We’re going to have to talk about snow. Snow is fabulous, it is unique, it is beautiful. But it also turns ecological processes and principles on their head: snow accumulation determines ground temperature, light conditions and moisture availability during winter. It also affects the start and the end of the growing season, and plant access to moisture and nutrients. And that critical role, which can give ecologists a bit of a headache, as snow is also highly elusive, and very tricky to measure (and not only because it is SO COLD to go out to measure in the Arctic tundra in winter).
The number of studies on snow has increased considerably in recent years, yet we still lack a good overview of how altered snow conditions will affect ecosystems. In a recent review, spearheaded by Christian Rixen from the WSL Institute for Snow and Avalanche Research SLF in Davos, Switzerland – as the name suggests quite the experts on the matter – we tried for the first time to create such a comprehensive summary.
We provided a ‘state-of-the-art’ of what we currently know about the snow cover’s role for vegetation, plant-animal interactions, permafrost conditions, microbial processes and biogeochemical cycling. With topics ranging from snow effects on temperature (buffering frost, but shortening the growing season), over light (increasing reflection of light away from the earth, and darkening the vegetation underneath it) to moisture (meltwater can provide vital but also short-lived water sources), we paint a picture of how snow is often the defining factor in cold-region ecology.
We also dive into the depths and complexities of what is happening (and will happen) with our tundra ecosystems as climate changes. Changes in snowfall and snow cover across the cold environments will be (and is) substantial, with both increases and decreases in amounts of snow. Effects of these changes are also not intuitive: less snow in winter may for example lead to colder soils as climate changes, as soils lose their insulating blanket. More snow in winter, on the other hand, generally has the opposite effect and causes warmer winter soils.
Finally, we took a good look at the ways in which scientists are currently experimenting with snow effects. Interestingly, we found that experimental research aiming to manipulate snowmelt timing worked with much smaller changes in snowmelt than those observed over spatial gradients (e.g. across a mountain slope). Indeed, experiments managed to change snowmelt on average 7.9 days (when aiming for faster melt-out) or 5.5 days (when aiming for delays). On the other hand, spatial variation in snowmelt easily reached up to 56 days, ten times higher! Similarly, snowmelt timing in the same location over time on average differed 32 days. Additionally, great differences could be found depending on WHEN in the season snow was manipulated. Here again, the main conclusion is: snow is complicated, even to manipulate!
If we want to get a better hold of snow and its mysteries, we will have to ensure a better comparability between studies. In this review, we have taken the first steps in that regard, by providing an improved baseline for future studies of the influence of snow. Differences between snow study approaches need to be accounted for when one wants to generalize conclusions and, especially, when projecting snow dynamics and their impact into the future.
It was the year 2005. A group of mountain ecologists gathered in Vienna, Austria, for what would turn out to be an appointment with history. Their topic? Plant invasions in mountains! A consensus was soon reached that there was an important research gap to fill. While the overall view was, up till then, that mountains had been spared from invasion by non-native plant species, global change and increasing land-use pressures in mountains across the globe were rapidly changing that reality. However, there was very little global information on these patterns, with only a fairly recent regionally scattered literature emerging. Time was ripe, so they decided on a globally coordinated protocol. The Mountain Invasion Research Network (MIREN) was born.
The next year, the team gathered again in Oregon, and it is there that the MIREN road survey protocol saw the light of day. The idea was to monitor non-native plant species along mountain roads, with a standardized survey design in the form of a T, and repeat that survey every five years – till eternity, so one might hope – to get the critical baseline information on how quickly non-native species are spreading along mountain roads.
Soon after, the protocol got expanded, and now it includes native species as well, allowing the study of range shifts of all plant species along elevational gradients, and the impacts of climate and roads on these, over time. In a recent paper, published in the open access journal Ecology & Evolution, we finally present the survey methodology and the summary of achievements to the world, hoping that it can become a standard monitoring tool in mountain regions across the globe.
What we present is a conceptually intuitive and standardized protocol developed by the Mountain Invasion Research Network (MIREN), designed to 1) systematically quantify global patterns of native and non-native species distributions along elevation gradients and 2) shifts in these distributions arising from interactive effects of climate change and human disturbance. Usually repeated every five years, surveys consist of 20 sample sites located at equal elevation increments along three replicate roads per sampling region. At each site, three plots extend from the side of a mountain road into surrounding natural vegetation, in the characteristic T-shaped design. In each of these plots, presence, cover and abundance of all vascular plant species are noted down.
The protocol has been successfully used in 18 regions worldwide from 2007 to the present. So far, analyses of the data already generated salient results, both in regional studies and global assessments. For example, we found region-specific elevational patterns of native plant species richness, but a globally consistent elevational decline in non-native species richness. Non-native plants were also more abundant directly adjacent to road edges, suggesting that disturbed roadsides serve as a vector for invasions into mountains. From the upcoming analyses of time series – in some regions we now have three timesteps, over a 10 year period, and the 4th one will be collected this year – even more exciting results can be expected. Indeed, as the covered time frame gets longer, our assessment of species range changes will further improve.
Think all of this sounds fun and important? Perhaps you can join us!
Implementing the protocol in more mountain regions globally would help to generate a more complete picture of how global change alters species distributions. By publishing our protocol for all to read, we hope to enthuse the global ecological community to join forces with us and apply the protocol in your own region. With the MIREN protocol, you would have a unique tool in hand to monitor the impact of climate, climate change and anthropogenic disturbance on the vegetation in your mountain, with interesting patterns bound to emerge from the first sampling onwards. Feeding your data into our increasingly large database can then generate interesting comparisons about how your region compares to plant species diversity patterns in mountain regions across the world. This information can – and already does – inform conservation policy in mountain ecosystems worldwide, where some conservation policies remain poorly implemented.
If I had some ideas about the emerging challenges for vegetation science, they asked. I sure did! If I wanted to join a virtual workshop with 21 other early-career vegetation scientists to discuss those challenges? You bet!
It was a very ‘2020’ kind of thing the Young Scientists of the International Association of Vegetation Scientists (IAVS) proposed. As Covid had effectively brought social gatherings to a standstill, opportunities for scientific brainstorming as often happen over coffee-and-cake at conferences had taken a big hit. A blow for new scientific ideas and research avenues, for sure. The IAVS Young Scientists figured that this issue had hit the next generation of scientists the hardest: even in the best of times, it was hard for a young scientists to get their good ideas heard. Nevertheless, it is the young ones from now who would be answering the scientific questions of the future.
Now, we would let our voices and ideas be heard, pandemic or not! We gathered – on Zoom, of course – with 22 young and enthusiastic vegetation scientists from a wide range of backgrounds to perform our Horizon scan. Each of us submitted their own idea of what they thought was the next big research avenue for vegetation science, the sub-field of biology that studies the ecology of plant communities.
Our horizon scan took place in the form of a two-day online workshop held in October 2020. Of the 24 topics originally proposed and discussed by participants, 15 topics were ranked as the most emergent and impactful for vegetation science.
This week, the outcome of this fun two-day workshop got published in the Journal of Vegetation Science (where else would you want it, right?). In this contribution, we present the selection of 15 topics that were ranked by our workshop participants as the most emergent and impactful for vegetation science.
The topics contain methodological tools such as next-generation sequencing, plant spectral imaging, process-based range models and resurveying studies, and permanent plots, which we expect will need to be integrated into vegetation science to lead it into the future.
Overarching, there is the looming impact of global changes, for which we stress the need to integrate long-term monitoring, the study of novel ecosystems, below-ground traits, and pollination interactions, and the creation of global networks of near-surface microclimate data.
Finally, we also emphasize the need to integrate traditional forms of knowledge and a diversity of stakeholders into research, teaching, management, and policy-making to advance the field of vegetation science, a research field that will more and more be intertwined with society as a whole as natural areas remain under pressure.
Much work to do, we believe, as nature is increasingly under pressure by climate and other global changes. We hope that our horizon scan can help identify the ways forward to tackle the issues that are and will come. But most of all, we hope it can become an inspiration, and energize ecologists and vegetation scientists, especially the young ones, with the knowledge that their work is of uttermost importance to save our planet.
Reference: Yanelli et al. (2022) Fifteen emerging challenges and opportunities for vegetation science – A horizon scan by early career researchers. https://doi.org/10.1111/jvs.13119
Cutting-edge modern technology has brought us so far that scientists can now find ghostly prints from former human activities with breath-taking accuracy. Ghosts from the past, that is, and that modern technology is called LiDAR (light detection and ranging).
LiDAR feels like a magical way of looking at things and revealing hidden artefacts. It is basically a laser scan of an environment with extreme precision (often up to centimetres in accuracy), which allows us to recreate environments such as forests in 3 dimensions. LiDAR scans can be made from the ground or from the air, and in its simplest form consists of sending out a laser beam, The Light Fantastic, and capturing it again when it bounced back from an object.
In a new review paper recently published in Journal of Ecology, we summarize the exciting potential of LiDAR for forest research. Indeed, when we can map a forest in 3D at the centimetre scale, we can find back structures that are impossible to see with the naked eye, and that hide former land uses, management practices or impacts of climate change.
An impressive example of this potential can be seen in the Compiègne forest, in northern France, where LiDAR data allows us to trace back hidden structures in the forest all the way to the Roman times, much and much further than historical maps can ever do.
While digging up such ghosts of the past is obviously extremely fascinating, it has also important consequences for ecology; the main point we want to hammer home in this new paper. Indeed, such past management practices and land-use changes have big impacts on current species distributions. Basically, they can explain why you found certain plants in certain – sometimes weird – spots. Some barley on the forest floor? Perhaps there has been a medieval farm there!
These confounding effects of past land use can obscure the impacts of ongoing global changes such as climate change or atmospheric pollution on species distributions. And that is exactly why it is so critical to know about them. For example, Roman agricultural practices can still result in elevated nutrient concentrations in a forest soil, with consequently a higher presence of nitrogen-loving species in the forest understory. Without the technology to look back that far into the past, the presence of these species might mistakenly be attributed to nitrogen-deposition from the air during the 1980s, overestimating the impact of the latter on forest diversity.
Given how forest cover is increasing in Western Europe (France has seen its forest cover double since the 18th century!) there is bound to be a lot of historical artefacts and past land use hidden underneath our forests. Knowing these patterns will be critical for smart management decisions. Now LiDAR is there to reveal them.
In a new paper just published in Global Change Biology, we provide the first-ever global maps of soil temperature (0 -15 cm) at a 1 km² resolution, based on the global SoilTemp database of over 8500 in-situ soil temperature time series. We show that over the year, soils in cold and/or dry biomes are on average 3.6°C warmer, whereas soils in warm and humid environments are 0.7°C cooler, than shielded air temperature at standard height (1.25 to 2 m) as measured by weather stations.
SoilTemp has done what it hoped to do from the start: it brought together over 400 scientists and their over 8500 soil temperature time series from across the globe. This humongous collaboration has now resulted in a first and much-anticipated global product: global gridded layers of soil temperature and bioclimatic variables at a 1-km² resolution for 0–5 and 5–15 cm soil depth. Free for all to use! I can’t emphasize enough how big of a game-changer this can be: now, finally, ecologists working on any pattern or process in, on, or close to the soil surface can use global temperature data that are representative of the soil conditions.
That such a correction is far from trivial is shown by the mind-boggling numbers in the paper. First of all, we show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons: a 20°C (-10 to +10°C) range across the globe! Over the year, soils in cold and/or dry biomes, such as tundra, boreal forests or subtropical deserts, are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments, such as tropical rainforests, tropical savannas or temperate forests, are on average slightly cooler (-0.7 ± 2.3°C). We also show a significant reduction in the spatial variation in temperature in the soil in cold and cool biomes (and a slight increase in warm biomes). All this implies that soils will warm differently than the air as climate warms. How big that discrepancy will be, that’s a question up for future research, and a challenge SoilTemp is very happy to take up!
Global maps were created by first calculating the difference (i.e., offset) between in-situ soil temperature measurements, based on time series from over 1200 1-km² pixels (summarized from 8500 unique temperature sensors) across all the world’s major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land. Models, based on machine learning algorithms that linked the offset to predictor variables, come with maps of where predictions are most consistent (top) and where the model is extrapolating (bottom). This way, you can verify model quality in your area of interest and mask regions with higher uncertainty.
We hope these maps can mean a major leap forward and finally open up microclimate research to the global scale. But are we done now? Far from! SoilTemp has many other cool things up its sleeve. We are hoping to increase our spatial and temporal resolution, for example, and are working hard to fill the remaining gaps in our global data coverage. Global microclimate networks, it’s still the dream!
The database also has great potential for improving our mechanistic understanding of microclimate across the globe. Most of all, however, we are hoping for a massive surge in applications: if people actually start using our global microclimate products in their ecological analyses, then SoilTemp has achieved what it most dearly wanted.
Now, that’s what they call a milestone: The3DLab got to celebrate its very first PhD, this week. Charly Géron successfully defended his thesis on plant invasions in urban environments!
The defence brought us on a cold and sunny winter solstice to Gembloux in Wallonia, southern Belgium, his home university. There, we could have a covid-beaten version of an in-person defence, where he walked us skillfully through the many investigations he performed to get to the core of that very important question: how are urban environments facilitating plant invasions?
With that, four years of rigorous research comes to a close – a bittersweet feeling lightened up by the fact that I got to wear a toga for the first time! We’re going to miss Charly in the team; the plant expert, the unstoppable pursuer of goals.
He has made our lab a better lab, and contributed to the worlds’ knowledge: indeed, non-native species from warm origins preferably invade urban environments in Western Europe, while their cool counterparts stick to the countryside. Interestingly, they all suffer when it gets warm, though, a bit of an unexpected find. Finally, it turns out there are some signs of local adaptation to urban conditions, yet mostly there is a lot of plasticity (plants just ‘changing shape’ when conditions shape), and environmental maternal effects (mother plant performance deciding how they offspring will perform, for example through the size of the seeds).
Charly’s work opened a whole new box of research questions, as all good science should!