Ons 17 apr / År 42 / Nr 1 2024

Studies of ecosystems help to integrate sustainable forest management

Forestry is one of our most important industries in Sweden with a net export superior to all other industries. Our forests also fulfill an extremely important function in absorbing carbon dioxide. Conscious and sustainable forest management may counteract climate change, but in order to support the environment in the best manner, awareness of the role of nutrients is required. Biomass is removed from forests at final-felling and thinning. The purpose of thinning is to maintain high growth rate. By removing biomass the soil’s natural reserves of nitrogen and phosphorus are affected. These are important stimulants for further growth. This context is widely studied at the Swedish University of Agricultural Sciences. Nitrogen fertilization may stimulate tree growth and thereby increase carbon absorption, but may also influence biodiversity.

The Department of Ecology identifies knowledge that can be used for effective conservation and wildlife management, sustainable forestry and agricultural production. By studying the effects of modern forestry and the impact of climate changes, scientists can introduce an objective basis for decision making in the environmental field.
By studying nutrition-related issues and nutritional dynamics of the ecosystems present in our forests, we can analyse the impact that withdrawal of biomass has on growth and diversity in the forest.
However, uptake of carbon dioxide is closely related to a forest’s age. In Sweden, it takes about a decade before a newly planted forest becomes a net carbon sink. The uptake is largest for middle-aged forests, while the carbon balance of old forests is close to neutral, i.e., there is neither net uptake nor loss of carbon.

Sustainable systems for biofuel production
Energimyndigheten, the Swedish Energy Agency, finances numerous projects at the Department of Ecology, aiming to investigate opportunities to create sustainable systems for biofuel production, while at the same time promoting diversity in the forest. Riitta Hyvönen examines carbon storage and nutrients in the forest as a result of extraction of biomass.
“To minimize export of nutrients in harvested biomass, especially in conifer’s needles, is important for the next forest generation. If nutrient dynamics are disrupted, there is a risk of reduced growth. All forms of forestry affects the storing of nutrients in the soil and thus also the ability of the forest to absorb carbon dioxide, and so on. Being aware of this is a great step for sustainable forest management”, says Riitta Hyvönen.

Some impact is meaningful to promote growth
Hyvönen’s colleague Achim Grelle examines specific impacts of forest management using flux measurements.
“I am particularly interested in the atmosphere’s interaction with ecosystems. By measuring gas fluxes in the atmosphere above forests, wetlands and clear-cuts, the effect of forestry on greenhouse gas fluxes can be successfully estimated. I am concentrating on how forest management affects the ecosystem and how to manage the forest in order to improve the greenhouse gas balance. When is the best time to fell trees in order to absorb as much carbon dioxide as possible in the long run? This is an important issue”, Grelle underlines.
“Nature reserves are good for diversity. But if we want really effective carbon sinks some impact is beneficial. Clear-felling forestry yields high productivity, but during the clear-cut phase large amounts of carbon is lost from the forest soil. Selective harvest, on the other hand, is likely to enhance carbon uptake, while a comparable production level can be maintained. Still, modern felling methodology is not adapted to selective harvest, and there are many areas that could be improved. It is important to remember that the Nordic forest stands on a large carbon reservoir. Stirring the ground inevitably means that a substantial amount of carbon dioxide will be emitted”.

Creating balance for sustainability
Achim Grelle’s studies are long term and based on data from 14 monitoring stations located in different parts of Sweden. The measurements are in many cases essential for other research at the department.
Michael Freeman is studying the forest growth based on mathematical descriptions of processes and measurements. The aim is that the measurements will form the basis for long-term analysis of growth. Freeman particularly investigates trends in order to form a vision of the future of our forests and ecosystems in a changing climate.
“My studies are mostly about the value of creating balance in the entire forest system. Interventions in the forest disturb the ground, we know that. But are there any remedies to prevent this? Can we create sustainable forestry where it is possible to compensate for the imbalance caused in the ground? This is a common denominator in our entire research group here at the Department of Ecology”, Michael Freeman explains.

Facts to aid the decision process
Freeman’s colleague Joachim Strengbom focuses on ground vegetation in the forest and how it reacts to various forms of forest management but also to climate change.
“There is a conflict between the national environmental objectives concerning the ecosystems in our forests. We previously stated that fertilization is good for tree growth, which may help counteract climate change, but at the same time the process interferes with biodiversity. I examine how different species of vegetation are affected and how best to preserve these species while operating a favorable forest management”, Joachim explains.
Most of the research conducted within the Department of Ecology, including Joachim Strengbom’s research, is in one way or the other related to the national environmental targets.
“One of our most important tasks is to deliver knowledge, based on scientific grounds, that facilitate decision making”, says Joachim Strengbom in conclusion.