The 3D lab

Exotic species enter through the city gates

Posted on July 9, 2021 by lembrechtsjonas

3DLab-member Charly Géron’s second paper recently got featured on www.eoswetenschap.eu! Here is an English translation of the story they brought there:

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Plants from warmer regions feel perfectly at home in our cities. From there, they can colonize the countryside.

Exotic animal and plant species that settle outside their natural range cause biodiversity loss. They can displace indigenous species. To be able to do tackle that issue, it is important that researchers gain insight into how this colonization process takes place.

For 24 exotic plant species that occur in Western Europe, scientists investigated from which climate zones they originated. They also looked at the habitats they tended to colonize in our country. This excercise showed that exotic species that are more often found in urban areas generally come from warmer and drier regions.

In cities it is often several degrees warmer than in the surrounding countryside. This is a result of the so-called heat island effect, caused by the large amounts of stone and concrete in the city. It is also often drier in cities because the large percentage of impervious surfaces prevent water from seeping into the ground. ‘This connection between urbanity and climate of origin is therefore not surprising, but it had never been thoroughly investigated before,’ explains ecologist and author Charly Géron (UAntwerpen and ULiège).

‘Cities can serve as an outpost from which exotic species can colonize other areas when it gets hotter and drier there as well,’ says Géron. ‘In addition to the direct negative impact of urbanization on nature, this favouring of non-native species provides an additional negative effect of cities.’ Better monitoring of which species are popping up in cities could help nip the advance of exotics in the bud at an early stage, the scientists suggest.

Posted in Belgium | Tagged Cities, Ecology, Invasive species, Landscape photography, Nature, Outdoors, Plant invasions, Plants, Science, urban photography | Leave a comment

It is possible!

Posted on July 4, 2021 by lembrechtsjonas

I just received the beautiful lake-view above and, oh boy, is that an important picture!

It means that we made it happen, despite the ongoing pandemic and the kilos of extra administrative chaos it brought with it: we sent a research team to Abisko, northern Sweden!

Today, the first two members of the team arrived, later this month four more will dare international travel. What can and cannot be achieved in the field will remain a mystery for a while (the main bottleneck will be crossing the border to Norway), but at least several of our ongoing and new research ideas will see fulfillment.

And the significance of that can simply not be overstated.

Posted in Sweden | Tagged Fieldwork, Landscape photography, Nature, Outdoors | Leave a comment

Fieldwork preparations

Posted on June 27, 2021 by lembrechtsjonas

Hot summer day in the heathlands of Kalmthout, north of Antwerp, last week. With a team of two PhD students and four master students, we had a trial fieldwork day for this summer in northern Sweden.

Trying out vegetation surveys, preparing practicalities and looking at plants. 75% of species we saw in this Flemish heathland matched with those we find above the polar circle!

So ready to make this summer happen for the students, despite the tons of extra chaos due to Covid!

Posted in General | Leave a comment

The hunt for Arctic aliens

Posted on May 16, 2021 by lembrechtsjonas

Whilst they do not hunt for extra-terrestrial aliens that may or may not be hidden under the ice (as some on the more unbridled sections of the internet would rather they did), hunting for terrestrial aliens is exactly what they do. Ronja Wedegärtner and Jesamine Bartlett recall their team’s expedition in the high-Arctic Svalbard to monitor alien flora and publish their latest research which presents the most complete survey of alien vascular species in the archipelago to date.

feature_high res_compressed — The hunt for aliens on Svalbard © Lawrence Hislop, Norsk Polarinstitutt

You can read their full story here. Special shout-out for this fantastic animated movie to explain the risks of bringing sneaky beasties to the Arctic!

Posted in Svalbard | Tagged arctic, Ecology, Global change, Invasive species, Nature, Outdoors, Plants, Science, Svalbard | Leave a comment

The hottest lawns are not always in the city

Posted on May 15, 2021 by lembrechtsjonas

According to the first results of our citizen science project ‘CurieuzeNeuzen in de Tuin’, lawns in urban gardens can also be quite cool. This came as a bit of a surprise.

[English summary based on today’s discussion of our results in De Standaard by Ine Renson]

Today, we are launching something amazing: the daily updated temperature maps of our 4400 temperature sensors in our citizen science network. These maps have been highly anticipated, as we all were wondering about the patterns that would show up on them. Most importantly, one thing we wanted to see: are garden soils in cities warmer than those in the countryside due to the heat island effect?

It turns out that they are not. The map of soil temperatures shows a fairly diffuse picture, where cities do not immediately stand out. This is perhaps different from what we expected to see, but it is precisely why it provides interesting insights.

Our TOMST-built lawn daggers have three temperature sensors: one at a depth of 10 centimeters, one just at the ground surface and one at 12 centimeters above the ground. Those three curves show a different rhythm through the day. The air temperature at or just above the ground fluctuates strongly, while the soil temperature goes up and down in a gentle manner. So an earthworm feels a very different temperature than the one we experience ourselves in the garden.

Soil as a buffer: the average soil- and air temperature in Flemish lawns on April 13th. The two curves show the air temperature (green) and the soil temperature (brown). Soil Temperature remains rather stable, while air temperature fluctuates heavily. Soil warms much slower than the air, and reaches its maximum temperature late in the afternoon. Infographic as appeared in De Standaard newspaper.

We see that the soil buffers the temperature fluctuations, and that this pattern occurs consistently in every garden in Flanders. Here, our gardens nicely follow the rules of the soil physics textbooks. But when we compare soil and air temperatures, we encounter a remarkable phenomenon. When we plot the nighttime minima of air temperature on a map, the cities clearly stand out (see map below). In the early morning, city gardens are clearly warmer than the surrounding countryside. On the map of maximum soil temperatures, the pattern is a lot more subtle. There you see a lot more local variation across the whole urban-rural gradient. Very interesting: you’ll find most of the warm gardens there in the city outskirts, so halfway the urban-rural gradient. From the soils’ point of view, urban gardens are not necessarily warmer than average.

Heat islands in the coldest nights. This map shows the **minimum air temperature** (12 cm height) on April 13th, and visualizes the ground frost in early morning. Cities immediately pop out as warmer, with differences across the region of up to 15°C (-10 to +5°C)! Infographic as appeared in De Standaard newspaper.

We believe this goes to the heart of how the heat island effect works. Structures like buildings and roads absorb a lot more heat, so the air temperature close to the ground heats up quickly. Wind and air currents cause that warm air to spread, even to places in the shade. So the city as a whole heats up. Much of that heat is re-emitted in the evening and retained between the buildings. That’s why the heat island effect in the city is so obvious at night.

In the soil, things are different. It absorbs heat by radiation from the sun, but that heat is not transmitted laterally as much as in the air. A soil that is covered with plants, and not asphalt or concrete, will heat up less. Also, a soil that is shaded by buildings or by trees and shrubs stays cooler The fact that cities don’t really stand out on the soil temperature map might thus be because city gardens are often smaller and therefore catch extra shade, highlighting the critical aspect of shade for cool garden microclimates, even in the heart of the city.

Posted in Belgium | Tagged Citizen science, Climate, CNidT, Curieuzeneuzen, Gardens, Heat islands, Microclimate, Nature, Outdoors, Temperature | Leave a comment

On the measurement of microclimate

Posted on May 14, 2021 by lembrechtsjonas

Ecologists nowadays are trying to get closer to measurements of the microclimate that organisms are actually experiencing. Weather stations are great, standardized sources of temperature data at 2 m in the air, yet organisms often relate more strongly to what happens much closer to the ground. This rapidly increasing interest in microclimate ecology is great and much needed, but sometimes it is important to take a step back and ask that one important question: how good are we actually now at measuring the temperatures that we care about?

Indeed, microclimate measurements are done with a wide range of temperature sensors and radiation shields, professionally-built or home-made creations, and we lacked a good insight in how different the results could be. The big question is: are the temperatures as these sensors measure them close to the temperature as a beetle would experience it at the same location? This is exactly what we set out to answer in a recently published paper in the journal Methods in Ecology and Evolution.

The experimental set-up, where we installed a series of microclimate sensors at different heights above the ground (on the right, you see an iButton and the dim profiles of TOMST TMS4-sensors).

Let’s start with some good news: for measurements of soil temperatures, we don’t expect too many issues. What you measure should match fairly well with what’s actually happening. However, it is above-ground that the trouble starts. More precisely: when the sun is shining and especially when and where wind speeds are low. Indeed, most commonly used sensors yield large errors under direct sunlight, reaching up to a whopping 25°C.

Temperatures on a sunny day as measured with different iButton sensors are often up to 20°C different during the day from those given by a minuscule thermocouple.

Unfortunately this problem cannot be wholly overcome by shielding the thermometer from sunlight, as the shield itself will influence both the temperatures being measured and the accuracy of measurement. Importantly, however, when there is no direct sunlight, for example at night or in shaded environments like forests, errors turned out to be much smaller (see graph).

What’s the impact of shade on air temperature measurements? You see TMS4s with and without hats, and in the background a ‘shading table’. Differences are – as could be expected – substantial. Picture by Koenraad Van Meerbeek

So, what to do if one wants to measure air temperature close to the ground? In our paper, we provide two clear suggestions:

Whenever possible, use the smallest temperature sensors you can find, as these will be affected much less by heat absorption. Low‐cost and unshielded ultrafine‐wire thermocouples were clearly ‘best of the test’, as they will affect the surrounding temperatures the least due to their small size.
In shaded environments, there are more options available, and in some circumstances the use of other logger types, particularly TMS4 dataloggers, is appropriate. The latter are an especially good choice when trade-offs for costs and practical use have to be made. These might also be your go-to solution when the measured effect sizes (i.e., the difference between your location and weather station data) are large compared to the expected errors, such as may occur when regional or elevational variation in temperature is the primary concern, or in locations where weather stations are sparsely distributed.

The best of the test of the ‘traditional’ microclimate sensors: the TOMST TMS4. However, on such an open area as this carrot field, air temperatures can still be several degrees different from the truth when sun is shining. In this set-up, soil and surface sensors are below the surface and thus spared from the issues.

In short: there is no perfect way to measure microclimate temperatures, but there are definitely better or worse ways to do it. When working with such data, one should thus be *very* careful that no conclusions are made that should not be made.