Kristiina Visakorpi: The future of Alpine meadows: Can we predict winners and losers in a warmer climate?

In this new post Kristiina Visakorpi—a postdoc at the Norwegian University of Science and Technology—discusses her last research ‘Eco-physiological and morphological traits explain alpine plant species’ response to warming’. She considers the connections between functional traits and climate change, highlights the importance of eco-physiological traits, and provides some thoughts to fight apathy towards our current environmental crises.

About the paper

In our paper we investigated whether plant functional traits can be used to predict which species are likely to suffer or benefit from climate warming in the Alps (Switzerland). Specifically, we explored which types of traits are most useful in these types of predictions. As environmental change accelerates and becomes more severe, there is an increasing need to find reliable ways to predict the impacts of those changes on different species. One way to do this is to measure functional traits, i.e. different characteristics of a given species that are supposed to correlate with how the species functions and responds to a given environment. Many of these “trait-based” studies tend to use the same relatively small set of traits with varying success. These “traditional” functional traits are often morphological, and they are chosen because they are relatively easy to measure (e.g. plant height or leaf mass per area). The varying outcomes of trait-based studies have raised the question of whether failures of traits as predictors reflect the limitations of those traits commonly measured, or limitations of the trait-based approach more generally. In our paper, we tested how well a set of traditionally measured functional traits can explain warming-driven abundance changes in an alpine plant species. We compared the explanatory power of these traditional traits to a set of more detailed eco-physiological traits rarely measured in trait-based studies.

The view from the field site into the Chur valley. The highest experimental site was at 2000 m, just above the timberline. The field work took place on Calanda mountain in the Swiss Alps (credit: Kristiina Visakorpi)

Being able to predict the impacts of environmental changes on different species is perhaps one of the most exciting goals of ecological research. By taking a few simple measurements, can we tell, in advance, which species are likely to “win” or “lose” under new environmental conditions? Could we predict how ecological communities will look in the future by just measuring characteristics of different species in their current environment? Functional traits are expected to be able to do exactly this, and consequently, have been hailed as the Holy Grail of predictive ecology. Nevertheless, many of the traits most commonly measured have not proven to be universally successful as predictors of demographic trends. Moreover, they often fail to explain why certain species might flourish or suffer. For example, one of the most commonly measured plant traits, leaf mass per area, can be used to explain cold tolerance, herbivory resistance, growth rate and general life history strategy. How are we then supposed to understand a relationship between leaf mass per area, a species’ demographic response, and the environment?

Compared to simple morphological traits, measurements of eco-physiological processes can potentially give more detailed information on the mechanisms behind observed trends. This was one of the main ideas behind our paper: if we could measure some of the physiological processes directly, could we achieve a better understanding of species’ responses to climate warming compared to using “traditional” plant traits alone? To test this, we used an existing experiment in the Swiss Alps in which turfs of alpine vegetation have been translocated from their original elevation at 2000 m to three lower elevations, mimicking climate warming of up to 5°C. The frequency and cover of each species in these turfs was monitored for four years. Thanks to this experimental setup, we could follow which species disappear in warmer and drier climates at the lower elevations. “All” we had to do was measure both the “traditional” functional traits and eco-physiological traits of a subset of these species and relate them to their demographic responses. We could then compare which set of traits (if either) would be able to predict those responses.

Alpine meadow at 2000 m altitude (credit: Kristiina Visakorpi)

Despite several previous studies on the predictive power (or lack thereof) of functional traits, studies comparing different sets of traits or aiming to find alternative sets of traits to measure are relatively rare. Our study also stands out by because it included aspects of plant physiology rarely measured in the field or included in trait-based studies, such as night-time respiration and water-use strategy measured with stable isotopes. Moreover, the size and scale of the experimental setup makes our study different from many of the previous trait-based studies: we were able to observe how different species responded to a manipulation of the climate, rather than observing trends along natural climatic gradients. 

About the research

We included several night-time physiological processes in our trait dataset. This required setting up camp next to the experimental sites (credit: Kristiina Visakorpi)

With our paper we wish to advance the discussion about the usefulness of functional traits as predictors. Our results should also give some hints with regards to how alpine plant communities are likely to change in the future, and, most interestingly, why they are changing the way they are. Our measurements also provide trait data from several species and traits which are not often included in current online databases.

Gathering eco-physiological trait data in the field from small alpine plants wasn’t exactly straightforward. For many of the measurements, we used gas analyzers—machines that are at the same time astronomically expensive, incredibly sensitive and likely to malfunction from the smallest drop of water or speck of dirt in the wrong place. Many of our days would start by carrying two of these machines to the experimental site and powering them up with car batteries, only to then notice that a thunderstorm was approaching from the other side of the mountain which required us to dismantle the whole setup and start all over again after a couple of hours. Despite being challenging, the field work also provided moments of beauty: seeing the sunrise over the mountains after a night of measurements was magical.

View from the field site as the sun is rising over the mountains (credit: Kristiina Visakorpi)

The big questions that still remain unanswered in the field of functional traits are to some extent the same big questions that remain unanswered in the field of ecology in general: can we find universal, or near-universal (or even just common) trends that apply across species and ecosystems? In our study, traits related to plant size and water-use strategy were successful in separating species that suffered from climate warming from those which benefitted or were indifferent to these changes. Do these traits function as useful predictors outside the set of 16 species we measured? How about outside our experiment? On another alpine grassland? In a different type of a system altogether? One of the most interesting findings of our study was that the interpretation of the mechanism behind the species’ abundance changes would have been different depending on which traits were used for the predictions. Eco-physiological traits showed that species with conservative water-use strategies ended up as the “winners” in the new environment, suggesting that water limitation might be an important driver of plant community change in the Alps. Morphological traits, on the other hand, showed that plant size was an important predictor of success. Had we used these morphological traits alone, we would have most likely ended up with some other interpretation of the mechanism behind species’ abundance change. This opens up a new question for the field of functional trait ecology: how will our interpretation of trait-environment relationships change once we start expanding the set of traits we include in our studies?

We used gas analysers to measure many of the eco-physiological traits (credit: Kristiina Visakorpi)

The next steps in functional traits research will likely be addressing these questions: what can we generalize, if anything? How can we best account for the differences between species and systems and their responses to the environment? How can we take these differences into account in our research plans, experimental set-ups, and interpretations of our results? Even though these questions remain, our study shows that even relatively simple trait measurements can be useful in predicting species’ responses to the environment.

About the author

Kristiina Visakorpi

I got into ecology out of a love towards the natural world. The world is full of “endless forms most beautiful”, in the words of Darwin, and to get to know them more closely gives me joy. I was also inspired by the words of Carl Sagan: “we are a way for the universe to know itself.” I am inspired by the idea of accumulating knowledge about the natural world, which could potentially benefit someone at some point in time, even if that benefit is unknown to me.

I am currently a postdoctoral researcher at the Norwegian University of Science and Technology, Trondheim. My current project focuses on the invasive species, Himalayan balsam, and the eco-evolutionary dynamics that have allowed its spread across Europe. The species provides an interesting “mystery”: how has a species that occupies a relatively restricted geographic range in its native Himalayas come to dominate large parts of Europe, spanning from the Mediterranean to far above the Arctic circle?

I struggle with what I think many ecologists nowadays struggle with: appreciation towards the natural world is very difficult to reconcile with the knowledge of its current state which precipitates feelings of sadness and frustration. We are facing a biodiversity crisis, a sixth mass extinction, but decades of scientific evidence have failed to make enough of a difference. As a result, studying the natural world as an ecologist sometimes feels like taking the pulse of a dying patient, without any possibility to help. Am I supposed to simply keep studying the natural world until nothing “natural” is left anymore? The biggest barrier I see to continuing my career is the loss of meaning I find in the production of knowledge alone.

As a piece of advice to anyone who is feeling the same desperation when facing the crises of the natural world: we can do more than just measure the pulse of a dying world. In fact, I would say it is our responsibility as members of a profession which has produced so much knowledge on the drivers and consequences of these crises. There are many ways to influence, but one of the most effective ways to create societal change throughout history has been non-violent civil disobedience. Thanks to the climate movement becoming more visible across the world, environmental activist groups practicing direct action exist in almost every part of the world. Find the closest one to you. I guarantee it will shake away the apathy.

Enjoyed this blogpost? Read the research here!

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