Tribute to Martyn M. Caldwell

You can read here a tribute to the life and research career of Martyn M. Caldwell who died earlier this year, in a piece written by Paul Barnes, Steve Flint and myself for the UV4Plants special issue of Physiologia Plantarum.  In addition to his personal qualities, Martyn made a  great contribution to plant ecophysiology and in particular understanding the ecological effects of UV radiation.

Martyn M Caldwell

Long-Term Ecological Research into plant UV adaptation high in the French Alps

Santa Neimane and Twinkle Solanki recording diurnal patterns in leaf optical properties of alpine plants under UV filters

We spent the last two weeks of May 2019 at the Station Alpin du Lautaret in the French Alps, which has been designated a Research Platform for long-term ecological studies under the framework of Horizon 2020 Transnational Access – who funded our research visit through the French National Centre for Scientific Research, CNRS.


Pedro J Aphalo measures solar radiation; to better understand how reflection from the snow pack affects exposure of plants in the environment.



Our team of researchers, collaborating with José Ignacio García Plazaola and Beatriz Fernandez-Marin from the University of the Basque-Country, to study how plants response to the steep increases in UV radiation that they receive on emergence from under snow cover in spring.

You can read about our finding in Physiology Plantarum following this link: Full Text Access

By characterising the patterns of response to UV radiation in terms of the photoprotection and UV-screening of plants across a diversity of species, we hope to better understand how and why these response evolved and what environmental cues underpin their induction.

Fitness of beech seedlings growing in Finland

We tested how European beech seedlings from across Europe respond to manipulations of light and watering conditions during the growing season in Finland. Our recent paper in Trees: Structure & Function reports on differences among populations receiving combinations of drought, and sun or shade conditions, including gas exchange, water relations, and UV-abs compounds in the leaf epidermis.

Beech seedlings under drought (front) & well watered (back) treatments.

Wang F, Israel D, Ramírez-Valiente J-A, Sánchez-Gómez D, Aranda I, Aphalo PJ, Robson TM. (2021) Seedlings from marginal and core populations of European beech (Fagus sylvatica L.) respond differently to imposed drought and shade. Trees Structure and Function, 35, 53-67.


2020 update assessment of ozone depletion, UV radiation and climate change

The UNEP EEAP 2020 Update has just been published in Photochemical and Photobiological Sciences. This year the assessment includes a sectionsupplement on the implications of these environmental effects for the COVID-19 pandemic.

Meltwater accumulating on Eagle Island, Antarctica

We also make seven points related to Terrestrial Ecosystems:

  1. Changes in UV radiation and climate have the potential to alter habitat suitability for plant species in terrestrial ecosystems.
  2. Species native to Antarctic are adapted to live under the extreme conditions, but continued changes in UV radiation and climate in this environment could exceed the limits of tolerances and survival of many native species of animal and plants.
  3. Stratospheric ozone depletion affects the Antarctic climate with direct consequences for the environment of terrestrial Antarctic ecosystems.
  4. Plant responses to UV radiation are contingent on other changing environmental conditions, and these effects collectively influence crop quality and production
  5. Acclimation of plants to changes in UV radiation may depend on the adaptation of species to grow in more open or shaded environments and could lead to shifts in functional diversity as vegetative cover changes with climate change and land use.
  6. The sensitivity of pollen to UV radiation and its preservation in the fossil record make it attractive for use in reconstructing UV radiation from the geological past.
  7. Technological advances are allowing for the use of UV radiation to improve agricultural sustainability.

To find out more the open-access publication: Neale, et al. (2021) Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate: UNEP Environmental Effects Assessment Panel, Update 2020. Photochemical & Photobiological Sciences,

2021 brings two doctoral students studying sun and shade in canopy

Two PhD students in the CanSEE group will start their studies joining our Academy Project studying how climate change, altering cloudiness and atmospheric features, affects the light use of forest and crop canopies.

Santa Neimane received a grant from the Wihuri Foundation to start her project on diffuse radiation use by plant canopies. (Atmospheric Science Doctoral Programme – ATM-DP)

Santa Neimane and Twinkle Solanki recording diurnal patterns in leaf optical properties of alpine plants under UV filters

While, Baiba Matule will continue to develop her project studying how plant acclimate to short fast under-canopy sunflecks (AGFOREE doctoral programme)

Baiba Matule + Jalmar Donner harvest upper canopy leaves for analysis

Photodegradation contributes to forest leaf litter decomposition

Qing-Wei Wang and Marta Pieriste inspecting leaf-litter decomposition filters in the understorey site of a Japanese beech forest

The contribution of photodegradation to litter decomposition in a temperate forest gap and understorey

In a study recently published in New Phytologist with our collaborator Qing-Wei Wang, we found that the spectral composition of light in a forest gap and understorey through the year affected the rate of photodegradation of senescent leaf litter material across a variety of native plant species. This finding that photodegradation plays an important role in forest litter decomposition has potentially far-reaching consequences, and could partially explain the hole in the carbon budget in this ecosystem.

Wang QW, Pieristè M, Kenta T, Liu C, Robson TM, Kurokawa H (2020) Photodegradation enhances litter decomposition modulated with canopy openness in a temperate forest. New Phytologist. NPH17022

Enhanced decomposition can occur through direct photochemical mineralisation, but in temperate forests effects of increased temperature and the availability of substrates for microbial decompositions can be even more important. These actions of photofacilitation are highly wavelength dependent and the subtilties of these responses can only be identified through very large scale experimental manipulations of sunlight, as was done in this ambitious experiment.

Light after Death: Marta Pieristè’s PhD defence

Marta Pieristè successfully defended her PhD dissertation, “Light after Death: the importance of spectral composition in litter decomposition processes” on Tuesday 16th June 2020 at 10:30 a.m. EET Finland.  You can relive the PhD defence using the following video linkMarta Pieristè PhD defence

In addition to the Thesis Summary, the dissertation is composed of three published papers and one manuscript below:

  • Pieristè Neimane et al. (2020) Ultraviolet radiation accelerates photodegradation under controlled conditions but slows the decomposition of leaf litter from forest stands in southern Finland. Plant Physiology and Biochemistry. PLAPHY5920 146, 42–54.
  • Pieristè et al., (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.
  • Pieristè et al., (2020) Sunlight affects the microbial functional structure of beech leaf litter. Plant & Soil,
  • Pieristè et al., (manuscript – embargoed) The crucial role of blue light as a driver of photodegradation in terrestrial ecosystems on the global scale: a meta-analysis.
Litter-boxes in the beech forest during the decomposition experiment in Rouen.

As a joint PhD between Normandie Universite Rouen and the University of Helsinki, Marta’s Examination was be conducted by:

Opponents: Prof Laura Llorens Guasch, University of Girona (Spain) and Dr Stephan Hättenschwiler, CNRS Montpelier (France).

Pre-examiners:  Prof Christiane Gallet, University Savoie (France) and Dr Tarja Lehto, University of Eastern Finland (Finland).

Custos : Prof Kurt Fagerstedt, University of Helsinki (Finland).

President: Prof Matty Berg, Vrije Universiteit Amsterdam (The Netherlands).

To meet the requirements of the co-tutelle PhD, the defence commenced with a 50 minute presentation – followed by 20-30 minutes of questioning by each examiner in turn.

UNEP EEAP 2019 Update published

The 2019 Update on the 2018 Quadrennial Assessment by the UNEP Environmental Effects Panel assessing how climate change, ozone and UV-B radiation interact is now published in Photochemical & Photobiological Sciences.

Bernhard et al., (2020), Environmental effects of stratospheric ozone depletion, UV radiation and interactions with climate change: UNEP Environmental Effects Assessment Panel, update 2019. Photochemical & Photobiological Sciences DOI: 10.1039/d0pp90011g

The Panel met in Alexandria on the South Island of New Zealand in September-October 2019 to consider the latest research into these effects on climate, human health, terrestrial and aquatic ecosystem, materials, pollution, and biogeochemical cycling; as well as cross-cutting factors affecting all of these global concerns.

This year 2020, we will reconvene in September to consider what has been a very unusual year for ozone depletion and climate interactions in both the northern and southern hemispheres.

Sunset over Shoal Bay, New South Wales, Australia (Photo: Scott Byrne).

Craig Brelsford PhD Defence: Light quality affects leaf pigments and leaf phenology

Craig Brelsford from the CanSEE group at the University of Helsinki will defend his PhD dissertation entitled, “Light quality affects leaf pigments and leaf phenology”, on Thursday June 4th,  2020 at 12 noon EET in Finland (11 a.m. CET in the rest of continental Europe).

The defence is open to the public so you can watch the defence remotely with this link:

Or join the defence remotely with the following link:

And ask questions with this link:

Or in person, subject to some social distancing restrictions at: Porthania, Room P673.

Craig’s Opponent will be Professor Gareth K Phoenix from the University of Sheffield. Gareth is an ecophysiologist and expert on the response of plants and vegetation to climate change at high latitudes.  He will give a seminar on Wednesday 3rd June 2020 at 14:00, entitled:  Arctic Browning: extreme events causing large scale damage to arctic vegetation.
You can participate in the seminar of 3rd June using the following link:

Treharne et al., (2019) Arctic browning: Impacts of extreme climatic events on heathland ecosystem CO2 fluxes. Global Change Biology,