Periodic Reporting for period 1 - WarmTraits (How does climate warming duration affect above- and belowground plant traits and overall tundra ecosystem functionality?)
Reporting period: 2021-05-01 to 2023-04-30
In the Arctic, climate change is causing tundra landscapes to warm at a rate twice that of the rest of the world. A key objective in ecology is to predict how climate warming will alter plant communities and to measure its impact on the ecosystem. Plant functional traits, such as plant height or leaf size, are measurable characteristics that reveal various strategies for competition with other plants and adaptation to climate change. For instance, variations in leaf thickness or nitrogen content have a significant influence on the carbon balance within ecosystems by directly affecting photosynthetic carbon uptake and the rates of microbial litter decomposition. As a result, plant traits establish a quantifiable connection between changes in vegetation and ecosystem processes that, in turn, have implications for the climate.
As the tundra heats up, the vegetation absorbs more carbon dioxide through photosynthesis while microbial decomposition of soil carbon increasingly releases greenhouse gases into the atmosphere. Permafrost soils hold twice as much carbon as is currently present in the atmosphere. This raises significant concern regarding whether the tundra biome will act as net source or sink of atmospheric carbon, and consequently, whether it will exacerbate or mitigate future climate change. Ultimately, this hinges on the balance between plant carbon uptake and soil microbial decomposition losses. However, plants play a dual role—they not only sequester carbon but also regulate decomposition rates through changes in their leaf and root traits. Nevertheless, our understanding of how plants respond to long-term tundra warming in terms of their functional traits remains limited.
In this project, my aim is to quantify the impact of climate warming duration on a comprehensive set of plant functional traits, both above- and belowground. To achieve this, I will take advantage of a unique opportunity to collect samples from a long-term field experiment. In this experiment, mini-greenhouses have been warming arctic tundra plots for durations of two, 12, and 22 years, respectively.
Additionally, I will examine how plant responses to warming influence essential ecosystem functions, such as carbon and nitrogen mineralization rates, using stable isotopic labelling techniques. To enhance the project's impact, I plan to organize and host a field workshop. This workshop will not only educate students in the field of trait-based functional ecology but also provide them with valuable hands-on experience in field research methodologies. In doing so, I aim to efficiently collect project data while offering students invaluable research exposure and skill development.
This project enhances our mechanistic understanding of how tundra ecosystems respond to prolonged climate warming, carrying direct implications for their feedback into the global climate system. The findings will assist researchers and modelers in refining climate change predictions, ultimately benefiting us all.
As the tundra heats up, the vegetation absorbs more carbon dioxide through photosynthesis while microbial decomposition of soil carbon increasingly releases greenhouse gases into the atmosphere. Permafrost soils hold twice as much carbon as is currently present in the atmosphere. This raises significant concern regarding whether the tundra biome will act as net source or sink of atmospheric carbon, and consequently, whether it will exacerbate or mitigate future climate change. Ultimately, this hinges on the balance between plant carbon uptake and soil microbial decomposition losses. However, plants play a dual role—they not only sequester carbon but also regulate decomposition rates through changes in their leaf and root traits. Nevertheless, our understanding of how plants respond to long-term tundra warming in terms of their functional traits remains limited.
In this project, my aim is to quantify the impact of climate warming duration on a comprehensive set of plant functional traits, both above- and belowground. To achieve this, I will take advantage of a unique opportunity to collect samples from a long-term field experiment. In this experiment, mini-greenhouses have been warming arctic tundra plots for durations of two, 12, and 22 years, respectively.
Additionally, I will examine how plant responses to warming influence essential ecosystem functions, such as carbon and nitrogen mineralization rates, using stable isotopic labelling techniques. To enhance the project's impact, I plan to organize and host a field workshop. This workshop will not only educate students in the field of trait-based functional ecology but also provide them with valuable hands-on experience in field research methodologies. In doing so, I aim to efficiently collect project data while offering students invaluable research exposure and skill development.
This project enhances our mechanistic understanding of how tundra ecosystems respond to prolonged climate warming, carrying direct implications for their feedback into the global climate system. The findings will assist researchers and modelers in refining climate change predictions, ultimately benefiting us all.
During the project, WarmTraits surveyed more than 2.000 plant individuals and performed more than 22.000 individual trait measurements on aboveground plant parts while quantifying root traits for all species present in the experimental plots. This large body of work was made possible through participation of students in two field workshops that trained the next generation of ecologists with hands-on practical experience in research methodologies and in ecological theory.
WarmTraits results demonstrate strong evidence for dynamic plant community responses across three decades of experimental warming in tundra plant communities. Specifically, I find that most aboveground traits change continuously with increasing warming duration. Some traits even shift their direction of change between short- and long-term treatment duration. For example, leaf nitrogen initially decline in the short-term but increase substantially in the long-term. Consequently, while models often rely on the assumption that trait values remain constant over time, we provide direct evidence that community trait responses to warming continue to change over time. Similarly, we find that that the importance of intraspecific trait variation – that is, the trait variation observed within species – also differ over time in more than half of the measured traits, with results suggesting that intraspecific trait variation is indeed important for overall warming responses.
Belowground, we find that plants allocate fewer resources to roots and more resources to aboveground stems and leaves in order to compete more efficiently. Root traits tend to become more conservative following warming. This is directly opposite community trait responses aboveground where plants exhibit more opportunistic and resource acquisitive growth over time.
Together, our findings show that climate warming duration is an important determinant of community trait values and their plasticity. Trait values remain predominantly plastic, at least over the three decades of this study. Manuscripts are currently in preparation for submission to high impact journals in fall 2023.
WarmTraits results demonstrate strong evidence for dynamic plant community responses across three decades of experimental warming in tundra plant communities. Specifically, I find that most aboveground traits change continuously with increasing warming duration. Some traits even shift their direction of change between short- and long-term treatment duration. For example, leaf nitrogen initially decline in the short-term but increase substantially in the long-term. Consequently, while models often rely on the assumption that trait values remain constant over time, we provide direct evidence that community trait responses to warming continue to change over time. Similarly, we find that that the importance of intraspecific trait variation – that is, the trait variation observed within species – also differ over time in more than half of the measured traits, with results suggesting that intraspecific trait variation is indeed important for overall warming responses.
Belowground, we find that plants allocate fewer resources to roots and more resources to aboveground stems and leaves in order to compete more efficiently. Root traits tend to become more conservative following warming. This is directly opposite community trait responses aboveground where plants exhibit more opportunistic and resource acquisitive growth over time.
Together, our findings show that climate warming duration is an important determinant of community trait values and their plasticity. Trait values remain predominantly plastic, at least over the three decades of this study. Manuscripts are currently in preparation for submission to high impact journals in fall 2023.
I developed a new plant functional ecology and climate change ecology themed stand for the annual outreach event “Kulturnatten” in Copenhagen. This is Copenhagen’s biggest annual one-day event, gathering ~100.000 people across 240 cultural institutions. More than 2300 people attended the Faculty of Science exhibition hall, which included my stand.
I designed and ran two field workshops in Abisko. Students involved in WarmTraits research came from France, Norway, the Faroe Islands, Poland, and Denmark, ensuring knowledge flow and competence building across borders.
I used WarmTraits field data to develop new course material for the MSc course “Terrestrial Ecosystem Processes and Global Change”, including lab exercises where students got access to a small WarmTraits dataset and were tasked to calculate and interpret vegetation responses to climate warming. I taught this course in two successive years.
I designed and ran two field workshops in Abisko. Students involved in WarmTraits research came from France, Norway, the Faroe Islands, Poland, and Denmark, ensuring knowledge flow and competence building across borders.
I used WarmTraits field data to develop new course material for the MSc course “Terrestrial Ecosystem Processes and Global Change”, including lab exercises where students got access to a small WarmTraits dataset and were tasked to calculate and interpret vegetation responses to climate warming. I taught this course in two successive years.