Throwback to last summer fieldtrip in Belgian cities

Guest post by Charly Géron, our urban ecologist!

Last summer was -normally- the last field season of my PhD which tries to better understand how cities influence alien plant invasions. One would think that the last field season would be easy and a bit melancholic, but actually it was most stressful to organize. Due to the Covid-19 situation, the trips I had to do between the Belgian cities but also the help of the students were maybe not possible which questioned my fieldwork organization.

However, I really cannot complain as we found ways to make it work, so I was really lucky compared to some less fortunate colleagues. Even better, the team we formed with the students was very efficient and the mood was always very positive!

We then began our quest for alien plants in urban and rural Belgium, driving more than 1700 km.

I already hear what you are going to say, plants in cities are rare except in parks and gardens. Well, that is totally untrue! Actually, plants are everywhere, in every pavements cracks, walls, or road sides. As a plant lover this makes me very happy. The most fascinating point of this fieldwork is that alien plants grow in the most unexpected spots!

The elaborate look of these exotic species play with us. We tend to love those bright flowers and gigantic leaves, so we plant them and introduce them to new areas, from where they can escape and potentially impact native plants. That is one of the reasons why we need to better understand why and how they thrive in cities.

Another characteristic of urban areas is their perpetual evolution. A parking lot can become a chic housing estate within a year, when in the same time frame an old house becomes an abandoned brown site. With that in mind, some of the plants I studied simply disappeared… However, we had many good surprises, with tiny sprouts becoming lush and strong trees.

How amazing! Great for my experiment, not so much for the local environment. That is an important dilemma of being a biologist studying alien plant invasions, being amazed by a gigantic invader yet being concerned for the local ecosystem!

Buildings with high amount of alien plant species. They seem to enjoy these footwalls!

In the end, we got enough time to finish the field work and be back at the university with our hands full of samples!

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Our #NatureOrNot survey has been an unexpectedly big success! More than 1300 people informed us about what they consider nature and what not. The poster above, made by master student Naomi De Vries who’s in charge of the project, summarizes nicely (and beautifully) what all of this is about.

Wander through her ‘Instagram-feed’ and learn what her thesis is about. And then, stay tuned for the actual results, which we are frantically working upon!

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History in the making

What you see brightening up my garden on the picture above is what we hope will be the future of microclimate monitoring: a TMS-logger with connection to the internet! Yes, you read that correctly, TOMST is currently working on a new version of their beloved logger that allows real-time data transmission, opening up a world of possibilities towards remote monitoring, science communication, and climate network management.

What I have here, is the first prototype (serial number …00000 of this new device!), ready to test it out in the garden. For the first time, we’ll see if data transmission from the field to the database works out as planned, bringing that bright future another step closer.

The prototype in all its glory, with see-through casing!

So this prototype now joins the army of microclimate loggers already occupying my garden, all in full preparation of what’s coming to us in Flanders next year: the biggest community science project on climate change ever!

Some other members of the army of TMS-microclimate loggers between the daisies in my garden – these ones measuring the impact of depth of device placement on the surface temperature

Fingers crossed for smooth testing!

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Welcoming Stijn

Last week, we had a new PhD candidate starting in the lab! His name is Stijn, and he is here to pull our fabulous citizen science project ‘CurieuzeNeuzen in de Tuin’, in which we will measure summer heat and drought in 5000 gardens, parks and farms across Flanders.

Stijn in action last summer – installing our microweather stations in a grassland

He will be doing the big data crunching on this one: modelling drought and heat indices over the summer, making pretty maps of temperatures across the region, and disentangling what drives the small-scale variation in our temperature and soil moisture. Exciting stuff to say the least!

Mysterious mushroom circles in the gardens, that’s the trial project of ‘CurieuzeNeuzen in de Tuin’ Already looking forward to see these mushrooms popping up all over Flanders next spring!

You will definitely hear more from him, as not only is he tremenduously motivated to get things rolling, he also fell in love with science communication already. And let that be exactly the kind of thing we love to do around here!

To be continued…

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Chicken or egg?

Guest post by Jan Clavel

By now we know quite well that non-native plant invaders are fond of human disturbances. We have seen many times, across many different ecosystems, that these foreign plants use the more welcoming disturbed sites as their entry points towards new ecosystems. Roadsides and trails in particular make for great pathways for these non-native plants, which use them to spread out to new ranges that would have otherwise remained unattainable.

While this pattern clearly exist, we are still in the process of trying to understand exactly what it is about these disturbed sites that makes them so welcoming for non-native plants. Is it due to reduced competition? Abiotic changes to pH and nutrient availability? Or maybe increased seed availability thanks to transport by cars and blissfully unaware hikers? As is often the case in ecology the answer is most likely: “a bit of all of the above”.

Cars are known to transport seeds of non-native species along mountain roads, like here in northern Norway.

However, there is another factor that could prove to play a large role in facilitating non-native success and that has remained largely unstudied. That is, the relationship between plants and their fungal mutualists: mycorrhizas. This crucial symbiosis between plants and fungi, in which plants exchange sugars for precious nutrients, is a difficult one to study as it takes place wholly belowground and at microscopic level. However with ongoing improvements to our methods, it is becoming clear that these little fungi are instrumental in shaping the processes and composition of ecosystems all across the world. And as such, it is not unreasonable to think that they could shape how non-native plants benefit from human disturbance. 

To test for that hypothesis we went back to our trusty roads in the beautiful northern Scandes. The great thing about these roads is that not only do we already know that they favor non-native species thanks to our previous surveys (see chapter 2 here), there is also a clear distinction between the type of mycorrhizas that naturally associate with the local plants (called ericoid and ecto-mycorrhizas) and the type that non-native plants like to associate with (arbuscular mycorrhizas or AM). This clear distinction in mycorrhizal types is really helpful as we can simply track the changes in AM and have an idea of how impacted our non-native plants are going to be.

Part of the team digging for roots of non-native species along Norwegian mountain roads

After many a day of root collecting, soil sampling and mosquito swatting, we sent a few hundred of samples taken all over our mountains roads to our home base in Antwerp, where we went looking for mycorrhizas. We did so both visually, under the microscopes, to know the quantity of mycorrhizas there was in each root, as well as through DNA analysis, to know which ‘species’ of mycorrhizas were present . 

Figure 1: we found many more roots with arbuscular mycorrhizae in the roadsides than in the natural vegetation (left), as well as a much high diversity, with 23 OTUs (‘species’) unique for roadside roots.

By far the clearest result that came from all that work is that there is a very clear effect of the road disturbance on AM. There are way more of these arbuscular mycorrhizas in roadside roots than in the natural vegetation and they are also much more diverse! More AM in the roadsides means more non-native plants in the roadside, thus disturbance impacts mycorrhizas which in turn facilitate invasion success. Question answered, right? Well, if you have been around ecology for a while, you will know that things are never that easy. After all, the higher presence of AM could be a consequence of non-native plant success instead of a cause, or maybe these two things are wholly unrelated and they are both the consequence of some third factor, changes in pH for example. That’s what’s both fun and sometimes frustrating about ecology, it always keeps you guessing. But what we have found for sure is that this big difference in mycorrhizas is truly there. And that opens many exciting future research opportunities that are only asking to be seized! That chicken-and-egg problem of who’s driving what? That needs to wait till next summer, when we’ll get back to see how things have changed over time.

So we can be clear here, roadsides are full of mycorrhizae that can benefit our non-native plant species. Yet, there is something rather funny with this observation: while non-native plants have not yet reached the highest elevations of our mountain roads, that is not for a lack of adequate mycorrhizas. Indeed, contrary to our expectations we found AM to be present all over our elevation gradient, even well above the highest elevation reached by non-native plants. Moreover, the difference in mycorrhizas between roadside and natural vegetation was also constant all over that gradient. That tells us that adequate mycorrhizas are already available for non-native plants climbing up the roads, which is one less potential barrier to further invasion. So that is another chicken-and-egg problem for which we do have the answer already: while we don’t know who came first in the system, non-native plants or their mycorrhizae, the mycorrhizae where clearly first to reach the top. That non-native plants haven’t colonized highest elevations yet, is thus not from a lack of mycorrhizae. At least one potential explanation we can erase from the drawing board.

Fieldwork with a view, above a Norwegian fjord close to the city of Narvik

More information:

Clavel, J., Lembrechts, J., Alexander, J., Haider, S., Lenoir, J., Milbau, A., … & Verbruggen, E. The role of arbuscular mycorrhizal fungi in non‐native plant invasion along mountain roads. New Phytologist.

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A fresh look on nature

Introducing the world to a child gives conflicting feelings.

We started using the GR-routes – meandering throughout Europe – to discover the beauty of the world around us

On the one hand, there is a feeling of doom: how do I dare adding another child to this deteriorating world, without asking her if she wants to live in it – and without being able to promise her the safe and happy live I got myself, when our nature wasn’t on the brink of destruction yet. It is an argument recently more frequently used to restrain from procreating at all.

If the best nature around her is straight and artificial canals like this one – what is left to love?

Yet, perhaps a bit surprisingly, what I feel is mostly hope. Introducing the world to this fresh set of eyes, filled with wonder and curiosity, made me realize much more clearly that all is far from being lost. Even in our heavily populated corner of the world, between Brussels and Antwerp in the heart of Western Europe, there is natural beauty around us that fills my child with aw.

In a recent survey of more than 1200 Belgians and Netherlands, we asked if people experience a decline or increase in nature around them. 75% reported the former: they had the feeling that nature had deteriorated over their lifetime. This paints a gloomy picture at first sight, and the decline over time is undeniably there.

The open horizon with view of the church tower – a landscape that has been getting harder to come by in Flanders over the last decennia

Yet what that babies amazement made me realise more clearly is that we shouldn’t dwell too much in the past. Observing what has been lost is important to see the gravity of the situation we are in, but what matters is what we do with that knowledge, now and in the future. She did not observe a decline yet over her lifetime, and we can do our absolute best to keep it that way.

Impressed by an oak leaf

What I also realized this way, is that nature can be in the smallest things – an oak leaf, a bird or a meandering stream. It is not only about the forests or mountains, or the world heritage sites those lucky few on your Instagram feed get to visit. But that’s another thing we asked our 1200 survey respondents: what IS nature to you? Results are mixed: those agricultural landscapes that made me and my baby so thoroughly happy this weekend, would you call those nature? For us, at that moment, it most definitely qualified.

A Flemish agricultural landscape. Nature? Or not? The definition is far from clear on the matter, but dear lord that place was beautiful!

This baby has given me lots already, but one important present is a fresh look on nature around me. I am ready to fight harder than ever before to save this precious resource for her and everybody.

Want to help? You can start by giving us your opinion on your definition of nature (if from Belgium or the Netherlands), via!

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