Forests partnership programme with the University of Helsinki

Eduardo Maeda, University of Helsinki

Juha Aalto, University of Helsinki

Steven Hancock, School of GeoSciences, University of Edinburgh

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The University of Edinburgh and the University of Helsinki are collaborating in a research project focusing on examining and quantifying the effects of forest management practices on microclimate in northern forests. Started in January 2021, the project’s aim is to understand forest management’s role in modifying microclimate and buffering the effects of climate warming.

Microclimate is closely linked to organisms’ performance, thus directly affecting the maintenance of biodiversity, ecosystem services and wellbeing of human population. Forestry is an important sector in both Scotland and Finland’s economies, and although the management of forests in Finland and Scotland follow established protocols, there is a debate on how management or reforestation practices can be improved for optimizing timber production and maximizing carbon sequestration, while preserving recreation areas. Scotland’s Forestry Strategy 2019–2029 includes ambitious plans for the replanting of forests in the country in the coming years, with strong focus on sustainable development. Finland, in turn, is one of the most forested countries in Europe, where forest management has relied on even-aged management for the last 70 years. Starting 2014, continuous cover management has been applied as an option to increase ecological functions of forests. Nonetheless, the implications of these upcoming changes in forest management strategies for climate change mitigation are not fully understood. For instance, although climate change mitigation is a key component of Scotland's Forestry Strategy 2019–2029, the plan focuses mainly on optimizing carbon sinks. However, studies show that carbon-centric approaches alone cannot comprehensively account for the negative effects of global warming.

The project has focus areas in both Scotland and Finland, where field plot sites are being established to study microclimate with high-resolution temperature and soil moisture loggers. In Scotland, the experiments will be set up in forests with different canopy structures, while in Finland the focus will be on comparing even-aged and continuous cover forests. Forest structure variables will be mapped using terrestrial and airborne laser scanning data. Together the data will be analysed to acquire understanding of microclimate spatial patterns and to model the impacts of forestry strategies in climate change mitigation.

Michael Boy, University of Helsinki

Paul Palmer, School of GeoSciences, University of Edinburgh

The Universities of Helsinki and Edinburgh are collaborating on a research project that is focused on improving current understanding of whether the radiative properties of clouds result in a net cooling or warming of Earth’s surface. This PhD project, started in January 2021, will examine how aerosols formed from gases emitted by forests can modify the microphysical properties of clouds and subsequent impact climate. 

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Increases in gross primary production (GPP) and temperature are linked to increased emissions of biogenic volatile organic compounds (BVOCs). Oxidation of these elevated atmospheric BVOCs result in an increased formation of secondary organic aerosols (SOA). Under certain environmental conditions these aerosols can result in cloud condensation nuclei (CCN), which can be activated to form cloud droplets. How effective a particle can act as CCN, at given water vapor supersaturation, depends on the size and the fraction of soluble matter it contains. The variability in particle size typically exerts the strongest influence on the variability of particles to be able to act as CCN. Increasing the number concentration of CCN can lead to formation of more cloud droplets, which, in turn, have smaller size. The increase in cloud droplet number concentration increases the cloud optical depth, which increases in the cloud albedo making clouds appear whiter. The indirect effects of aerosols result mainly from their ability to act as CCN, through which aerosols change the size and chemical composition of cloud droplets and subsequently cloud optical properties, their lifecycle and radiative forcing that eventually affects GPP and temperature thereby closing the feedback loop.

This project will study the processes that govern this feedback loop over the Amazon rainforest and over Eurasian boreal forests. Isoprene is the dominant BVOC emission from tropical rainforests and monoterpenes are the dominant BVOC emission from boreal forests. The contribution of BVOCs to SOA formation and their growth into CCN can be larger over boreal forests compared to tropical rainforests. This is due to the oxidation of monoterpenes producing substantially more low-volatility organic molecules than isoprene oxidation, which are crucial in the formation of aerosols. This study will link the processes that control SOA formation over contrasting forest ecosystems and quantify the impact of these aerosols on the concentration and distribution of CCN and their potential to be activated to form cloud droplets. This will improve quantitative understanding the radiative properties of clouds, which poses the single largest source of uncertainty within the total global radiative forcing.

Mathew Williams, School of GeoSciences, University of Edinburgh

Annikki Mäkelä, University of Helsinki

Jouni Pulliainen, Finnish Meteorological Institute

Climate change is occurring most rapidly at high latitudes, which are regions with large C stocks in soils and extensive forest cover. But the response of boreal forests to climate change remains poorly understood. Some of the key uncertainties are related to below-ground allocation and respiratory losses of carbon. While ample sources of different types of environmental and ecosystem data are becoming available, the data need to be integrated and interpreted with models to provide complete ecosystem analyses, and to underpin predictions.  This project will test alternate representations of processes of forest C balance contained in models from Finland and the UK. Testing will use rich sets of observations from field sites at Sodankylä and Hyytiälä in Finland and Harwood Forest in the UK, supplemented by targeted new measurements. By using Bayesian calibration processes, the research will include uncertainty in parameter estimation. This uncertainty can be propagated into forecasts of forest C cycling, and C cycle climate sensitivity. The research will determine the role of process uncertainty in determining future C sources and sinks in high latitude forests to guide future research. The modelling will be used to explore the interactive role of climate change, management (e.g. harvest frequency) and disturbance on C storage.

The research project addresses a significant research challenge around climate change impacts on forests that is a focus of both Universities. This work will have value for both the UK and Finland in supporting land use planning for different climate scenarios, and international reporting on C for the United Nations. The work will also have value at landscape scale in supporting forest industry and land managers. The originality of the work builds on the complementary skills from both countries in using Bayesian approaches to link multiple data time series, both in situ and from earth observation, with models of ecosystem C cycling to analyse highly dynamic, managed forest systems.

Diana Jerome (https://dianakjerome.wixsite.com/home)

Dr Isla Myers-Smith (https://teamshrub.com/), School of GeoSciences, University of Edinburgh, 

Dr Anna Lintunen (https://researchportal.helsinki.fi/en/persons/anna-lintunen), Institute for Atmospheric and Earth System Research / Forest Sciences, University of Helsinki

Dr Lorna Street, School of GeoSciences, University of Edinburgh

Prof Teemu Hölttä, Institute for Atmospheric and Earth System Research / Forest Sciences, University of Helsinki

This PhD project will examine the physiological responses of shrubs to environmental change in tundra, sub-arctic and boreal ecosystems testing the climate sensitivity of shrub growth from the boreal forest to Arctic tundra.

High-latitude ecosystems are warming twice as fast as the global average and are considered to be especially sensitive to climate warming. Concurrent with warming, the expansion of shrubs and trees across high-latitude ecosystems is one of the most dramatic ecological manifestations of climate change. Yet, the climate sensitivity of shrubs across ecotones from the boreal forest to Arctic tundra and the sensitivity of shrubs to drought and frost is under studied.

Changes in shrub cover influences nutrient cycling, carbon storage, and the reflectance of energy at high latitudes, thus creating climate feedbacks that could affect the planet as a whole. Even in boreal ecosystems, carbon uptake by shrubs (and other ground vegetation) can make up 10 – 20% of the whole ecosystem carbon uptake. In addition to these direct effects, shrubs also provide a buffer between air and soil affecting soil temperature and moisture, which are crucial factors in many ecosystem processes, including decomposition and tree water usage.

Climate warming, winter thaw events and resulting frost damage and changes to soil moisture could be influencing boreal shrub growth. However, our understanding of the varying factors underlying changes in shrub cover and growth in high-latitude ecosystems is still limited. And boreal forest shrubs have suggested to have much lower climate sensitivity of growth relative to tundra shrubs.

The research will reveal how sensitive shrubs in these ecosystems are for drought and frost stress. This PhD project will focus on the ecophysiology and structure of boreal and tundra shrub species and their environmental responses, and compare them between three Northern biomes: the boreal forest, the latitudinal treeline ecotone and Arctic tundra.

The project will involve the analysis of existing dendroecology data, field campaigns to collect new data, research in an established common garden experiment and experiments in controlled laboratory and field conditions. The results will inform Earth system models to improve future projections of climate change impacts in high latitudes particularly from the boreal forest to Arctic tundra.