PhD Position on Forest Microclimate and Biodiversity Under Anthropogenic Climate Change

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Originally posted on Jonathan Lenoir:
The research unit “Ecologie et Dynamique des Systèmes Anthropisés” (EDYSAN) is launching an open call for a PhD position in Ecology & Biostatistics. We are looking for a PhD candidate interested in climate change biology,…

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Communication is key

If you want to do science with impact, communication is key. Thanks to the Flemish PhD Cup, a ‘scicomm’ competition for recent PhD graduates, I got the once-in-a-lifetime opportunity to learn this from professionals.


When you see this tower on a crisp sunny morning, you know that magic is going to happen. It is the old broadcasting tower of the VRT, the Flemish public-service broadcaster, and it towers over the city of Brussels. And the VRT, that is where we were heading for the second weekend of intensive media training.


The banner of the Flemish PhD cup in the hallway of the VRT

There, you can learn communication skills from those who know how it works: telling stories that grab people by the troath, facing the news camera without freezing into a cramp, or talking with a voice that breaths authority. They know the tricks, and showered us in them.


A session on story telling from Tim Verheyden, chief storyteller of the Flemish broadcaster

Even better, we learned how to think like a journalist, to facilitate the transition of our message from our heads to the little screen or the pages of the newspaper. We were trained in fascing sceptical interviewers and how to use tricky questions to strengthen our message.


Learning how to face the cameras, in a real studio

And most of all, we were given opportunities: to write an article (here, in Dutch) about our work, for example, and give a 3-minute pitch about the core pointof our research.

Those presentations were judged yesterday, and 8 of the most convincing ones were given the opportunity to continue the competition and broaden their impact. I was not one of those lucky ones – dear lord were there many amazing presentations, yet for me the main reward was already won.


The 8 finalists of the Flemish PhD cup, each of them presenting their science with a bang

That main reward was in the whole learning process, and that was something all 16 participants earned the benefits from: they provided us all with the tools, the knowledge and the experience to step up our communication game in the future. And, oh boy, do I look forward to that!

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Nothing says pink like the Flemish heathlands at the end of summer. I was lucky enough to spend one of the last hot summer days on the vast pink plains of the ‘Kalmthoutse Heide’, where we have our sites for the global Dark Diversity Network.


Fieldwork was of the type that I love the most: randomly selecting a plot, roaming throug it, and writing down the plant species that grow there.


We have a good idea now of the species that occupy this harsh environment; and there is not that many. The heather species, of course, the stars of the show, and a handful of grass species. Birches and pines, the occassional fern and blackberry. Only the toughest ones of the bunch, that can deal with the poor soil conditions in the sandy soils of the Campina region.


For now, this fieldwork chapter is closed again. We boxed our sandy soil samples and send them on their way to Estonia and Spain for analysis. Now it’s just typing out species list and submit them to the growing global network to explore what’s up with this Dark Diversity.


Good thing is: we’ll have to go back to the field soon, hopefully on a crispy cold winter day, to replace our temperature loggers. That’s our luck, as it is those occasional days in the field that do keep an ecologist sane.



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Elevation and climate as drivers of non-native species distributions

For MIREN, we are working on an awesome blog series summarizing our scientific findings from the last 15 years for conservation, policy makers and the global public. This is chapter 3 in the series, follow the whole story on

If there is one certainty about non-native plant invasions in mountain regions, it is the following: there are less non-natives at high elevations than in the lowlands 1,2. This pattern is indeed recurring in all mountain regions studied within the network, albeit with some regional variation (most notably another decline at low elevations in tropical regions where the lowlands are too hot for many species3-5.


Presence of non-native species at high elevations is much lower than what is seen in the lowlands. Here: Taraxacum officinale in southern Chile, defying all odds.

Yet what is behind this general observation? The answers can be found in the introductory history of these mountain colonizers. Most of these non-native species are first introduced in the lowlands, and they are pre-adapted to the relatively mild climatic conditions found there 3. From there, they start colonizing areas at higher elevations, often following human constructions like roads and trails 6. This expansion of non-native species from anthropogenic sources at low elevations towards the alpine zone, and the progressive dropping out of species on the way to the top, follows a process that we call ‘directional ecological filtering’ 7: one starts with a large non-native species pool at the bottom, and then sees a progressive drop-out of species on the way up.

As a consequence of this directional filter, the non-native plants reaching high elevations around the world are not the highly specialized stress and cold tolerators one might have expected there. On the other hand, these are mostly species with broad climatic tolerances capable of growing across a wide elevational range 7, with the high-elevation non-native species pool as a whole being a subset of the adjacent lowland pool 8. These ‘winners’ found at high elevation often are perennials (and not annuals), are from temperature origin (and not Mediterranean or tropical) 5,9, and have fewer flowers yet larger seeds 10.


Harsh climatic conditions at high elevations (here early November snow and short days in the Norwegian mountains) are commonly seen as the main limitation for non-native lowland species to invade the alpine zone.

Mountains thus act as a filter on non-native species 3,7. But how exactly does that ‘mountain filter’ work? The most obvious filter is the reduction in temperature and the increase in abiotic stress 11, which is a major limitation for many of these lowland species. This increased abiotic stress is however accompanied by other filters: a decline in the amount of seeds (through a reduction in human presence) 2,11,12 and a simple delay due to the longer physical distance from the introductory point  2,3. On the other hand, one might also observe a higher resistance against invasion by new-comers in mountains 11, while the power of the nonnative species to invade is reduced at this far edge of their distribution 2.

So which one of these drivers is the most important? Our experimental research showed that many non-native plants can establish, grow, and flower well above their current elevational limits in high-latitude mountains 13, defying the theory of the temperature filter. These results imply that cold-climate ecosystems are likely to see rapid increases in plant invasions in the near future as a result of increasing human-mediated disturbances and climate warming.


In studies on a selection of daisy species (family Asteraceae, here Solidago canadensis), all but one reached the same or even a higher altitude in the new range, so neither climatic adaptation nor propagule limitation seemed to be playing a crucial role 14,15.

Non-native species are indeed still moving upwards over time, albeit relatively slowly 2. The elevational ranges of species for example tended to increase with time since introduction on Tenerife, and the species reaching the highest altitudes were mostly old introductions 3. This movement is likely accelerated by climate warming 2,16. Nevertheless, we found little change in the elevation ranges limits of species over time in Switzerland, suggesting that at least in the Alps most species are not rapidly expanding at their high elevation range limits 17. For most species, populations were however more dynamic (with more colonizations and extinctions) at the upper range limit where their occurrence rapidly declined 17.


Common yarrow (Achillea millefolium) has been shown experimentally to be able to survive, grow and flower far above its current range limit in cold-climate mountains.

In short: invasion by lowland species at high elevations is slow yet ongoing, and most non-natives have not reached their upper limit yet. We should thus be prepared to see the problem become a lot more critical over the coming years and decades. Nevertheless, even though most of the current non-native mountain species have a lowland origin, invasion by cold-adapted non-native species actually provides a higher threat 16, as climatic matching increases invasion chance 9. Special care should thus be taken to limit introduction of cold-adapted alpine species from one mountain region to another.


  1. Otto, R. et al. (2014). Road edge effect and elevation patterns of native and alien plants on an oceanic island (Tenerife, Canary Islands). Folia Geobotanica 49, 65-82.
  2. Becker, T. et al. (2005). Altitudinal distribution of alien plant species in the Swiss Alps. Perspectives in Plant Ecology Evolution and Systematics 7, 173-183.
  3. Haider, S. et al. (2010). The role of bioclimatic origin, residence time and habitat context in shaping non-native plant distributions along an altitudinal gradient. Biological Invasions 12, 4003-4018.
  4. Arévalo, J. R. et al. (2005). Distribution of alien vs. native plant species in roadside communities along an altitudinal gradient in Tenerife and Gran Canaria (Canary Islands). Perspectives in Plant Ecology Evolution and Systematics 7, 185-202.
  5. Sandoya, V. et al. (2017). Natives and non‐natives plants show different responses to elevation and disturbance on the tropical high Andes of Ecuador. Ecology and evolution 7, 7909-7919.
  6. Lembrechts, J. J. et al. (2017). Mountain roads shift native and non-native plant species’ ranges. Ecography 40 353-364.
  7. Alexander, J. M. et al. (2011). Assembly of nonnative floras along elevational gradients explained by directional ecological filtering. Proceedings of the National Academy of Sciences of the United States of America 108, 656-661.
  8. McDougall, K. L. et al. (2011). Alien flora of mountains: global comparisons for the development of local preventive measures against plant invasions. Diversity and Distributions 17, 103-111.
  9. Arteaga, M. A. et al. (2009). How do alien plants distribute along roads on oceanic islands? A case study in Tenerife, Canary Islands. Biological Invasions 11, 1071-1086.
  10. Alexander, J. M. et al. (2009). Establishment of parallel altitudinal clines in traits of native and introduced forbs. Ecology 90, 612-622.
  11. Alexander, J. M. et al. (2016). Plant invasions into mountains and alpine ecosystems: current status and future challenges. Alpine Botany 126, 89-103.
  12. Jakobs, G. et al. (2010). Introduced weed richness across altitudinal gradients in Hawai’i: humps, humans and water-energy dynamics. Biological Invasions 12, 4019-4031.
  13. Lembrechts, J. J. et al. (2016). Disturbance is the key to plant invasions in cold environments. Proceedings of the National Academy of Sciences of the United States of America 113, 14061-14066.
  14. Alexander, J. M. et al. (2009). Plant invasions along mountain roads: the altitudinal amplitude of alien Asteraceae forbs in their native and introduced ranges. Ecography 32, 334-344.
  15. Poll, M. et al. (2009). Seedling establishment of Asteraceae forbs along altitudinal gradients: a comparison of transplant experiments in the native and introduced ranges. Diversity and Distributions 15, 254-265.
  16. Pauchard, A. et al. (2009). Ain’t no mountain high enough: plant invasions reaching new elevations. Frontiers in Ecology and the Environment 7, 479-486.
  17. Seipel, T. et al. (2016). Range limits and population dynamics of non-native plants spreading along elevation gradients. Perspectives in plant ecology, evolution and systematics 20, 46-55.

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The 3D Lab

Proudly introducing: The 3D Lab!


The 3D Lab is a virtual lab. It is not a research group in the strict sense of the word, as it is not a physical lab. Instead, it is the team of scientists, PhD- and masterstudents working with me, Jonas Lembrechts, in chasing the same goals: studying species distributions and their dynamics in a rapidly changing world.

So why create a virtual lab? The answer is simple: to bond, to unite behind a common cause, even when not physically together. I currently co-supervise 3 PhD-students: Ronja, based at NTNU in Norway, Charly, who is housed at Gembloux in Wallonia, and Jan, who works at the University of Antwerp with me. On top of that, there is a varying set of master students involved in projects with us.

Some of us rarely meet each other in real life, yet all of us are tackling similar questions and we are united behind that commong cause to understand what is happening to our biodiversity, before it is to late.

Hence, the virtual lab. We communicate our science together (see for example this first guest post from Charly), we have meetings together and we learn from eachother.


Master student Robin and PhD-student Ronja studying plants together in northern Sweden

For the name and logo, we have to thank Ronja, but I find it very fitting: our work focusses on the dynamics in distributions in 3 dimensions: longitude, latitude, and time. And while we might all be working in different systems – from cities over heathlands to mountains – we all want to discover the dynamics in these distributions. And we are all using the power of statistical analysis to tackle these questions, hence the Gaussian distribution replacing the D.

So, be welcomed on, and follow us on our joint quest to discover dynamics in species distributions, while we try to understand the mysteries of our biodiversity before it is too late to save it!

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About wrapping up 2 field seasons

This is a guest post by Charly Geron, PhD-student at Gembloux Agro-Bio Tech and in our Virtual Lab.

One month ago, I was left with mixed feelings about finishing up my second field season, and acquiring massive amount of data on a part of my PhD. It was so nice to actually have finished everything on time in the field, but also a bit sad to not going back to the places I visited 2 years in a row!

But please, let me recap what happened since april 2018!

At that time, with my supervisors, we decided to study how urban environments are impacting alien plant development. We then focused on studying the development of the most widespread alien Asteraceae species along Belgian urban-rural gradients. Indeed, this is one the plant family with an impressive high number of aggressive invasive species.

It was with great excitement, that I dived in the practical organization and looked for ways to select and find plants in areas of interests. In fact, for the success of my experiment, I needed plants in every possible anthropogenic habitat in my study zone, an area as big as half of Belgium. No need to say that I was a tiny bit anxious to drive around thousands of kilometers looking for my plants with no clue of where they could be.

That’s when we had the idea (not knowing if it would work) to use the data of a naturalist citizen science platform named or (depending if you prefer the Flemish or Wallonian version) as a source of observations. Now owning thousands of records (GPS points that can be as precise as a few meters) of my chosen species, I selected focal areas to look for my plants.

Picture 1.jpg

Map of the selected areas to look for my plants in Belgium. Each red dot corresponds to an area where the alien plant species had to be spotted. Just to give you an idea, more than 250 plant individuals were studied during each of the 2018 and 2019 field seasons.

The first field days began in July 2018 under a scorching sun, excited to find out if the plan could be successful (luckily, I got help of so many kind people during these long field days in urban labyrinths). And so it seemed: the method was great. I often found the plant exactly at the coordinates uploaded by kind strangers to the internet some time ago. Indeed, happily enough, from times to times, I was discovering tiny, almost undetectable plants in an urban jungle.

Picture 2

Found it! This tiny Solidago gigantea was found back at the exact spot where a kind stranger did register it some time ago. Amazing!

We had glorious surprises (for my experiment, less so for local biodiversity) such as finding huge colonies of flowering non-native species glistening in nice understory vegetation.

Picture 3

Telekia speciosa in full bloom spreading around in a forested park close to Bruges, picture courtesy of Jonas Lembrechts.

After only 11 field days, recording stress levels of the plants (leaves’ pigments, development variables, etc.), the 2018 field season of this part of my PhD was already finished! Hooray! Even better for me, the weather was nice enough to offer record breaking bright and warm days, perfect to study the impact of urban environments under global warming!

Picture 4

Measuring leaves’ pigments such as chlorophyll to detect whether or not this Artemisia verlotiorum is feeling good.

This summer, more precisely in late June, I did re-survey the locations of my 2018 field season. Indeed, to better understand the conditions experienced by alien plants in urban environments, it is nicer to include inter-annual variation. I got lucky enough to get two contrasting weather periods between summer 2018 and summer 2019.

Picture 5

Almost 39°C in the full sun back in July 2019 in Brussels. Summer 2019 was less warm, but more variable, with intense heatwaves. I’m sure you experienced the uncomfortable heat escaping from urban structures such as pavements in hot days.

I was happily surprised to be reunited with most of my plants from last year. Of course, some places changed drastically. That’s when I really understood how fast anthropogenic environments are evolving! Urban brownfields where I could see thousands of my ruderal alien plants last year now turned in to fancy brand new housing. Despite some bad luck spots, I was also able to wrap up my second field season, studying about 270 plants and this time in only 7 days!

Picture 6

A rather strange place to keep your stroller, but a perfect place to spot ruderal alien plant species.

Following a recent blogpost here, I am so grateful to all the people that are doing citizen science initiatives! They are helping science more than they expect! They saved me so many working days, especially the difficult but exciting task of finding species where they develop.

More will follow later about the findings following these two years of data acquiring. So please stay tuned to learn how urban versus rural environments are limiting or helping alien plant species. For now, off to work to incorporate the data acquired this year to my expanding data sheets.

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Calling in the plant doctor


The Li-COR in action

Sometimes you really want to know how a plant is feeling. That’s when you call in The Plant Doctor!

The Plant Doctor is sitting next to me in the office and he knows a lot more diagnostic tools than the ‘I’ll-just-look-if-the-plant-is-there’-ecologist that I have traditionally been.


I have to admit the latter has dramatically improved, and I can now call myself familiar with a ton of ecological measurement techniques – from fluorescence to root staining, yet this particular tool has always looked incredibly sofisticated and far beyond my reach: the Li-COR.

The idea is simple, though: the Li-COR measures photosynthesis, which is of crucial importance if one wants to know how well a plant is doing. In practice, though, it involves a lot of buttons to push, decisions to make (like: do we want to measure at the same levels of CO₂ as previous studies, the background levels in the field on the day itself, or the average value from Hawai’i accepted as ‘this year’s CO₂’?), and heavy equipment to take (like: how many kilos of batteries does this thing need to survive throughout the day?). Enough to walk around it up till now, but sometimes you really want to KNOW!


Yet there is even more to this than just photosynthesis measurements: we can capture the air the Li-COR uses to measure photosynthesis (yes, we basically collect it into little baloons) and take it to the lab of The Plant Doctor. There, we can send the air through the even more complicated ‘PTR-TOF’ to measure so-called Volatile Organic Compounds; which is basically the smell of the plant, the molecules it emits. Some of these molecules will relate to its stress levels, and that is exactly what we are after: how happy are our plants, and what is driving their happiness levels?

So you can imagine I’m pretty excited for this new project, where finally, really, we’ll get to ask the plants themselves how they feel, instead of looking at them from afar, or using simple proxies.

Stay tuned for the results!

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