Spring 2024 seminar programme
Friday 16th of February 2024, at 14:30
Direct measurement of leaf chlorophyl fluorescence and optical properties
Dr. Luis Alonso
Metsätieteiden talo, sali 332 and https://helsinki.zoom.us/j/69981525621?pwd=WCt1YUg2OGNPUjdVT3RCU2NTTDY4UT09
The fluorescence of chlorophyll in vegetation is a weak signal emitted between 650 and 850 nm that is mixed with the much more intense light reflected by the leaf, which is why active methods are commonly used (through the additional contribution of controlled artificial light) or using indirect measurements instead. So, the measurement is provided just in relative units in the first case, or the accuracy of the estimate in the second case is uncertain without proper direct validation.
The FluoWat device has been designed for the direct measurement of the fluorescence emission of leaves in vivo under natural conditions in the field with sunlight, in the lab with artificial light or a combination. It has been part of the activities supporting the preparation of ESA’s FLEX mission for the global monitoring of vegetation fluorescence.
The device consists of a small dark chamber implemented as a clip, so that the leaf can be housed inside without damaging it, with an opening to illuminate the sample by pointing at the sun (or any light source), and a sliding filter holder with a low-pass filter that blocks sunlight in the same spectral range as fluorescence is emitted while allowing the excitation light to pass through, then a spectroradiometer connected to the clip measures the fluorescence spectrum without interference from sunlight. In addition, it is possible to measure the leaf optical properties, i.e. reflectance and transmittance factors, and hence, the absorptance necessary to determine the absorbed photosynthetically active radiation (APAR), an essential parameter to properly interpret the fluorescence signal in relation to photosynthesis. Similarly, the reflectance and transmittance spectra in the visible range make it possible to determine the degree of photoprotection of the leaf and/or its chlorophyll content. A sensitivity analysis of different factors likely to affect the measurement has been carried out, such as the residual light that passes through the filter, or the effect of transients on fluorescence emission, among others. Processing methods have been developed to mitigate their effects on the fluorescence measurement, increasing the accuracy of the results. Finally, a series of experiments are presented in which the system is put to the test and that illustrate how, with the measurements provided by this new device, a better understanding of the dynamics of fluorescence emission while the vegetation adapts to different illumination changes, levels of stress and changing environmental conditions.
Autumn 2023 seminar programme
Friday 13th of October 2023, at 14:00
Optics of Photosynthesis Lab research - from hyperspectral imaging to chlorophyll fluorescence
Iiro Miettinen: Hyperspectral imaging of pine trees under drought stress and spring photosynthetic recovery
Dr. Weiwei Liu: 3D rice simulation and the importance of leaf inclination angle on remote sensing
Academy postdoc Dr. Chao Zhang: Optical signals to investigate biogenic volatile organic compound emissions to drought or heat stresses.
Dr. Steffen Grebe: Temperature response of leaf chlorophyll fluorescence
Metsätieteiden talo, sali 340
Miettinen, Hyperspectral imaging of pine trees under drought stress and spring photosynthetic recovery.
Here I present the results of my master's thesis and the first chapter of my PhD. I collected hyperspectral imagery of young Scots pine in two separate experiments conducted in the Viikki greenhouse. In the first experiment trees were subjected to a drought. In the second experiment we followed the photosynthetic recovery from cold winter to warm summer over many weeks.
Zhang, Optical signals to investigate biogenic volatile organic compound emissions to drought or heat stresses.
I will present preliminary results from a leaf-level experiment in greenhouse in the summer of 2022. We aim to investigate how the relationship between photochemical reflectance index (PRI) and biogenic volatile organic compound emissions (BVOCs) change in response to drought or heat stresses in Scots pine and English oak saplings during the peak of growing season.
Grebe, Temperature response of leaf chlorophyll fluorescence
Here we investigated the temperature response of leaf ChlF in pine (Pinus sylvestris) and birch (Betula pendula) induced in a weather chamber (+20°C → -20°C → +20°C), using a Fluowat Clip coupled to a PAM fluorometer and a spectrometer. We present the first preliminary results of changes in leaf PAM fluorescence and ChlF spectra in response to freezing temperatures. These results are discussed in terms of NPQ/PQ and PSII/PSI dynamics as well as future research directions.
Friday 29th of September 2023, at 14:00
Dr. Kaisa Rissanen: Tree physiology across varying urban environments - potential implications of stress for ecosystem services and disservices
Metsätieteiden talo, sali 340
Cities seek to resolve environmental problems and mitigate climate change impacts with ecosystem services provided by trees and other green infrastructure. Many of trees’ ecosystem services are directly related to their physiological processes such as photosynthesis or transpiration, thus, to be able to provide the desired services trees need to function normally or even optimally. The urban environments are however distinct from the natural growth environments of trees, and the unique stress factors of the urban environment such as the paved impermeable surfaces may negatively affect tree processes. Yet, other characteristics of cities such as high CO2 concentrations may benefit tree functions. These stress-inducing and beneficial environmental conditions often vary sharply across the urban mosaic of land uses, constituting potentially large differences in the ability of urban trees to function optimally and act as a solution to cities’ environmental questions.
Friday 8th of September 2023, at 14:00
Professor Olli Tahvonen (UH): Forest soil and BECCS in optimizing forestry for wood production and carbon sinks
Metsätieteiden talo, sali 340
Olli Tahvonen (University of Helsinki, Dept. of Economics, Dept. of Forest Sciences)
Antti Suominen (Aalto University School of Business, Dept. of Information and Service Management)
Vesa-Pekka Parkatti (University of Helsinki, Dept. of Forest Sciences, Dept. of Economics)
Pekka Malo (Aalto University School of Business, Dept. of Information and Service Management)
We optimize forest management to maximize the value of stands for wood production and absorbing C from the atmosphere. For this purpose, we specify a highly detailed model for wood production economy that incorporates three distinct models for forest growth along with wood revenues, harvesting costs and intertemporal objective function. C pools include above ground biomass, C in forest soil and in wood products.
Optimization of thinning and rotations are carried by reinforcement learning, a specific machine learning method. The results show that ca. 63% of C will be stored in forest soils, ca. 24% in above ground biomass and ca. 12% in wood products. The maximum total C storage range from 1.9 to 3.8 times higher compared to baseline that solely maximize the value of wood production. These increases are achieved through solutions that involve harvesting while solutions with no harvesting increase the total C stock by 0.96 to 2.4 times. Given a social price of C of €40 per tCO2, the optimal increase ranges from 1.2 to 2.4. This increase can be achieved by modest cost of €19-25 per tCO2 and without compromising the long run wood production. BECCS increases wood production and the optimal carbon stocks in living trees and forest soil are only slightly lower than without BECCS. The economic values of both C sinks and wood production depend on stand ages, and the value of C sinks can exceed the value of wood production for individual stands as well as regions with a uniform age class structure.
Our results challenge the analysis setups and findings in Skytt et al. 2021 (Environmental Research Letters), Roebroeck et al. 2023 (Science) and Peng et al. 2023 (Nature).
Key words: forest carbon, optimization, soil carbon, value of carbon sinks, BECCS, reinforcement learning
Friday 21st April, 14:00
Prof. Sari Palmroth (Duke / UH): So different yet so similar—Crown architecture, eco-physiology and growth of five Southern pine species
h332, Metsätieteiden talo, sali 332 and https://helsinki.zoom.us/j/64741303390?pwd=ZnZIVmhoNkNpM0t1UVBDTG10VjJEZz09
Pinus virginiana (Virginia pine), P. echinata (shortleaf pine), P. taeda (loblolly pine), P. elliottii (slash pine), and P. palustris (longleaf pine) are the five most common shade-intolerant pine species in the southeastern US. They have overlapping geographic ranges and can tolerate poor soil nutrition. Yet, needle length varies greatly among these species; from ~6 cm in P. virginiana to ~30 cm in P. palustris, and, together with accompanying branching pattern, may have implications to both water transport to and light interception by needles. To better understand the inherent differences in growth rates among these species, we studied their performance in a ‘common garden’ setting and explored the effect of needle length on anatomy, function, and leaf display, and how leaf traits may be reflected in hydraulic structure, canopy transpiration, biomass growth rates and allocation. The aim is to evaluate the idea that crown architecture associated with short needles is efficient in intercepting light but less so in providing water to needles, while the opposite is true for crowns of long-needle pines. Needles representing the mid-range of length may be associated with crown architecture balancing light interception and water delivery and, thus, supporting the highest growth rate.
Friday 31st March, 14:00
Dr. Charlotte Angove (LUKE): Unlocking the physiological and climatic hydrogen isotope signal from long-term bioindicators in a boreal forest
h332, Metsätieteiden talo, sali 332 and https://helsinki.zoom.us/j/65746683557?pwd=NnZoSFhseWdrbEVLeDhVbStTNWN1QT09
It is essential to comprehensively understand past climate and tree response to climate change because trees are directly exposed to current rapid, intensifying, and widespread climate change. Interpreting carbon and oxygen stable isotopes in tree rings contributes to unlocking the understanding of past climate and tree response to climate change, but greater insight could be achieved if hydrogen stable isotopes can additionally be interpreted from tree rings for such purposes. To allow for interpretation of hydrogen isotopes in tree rings to understand past climate and tree response to climate change, it is necessary to discover which aspects of climatic variability and tree physiology are represented by hydrogen isotopes in tree rings. The climatic signal of hydrogen stable isotopes is also represented by another long-term bioindicator; n-alkanes deposited to soil from plants, but there are still aspects of tree physiology that have not been accounted for during n-alkane hydrogen isotope interpretation which limits the reliability of their interpretation. This project makes steps towards unlocking the physiological and climatic hydrogen isotope signal in tree rings and it helps increase the reliability of interpreting climatic signals from n-alkanes. This project uses a unique dataset from a field survey during a growth season in a boreal forest in southern Finland, and sometimes main findings are supported by review data. The hydrogen isotope signal is traced from the climatic signal in leaf water, to the physiological and climatic signal in sugars, starches, tree rings and n-alkanes. This presentation gives the project outline and some main findings.
Thursday 16th March, 15:30
Professor in plant physiology Tracy Lawson, University of Essex, UK: Stomatal kinetics: Impacts on photosynthesis and Wi
h332, Metsätieteiden talo, sali 332 and https://helsinki.zoom.us/j/64461230979?pwd=OHh4U2h4UjloTUtibXpPZDNrVnRyUT09
Stomata, small adjustable pores on the aerial parts of plants balance CO2 uptake for photosynthesis with water loss, and their behaviour is therefore key to maintaining plant productivity and water status. Here we explore the kinetics of stomatal responses with photosynthetic demands and ways in which we can manipulate these processes for greater carbon assimilation and/or WUE. Using transgenic plants with alterations in carbon metabolism the signaling mechanism that co-ordinates stomatal conductance with photosynthesis can be examined. Using a novel split chamber developed in the laboratory we have also examined the impact of differential stomatal densities on the two leaf surface on leaf gas exchange.
Fri. 10th February, 14:00
Prof Annikki Mäkelä: Do mycorrhizal symbionts drive latitudinal trends in photosynthetic carbon use efficiency and carbon sequestration in boreal forests?
Metsätieteiden talo, sali 340 and https://helsinki.zoom.us/j/65123619840?pwd=UnZzTUQ1WXFkV01sQjdJWVlISWR0UT09
There is evidence that carbon fluxes and stocks decrease with increasing latitude in boreal forests, suggesting a reduction in carbon use efficiency. While vegetation and soil carbon dynamics have been widely studied, the empirical finding that ectomycorrhizal fungi (ECM) become more abundant towards the north has not been quantitatively linked to carbon use efficiency. We formulated a conceptual model of combined fine-root and ECM carbon use efficiency (CUE) as NPP/GPP (net primary production/gross primary production). For this, we included the mycorrhiza as gains in plant NPP but considered the extramatrical hyphae as well as exudates as losses. We quantified the carbon processes across a latitudinal gradient using published eco-physiological and morphological measurements from boreal coniferous forests. In parallel, we developed two CUE models using large-scale empirical measurements amended with established models. All models predicted similar latitudinal trends in vegetation CUE and net ecosystem production (NEP). CUE in the ECM model declined on average by 0.1 from latitude 60 to 70 with overall mean 0.390 ± 0.037. NEP declined by 200 g m-2 yr-1 with mean 171 ± 79.4 g m-2 yr-1. ECM had no significant effect on predicted soil carbon. Our findings suggest that ECM can use a significant proportion of the carbon assimilated by vegetation and hence be an important driver of the decline in CUE at higher latitudes. Our model suggests the quantitative contribution of ECM to soil carbon to be less important but any possible implications through litter quality remain to be assessed. The approach provides a simple proxy of ECM processes for regional C budget models and estimates.
30 September at 14:00
Lei Gao: Modifying MAESPA for application in a spatially two-dimensional vineyard
MAESPA, a process-based ecophysiological and ecohydrological model, combines the radiation interception and leaf physiology routines from MAESTRA and the water balance routines from SPA. In order to apply this model in a spatially two-dimensional vineyard, in this study, MAESPA was modified to set two soil buckets, one under the canopy and the other representing the inter-row bare soil. Data obtained from an eddy covariance system, sap flow system, microlysimeters, and soil moisture sensors were used to evaluate the modeled photosynthesis, transpiration, soil evaporation, and soil water dynamics.
2 September at 14:00
Sanna Sevanto: Directed plant-microbiome evolution to improve plant drought tolerance
Microbiome optimization could be a solution to improve the performance of biological systems. Yet, owing to challenges in finding and cultivating microbiomes that maintain their function in field conditions, use of microbes to improve plant productivity, crop stress tolerance or ecosystem carbon sequestration has not become widespread despite years of trials. Based on the strong interactions and interdependency of rhizosphere microbes and plants, directed plantmicrobiome evolution has been suggested as a means for developing microbiomes for these purposes. Here, this directed evolution approach was used to test whether microbiomes that influence plant physiology and improve plant performance under drought could be produced consistently. We cultivated Zea mays from seed in an artificial soil inoculated with microbiomes originating from a pine forest or a historically-droughted maize field. In the initial generation, water use efficiency (WUE) and stomatal closure point (SCP) were measured once the plants grew 10 leaves. The microbiomes of three plants demonstrating the best or worst WUE or SCP values for each microbiome source were selected for propagation to the next generation of plants, and the process was repeated for two additional generations. After three generations of directed evolution, the microbiome originating from the forest soil was able to consistently influence the SCP of the plants, while the microbiome from the agricultural field had no significant effect on SCP or WUE even if the microbial communities of best and worst planst diversified consistently. No single microbial strain was responsible for these effects, but consortia of bacteria related to the plant traits were identified using a dimensionality reduction method called Latent Dirichlet Allocation (LDA). Our results suggest that rejuvenation of agricultural soils might be critical for improved plant performance and carbon sequestration. Results on the reproducibility as well as use of these microbiomes in field conditions will be discussed.
Friday 27th May 14:00-15:00
Dr. Elisa Stefaniak. "Modelling optimal plant carbon storage under stress"
Metsätieteiden talo 332/ https://helsinki.zoom.us/j/66176963105?pwd=QUk3Yzk1UDRLK0dQR1dxL1lHSXB4dz09 (passcode 908134)
Predicting how environmental stress modifies vegetation function involves understanding how plant tolerate stress. For example, plants store non-structural carbohydrates which provide them with energy and materials during stress and expedite post-stress recovery. However, storing carbon requires an a priori action that, while having positive effects on future survival during stress, may be detrimental in the short-term by re-directing carbon from other crucial processes such as growth. I explore this growth-storage trade-off by employing a range of modelling techniques to describe the response of the optimal storage utilisation trajectory. The three methods used: optimal control theory (OCT), gap model simulation and model predictive control (MPC), allow for the characterisation of an optimal trajectory during a single stress event (OCT), the investigation of the long-term success of alternative storage strategies in a community of plants under stochastic stress (gap model) and exploring the acclimation of carbon storage to a stochastic environment (MPC). The results from these modelling exercises identify candidate storage-related allocation traits that can potentially link carbon storage strategies with other observable plant traits and processes.
Friday 6th May 12.30-14.00
Metsätieteiden talo 332/zoom: https://helsinki.zoom.us/j/62470581272?pwd=aWJjUzNpZlZaVmVWWkJSNW1VeGp3Zz09/
Prof. Jaana Bäck, Biodiversity Digital Twins
Prof. Mari Pihlatie, TBA
Prof. Teemu Hölttä, Center of Excellency in Tree Biology
Prof. Jussi Heinonsalo, The formation and dynamics of deep soil organic matter storages (DEEP-SOM)
Join Zoom Meeting
Meeting ID: 624 7058 1272
|Chao Zhang, UH
Remote sensing of vegetation photosynthesis and biogenic volatile organic compounds: recent work and Academy Research Postdoctoral Researcher project plans
|Katja Rinne-Garmston and Elina Sahlstedt, LUKE
|Ultra-high resolution carbon isotope analysis (d13C) of tree rings for tree physiological and climate change studies
Ram Oren, Duke/UH
Nitrogen in forest ecosystems
If you are interested in giving a presentation, don't hesitate to contact Jon Atherton and book your slot!
Once a month on Fridays (dates can vary!), starting 14
Zoom and/or Room 332 unless announced otherwise, Forest Sciences Building, 3rd floor, Viikki
The Wine & Science seminars provide a valuable channel of constructive criticism from a wide and multidisciplinary audience on your work. Anyone from a PhD student to a Professor can give a presentation. Wine Seminars are a great way to present ongoing work and discuss preliminary results so that the seminar has a chance to feedback on your work. Finalized studies can also be presented. The audience is usually composed of MSc and PhD students, postdocs and senior staff with diverse backgrounds, so it is good to prepare a few introductory slides.
Topics cover the measurement, characterization and modelling of physical and physiological ecosystem processes and their interactions with the environment and climate (very broad indeed!). If you doubt whether your subject fits in, don't hesitate to contact Jon Atherton.
Wine & Science seminars are a great chance to learn new things, interact with other research topics, and come up with new ideas, synergies and even collaborators! The series is also a great place for visiting scholars to give a talk.