Kristiina Visakorpi

I am post-doctoral ecologist working at the Norwegian University of Science and Technology in Trondheim. I am interested in species interactions, and how they influence community structure, ecosystem-level processes, and evolutionary dynamics.

My current work focuses on the eco-evolutionary dynamics of the invasive plant species Impatiens glandulifera. I am interested in finding out what determines the distributional limits of the species, and what makes the species so successful on its invasive range in Europe. For this, I use a combination of field surveys, greenhouse experiments and genomic analyses.

During my previous post-doc at ETH Zürich, I studied how tolerance to environmental stress varies across seedlings of temperate tree species, and how eco-physiological traits can predict plant species’ demographic responses to warming in the Swiss Alps. During my PhD at the University of Oxford, I studied how insect herbivory changes the physiology of the host plant, and how these physiological changes further affect community- and ecosystem-level processes. For my Master’s degree at the University of Helsinki, I investigated trophic cascades in a high-arctic food web in Eastern Greenland.

Alongside research, I am a climate activist. In my experience, non-violent, disruptive actions are the most effective way to start important discussions, and to push for the systemic changes needed to bring down carbon emissions. I have been active in groups such as Extinction Rebellion, Scientist Rebellion and Stopp Oljeletinga.

Research interests

• How do evolutionary processes, such as rapid evolution and local adaptation, affect ecological dynamics?
• How do plant physiological traits affect community- and ecosystem-level processes?
• How does insect herbivory affect the host plant, and what are the ecosystem-level impacts of this?
• What should be the priorities of ecological research? What type of research is useful?
• Is ecological research reliable? Do our most influential studies replicate?
• What should be the role of ecological researchers in the times of the climate and ecological crises?

Current and previous research projects

The role of species interactions and local adaptation in determining the range limits of Impatiens glandulifera

Himalayan balsam (Impatiens glandulifera) was brought to Europe in 1839. Since then, it has spread across the continent from Southern Europe to Northern Scandinavia, replacing native plant communities. How is a species which is restricted to a relatively small geographic area in its native range able to establish and spread successfully across such a wide range of climatic and biotic conditions? I am studying the importance of local adaptation, phenotypic plasticity and enemy release in enabling the species to spread successfully.

Seedling tolerances to heat, drought and frost are correlated across temperate tree species

Most trees die as seedlings, and a large part of this mortality is caused by environmental stress, such as drought or frost. Whether there are trade-offs or positive correlations between tolerances to different climatic stressors can determine species’ survival in the rapidly changing climate. We show how stress tolerance to frost, drought and heat at seedling stage correlates across temperate tree species, but, surprisingly, is not related to the distributions of adult trees. This shows how adult distributions, especially of long-lived species like trees, might not be indicative of the optimal climate for the seedlings.

Read the article here.

Ecophysiological and morphological traits explain species' responses to climate warming

Being able to predict species’ responses to environmental change is one of the central goals of ecological research. Functional traits have often proved to be successful in this. Nevertheless, what has been often lacking is the understanding of the mechanism behind why a specific trait is related to an environmental gradient or a demographic trend. We show that both morphological and eco-physiological traits are good predictors of alpine plant species’ demographic responses to warming. Nevertheless, only eco-physiological traits explain why certain species can survive in the new climate.

Read the article here, and the related blog post here.

Community and ecosystem -level effects of insect herbivory in temperate forests

During my PhD I studied how herbivory by caterpillars of Winter moth (Operophtera brumata) affect the gas exchange and chemistry of their host plant, oak (Quercus robur).

Read about the effects of insect herbivory on oak physiology here, and here. This paper describes the effects of early-season herbivory on the late-season insect community on oaks. And in this preprint I estimate the effects of insect herbivory on the carbon cycle of a temperate forest.

The role of the wolf spider Pardosa glacialis in an Arctic food web

Trophic cascades are expected to be common in simple food webs, such as in the Arctic. We tested this by manipulating the abundance of the wolf spider Pardosa glacialis, the top predator of the arthropod food web in the Zackenberg valley in Eastern Greenland. No trophic cascade was detected, most likely because the top-down effect of the spider extends from herbivores to detritivores and other spiders.

Read about the study here.