Research

How boreal forests and other boreal ecosystems work?

How climate change affects boreal forests?

How environment affects the physiology and photosynthesis of an individual tree?

What are the effects of forests on climate?
 

Researchers and infrastructure working

Due to climate change, for example, the winters of boreal areas will become milder and we can expect changes in the strength, duration and frequency of dry spells. These factors have important impacts on the growth and metabolism of trees and other plants. On the other hand, trees contribute to the climate by absorbing atmospheric carbon, by transpiring water, by participating to cloud formation and by reflecting radiation from the surface of the planet. In addition, forest actively store a huge amount of carbon in the tree trunks and forest soil.

Our research concentrates on the role of vegetation in the fluxes of energy and matter in and between forests, atmosphere and water bodies. We also aim to understand the functions and responses in detail on tree level. We work in a multidisciplinary way, as our group consists of forest scientists, physicists, chemists and environmental scientists. This is also reflected in our wide range of research themes presented below.   

We combine modelling, intensive field measurements and laboratory experiments. Our main study sites are the three Stations for Measuring Forest Ecosystem-Atmosphere Relations (SMEAR I, SMEAR II and SMEAR III), operating since 1991 (SMEAR I).

 

Research themes

In tree physiology, we concentrate on studying the dynamics and processes of a single tree. The processes ongoing in a tree are for example photosynthesis and carbon fixation, water transpiration, transport of sugars, and production of secondary metabolites, not to forget the growth and nutrient scavenging happening in the roots. These processes are strongly interlinked in whole tree dynamics, but at the same time they respond to different variables in the environment. For example, photosynthesis depends mostly on light and temperature, whereas water uptake and transpiration are also regulated by the amount of available water in the soil.

To achieve better understanding on the tree physiology, we measure photosynthesis and forest and tree carbon exchange, water transport, emissions of secondary metabolites called volatile organic compound (VOCs) as well as O3, NOx, NO emissions, and the root dynamics.

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Process-based growth models based on carbon balance has been our core research activity since early 1980´s.

The forest modelling group

  • develops theories and models of tree function, structure, and growth,
  • applies these to questions relevant to forest management under changing environmental conditions and alternative management objectives.

The work employs a wide range of advanced mathematical, computational and numerical methods and is carried out in close collaboration with empirical scientists and users of the results. Applications of the models include predictions of timber yield and quality, growth of heterogeneous stands, large-scale effects of climate and weather on productivity and carbon fluxes, and a visual stand simulator for research and teaching (PuMe).

Read more on the Forest modelling group website

Soil plays an important role in the sequestration of atmospheric carbon and regulating the ecosystem water balance. Soil is also a substantial storage of organic nitrogen, an important limiting factor for biomass growth. Soil carbon and nitrogen pools are intimately linked, and changes in these pools may have a significant impact on ecosystem productivity and to the radiative balance of the atmosphere. Soils are identified as sources of several trace gases, such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) as well as biogenic volatile organic compounds (BVOCs) and volatile organic nitrogen (VON), which have a strong role in the climate change, air quality issues and tropospheric chemistry.

The aim of the soil studies is to quantify and understand the processes underlying the material and energy fluxes in the soil and between the soil and the atmosphere. We are studying the budgets, fluxes and processes of carbon, nitrogen and water within boreal ecosystems with a multitude of measurement techniques (e.g. chambers, gas gradients and eddy covariance). We also work with process-based modeling of carbon, nitrogen and water cycling within the soil and the whole ecosystem. Moreover, we use molecular biological techniques to study the effect of microbial communities, especially ectomycorrhiza, on soil processes.

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Viikki Urban Tree Laboratory is our shared research effort with Helsinki City Public Works Department and other collaborators. It aims to find ways to provide adequate underground resources for the whole life-span of urban trees in intensively built areas that are challenging growing environments for trees.

The project aims to find suitable soil volume and composition in the local climate and to develop street planning and construction practices to be more favourable for trees. This way they could provide a full amount of ecosystem services for the community. Research setup, built in 2003 in Viikki, Helsinki, follows continuously tree water use, stem diameter variation and growth along with above and belowground variables  (light, temperature, soil moisture and soil gas concentrations). The collected data has been used to assess and model urban water and carbon cycling and to derive practical construction and tree care recommendations.

Even though terrestrial and aquatic parts of ecosystems are often studied separately, they are closely connected. For studying the functioning of the carbon cycle, it is necessary to understand how carbon enters and leaves the soil. Globally, the loss of terrestrial organic carbon to rivers is equivalent to 10 % of the net ecosystem production, few streams and rivers have been studied for CO2 fluxes.

We yield new information about carbon transfer in terrestrial-aquatic continuum on landscape level by combining eddy covariance method and CO2 concentration measurements in lake and stream waters and in the littoral zone. We examine the carbon dynamics on both interannual and seasonal scales and pay special attention to the time periods following special weather events.

Our study sites are located at lake Valkea-Kotinen ICP integrated monitoring area in Southern Finland (TransCarbo) and in lake Kuivajärvi at Hyytiälä Forestry Field Station (Vesihiisi). These projects aim at closing the carbon balance of forest and lake at landscape level including both  inorganic and organic parts of carbon cycle.

Our research is dealing with the effects of disturbances on the biogeochemical cycles in boreal and sub-arctic forests in the circumpolar region. Our multidisciplinary research team consists of forest ecologists and soil scientists and we are collaborating with microbiologists and atmospheric scientists.

Climate change is predicted to increase the vulnerability of forests to various disturbance effects resulted from e.g. drought events, forest fires and permafrost melting. Currently we are study the effects of disturbances (fire, mammalian herbivores (reindeer), wind, etc.) in several projects.

For more information visit the Disturbances and biogeochemistry group web page.