luckily, the plantain was nowhere to be found; one species less to keep an eye out for!

Soon, however, things started to change. The vegetation became more alpine, and the grassy patches slowly dissappeared at around 2000 meter. With them, our three species vanished. That was no reason to stop hiking, though. The higher elevations might hold some surprises, and the absence of occurrences is highly valuable as well. We are planning to use these detailed observations to model the distribution of the species along mountain trails with high accuracy, and knowing the ‘true absences’, i.e. where the plants do not occur, is in that regard very important. So I kept hiking up, and enjoyed the fact that it just went a lot faster!

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At high elevations, the alpine vegetation gets sparser, and our study species disappear

And indeed, the high elevations did hold a surprise: at around 2500 meter, so 500 meter higher than their last occurrence, the species suddenly reappeared! The reason: a ski lift and a restaurant. Such introductory points are crucial for the distribution of our species, so the app allows you to mark their location as well.

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The ski lift, a quick way to the top for seeds of our study species

After that, it was over. Vegetation cover decreased rapidly, and only rocks remained. No chance for our species. Yet again, hiking up provides us the ‘truly observed zeros’ that are so crucial, so I added another 400 meters to the top. A relaxed climb that felt like a holiday, as did the beautiful views on the leisurely way back.

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The trail at the top of the Pischahorn

So after less than 6 hours of hiking, I made it back to the car, having realised a hike of over 10 kilometers that delivered me tons of beautiful views, a bunch of unforgetable memories and 300 interesting datapoints. Who knows a better way to spend his time?

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Trailside vegetation with alpine daisy flower, and the ski lift in the background

Interested, and tempted to try as well? You should! We welcome data from any mountain anywhere in the world. Just one more hint: I noticed the gps of my phone needs some time to become accurate after it fell asleep. This is important to keep an eye on, as the power of our approach lies in the high accuracy of the observations. We need an accuracy of around 5 meters, as we will use the data as presence/absence in pieces of trail of 5 meter.

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The chapel of Tschuggen in the early morning: the start of my hike


You’ll never hike alone

This post first appeared on

It can be quiet lonely out in the mountains: the open vastness of the alpine tundra, the kilometers of rolling mountains in the distance without a soul in sight, or the silence that resonates through the rustling of leaves and the splattering of streams tumbling down a water slide.

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Reindeer with calf in Laktatjakka valley, northern Sweden

But that loneliness never lasts long, as one never hikes alone in the mountains. There is often an animal in sight, and this post aims to celebrate the companionship these animals offer to the lonely scientist or hiker out in the field.

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Marmoset overlooking the world from his den, Davos, Switzerland

From the tiniest songbirds hopping from shrub to rock to the herds of reindeer in search for a cool snowbed; from the characteristic squeaking of marmosets in the Swiss Alps to the angry cry of a skua in a Swedish valley. It is those unexpected visits that make mountain fieldwork that extra bit exciting, even – or specially so – for a plant ecologist like me.

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Skua taking a bath close to our campsite on mount Nuolja, northern Sweden

We had many of those encounters in this year’s fieldwork period. Especially in the northern Scandes, it seemed to be a good year for many animals. After a few years of silence, voles and lemmings were back in fairly large numbers. As a consequence, their hunters were also out in force: skuas, owls, foxes, ravens and buzzards, all of them were profiting in a way from the sudden abundance in food.

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Buzzard scanning the valley from above

For us, all these animals were a blessing: enjoying the sunset with the sound of golden plovers in the background, or surveying vegetation while some reindeer race by: it makes one forget more easily how long fieldwork days can be.

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Golden plover, Laktatjakka, northern Sweden

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FEASTing in Abisko

It promised to be a windy day with some scattered rain clouds, when we head out to mount Nuolja to join the FEAST-project.

FEAST stands for Functional Ecology of Alpine SysTems, a large-scale project to assess soil conditions in mountains worldwide. Such a noble joined effort I find hard to resist, so we signed up to add our study sites in the northern Scandes to the growing network. One day of fieldwork, collecting soil samples and associated species occurrences, would be sufficient to move global mountain ecology huge leaps forward.

Measuring soil conditions for the FEAST-project

Of course we needed a representative mountain, one that would prove valuable in the global analyses. Our eyes fell on mount Nuolja, the 1200 meter high mountain peak overlooking the village of Abisko and the Abisko National Park. For decades, this mountain has been intensively studied by scientists from countless different disciplines in the Abisko Research Station, and it is safe to say that virtually no mountain above the polar circle has better data on all aspects of its ecology. CIRC, the Climate Impact Research Center of the nearby Abisko Research Station, now even re-installed long-term vegetation survey plots that continue century-old scientific traditions.

Wooden poles of the century-old long-term vegetation survey are scattered along the whole elevation gradient of mount Nuolja

Nevertheless, despite all this amazing data, information on the soil functions was still largely lacking. The FEAST-project proved a great first step in the right direction to change just that.

The vast open stony tundra at the top of mount Nuolja

The FEAST field day turned out to be a great success. We got some strong winds, I tell you, on top of that unprotected mountain, but we avoided most of the predicted rain. We managed to collect data for the two FEAST-experiments, with the first one looking at typical alpine soils along an elevation gradient and the second one focusing on snowbeds. Snowbeds are areas were snow persists long into the growing season, even when it has molten away everywhere else.

Surveying plant species diversity in the FEAST-plots

The latter proved especially interesting on mount Nuolja, as the region just emerged from a year with extraordinary weather conditions. With little precipitation in winter and temperatures soaring in summer, even the most persistent snowbed on the mountain was far gone by the time we did the experiment. Extreme weather events that are getting far more common in the north nowadays as a result of the changing climate.

Astragalus alpinus seeds on top of the mountain

Now all soil samples are packed and send to the UK, where they will be analyzed and compared with those from tens of other mountains all over the world. And then, finally, we can set some long-awaited steps forward in understanding the mysteries of the belowground world in mountains. And that’s truly going to be a FEAST!

Working with a view: Abisko National Park and the Lapporten mountain range where always visible in the distance

Worth it

Just imagine: your commute to your office includes a one hour drive, followed by a six kilometer hike with a 600 meter elevation increase. Two hours of consecutive hiking, if you follow a decent pace. And then your office day still has to start. And after 8 hours you still have to head back.

Heavy? No doubt, but imagine now that this would be the view from your office:

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Then it does not matter anymore how long the hike, how high the climb, how hard the work, this view is worth it all.

This was exactly what we got on the last day of our second 10-day-fieldtrip to Northern Scandinavia this summer. We had had some disappointments along the way: closed road barriers, whole valleys shut down due to a broken truck on the only access road, hours of rain… All of these disappointments added up to us having to include a pretty hard day at the very end of our trip.

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Luckily, weather was (finally truly) on our side that day, offering us a morning with the brightest, nicest, sunniest Arctic summer weather one could imagine. If that doesn’t make your day, nothing will.

With morning unfolding around you, slowly hiking up towards and above the treeline, and seeiing the beauty of the northernmost Norwegian mountains unfold around you; it is those things that make you fall in love with the mountain ecology everyday.

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As soon as we reached the top, we spend the rest of our day monitoring plants up there, overlooking fjord Rombaken and the wild mountains surrounding it.

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Fieldwork with a view over fjord Rombaken in northern Norway

I have to apologise to you now: this story is not building up to any kind of punchline. Even worse, you might have read the best of it already; it just serves as an opportunity to share the beauty of our workspace with you. After this, the story will only go down again. As we did. Down the road to the valley in the evening, following the setting sun and admiring the changing colors.

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Evening in the mountains

It was definitely a day to remember, this last day of our 2017 field campaign in the north, thanks to the mountains and weather playing together to set up an incredible show. Probably just to make sure I’ll be back next summer.

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Fireweed (Epilobium angustifolium) overlooking fjord Rombaken


The roadside effect: visual proof

Garden angelica (Angelica archangelica) in a roadside in northern Norway, profiting from the wet conditions caused by the roadside ditch.

Mountain roadsides, the most fascinating places on earth. That is, if you believe a PhD-student who has been studying them for more than 5 years now.

Alpine species like the pincushion plant (Diapensia lapponica) and the alpine bearberry (Arctostaphylos alpinus) enjoy a roadside ‘rock garden’.

We returned safely from our fieldwork season in the northern Scandes, with suitcases full of data proving the fascinating role of mountain roads in plant species distributions. Whether they are non-native species advancing in cohorts from the valley, or alpine species exploring the rocky conditions, countless species seem to profit from this peculiar ecosystem.

Yellow mountain saxifrage (Saxifraga aizoides), a plant typical for rocky alpine environments, thriving in between the roadside gravel.

This pattern is strikingly visible with the naked eye already: next time in the mountains just look at the roadside and admire the differences with the natural vegetation next to it. But we aim for more than visual proof only, of course.

We have never been more ambitious in trying to get to the ‘why’ behind it: why is this plant exactly here, and not a few meters further away from the road? What is it that attracts alpine species in roadsides below the treeline? Why is it that fireweed is so extremely common in roadsides, and plays only a minor role in the natural vegetation

Fireweed (Epilobium angustifolium), the most common roadside forb in the Scandinavian subarctic.

Now we dive into the lab and the data, aiming to answer all questions that popped up. Most important one of all: what has happened in the 5 year period since our first survey in exactly the same plots?

A tip of the veil? A lot!

The pincushion plant (Diapensia lapponica) within one of our study plots, bordered by the yellow measurement tape.


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.


Live from the field

We are currently on a ten day fieldtrip to the beautiful Lapland, where we are monitoring the movement of plants along mountain roads.


A job with a view, plenty of beautiful alpine and arctic plants, and a ton of great and interesting data coming in. More pictures and stories will follow, but now the field calls!