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

Short: we are looking for soil temperature data from all over the world for inclusion in our global database.

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.

SoilTemp - soil temperature and climate

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

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Topography (2)

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.

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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.


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.


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).


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.


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


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.


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

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Mapping the trail survey

This summer has been highly successful for our MIREN trail survey. We can proudly present this map showing all the (approximated) locations where people have observed one of our focal plant species (red and white clover, common yarrow and narrowleaf plantain) along mountain trails.


Hiking trail in Abisko, northern Sweden

This map is a work in progress, of course, and we will be updating it while data keeps flowing in. We are currently still expecting observations from at least 200 more kilometers of trail!

With spring creeping up in the southern hemisphere, we will now switch our focus down under. This is thus a call for anybody who will be visiting mountains on the southern hemisphere to join the project and get your own star on our map! South American, African or Australian mountain enthusiasts, if you are lucky enough to be going out in the amazing nature, please think of us while you are there, and record the location of our study species if you happen to see them.


Even when you are lucky enough to see a guanaco on your hike through the Andes, don’t forget to look at your feet to check for our non-native plant species!

The southern hemisphere is of particular interest to us for this study, as all of our study species are either non-native there, or not (yet) present. This will help us comparing how their spread along mountain trails happens in both their native and introduced range, and which regions are currently invader-free.

All information on how to join can be found here.

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The Bayou

A little throwback post to the great time I had attending the annual meeting of the Ecological Society of America in New Orleans, beginning of August.


Alligator floating through the Old Pearl River in the Mississippi delta

You can read all about the theme of the conference, and how that made me feel very much at home, in this blogpost.


Old bridge over the Old Pearl river

Now, I just want to treat you to some pictures from the marshes, swamps and ‘bayous’ of the Mississippi delta, one of the natural wonders Louisiana and New Orleans are famous for.


The green wonders of the Louisiana bayou

As I learned on our little boat trip during our half a day break from the conference, a bayou is a slow-flowing river in the flatlands. What I also learned, is that it often hosts a variety of fantastic animals.



Curious raccoons

A more important thing we learned, unfortunately, is that Louisiana is experiencing rapid wetland loss in its coastal area, as a result of large-scale attempts in the last decades to get water levels under control.


The bayous and marshes on the Mexican Gulf play a crucial role as coastal protection.

One of the devastating results of this rapid wetland loss is a much higher vulnerability for storms and hurricanes, which brings us back to the main theme of the conference: with weather events observed and predicted to become more extreme, and humans increasingly disturbing the landscape, the negative impacts of global change are bound to accelerate in the near future.



You feel that when you are floating on the slow waters of the bayou, I can assure you. And you just hope these natural wonders are here to stay for a very long time.


A heron hunting for fish


Alligator munching on marshmallow snack

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Catching the Arctic summer

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

As usual: more soon!

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Adding stones to the mountain

I felt humbled and proud at the same time when I realized my paper citation count on Google Scholar reached 100 this week. I know, modern science is focussing way too much on the numbers, but what this particular number mostly means to me, is that my voice is starting to be heard. The science we do, the answers we find, they are being used as little building blocks for the giant and ever-growing mountain that is our collective scientific knowledge.


Adding your stone to the top of the pile

Adding your little stone on top of that pile is the most exciting feeling I had as a PhD-student. But now, I feel that my stones start supporting new stones, as the pile keeps growing, and that is even more satisfactory. So I know that this ‘100’ does not mean anything on its own, yet the knowledge that I can contribute, that I can help push science forward, does. A lot.



Making your voice heard in science takes time, but is oh so rewarding

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