Frontiers in soil ecology

Story accompanying the new paper Eisenhauer et al. (2022) Frontiers in soil ecology—Insights from the World Biodiversity Forum 2022.

There was an almost tangible sense of urgency at the World Biodiversity Forum in Davos, last June. A string of the world’s experts on biodiversity research gathered there under a pleasant mountain sun to discuss the state of and – perhaps even more important – the way forward for our biodiversity in a world under pressure from all sides. A story significantly grimmer than the sunny landscape!

I joined the session on soil biodiversity, that subset of biodiversity hiding underneath our feet and therefore even more obscure than the plants and animals we see aboveground. The consensus of that session was cloudy, yet with clear rays of that sun still shining through: our understanding of soil biodiversity, its drivers, and functioning is rapidly increasing, although there is still a long, long way to go.

To make that long road ahead more concrete for scientists and policymakers alike, we decided to take a step back, have a good thorough discussion and write down the main issues in front of us. The result of that effort is now published in the Journal of Sustainable Agriculture and Environment, summarizing the eight most urgent frontiers in global soil biodiversity to urge the international scientific community to help tackle them.

So what are these big tasks to tackle urgently? They range from 1) data integration, building on the recent splurge of global databases and products to create better integration of soil biodiversity monitoring across the globe, over 2) the mechanistic understanding of soil biodiversity (causal inference) to 3) the creation of more accurate scenarios of soil biodiversity in an uncertain future and 4) the increased understanding of other aspects of biodiversity (traits, genetic diversity, hidden diversity)…

They include 5) the need for better global data on drivers of soil biodiversity (from microclimate to heavy metals in the soil) and 6) the call for increased global collaboration and exchange of knowledge, e.g. surrounding the precious and rare taxonomic knowledge of many obscure soil species groups.

Finally, they highlighted 7) the need for the application of our increasing knowledge in conservation and 8) improved communication of our knowledge – and needs – to public and policy to get to that final and most critical step: actually protecting that soil biodiversity before it is lost.

These eight frontiers will need to be overcome in the near future to ensure the conservation of soils for the next generations. Critical, as with the words of Franklin D. Roosevelt (1937):‘The nation that destroys its soil, destroys itself’.

Soils have unfortunately long been neglected and only now our understanding of – and enthusiasm for – them is making a comeback. Indeed, the significance of soils has now moved more and more into the scientific focus, finally changing from a niche topic with many specialized journals and conferences to a mainstream topic in ecology, earth‐system sciences, and nature conservation over the last two decades.

Let’s keep it there, where it belongs!

The Swiss mountains, home to a fabulous diversity of landscapes and soils
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Are non-native plants adapting to city life?

With chapter 4 now published, the now finished PhD of Charly Géron has created quite the storyline on how non-native plants are invading our urban environments!

In his first paper, we found out that alien plant species in European cities originated from warmer and drier native ranges, as they are often much better at ease in the warm and often drier climates in our cities than many native plants. The urban heat island in action!

Pauwlonia tomentosa, one of our studied tree species, at ease on a rooftop

In the second ‘Géron et al.’, we dove deeper into the performance of alien plants in the city, with the help of 6 species from the Asteraceae family, one of the families of plant species with the most global invaders. A hitherto unresolved question was how stressful the urban environments become during climate extremes such as heatwaves and droughts. Do such episodes still favor alien plant species, or set them back? The results were a tad surprising: all studied species, regardless of their climate of origin and thus their love for heat or cold, showed fewer signs of stress during a heatwave when shaded (by nature or concrete alike).

Interestingly, this positive effect of shading was found again when focussing on woody invaders, again both for species from warmer ánd from cooler origins. Interestingly, however, we did see a clear contrast in WHERE along the urban-rural gradient species were growing: those from warmer origins preferred the city, those from cooler origins the countryside. Yet despite this clear segregation, all of them were remarkably less stressed when trees or buildings provided them with shade during one of Western Europe’s recent hot and dry summers!

So now, there is Géron et al. number 4, and it takes us even deeper into the story. We wondered if the strong variation in environmental conditions along the urban-rural gradient (hot/dry vs. cool/moist) would result in natural selection within a species: would populations from urban environments perform better in warm and dry conditions than their nephews from the same species yet coming from cool environments? Pineapple* weed (Matricaria discoidea), a tiny Asteraceae plant, came to the rescue.

Pineapple weed in its favorite environment: cracks! (c) Charly Géron

We harvested seeds from several populations from urban and rural environments across Belgium, and put them in growth chambers with either urban or rural climate and/or soils. With a smart experimental design (‘a simulated reciprocal common garden experiment’, in scientific terms), we could disentangle performance differences between the different populations and, very important, if these were due to plasticity, natural selection, or an influence of the mother plant.

Racks of tiny test tubes with seeds of pineapple weed – ready to be subjected to urban climate conditions in the growth chamber. Working with small plants is definitely convenient from the space-perspective! (c) Charly Géron

So, what did we find here? First of all: things are pretty complicated in the realm of population genetics, as tons of things interact with each other. Secondly: most of the observed variation in the growth chamber was related to the conditions of the mother plant (working through e.g. seed size), while our little pineappleweeds from the same populations also showed substantial plasticity when subjected to different environments. The ‘holy grail’ we were looking for – local adaptation, populations changing genetically as a result of the urban environment – could however not be found.

And thus: are non-native species adapting to a city life? No clear genetic adaptation could be observed in our case, at least nothing that resulted in a different performance. But that’s just our little stone on the pile of science – others might find other things in other environments, as so often in ecology.

The 4 papers in a row:

Géron et al. 2021a. Biological invasions

Géron et al. 2021b. Ecology and Evolution

Géron et al. 2022a. Urban forestry & urban greening

Géron et al. 20202b. Plant ecology

*Pineapple weed does smell quite nicely like pineapple!

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Scicomm award

We won!

The CurieuzeNeuzen team is one of the winners of the Annual Science Communication Prize of the Royal Flemish Academy of Belgium! The prize is awarded to researchers who are committed to creative and accessible science communication.

CurieuzeNeuzen in de Tuin was praised by the jury for the ‘clever communication campaign and innovative Internet-of-Things technology’, with which we reach a large audience, and thus ‘widely raise awareness about an important climate theme: heat and drought’.

This would of course not have been possible without our partners and enthusiastic participants: so this price is definitely for all of you!

Nice extra: we are still in the running to take home the EOS audience award: you can vote via

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The end

The end has arrived: this weekend, the 3000 participants of our large-scale citizen science project sent back their ‘garden dagger’ to us, closing the lid on the data collection for the most ambitious thing I have ever undertaken.

Starting of with 50.000 enthusiastic citizens, selecting a representative set of 4400 of them, augmented with a few hundreds of agricultural fields and nature reserves, we set off on a wild measuring rollercoaster in the spring of 2021. After an extremely wet year that made us wade through an unprecedented wealth of data on how garden soils buffer extreme precipitation events, 3000 of our original citizens were found willing to join us again in 2022 for part 2. A little bit less rain, we hoped this time around, for the sake of science…

We were not disappointed, although our gardens and groundwater reserves definitely were.

We could track average soil moisture in Flemish gardens throughout the dry season of 2022, and compare it with the extremely wet summer of 2021.

Yet, even such an exciting project like this one has an end. We have (more than!) enough data to now dive deep into the science. Unexpectedly interesting data as well, with two extremely contrasting summer seasons, and some interesting cold spells in spring.

What’s funny: normally, I would tell you to now ‘stay tuned for the results’! Yet what makes this project especially exciting is that results rolled in every day, and we had plenty of opportunities to keep the participants – and the general public – on what was happening across Flanders’ gardens. Just scroll through the list of articles on De Standaard newspaper website to see (in Dutch) the many interesting insights we got to communicate so far!

August 2022, Flemish lawns have turned brown after one of the most intensely dry summers since measurements started. A sharp contrast with the wettest summer ever the year before!

Much more to come, of course, so I’ll say it anyway: stay tuned for more cool results!

So, what’s next? My main wish is that this creates a spark, a movement. We want scientists and society to join forces and start monitoring the environment together, as we did here and as is done in other large-scale community science projects (iNaturalist or eBird, to name two). We want more microclimate networks like this, to get a better view of the very local variation in weather conditions there where it matters for plants.

The good news is: that spark is clearly there. We have MANY talks ongoing with people who want to build on what we have here. So again: stay tuned for more!!!

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To the roots

Can one go on a three-day sabbatical? Cause I just gave myself a three-day sabbatical.

Autumn along the mountain trails in the northern Scandes, the perfect atmosphere for creative thinking

I travelled to the northern Scandes on a short trip back to the roots of my research, where it all began in 2012 and where still so much of my favourite science is happening.

I went there to think about how to shape future research plans. I went there to let the plants and the mountains talk to me, let them show me what important questions need to be answered. I went there to puzzle all pieces together of what we learned over 10 years of research up north, on the fingerprints of climate and land use change on our precious tundra vegetation.

Salix herbacea on a rocky cliff. While nature looks stable and unmovable as rocks in the area, change is there for those who see its subtle fingerprints. How long has this little willow been here? And how long can it stay?

I went there for long conversations with Keith, my closest local collaborator, while walking through the autumn landscape, surveying plots and observing changes.

The main goal of all this is trying to wrap my head around 120 years of vegetation change in the region. We have a unique situation up there, with a series of old vegetation, soil and landscape surveys ranging all the way back to 1903, plus an increasingly clear understanding of the dynamics in climate change (the local weather station has measured continuously since the 1910s) and land use change (dynamics in Saami people reindeer herding, railroad building for mining and the ups and downs of tourism over the century.

Such ideas and revelations don’t come to you that easily over yet another Zoom-meeting. Just like Alexander Von Humboldt so many years before us, you have to observe the system while you’re in it to dig the deepest. The more you get to know an ecosystem, the more questions pop up. And so I realized, when standing on a cliff where Thore Fries must have been standing all the way back in 1917: thanks to these historic datasets, we know there was no forest there, as its upper boundary was a mindboggling 200 (elevational!) m or so lower on the hill. Thanks to him, we know what plants were growing there a century ago, and when and how they were flowering.

There was no forest so high up the slope, when Thore Fries was standing there and doing his pioneering vegetation survey in 1917. There was no forest there in the 1950s either? Was it climate change that allowed this rapid upward expansion, or are there other factors at work?

The question will be: can we get to the root cause of what is driving these changes? Can we disentangle the complex interactions that are at play over time in such an ecosystem, making it into what it is now? And can that help us looking forward, to a future in which the Arctic is experiencing ever more unexpected extreme events?

Another caterpillar outbreak has been devastating to the birch trees this year, but even the crowberry (Empetrum nigrum) has now turned brown. Is there a sudden change to the system imminent?

That is something I want to find out over the coming years, as I believe that area, with its unprecedented old datasets, can be a blueprint of what is happening in all these places where we humans perhaps looked less carefully.

Campanula rotundifolia, one of the few plants flowering this late in the season. How are the flowers in the region reacting to increasingly unpredictable year-to-year changes in the weather?
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Global microclimate conference

When we started SoilTemp, we had one main goal: making microclimate research into a global science. Achieving that would mean two things: bringing all the data together in a global database was an obvious first, but we had something perhaps more important up our sleeves: bringing the global microclimate community itself together. The latter was the main ambition of the first international Microclimate Ecology & Biogeography conference we organized last week and for this reason alone, it would in any case be one of the main highlights of my scientific career.

Kicking off the conference in the pink heathlands of Flanders’ National Park

Covid tried to derail our plans (see also this breakdown of how the conference came to be), but in the end, the conference exceeded all expectations and my darkest fears*: 128 participants from 28 countries, for starters, to make crystal clear that the microclimate community is alive ánd everywhere. Talks had topics ranging from shrub expansion in the high Arctic tundra to coffee plantation microclimate in tropical Africa, from global high-resolution microclimate maps (keep an eye out for the exciting ‘DirtClim’-work by David Klinges, for example) to the implications for tiny bryophytes. the conference had it all.

Discussing scientific advances at the poster session

I might be a bit biased, of course, but I think this first ME&B-conference was the best conference I ever attended. An incredible density of high-quality talks, a poster session with even more good stuff, and a never-ending chatter during coffee breaks, for example. Or the pre-conference excursion on the first day, taking an interested audience past some of Flanders’ best ecological infrastructure (and the purple heathland of our National Park).

Visiting the ecotron of the University of Hasselt on the pre-conference excursion. A giant building filled with giant blocks of living heathland, probed by sensors on all sides. Big infrastructure ecology, quite impressive and very different from the mini sensors I am used to

So what to take home from this high-energy week? The ecological community – and adjacent fields – has clearly embraced the notion that we need climate data there where it matters for organisms. The amount of solutions – ranging from low-cost sensors over mechanistic models to LiDAR-based environmental mapping – is now also booming. A lot of work remains ahead, of course, as the realisation that each research question, each organism, and each study system might need its tailored microclimate data is making us scramble for ever more creative solutions.

Full house at the keynote lectures

Time is also not on our side, unfortunately. While we are measuring microclimate, that very microclimate is rapidly changing as macroclimate warms and land use restructures (or often removes) vegetation. It might thus serve us scientists well to remain a bit in a hurry. Yet the conference strengthened my hope in that regard, as what I saw here was a community eager to learn from each other, eager to collaborate and eager to work together on correct data-driven answers to the precarious situation our planet is in.

I came into microclimate science with a simple dream: knowing the climate as experienced by my study plants. I soon realized many across the world were having the same dream, and were working on creative solutions to solve that issue. The end result of all that is the SoilTemp network and the SoilTemp database, and the most visible product of it all was this beautiful conference. More to come!

Ending with a big big thank you to the co-conspirators: Pieter and Koenraad, thanks for sharing this dream and working so hard together to make this conference a reality!

* I truly got to think a week before the conference that all my emails would have gone to spam-folders and nobody would show up at the conference itself. Ridiculous, in hindsight…

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