UNEP EEAP panel preparing 2020 update

UNEP have put together a video explaining the work of the UNEP panels that assess ozone depletion, UV-B radiation and their interaction with climate change.

The UNEP Environmental Effects Assessment Panel in New Zealand

In late September, the UNEP Environmental Effects Assessment Panel met in Alexandra, New Zealand, home of Richard McKenzie, for our annual assessment of new research into the environmental effects of ozone depletion, UV radiation, and their implications with respect to climate change.

This year Janet Bornman, Paul Barnes, Carlos Ballaré, Sharon Robinson and myself were particularly tasked with understanding how plant-level effects on biodiversity and key ecological processes scale-up to the ecosystem level.  We also focussed on crosscutting themes affecting not only terrestrial ecosystems, but mankind and the entire global environment.

A traditional Pōwhiri – Māori welcome – for the UNEP panel.

The capacity for us to address ozone depletion through the successful implementation of the Montreal Protocol, which limited the production of ozone depleting chemicals, can be seen as a flagship example of our capacity to address global environmental problems through concerted international action.  In this respect, one of the panel’s responsibilities in future reports will be to provide quantitative comparisons of how our environment differs today from what it would have looked like without the Montreal Protocol.

The World Avoided – Projection of the UV index in March 2065 with (left) and without (right) the implementation of the Montreal Protocol – from Barnes et al., (2019) Nature Sustainability 2, 569–579 https://www.nature.com/articles/s41893-019-0314-2

Do UV-radiation and blue light have a role in photodegradation affecting decomposition in Finnish forests over winter

The rate of decomposition of leaf litter on the forest floor controls the thickness of the litter layer and nutrient recycling within the ecosystem. Decomposition is well known to depend on moisture and temperature which hasten both the microbial and non-microbial breakdown of leaves following their autumn senescence.

In this paper, just accepted in Plant Physiology and Biochemistry we test the extent to which light plays a role in the decomposition of autumn leaves. Photodegradation, the process by which sunlight accelerates decomposition, has typically been considered important only in dry environments. However, Santa Neimane and Marta Pieristè found in this experiment that it can also participate in decomposition during winter and spring prior to forest canopy closure.

The paper also considers how photodegradation acts on leaves of silver birch and European beech. Using spectrally selective filters over leaf litter in the understorey of different stands in Viikki arboretum and under controlled conditions, the distinct roles of UV radiation and of blue light, which facilitates microbial colonisation could be identified.

The experiment also exploited natural UV filters found in the epidermis of leaves as a means to see whether screening UV-radiation from the mesophyll when leaves are orientated with their upper-face upwards would affect the rate of photodegradation.

This research formed part of Santa Neimane’s undergraduate thesis on Erasmus exchange in Helsinki. It complements the subsequent long-term study of decomposition in a temperate beech forest published this summer, Pieristè et al. 2019, which considers the dynamics of photodegradation in leaves of tree species spanning a continuum of succession.

Read more in the papers:

Pieristè M, Neimane S, Nybakken L, Solanki T, Jones AG, S, Forey E, Chauvat M, Ņečajeva J, Robson TM. (2020) Ultraviolet radiation accelerates photodegradation under controlled conditions but slows the decomposition of leaf litter from forest stands in southern Finland. Accepted in Plant Physiology and Biochemistry. PLAPHY5920. https://doi.org/10.1016/j.plaphy.2019.11.005

Pieristè M, Chauvat M, Kotilainen TK, Jones AG, Aubert M, Robson TM, Forey E. (2019) Solar UV-A radiation and blue light enhance tree leaf litter decomposition in a temperate forest by accelerating photodegradation rate. Oecologia, 191(1), 191-203. https://doi.org/10.1007/s00442-019-04478-x

Understanding plants’ readiness to grow beneath the snowpack

A quick start to the growing season for plants emerging from the snowpack can provide them with a fitness dividend in locations where the summer is short.

In our latest paper, Transmission of ultraviolet, visible and near-infrared solar radiation to plants within a seasonal snow pack, just out in a Special Issue of PPS devoted to plant UV responses, we measured how much sunlight plants receive under snow and how the properties of the snowpack affect the irradiance spectrum.

Changes in the spectral composition of light under the snowpack may help plants perceive the onset of spring and physiologically prepare for exposure to the full sunlight and cold temperatures they will experience once they emerge.

This field work involved spending some very cold clear days hiding in deep snowpacks! 

Range‐wide variation in local adaptation and phenotypic plasticity of fitness‐related traits

Last year, we published a database of traits from European beech provenance trials; the most extensive set of such data to be collected (Robson, Benito-Garzon et al, 2018 Scientific Data), and earlier this year provided a road map of how to use these sort of trait data in Species Distribution Model to predict responses to climate change (Benito-Garzon et al., 2019 New Phytologist). So it’s fitting that Homero Garate, working with Marta Benito-Garzon in Bordeaux in collaboration with us, should give a practical illustration of the application of these models to this data set, presented here in a new paper just out in Global Ecology and Biogeography.

Spatial projections of vertical growth (cm) for (a) vertical‐radial growth model and (b) vertical growth‐leaf flushing models

The paper entitled, Range‐wide variation in local adaptation and phenotypic plasticity of fitness‐related traits in Fagus sylvatica and their implications under climate change, quantifies local adaptation and phenotypic plasticity of vertical and radial growth, leaf flushing and survival across the species range to estimate the contribution of each trait towards explaining occurrence.

 

The place of spectral composition among cues controlling tree phenology

In this review, just out in Tree Physiology, we assess the literature researching how the composition of UV, blue, and red/far-red regions of the spectrum affect bud burst and leaf senescence  phenology.

The role of plant photoreceptors in detecting diurnal shifts in spectral composition

The effect of climate change on phenology is a strong determinant of fitness. But shifts in the timing of annual events and the polewards displacement of species ranges both have the potential to interfere with the interactive control of phenology by temperature and photoreceptor-mediate processes.  This dictates that to anticipate plant responses to climate changes, we must gain an understanding the mechanisms underlying the role of spectral composition in phenology.

These ideas and more are explored in the Tree Physiology review article, Brelsford et al., 2019: The influence of spectral composition on spring and autumn phenology in trees. https://doi.org/10.1093/treephys/tpz026

Moving Forward in Plant-UV Research

Our new and comprehensive review and perspective on the future of plant-UV research assimilates the knowledge and insight across the breadth of plant science from researchers in UV4Plants Association. We hope that it will inspire researchers in their attempts to better understand plant responses to UV radiation and to put this knowledge to practical use.

Let us know what you think! Photochemical & Photobiological Sciences, 2019, DOI: 10.1039/C8PP00526E

How can we track long-term trends in solar UV-B irradiance?

Is there potential to apply our knowledge that  plant phenolic compounds respond to UV-B radiation to infer past changes in global solar UV-B irradiance?  This is the possibility that we explore in a Perspective paper just out in Photobiological & Photochemical Sciences.

Our collaborators from the University of Bergen in Norway and University of Innsbruck intend to test the potential for us to use fossilised pollen grains to do just that. By testing whether the UV-screening phenolics in the pollen of trees growing today tracks their exposure to UV-B radiation they will try to establish a mechanistic link that will allow past UV irradiances to be revealed in cores of fossilised pollen.

In this perspective piece we formulate a model for how this approach might be put into practice.

How can we compare solar spectra with each other?

Assessing differences in spectral irradiance is at the heart of our research group’s work, and yet considering entire spectra at once is not something that is straight-forward to do. Traditionally, most research has broken-down spectra into their component regions in order to compare one light environment with another, but looking at the whole spectrum has the potential to yield much more detailed information.

Our open-access paper just out in Ecology & Evolution considers ways to quantitatively assess differences between entire solar spectrum. This approach is illustrated by tracking changes in the forest canopy through the spring and amongst stands dominated by different tree species.

The method we used, called thick pen transform, involves redrawing our spectra of interest with increasingly thick lines and then comparing their similarity. This allows the coarse and fine features of spectra to be compared, and a “Thick Pen Measure of Association” to be calculated to quantify their similarity, as illustrated above.

Using this technique, we were able to trace differences in the spectral irradiance at ground level between forest stands of birch, oak, and spruce at Lammi Biological Station in central Finland. This is the first time such fine-scale differences in the light environment due to the species, phenology, height and leaf-optical properties of canopies have been distinguished. By better understanding how light environments in forests differ we can start to better explain the factors that control species composition and ecosystem functioning in these environments.

As well as detailing the theory and methodology behind this research, the paper gives a comprehensive protocol of how to maximise the information obtained from hemispherical photos of the forest canopy. These are used to assess leaf area index and the sunlight reaching the floor throughout the year.

Read the full text at Hartikainen SM, Jach A, Grané A, Robson TM. Assessing scale‐wise similarity of curves with a thick pen: As illustrated through comparisons of spectral irradiance. Ecol Evol. 2018;00:1–13. https://doi.org/10.1002/ece3.4496

Springtime recovery of Vaccinium vitis-idaea leaves above and below the snow pack

In Arctic and alpine environments warming temperatures are expected to result in longer growing seasons and to encourage growth, but snow will melt faster and more will fall as rain. This means that the protective winter blanket of snow cover may no longer be present to hide plants from the extremes of cold that periodically occur. Whether plants can overcome this paradox to benefit from the increased sunlight and warmth above the snow, while resisting the greater fluctuations in temperature, will depend on their physiological capacity to cope with the changing conditions.

Is the paper, Solanki et al., 2018, published in a special issue of Plant Physiology and Biochemistry on UV-cross protection, we explore the ecophysiological response of Vaccinium hummocks to snow cover over the course of a year in central Finland.

Twinkle Solanki taking Dualex measurements in central Finland

We focus on the role played by UV-absorbing compounds in protection against high light and low temperature combinations as shoots emerge from under snow in the early spring.

Solanki T. et al., 2018 UV-screening and springtime recovery of photosynthetic capacity in leaves of Vaccinium vitis-idaea above and below the snow pack Plant Physiology and Biochemistryhttps://doi.org/10.1016/j.plaphy.2018.09.003