The hunt for Arctic aliens

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.

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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!

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The hottest lawns are not always in the city

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.

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On the measurement of microclimate

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.

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:

  1. 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.
  2. 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.

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Good family man or sulking teenager: an update on our data network

May be an image of outdoors

The data from the lawn network of our citizen science project (CNidT) is transmitted via the Internet of Things. With its 5,000 connected sensors, CNidT is also the largest Internet of Things network in Belgium. Pioneering work, therefore, and that gives as many interesting surprises as challenges.

The name, Internet of Things, or IoT, refers to a set of devices that are connected to the Internet. In this way, the devices can send data to the cloud, communicate with databases or exchange data among themselves.

Many devices on the IoT are equipped with a sensor to collect data. In the case of CNidT, the soil sensor has several sensors that measure air temperature, soil temperature or soil moisture every 15 minutes. Via a SIM card, the sensors are connected to Orange’s IoT network and once a day the collected data is transmitted to our database and the participants’ dashboards (you can check out the dashboard of the sensor at the University of Antwerp here!).

After over a month of data collection, we now have a great view of how faithfully the lawn daggers transmit their data to the CuriousNoses database at UAntwerpen. What is surprising is that part of the network reacts like a “good family man”, while another part acts more like a “sulking teenager”.

Schermafbeelding 2021-05-11 om 11.24.41

About 50% of all sensors send their data every 24 hours (these are the good family men). The other 50% still like to hold the data for one or more days, only to send it all in one burst at a later time (these are the stubborn teenagers).

Is your garden dagger by any chance a sulking teenager? No need to panick yet. You won’t indeed see new data appearing on your dashboard every 24 hours. But this data is not lost: the data is stored in the internal memory of the soil sensor and transmitted when there is connection again. Either way, this data gets ultimately included in our analyses.

From an Internet of Things perspective, these good and bad lawn daggers are highly fascinating: why is the network reacting the way it is? Is there reduced coverage in certain locations? Are there large trees or buildings nearby? Or does the weather play a role in connection reliability? And what can we learn from this for the future rollout of large IoT networks? We are currently investigating these interesting questions with partner Orange, sensor builder TOMST and the Internet of Things wizards at ID lab at UAntwerpen.

Text by Sanne de Rooij, translated by Jonas Lembrechts

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Cold fieldwork news

I received some pictures from the snowy colds of the Norwegian mountains this week, where The3DLab-member Ronja went on a cross-country ski tour to her seed addition experiment to measure snow depth.

Snow is a crucial component of microclimate as it serves as a blanket: a thick snow pack can keep soil- and near-surface temperatures close to 0°C all winter.

Ronja in a black-and-white world, on the road to her fieldwork plots. Picture by Eivind Bering

In Ronja’s experiment, we are especially interested in local variation in these snow covers, as we are comparing exposed with sheltered locations. In the exposed location, wind prevents the accumulation of a thick snow pack, with potentially much more intense freezing around our seedlings, yet also an earlier onset of spring. In the sheltered locations, snow can accumulate, providing this important blanket against heavy freezing, yet also delaying the start of spring for the plants underneath the blanket.

Locating your fieldwork plots under a blanket of snow needs good GPS-coordinates. Picture by Eivind Bering
A sheltered location, where no plots can be seen. Picture by Ronja

Often these winter measurements of the snow depth are lacking – few are brave enough for winter fieldwork. But Ronja fears no cold (and has equally brave friends to provide fun fieldwork company) and got us the precious data we need.

Very much looking forward to see how the seedlings look when snow is gone!

An exposed plot, with very little snow cover. Picture by Eivind Bering
The precious winter data! Picture by Ronja
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Saving the world isn’t rocket science

The3DLab member Ronja got interviewed for a podcast at her university in Trondheim! A very nice summary of her research. You can find the podcast here, or on Spotify!

The podcast investigates the environmental impacts of hiking trails in the Trondheim area. Norwegians are active practitioners of “friluftsliv” and hiking is one of the most popular activities. Ronja Wedegärtner, Ph.D. candidate at NTNU, discusses the influences of hiking trails on vegetation shifts in mountains in the Northern Scandes, giving away some cool insights about her PhD-research!

Ronja in the Swedish mountains in search for impacts of trails on vegetation

Want the scoop of some of the most fascinating results from her work, then this podcast is a must-listen!

Saving the world isn’t rocket science

The rapid growth and challenges related to agriculture, urbanization, tourism and human-wildlife conflicts require knowledge to take action. Listening to this podcast, you will be updated on state-of-the-art science related to issues in Trondheim. “Saving the World isn’t Rocket Science” shares knowledge from the science community by interviewing local researchers about sustainability problems in Trondheim and possible solutions.

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