New publication – The fate of carbon in a mature forest under carbon dioxide enrichment

Originally published in site (link).


Nature: Don’t hope mature forests to soak up carbon dioxide emissions


Globally, forests act as a large carbon sink, absorbing a substantial portion of the anthropogenic CO2 emissions. Whether mature forests will remain carbon sinks into the future is of critical importance for aspirations to limit climate warming to no more than 1.5 °C above pre-industrial levels? Researchers at Western Sydney University’s EucFACE (Eucalyptus Free Air CO2 Enrichment, see the photo) experiment have found new evidence of limitations in the capacity of mature forests to translate rising atmospheric CO2 concentrations into additional plant growth and carbon storage. The unique experiment was carried out in collaboration with many scientist over the world. The Head of the Centre of Excellence EcolChange Professor Ülo Niinemets and senior researcher Astrid Kännaste from the Estonian University of Life Sciences have contributed to data collection and data analysis of this study.


Carbon dioxide (CO2) is sometimes described as “food for plants” as it is the key ingredient in plant photosynthesis. Experiments in which single trees and young, rapidly growing forests have been exposed to elevated CO2 concentrations have shown that plants use the extra carbon acquired through photosynthesis to grow faster.


However, scientists have long wondered whether mature native forests would be able to take advantage of the extra photosynthesis, given that the trees also need nutrients from the soil to grow. This question is particularly relevant for Australia. In the first experiment of its kind applied to a mature native forest, Western Sydney University researchers exposed a 90-year old eucalypt woodland to elevated CO2-levels. “Just as we expected, the trees took in about 12% more carbon under the enriched CO2 conditions,” said Distinguished Professor Belinda Medlyn. “However, the trees did not grow any faster, prompting the question ‘where did the carbon go?’”.


The researchers combined their measurements into a carbon budget that accounts for all the pathways of carbon into and out of the EucFACE forest ecosystem, through the trees, grasses, insects, soils and leaf litter. This carbon-tracking analysis showed that the extra carbon absorbed by the trees was quickly cycled through the soil and returned to the atmosphere, with around half the carbon being returned by the trees themselves, and half by fungi and bacteria in the soil. “The trees convert the absorbed carbon into sugars, but they can’t use those sugars to grow more, because they don’t have access to additional nutrients from the soil. Instead, they send the sugars below-ground where they ‘feed’ soil microbes”, explained Professor Medlyn.


These findings have global implications: models used to project future climate change, and impacts of climate change on plants and ecosystems, currently assume that mature forests will continue to absorb carbon over and above their current levels, acting as carbon sinks. Professor Niinemets said: “What did we find? Increased uptake by the forest in elevated CO2, but not increased retention of this extra C. Instead, the extra C that was taken up was released back to the atmosphere. The future emissions could mean worse outcomes than we thought in terms of future climate, given this lack of response by nutrient-limited mature forests.”

Reference: Jiang, M., Medlyn, B. E., Drake, J. E., Duursma, R. A., Anderson, I. C., Barton, C. V., … Kännaste, A.,Niinemets, Ü., … & Crous, K. Y. (2020). The fate of carbon in a mature forest under carbon dioxide enrichment. Nature, 580(7802), 227-231. (link to full text)


Foto: Western Sydney University


Atmospheric carbon dioxide enrichment (eCO2) can enhance plant carbon uptake and growth, thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2 concentration. Although evidence gathered from young aggrading forests has generally indicated a strong CO2 fertilization effect on biomass growth, it is unclear whether mature forests respond to eCO2 in a similar way. In mature trees and forest stands, photosynthetic uptake has been found to increase under eCO2 without any apparent accompanying growth response, leaving the fate of additional carbon fixed under eCO2 unclear. Here using data from the first ecosystem-scale Free-Air CO2 Enrichment (FACE) experiment in a mature forest, we constructed a comprehensive ecosystem carbon budget to track the fate of carbon as the forest responded to four years of eCO2 exposure. We show that, although the eCO2 treatment of +150 parts per million (+38 per cent) above ambient levels induced a 12 per cent (+247 grams of carbon per square metre per year) increase in carbon uptake through gross primary production, this additional carbon uptake did not lead to increased carbon sequestration at the ecosystem level. Instead, the majority of the extra carbon was emitted back into the atmosphere via several respiratory fluxes, with increased soil respiration alone accounting for half of the total uptake surplus. Our results call into question the predominant thinking that the capacity of forests to act as carbon sinks will be generally enhanced under eCO2, and challenge the efficacy of climate mitigation strategies that rely on ubiquitous CO2 fertilization as a driver of increased carbon sinks in global forests.


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EcolChange seminar – Silvia Lotman about everyman´s right to care about nature

Seminars of Department of Botany and Centre of Excellence EcolChange

Speaker: Silvia Lotman is nature conservation expert and chairman of the board of the Estonian Fund for Nature (ELF). She studied in the Department of Botany, University of Tartu, and is now also the head of the species conservation program at ELF and leader of the LIFE project “NaturallyEST”.

Title of the talk: Estonian Fund for Nature and everyones’ nature conservation

Time: Thursday, 5. March 2020 at 14.15

Place: Tartu, Lai 40-218 (Vaga auditorium)

Summary: Silvia will give an overview of Estonian Fund for Natures’ strategic plan for nature conservation and the past, current and future plans for citizen science and everyones´ nature conservation projects.


Rights and obligations – everyman´s trade-off (pic from here)


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New publication – Population-level performance of Arabidopsis thaliana (L.) Heynh in dense monocultures

Text and pics by Susanna Vain

The tiny weedy species Arabidopsis thaliana can teach us quite a bit about agriculture, even though the species itself is not agriculturally important. Arabidopsis has played an immense role in helping us understand the molecular and/or genetic mechanisms behind plant functioning. Many such parallels have also been found in crops, hence the importance of Arabidopsis for agriculture.[1] In this particular study we were interested in using Arabidopsis to study competition on a population-level and its effects on seed yield, which is also something that could help us advance agriculture.

Plant breeding so far has focused on individual performance of plants, i.e. the best-performing individuals are selected. Farmers, however, do not pick out the best individuals, they are interested in the yield from the whole field where there are tens of thousands of plants, all growing and interacting together. This has brought discussion to alternatives – perhaps plant breeding should use group selection in which not best individuals but best groups are selected for further trials.[2] This method centers around the collective performance of plants and puts much greater emphasis on plant-plant interactions. Still, there are great gaps in our knowledge about plant-plant interactions, especially on a population-level scale.

Susanna arabidopsis 01

In this paper, the effect of plant density in two different photoperiod conditions was studied to learn how it affects the collective performance of plants. Plants were sown at five densities (17.6, 8.8, 4.4, 2.2 and 1.1 cm2 per plant) and grown either in 16 h or 12 h day length conditions. What is also relatively novel about the methodology of this experiment was that instead of small pots, quite large trays were used (44×25 cm). This ensured truer monoculture conditions – one sown population constituted minimum of 64 plants in the sparsest and 1000 plants in the densest treatment.

Surprisingly, populations across all sowing densities attained constant seed yield, which was greater for plants that grew in 16 h photoperiod treatment. This means that regardless of whether there were 64 plants, 500 or 1000 plants in a tray within a photoperiod treatment, all populations produced the same amount of seeds. Furthermore, no main effect of photoperiod treatment was found for vegetative biomass production. So, seemingly, differences in biotic and abiotic conditions did not trigger competitive responses which is usually indicated by differential biomass production (and that could have led to reduced yield as well).

Susanna arabidopsis 02

Did plants just make use of resources available to them, not minding their co-competitors at all? Not quite. Even though we found no evidence of differential vegetative biomass production, closer inspection revealed a sowing density and photoperiod treatment interaction for the average mass of 100 seeds. Plants that grew sparsely, produced seeds of similar weights in both photoperiod conditions. When sowing density was increased, the weight of individual seeds diverged in opposite directions – the average seed produced in 16 h conditions was heavier than that produced in 12 h photoperiod conditions. So, instead of varying vegetative biomass production, plants’ focus seemed to be on the seeds, which is not unexpected since Arabidopsis is a species with relatively short life-cycle (approx. 6 weeks).

In conclusion, this study showed that vegetative biomass and total seed yield are not the only things to consider when assessing the performance of plants. When plants produce the same amount of vegetative or generative biomass, then this does not automatically mean that plants have no reactions to different conditions at all. There is still a lot to be learned.

Susanna arabidopsis 03

Citation: Vain, S., Gielen, I., Liira, J., & Zobel, K. (2020). Population-level performance of Arabidopsis thaliana (L.) Heynh in dense monocultures. Journal of Plant Ecology, rtaa006, (link to full text)



Very little is known about the performance of non-agricultural plant species in monocultures, even though nearly all agricultural species have experienced the transition from multi-species environments to dense monospecific stands during the breeding process. In the light of recent work that highlighted the possibility that the weedy species Arabidopsis thaliana can offer novel insight into crop breeding, we aimed to test the effect of sowing density on group and individual performance in different photoperiod environments in A. thaliana.


We studied the performance of A. thaliana Cvi-0 ecotype. The choice of Cvi-0 was based on a preliminary experiment in which plants of Cvi-0 ecotype exhibited high competitive performance. Sowing densities used were 17.6, 8.8, 4.4, 2.2 and 1.1 cm2 per plant and photoperiod environments 12 h or 16 h of day light.


In this experiment, populations attained constant total seed yield for all densities. Some interaction effect occurred, as at high sowing density and at longer day length plants produced heavier seeds, whereas at shorter day length seed weight was negatively related to plant density. These results shed light on different strategies that annual plants can adopt when they face intense intraspecific competition, and could help to offer new perspectives for breeding crops with enhanced group performance.



[1] Gonzalez, N., Beemster, G. T., & Inzé, D. (2009). David and Goliath: What can the tiny weed Arabidopsis teach us to improve biomass production in crops? Current Opinion in Plant Biology, 12(2), 157–164.
[2] Weiner, J., Andersen, S. B., Wille, W. K.-M., Griepentrog, H. W., & Olsen, J. M. (2010). Evolutionary Agroecology: The potential for cooperative, high density, weed-suppressing cereals. Evolutionary Applications, 3(5–6), 473–479.
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EcolChange seminar – Aurèle Toussaint about traits on global scale

Seminars of Department of Botany and Centre of Excellence EcolChange

Speaker: Aurèle Toussaint is a research fellow in the Macroecology group at the University of Tartu. He is working on the functional diversity and its vulnerability in a context of biodiversity crisis. Using databases of traits for more than 80,000 species across five taxonomic groups (plants, mammals, birds, reptiles, amphibians, and freshwater fishes), he will show how the loss of vulnerable species will affect the functional diversity globally and across biogeographical realm.

Title of the talk: Global functional spectra of plants and vertebrates

Time: Thursday, 27. February 2020 at 14.15

Place: Tartu, Lai 40-218 (Vaga auditorium)



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EcolChange seminar – Jonne Kotta about climate change, human impacts and marine ecosystems

Seminars of Department of Botany and Centre of Excellence EcolChange

Speaker: Jonne Kotta is research director of the Estonian Marine Institute, University of Tartu. His research focuses on ecological investigations of marine biodiversity in benthic habitats in the Baltic Sea and the Gulf of Finland.

Title of the talk: Climate change, human impacts and marine ecosystems

Time: Thursday, 20. February 2020 at 14.15

Place: Tartu, Lai 40-218 (Vaga auditorium)

Summary: Marine ecosystems are often assumed to be highly vulnerable to ongoing climate change and introduction of exotic species. Although these stressors are completely different they both increase the risk of disrupting the pathways of energy flow through native ecosystems and result notable shifts in structure and function. The current lack of understanding of ecosystem interaction cascades, however, underscores the need for more basic exploratory research. Here I present a real data and modelling evidence from Arctic, Antarctic marine ecosystems and the Baltic Sea to show sensitivities of different environments to these global stressors. Incorporating ecosystem changes from climate change and exotic species is an important task of maritime spatial planning and marine resource management. We recently developed an online decision support tools capable of linking big data and modelling cumulative impacts of multiple stressors. Such scientific resources have huge unused potential as they can help decision-makers to select efficient mitigation actions in order to achieve environmental and socio-economic sustainability.

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EcolChange seminar – Teppo Rämä about Arctic marine fungi

Seminars of Department of Botany and Centre of Excellence EcolChange

Speaker: Teppo Rämä is a mycologist working with Arctic marine fungi since 2010. He took his PhD on the diversity and ecology of driftwood-associated fungi at University of Tromsø – The Arctic University Norway (UoT) in 2014. Since 2015, he is working with biodiscovery of antibacterial molecules from Arctic marine fungi and recently started in a tenure-track Associate Professor position in marine microbiomes at UoT.

Title of the talk: Arctic marine fungi, their ecology and potential for biotechnological applications

Time: Monday, 17. February 2020 at 12.15

Place: Tartu, Ravila 14A, Chemicum (auditorium 1019)


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New publication – Global gene flow releases invasive plants from environmental constraints on genetic diversity

Text originally posted in University of Queensland (link)

Plants that break some of the ‘rules’ of ecology by adapting in unconventional ways may have a higher chance of surviving climate change, according to researchers from the University of Queensland and Trinity College Dublin.

Dr Annabel Smith, from UQ’s School of Agriculture and Food Sciences, and Professor Yvonne Buckley, from UQ’s School of Biological Sciences and Trinity College Dublin Ireland, studied the humble plantain (Plantago lanceolate) to see how it became one of the world’s most successfully distributed plant species.

“The plantain, a small plant native to Europe, has spread wildly across the globe – we needed to know why it’s been so incredibly successful, even in hot, dry climates,” Dr Smith said.

The global team of 48 ecologists set up 53 monitoring sites in 21 countries, tagged thousands of individual plants, tracked plant deaths and new seedlings, counted flowers and seeds and looked at DNA to see how many individual plants have historically been introduced outside Europe.

What they discovered went against existing tenets of ecological science.

“We were a bit shocked to find that some of the ‘rules of ecology’ simply didn’t apply to this species,” Dr Smith said.

“Ecologists use different theories to understand how nature works – developed and tested over decades with field research – these are the so-called ‘rules’.

“One of these theories describes how genetic diversity or variation in genes embedded in DNA are produced by changes in population size.

“Small populations tend to have little genetic diversity, while large populations with many offspring, such as those with lots of seeds, have more genetic diversity.


Plantago lanceolata (pic from here)

“Genetic diversity sounds boring, but actually it’s the raw material on which evolution acts; more genetic diversity means plants are better able to adapt to environmental changes, like climate change.

“We discovered that, in their native range, the environment determined their levels of genetic diversity.

“But, in new environments, these rule breakers were adapting better than most other plants.”

The team found the plantain’s success was due to multiple introductions around the world.

Professor Buckley, who coordinates the global project from Trinity College Dublin Ireland, said the DNA analysis revealed that ongoing introductions into Australia, NZ, North America, Japan and South Africa quickly prompted genetic diversity,

It gave these ‘expats’ a higher capacity for adaptation,” Professor Buckley said.

“In Europe plantains played by the rules, but by breaking it outside of Europe, it didn’t matter what kind of environment they were living in, the plantains almost always had high genetic diversity and high adaptability.”

Dr Smith said the finding was fascinating and critical, for two crucial reasons.

“It’s important we now know that multiple introductions will mix genetic stock and make invasive plants more successful quite quickly – an important finding given invasive species cause extinction and cost governments billions of dollars,” she said.

“And secondly, research on invasive plants gives us clues about how our native plants might adapt to climate change.

There are three participating sites from Estonia, all related to Ecolchange, and managed by Aveliina Helm, Meelis Pärtel, and Lauri Laanisto.


Reference: Smith, A., Hodkinson, TR., Villellas, J., … Helm, A., Pärtel, M., Laanisto, L., … Buckley, Y. (2020). Global gene flow releases invasive plants from environmental constraints on genetic diversity. Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1915848117 (link to full text)



When plants establish outside their native range, their ability to adapt to the new environment is influenced by both demography and dispersal. However, the relative importance of these two factors is poorly understood. To quantify the influence of demography and dispersal on patterns of genetic diversity underlying adaptation, we used data from a globally distributed demographic research network comprising 35 native and 18 nonnative populations of Plantago lanceolata. Species-specific simulation experiments showed that dispersal would dilute demographic influences on genetic diversity at local scales. Populations in the native European range had strong spatial genetic structure associated with geographic distance and precipitation seasonality. In contrast, nonnative populations had weaker spatial genetic structure that was not associated with environmental gradients but with higher within-population genetic diversity. Our findings show that dispersal caused by repeated, long-distance, human-mediated introductions has allowed invasive plant populations to overcome environmental constraints on genetic diversity, even without strong demographic changes. The impact of invasive plants may, therefore, increase with repeated introductions, highlighting the need to constrain future introductions of species even if they already exist in an area.

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EcolChange seminar – Sabrina Träger about landscape-scale genetics of Primula

Seminars of Department of Botany and Centre of Excellence EcolChange

Speaker: Dr. Sabrina Träger is a post-doctoral fellow at the Department of Botany, University of Tartu. Her research focuses on landscape genetics of grassland plant species.

Title of the talk: Landscape genetic analysis of Primula veris in Estonian alvar grasslands

Time: Thursday, 13. February 2020 at 14.15

Place: Tartu, Lai 40-218 (Vaga auditorium)

Summary: Fragmentation of semi-natural habitats due to management changes is one of the major threats to genetic diversity. Recent high-throughput genotyping enables the detection of numerous genetic markers distributed over the whole genome, including regions of adaptive relevance. Here, I will present results of a landscape genetic investigation of Primula veris populations in Estonian alvar grasslands to estimate the effect of habitat deterioration on the genetic diversity and adaptive potential of this valuable grassland species.


Cowslip aka Primula (pic from here)

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Ecolchange seminar – Ivika Ostonen and Biplabi Bhattara talk about grassland warming

Seminar of Department of Geography, UT and Centre of Excellence EcolChange

Speakers: Ivika Ostonen is a senior researcher, and Biplabi Bhattarai is PhD student in the Department of Geography, University of Tartu.

Titles of the talks: “Subarctic grassland ecosystem’s response to warming (by Ivika) and “Functional adaptation of root-rhizobiome in warming grassland” (by Biplabi)

Time: Wednesday, 29. January 2019 at 16.00

Place: Tartu, Vanemuise 46-327 (JG Granö auditorium)


It´s warming alright… We have plants flowering in Estonia in January, which is unprecedented. (pic from here)

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EcolChange seminar – Mander, Pärn & Kasak reflecting about AGU2020 meeting

Seminar of Department of Geography, UT and Centre of Excellence EcolChange

Speakers: Ülo Mander, Jaan Pärn and Kuno Kasak all work at the Department of Geography, University of Tartu.

Title of the talk: AGU 2020 – Experiences, Insights and New Trends in Earth Sciences Around the Globe

Time: Wednesday, 18. December 2019 at 16.00

Place: Tartu, Vanemuise 46-327 (JG Granö auditorium)



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