Workgroup and EcolChange seminar – Kaia Kask about why Australia matters

Seminar of Chair of Crop Science and Plant Biology and Centre of Excellence EcolChange, Estonian Univ of Life Sciences .

Kaia Kask is a junior researcher and PhD-student in the Estonian University of Life Sciences.

Title of the talk: Measurements in Australia: what and why?

Time: Monday, 21. May 2018 at 10.15

Place: Tartu, Kreutzwaldi 5 – D-143 (Metsamaja, Aquarium-room)

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New publication – Structural controls on photosynthetic capacity through juvenile‐to‐adult transition and needle aging in Mediterranean pines

Text by Vivian Kuusk

Mediterranean pines are known for stress tolerance as they live in harsh environment where shortage of water is very common. All pines, but especially Mediterranean ones grow and keep different looking needles while they are young or adult. Young needles are quite soft and contain mainly photosynthetic tissue and have much less supportive tissue than adult needles. The study is about finding out the advantage of juvenile needles for the tree.

We concluded that due to different needle structure there are age-dependent differences in needle photosynthetic potentials, nitrogen use efficiency and mesophyll conductance that contribute to juvenile plants early growth and establishment. The experiment clarified more deeply our understanding of structural limitations to photosynthesis. Young seedlings need favorable conditions to survive, but when the chance is present, they grow needles that are as low cost and as efficient in photosynthesis as possible. Only after proper establishment of root system and couple of shoots, more durable needles are grown.

Citation: Kuusk, V., Niinemets, Ü., & Valladares, F. (2018). Structural controls on photosynthetic capacity through juvenile‐to‐adult transition and needle aging in Mediterranean pines. Functional Ecology, DOI: 10.1111/1365-2435.13087 (link to full text)

old-father-christmas-made-with-pine-cones-vintage-crafts-and-more

Old pine-man (pic from here)

Abstract

  1. Needle photosynthetic potentials strongly vary among primary (juvenile) and secondary (adult) needles (heteroblasty) in Pinus species, but there is limited understanding of the underlying structural, diffusional and chemical controls.
  2. We studied differences in needle photosynthetic characteristics among current‐year juvenile and adult needles and among different‐aged adult needles in Mediterranean pines Pinus halepensis Mill., P. pinea L. and P. nigra J. F. Arnold subsp. salzmannii (Dunal) Franco, hypothesizing that needle anatomical modifications upon juvenile‐to‐adult transition lead to reduced photosynthetic capacity due to greater limitation of photosynthesis by mesophyll conductance and due to an increase in the share of support tissues at the expense of photosynthetic tissues. We also hypothesized that such alterations occur with needle ageing, but to a lower degree.
  3. Photosynthetic capacity per dry mass was 2.4‐ to 2.7‐fold higher in juvenile needles, and this was associated with 3.4‐ to 3.7‐fold greater mesophyll diffusion conductance, 2‐ to 2.5‐fold greater maximum carboxylase activity of Rubisco (Vcmax) and 2.2‐ to 3‐fold greater capacity for photosynthetic electron transport (Jmax). The latter differences were driven by modifications in mesophyll volume fraction and changes in the share of nitrogen between structural and photosynthetic functions. Analogous changes in photosynthetic characteristics occurred with needle ageing, but their extent was less.
  4. These results indicate that conifer foliage photosynthetic machinery undergoes a profound change from a fast return strategy in juveniles to slow return stress‐resistant strategy in adults and that this strategy shift is driven by modifications in foliage biomass investments in support and photosynthetic functions as well as by varying mesophyll diffusional controls on photosynthesis. Changes in needle morphophysiotype during tree and needle ageing need consideration in predicting changes in tree photosynthetic potentials through tree ontogeny and during and among growing seasons.

 

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Workgroup and EcolChange seminar – Ivo Voor about fertilising peas

Seminar of Chair of Crop Science and Plant Biology and Centre of Excellence EcolChange, Estonian Univ of Life Sciences .

Ivo Voor is a PhD-student in the Estonian University of Life Sciences.

Title of the talk: The field pea yield and nitrogen balance depending different fertilizer rates

Time: Monday, 7. May 2018 at 10.15

Place: Tartu, Kreutzwaldi 5 – D-143 (Metsamaja, Aquarium-room)

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New publication – Fertilising semi‐natural grasslands may cause long‐term negative effects on both biodiversity and ecosystem stability

Text by Lauri Laanisto

Community ecology was once famously described as ‘collecting stamps’ by John Lawton, as every community is so different and unique in so many ways. Therefore, instead of making generalisations, one can only study unique communities the way a collector studies their unique collection – a very post-truth-style statement from 20 years ago! However, Lawton was merely being provocative, and he actually suggests that there are indeed general laws in ecology – widespread, repeatable patterns, although not universally true in all cases.

Through the enormous bulk of ecological literature, it is very difficult to pinpoint these laws. Most of us, when publishing new results, tend to focus on the validity of the results and formulate found patterns as more or less general rules that might indeed hold unless specifically tested in other scales and places. As a result, there are a number of contradictory ideas and concepts floating around in ecological literature. Everything seems contingent.

So, sometimes little bubbles form in science, where some fundamentals have gone missing, or are discarded for some reason. The impulse to discard fundamentals might come, not from the theoretical thinking itself, but from something outside of it. For example, waste from agriculture and biotechnology, which needs to be offloaded somewhere and preferably cheaply. Combine it with the ‘balance of nature’ concept that is known not to work in ecological systems, and it might as well culminate in ‘let’s give back to nature’ type-thinking, which can result in spreading slurry in grasslands, or at its worst, a cynical approach to waste management

Our Commentary addresses several studies that have sought ways to get rid of waste by giving it back to where it originally came from – grasslands. Specifically, recent publications have recommended fertilising semi-natural temperate grasslands with nutrient residues like digestate and slurry. These studies claim that fertilising grasslands increases productivity but has no negative effect on species richness. We highlight three aspects that should be considered before fertilising diverse grassland communities, which are based on fundamental ecological knowledge and long-term experiments.

Everything is not necessarily contingent after all …

/This blog post was originally written and publised in JAPPL blog/ (link)

Citation: Melts, I., Lanno, K., Sammul, M., Uchida, K., Heinsoo, K., Kull, T., & Laanisto, L. (2018). Fertilising semi‐natural grasslands may cause long‐term negative effects on both biodiversity and ecosystem stability. Journal of Applied Ecology, DOI 10.1111/1365-2664.13129: (link to full text)

800px-laelatu_puisniit

Laelatu wooded meadow in Western Estonia: one of the most diverse semi-natural grasslands in the world [Image by Margus6 va Wikimedia Commons]

Abstract:

  1. Some short‐term experiments in applied ecology and agricultural research have demonstrated that nutrient applications in semi‐natural grasslands can maintain productivity and will not result in the decrease of plant species richness. Such findings may have an impact on management choices and quality of valuable plant communities, and therefore, further discussion of this topic is necessary.
  2. We highlight three aspects regarding the management suggestions in grassland communities with high biodiversity: (1) short‐term study results may not reflect potential long‐term changes; (2) broad range of grasslands may respond to disturbance in site specific ways; and (3) practical advices should contain careful consideration of existing ecological literature regarding grassland management and sustainable biodiversity.
  3. Synthesis and applications. Considering effects of fertilisation on biodiversity, we argue against nutrient application to semi‐natural grasslands. Biodiversity supports the resilience of grassland ecosystems and maintains a stable biomass yield. Current short‐term experiments are good indicators about the need for a long‐term experiments and meta‐analysis for detailed understanding of ecosystem functions in different types and areas during global change.
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Workgroup and EcolChange seminar – Ragnar Viikoja about wheat stress

Seminar of Chair of Crop Science and Plant Biology and Centre of Excellence EcolChange, Estonian Univ of Life Sciences .

Ragnar Viikoja is a PhD-student in the Estonian University of Life Sciences.

Title of the talk: The impact of stress on the yield of wheat in different farming systems

Time: Monday, 23. April 2018 at 10.15

Place: Tartu, Kreutzwaldi 5 – D-143 (Metsamaja, Aquarium-room)

ukr-jitnitsa

Highly stressful (just a single plant species has survived!) wheat landscape in Ukraine (pic from here)

 

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Workgroup and EcolChange seminar – Dimitrii Krasnov about forest soil heterogeneity

Seminar of Chair of Crop Science and Plant Biology and Centre of Excellence EcolChange, Estonian Univ of Life Sciences .

Dimitrii Krasnov is a junior researcher and a PhD-student in the Estonian University of Life Sciences.

Title of the talk: Spatial heterogeneity of the soil in mixed forest

Time: Monday, 9. April 2018 at 10.15

Place: Tartu, Kreutzwaldi 5 – D-143 (Metsamaja, Aquarium-room)

dmitrii

Nightside steampunk soil profiling (photo from Dmitrii´s facebook page)

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New publication – Shifts in tree functional composition amplify the response of forest biomass to climate

Text from emu.ee news

The scientist of Estonian University of Life Sciences involved in a study demonstrating that drought-induced changes in forest composition amplify effects of climate variability on forest carbon gain

Healthy forests play a key role in global ecosystems as they contain much of the terrestrial biodiversity and act as a net sink for atmospheric carbon. As climate change affects the forests, so do the forests affect climate change. The species composition of forests is changing due to climate change-induced shifts in rainfall and temperature and this causes more dramatic alterations in forest productivity than climate effects alone, according to a collaborative study of scientists of University of Florida, Estonian University of Life Sciences and Princeton University published in Nature.

The result of the means that forests facing global change are already starting to look different, but more importantly, it means the ability of those forests to soak up carbon is being altered as well, which could in turn bring about further climate change.

The study was based on forests of eastern United States, but the results can be generalized worldwide to natural forests and multi-species moderately managed forest where species composition is not controlled. “The changes we documented are easily blurred by other disturbances, which is probably why nobody had previously documented them. Without a long-term dataset with millions of trees, we would have been unable to detect these changes” said Prof. Ülo Niinemets, the scientist involved from Estonian University of Life Sciences.

The team based their findings on systematic forest inventories of trees in the eastern U.S. from the 1980s to the 2000s. The team looked specifically at forest biomass, tree species composition, and climate variability. The researchers found that decades of changes in water deficit have reduced forest biomass, leading to an increase of abundance of tree species that are more tolerant to drought but slower-growing. This shift results in significant changes in forest species composition with their accompanying ecological effects and, moreover, affects the capacity of forests to store carbon.

Forests are affected by other human activities such as farming or logging, and many are in a stage of ecological succession with lower biomass compared to mature forests. This history of disturbance made the researchers’ analysis challenging. To solve this, researchers compared forests on the basis of their age. “We compared forests in the 1980s of a given age (for example, an 80-year-old forest) to forests of the same age in the 2000s,” said Niinemets. “In areas where the climate got wetter, our analysis showed increases in biomass over the two decades, whereas in the areas that got drier, there were decreases in biomass. When we look at the eastern U.S. as a whole, there was an overall trend towards a drier climate from the 1980s to the 2000s, and therefore the overall effect of climate over the two decades was to reduce forest biomass.”

Drought-tolerant tree species tend to allocate more carbon to fine roots and less to their leaves and woody parts that would sequester more carbon. Niinemets  said that although they expected an increase in drought-tolerant tree abundance would prevent biomass losses triggered by water deficits, the opposite appears to be true. “Functional shifts amplified the effects of climate by making forest biomass more responsive to drying or wetting,” he said. “In hindsight, this makes sense, because drought-tolerant species tend to be slow growing. So, if drought causes a shift towards more drought-tolerant species, biomass will decline compared to forests dominated by fast-growing, drought-intolerant species.”

Overall, the study shows that forest biomass and tree species composition and their combined impact on carbon storage are affected by climatic variability on a sensitive and short timeline — just a few decades. “We are confident that our findings on climate-driven changes in species composition and resulting biological controls on forest productivity will stimulate further research into relationships between species composition, ecosystem function, and climate variability.”

Citation: Zhang, T., Niinemets, Ü., Sheffield, J., & Lichstein, J. W. (2018). Shifts in tree functional composition amplify the response of forest biomass to climate. Nature, DOI: 10.1038/nature26152 (link to full text)

Abstract:

Forests have a key role in global ecosystems, hosting much of the world’s terrestrial biodiversity and acting as a net sink for atmospheric carbon. These and other ecosystem services that are provided by forests may be sensitive to climate change as well as climate variability on shorter time scales (for example, annual to decadal). Previous studies have documented responses of forest ecosystems to climate change and climate variability, including drought-induced increases in tree mortality rates. However, relationships between forest biomass, tree species composition and climate variability have not been quantified across a large region using systematically sampled data. Here we use systematic forest inventories from the 1980s and 2000s across the eastern USA to show that forest biomass responds to decadal-scale changes in water deficit, and that this biomass response is amplified by concurrent changes in community-mean drought tolerance, a functionally important aspect of tree species composition. The amplification of the direct effects of water stress on biomass occurs because water stress tends to induce a shift in tree species composition towards species that are more tolerant to drought but are slower growing. These results demonstrate concurrent changes in forest species composition and biomass carbon storage across a large, systematically sampled region, and highlight the potential for climate-induced changes in forest ecosystems across the world, resulting from both direct effects of climate on forest biomass and indirect effects mediated by shifts in species composition.

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