Pieter Sanczuk is a PhD student at the Ghent University in Belgium. He is a botanist interested in forest microclimates. Here, Pieter shares his recent findings on the understorey plant species range dynamics under climate change.
Pieter searching for bluebells transplanted 60 years ago (and 35 years before he was born). Although GPS coordinates were available, small bluebell populations can be hard to find in a 1,500 ha sized forest.
Personal links. Google Scholar
Institute. Forest & Nature Lab, Bioscience, Ghent University, Belgium
Academic life stage. PhD student.
Major research themes. The effects of forest microclimates and biotic interactions on understorey plant species range dynamics under climate change.
Current study system. In my PhD, I study the effects of small-scale environmental variation and biotic factors (e.g., competition or herbivory) on understorey species range shifts due to climate change in temperate forests of Europe. Many species are shifting their distributions towards higher latitudes and elevations. However, such a trend remains somehow elusive for forest understorey species, mostly due to the importance of processes operating at small spatial scales. For example, trees are ecosystem engineers, buffering the climatic extremes for species living within and below tree canopies. By including environmental variation related to small spatial scales into predictive models, I aim to obtain more accurate projections of future species ranges.
Recent JBI paper. Sanczuk, P., De Lombaerde, E., Haesen, S., Van Meerbeek, K., Van der Veken, B., Hermy, M., Verheyen, K., Vangansbeke, P. & De Frenne, P. (2022). Species distribution models and a 60-year-old transplant experiment reveal inhibited forest plant range shifts under climate change. Journal of Biogeography, 49(3), 537–550 https://doi.org/10.1111/jbi.14325
The Hallerbos in Belgium is nicknamed ‘the blue forest’ because of the carpets of spring-flowering bluebells, which attract yearly more than 100,000 visitors (Photo by Sanne Govaert).
Motivation behind this paper. Bluebell (Hyacinthoides non-scripta) is one of the most well-known species in the European forest understorey. During spring, this species can form a blue carpet that covers the understorey layer. For this reason, tourists worldwide are attracted to large flowering populations in France, Belgium and the UK. However, reports indicate that the colonization rates (i.e., the speed a plant population can move) in this species can be five orders of magnitude slower than the velocity of contemporary climate change. If climate change negatively impacts bluebells’ performance, this species is potentially vulnerable to local extinction, and range shifts that are fast enough to track the shifting isotherms are highly questionable. In our paper, we aimed to find out how climate change will affect range dynamics in bluebell and whether this species will be able to track the projected distribution shifts.
Key methodologies. The most emblematic part of our methodology was the experiment. That is, as far as I know, our experiment is among the longest running transplant experiments in the world. In 1960 (more than 60 years ago!), bluebells were transplanted from three natural source populations to several forest sites beyond its natural distribution in Belgium. Both the source and transplanted populations were resurveyed 45 and 60 years after the installation of the experiment, which allowed us to analyse temporal trends in the population performance and estimate colonization rates. Because long-term experimental research is typically done at smaller scales, we combined the results from the experiment with species distribution models to assess potential range dynamics across a broader spatial extent. The combination of experimental research with predictive modelling is highly powerful and often provides complementary insights not possible to obtain when using only one of the methods.
Two of the transplanted populations in 2020. Several traits were measured on ten flowering individuals within each population.
Unexpected challenges. One of the largest challenges was relocating the transplanted populations. Although GPS coordinates, maps, and descriptions of the overstorey structure were available for each population, relocating ~1 – 10 m² patches of bluebells in a 1,500 ha forest is difficult. Our first attempt was actually in 2019. However, this field campaign failed because we were too late in the growing season. We could only relocate one population, from which the flowers and leaves were in a senescent phase. Timing really matters! So, in 2020, we returned just right within the flowering period. This was a good decision, as we relocated all populations that were also found in the first resurvey of the experiment (except for one, where the forest was clear-cut). Finding the populations is really satisfying if you think that someone (actually, not just someone, but the pioneer of Belgian forest ecology) planted the individuals 60 years ago – that is, 35 years before I was born!
Major results. Unfortunately, we found clear signals that the populations in the source and transplanted areas have decreased. The species distribution models also predicted a similar decreasing trend in habitat suitability due to climate change. Hence, the decrease predicted by the models has already started in the study populations. Moreover, based on the colonized distance from the transplanted populations since 1960, we estimated that the average colonization rate was only 2 cm per year. Currently, this is 17,500 times slower than the velocity of climate change (the temperate isotherms for broadleaf and mixed forests are shifting at a rate of 350 m per year). Given the slow colonization rate presented by the plant, range shifts that are fast enough to track the shifting climate are virtually impossible. In essence, bluebell’s climatic envelope is currently running away from its natural distribution.
Bluebell is adapted to grow in deep shade below closed tree canopies of Beech (Fagus sylvatica), and therefore successfully occupies forest patches that are too stressful for many other plant species to grow. Picture from the Vecquée forest wherein the transplanted populations are located.
Next steps for this research. Luckily, forests are natural climate regulators. Depending on the forest structure, overstorey temperature can be buffered up to 8 °C, resulting in cooler microclimates. This buffering can attenuate climate change impacts on forest understorey species. If we want to predict understorey range dynamics under climate change accurately, we need to integrate the variation in understorey temperature conditions. Currently, we are running predictive models on a suite of common forest understorey plant species to investigate the effect of forest microclimates on their range dynamics under climate change. We aim to generate guidelines for forest managers to help mitigate climate change effects on forests.
If you could study any organism on Earth, what would it be? Herbs are great study organisms: they are easy to measure and perform experiments with and often show fast responses to experimental treatments under changing environmental conditions.
Anything else to add? In short: combining multiple methodological approaches is really cool! It can take a bit longer to familiarize yourself with the analyses, but you learn a lot from them, and it often provides novel insight into your study system. If you doubt it, go for it!