Does microclimate change move species?

Posted on May 18, 2023 by lembrechtsjonas

With 200 or so we came together, here in the scorching heat and relentless urban expansion of southwest Florida, to talk about ‘species on the move’.

How an unfortunately large part of southwest Florida seems to look nowadays. Imagine the extreme microclimates in these non-habitats!

Global change is pushing species from all sides, forcing them out of their traditional ranges into new ones. With ‘SOTM’ already at its third edition, this issue has only become more urgent. Species range shifts are picking up speed, increasingly moving into uncharted territory, and causing a complicated reshuffling of biodiversity. Yet there is something intriguing about these species range shifts: there are only very few that are tracking climate change as predicted. Many terrestrial species are lagging behind climate change, or even moving in unexpected directions.

Corkscrew swamps and marshland, original Floridan wetlands

It is in this context that I’ll be giving a keynote lecture on Friday on the role of microclimate in the matter, as it seems to be that microclimatic heterogeneity could be taking away a large part of the need for species range shifts: thanks to microclimate, species often have to move only a few kilometers to find the climate conditions they are looking for.

However, these microclimates are also warming! Problem is, we don’t know yet how fast. My work focuses on getting that question answered: how fast is microclimate changing, and how can we best slow down that changing climate?

Forests buffer microclimate. Question is, will they also be able to buffer microclimate change? Strangling fig on a cypress tree in Corkscrew Swamp Sanctuary

For this, we need lots of data! The SoilTemp database is that source of data, and we just launched a massive new call for data. So, if you have microclimate data, consider submitting it to our database! If you’re at the conference and have questions about SoilTemp, data submission, or microclimate in general, I’m organizing an informal session during the coffee break on Friday, at 10h00, in Calusa B!

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An efficient way to obtain soil texture data

Posted on April 27, 2023 by lembrechtsjonas

When we designed our large-scale citizen science project ‘CurieuzeNeuzen in de Tuin’, we soon realized we had a problem on our hands: if we wanted to get an accurate idea of soil temperature and especially soil moisture from our 5000 measurement locations, we needed to have data on local soil conditions, and at least the soil texture.

That was not entirely impossible, we thought, as we had a laser diffraction device in the lab to assess soil fractions that could be used. We just had to ask all citizens to take a soil sample and send it to us. The problem came to the surface when we calculated our time investments: most laser diffraction analyses – at least those we knew of – could handle four samples per hour. And that was at their best behaviour only, excluding errors, cleaning of lenses, replacing of components etc.

Sampling the soil around our ‘garden dagger’

Now, four samples an hour for 5000 samples gives a total of 1250 hours of soil texture analyses, which is 156 days of relentless work, or 8 months of continuous labwork for a lab technician; if not beaten to death halfway through by the extreme dullness of the task at hand.

A delivery to our university of 1276 boxes with soil samples, frankly hammering home the message that this was quite the amount of samples to deal with

It was obvious that we needed a better solution. That solution was found with our colleagues at the Earth and Life Institute of UCLouvain. They had a different way of measuring soil texture, using visible near-infrared spectroscopy. This technique was much faster – in a blink of an eye a soil sample could be scanned.

Laser diffraction involves boiling soil in acid, which is pretty cool at first, but can be rather time-consuming, especially for soils rich in organic material

Spectroscopy works fast, but the results need to be calibrated. For a subset of the data – say 10% – the traditional laser diffraction method still needs to be used, which can then provide you with a calibration curve to identify the fractions of clay, silt, and sand in your sample.

The spectroscopical analysis is as simple as putting a scanner on top of such a dried soil sample and processing the result

In a new paper together with the team at UCLouvain, we now provide a better calibration formula for this spectroscopical analysis, which takes into account one mathematical issue with texture data: the sum of clay, silt and sand is always 100%, so you need to model them together to avoid impossible soils with more (or less) than 100% of volume.

That issue has now been solved and published in the journal ‘Soil and tillage research’. Thanks to this fabulous method, our citizen participants also had to wait only four months to get information on their garden soil texture on their dashboard, a most remarkable achievement they are probably not even aware of.

One enthusiastic citizen – probably largely oblivious of the massive undertaking it would be to get their soil sample analyzed in time.
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Microclimate can save plant species from population migration

Posted on April 24, 2023 by lembrechtsjonas

Global warming would force plant species to move dozens of kilometres north at breakneck speed to still find suitable habitat. “A failure for flora,” was the scientific consensus for a long time. Recent research suggests that such population relocation would not be necessary in many cases. Plants could seek refuge in ‘microrefugia’: oases in the landscape where the climate is relatively cooler than in the surrounding area.

Those who look at the climatology models hold their breath. Global warming is pernicious for greenery in this world. In fact, temperatures would rise so fast that plants would not have the chance to seek cooler places in time.

Although two recent papers in the journal Nature Climate Change outline a less grim prospect. “So-called microrefugia, such as a dense patch of forest where temperatures under the canopy are much lower than in the open areas around it, can provide (temporary) shelter for species fleeing rising temperatures.” explains ecologist Jonas Lembrechts (University of Antwerp). Lembrechts is the author of one of the papers and helped note that so far the consequences have turned out to be less severe than expected. “Thanks to those cooler locations, plants over the last 20 years eventually had to move no more than one km northwards, Maclean and Early calculated, while traditional models indicated another 50 km or so.”

One type of warming is not the other

“The temperature as perceived by plants, close to the ground or under the canopy of a forest, is very different from what we are used to from our weather stations,” Lembrechts explains. For instance, trees form an insulating layer above the forest, and photosynthesis in leaves causes water to evaporate, drawing heat from the environment.

Now it gets really interesting when those microrefugia are not only cooler than their surroundings, but also heat up more slowly. This makes them a buffer against climate change for much longer. “Such slower warming now also appears to be effectively possible,” Lembrechts explains. “For instance, in previous research, we showed that temperatures warm up more slowly in forests than in the surrounding countryside, because the cooling effect of (healthy) forests increases even more when temperatures rise.”

The influence of microclimate. A representation of the rate of microclimate change resulting in species range shifts. Three scenarios are shown: increased urbanization, unchanged land use, and increased forestation. The macroclimate will warm by 2 °C between 2020 and 2040. Each microhabitat may experience a unique rate of warming, ranging from 0 °C to 4 °C per pixel. Increased urbanization accelerates microclimate warming and requires faster species range shifts, while increased forestation slows microclimate warming and may maintain viable species populations. Protecting natural areas and creating new ones, especially in urban settings, is essential. The graph (bottom right) shows microclimate temperature increase variation over the 20-year period in different land-use scenarios (red, yellow, and blue).

Smart nature management as a solution

Such findings show that local nature can play an important role in combating the effects of global warming. At the same time, it is also fragile and human intervention can cause significant damage. Lembrechts: “Cutting down a forest will kill that local air conditioning, resulting in a local rise in temperature. That warming process can be much faster locally than what we expect from global climate change.” As a result, plant species will still have to rush off to cooler places.

But things can be different: smart nature management is able to firmly slow down warming at the local level. “So from nature’s perspective, it is not just about to what extent we can limit climate change by reducing our CO2 emissions, for example,” Lembrechts stresses. “Certainly as important is what we do with our limited green space. If we let it become more and more urbanised, the temperature in the microrefugia will rise much faster than if we bet on more forests, marshes, and other greenery.”

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Botanical scouting

Posted on April 12, 2023 by lembrechtsjonas

I spent a beautiful spring day last week in one of Brussels’ most fairy-tale-like places: the botanical garden Jean Massart.

Springtime visits to the botanical garden, that’s abundant flowers wherever you look! Here: Fritillaria meleagris, a rare species planted – and thriving – in the botanical garden

This little piece of biodiversity sits in a picturesque valley bordering the E411 highway and that famous chunk of Brussels forest called the Sonian Forest.

Anemone nemorosa, the wood anemone

Of course, I wasn’t there just for the picture-perfect flowers: I was there to do some scouting for a potential new – and pretty exciting – project. If we get it all figured out, we’d be using this beautiful garden as our laboratory for an important research question: can botanical gardens play a role as microclimate refugia in urban areas?

The botanical garden hosts some replicas of highly biodiverse grasslands, so typical – and endangered – for Flanders. One of the show-offs on this April afternoon was this Primula veris

Requirements for this are two-fold: a vast range of microclimatic conditions, resulting from a highly heterogeneous landscape, and a high biodiversity.

A patch of relatively dense forest at the bottom of a valley, the dream-location for stable and relatively cool microclimatic conditions, even close to the city of Brussels

If all goes well, we’ll find both these requirements fulfilled at the botanical garden Jean Massart, but the extent of both remains to be quantified. That’s all I’ll say about it now, so stay tuned for hopefully the start of something new and promising!

Anemone nemorosa was thriving in the forest understory
If you say Flemish forest in spring, you say Hyacinthoides non-scripta
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ForestClim – bioclimatic variables for forest understory

Posted on April 7, 2023 by lembrechtsjonas

Those bioclimatic variables that we ecologists all love so much, but at a higher resolution and from right there where your study organisms are living? Wouldn’t that be a dream come true?

Time to pinch yourself, as we now released ‘ForestClim’, a dataset of all the familiar temperature-related bioclimatic variables, at a 25 x 25 m resolution. These bioclimatic variables are representative of conditions at 15 cm above the ground under all of Europe’s’ forest canopies, making them the perfect tool for anyone studying forest understory plants.

Overview of the different bioclimatic variables in the ForestClim database.

Now, for the attentive follower, these maps might look familiar. And, indeed, you might have seen at least one of them before: the underlying maps are building further on an earlier publication – by the same amazing PhD candidate Stef Haesen – where we showed a proof-of-concept for these forest microclimate models, based on data from the beloved – at least by me – SoilTemp microclimate database. In that first paper, the model was used to calculate mean annual temperature, but quite some more computer power needed to be consumed before we could create the other bioclimatic layers as well.

Now they arrived, and they are free for all to use, as it should be. So, off you go, go model some forest plant distributions using this neat new toy!

What temperatures are the bluebells of the famous Flemish ‘Hallerbos’ truly experience? Ask our high-resolution ForestClim-maps!
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The efficiency of microbes

Posted on April 5, 2023 by lembrechtsjonas

In order to truly understand climate change, we have to understand the carbon cycle – which describes where that notorious element called ‘C’ is moving to. In order to understand that carbon cycle, we need to know who is using that carbon, when and how much. As it turns out, that’s a rather complicated knot to disentangle.

In a recent paper led by Anita Risch, we took a look at the role of some of the more elusive players in that whole business of carbon cycling: soil microbes. Soil microbes play a surprisingly big role in that story, but exactly hów big remains – as so often – hard to grasp. What is known is that soil microbial processes play an important role in the build-up and maintenance of the big chunk of carbon that’s stored in our soils. At the same time, however, soil microbes RELEASE a bunch of carbon into the air via a process called ‘heterotrophic respiration’, best understood as the breathing out we humans also do.

Grassland soils (here at an experimental site in South-Africa) store surprising amounts of carbon (All pictures by the NutNet-network)

From a climate change perspective, one would want microbes to store as much carbon in the soil, and to ‘breath out’ as little as possible. That balance can roughly be considered the ‘efficiency’ of the soil microbial respiration. In a recent paper, we set out to test what defines that efficiency.

A NutNet site in Bogong, Australia

For this assessment, we made use of a fantastic global experiment called NutNet, where scientists took natural grasslands and manipulated the amount of nutrients and herbivores. Then, the scientists from 23 grassland sites took a soil sample and sent it to the lab for a five-week laboratory experiment to assess microbial respiration.

So what did we find? Microbes – at least those in grassland soils – did not seem to care too much about nutrient addition and/or exclusion of herbivores. Indeed, both factors did not significantly affect their efficiency. What they did care about, however, was the local soil and microclimate conditions, which strongly affected that illustrious efficiency.

Herbivory in action in Kilpisjärvi (Finland)

So what to do with this information? Most importantly, perhaps, it explains why local studies across the globe have been finding such contradictory results on the matter. If it is indeed all local soil and microclimate conditions that decide how much microbes respire, it makes sense that each regional study will find a different effect of disturbance factors like nutrient addition or herbivory. A wise lesson again for us all: ecology can be darn complicated.

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