Burning for biodiversity in Taiga forests
Prescribed burn in Taiga forest carried out to help to encourage biodiversity. Photographer Kjell Store
Wildfires are occurring less frequently in Taiga forests across Sweden and Finland, leaving a variety of fire-dependent species at risk. With natural fires less common now than in the past, the team behind the Life2Taiga project plan to use prescribed burns to create biodiversity and suitable habitats for pyrophilic species, as Julia Carlsson and Per Folkesson explain.
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A number of species depend on the
Life2Taiga project
habitats created in the immediate aftermath of a fire, while other species rely on the deadwood that results from these events. While fires have burned naturally throughout history in Taiga forests across Finland and Sweden, they tend to occur less frequently nowadays. “We do have severe wildfires annually in Sweden, but not as frequently as hundreds of years ago,” says Julia Carlsson, manager of the Life2Taiga project. This is adversely affecting biodiversity across Taiga forests, to a point where some firedependent – or pyrophilic – species are at risk of going extinct. “If we had natural fires occurring periodically then we would have a natural forest succession, with different species present. However, we lack the natural disturbance of fire nowadays, so many Taiga forests are going into an unnatural, less favourable state, with less natural biodiversity,” explains Per Folkesson, a member of the Life2Taiga project team.
This is an issue the project aims to address by bringing back the natural disturbance of fire with prescribed burns, aiming to create biodiversity and conserve natural habitats. In a prescribed burn, a fire is started by igniting strips along a line within a clearly defined area, with rigorous safety measures in place. “We always have water hoses placed around the entire burn and we also create fire breaks. Then we ignite the fire in lines perpendicular to the wind direction,” outlines Folkesson. The intensity of a fire can be modified by changing the ignition
patterns, in line with the goal of a prescribed burn and the particular characteristics of a site. “We can change how close together these lines are, which affects the intensity of the flame,” continues Folkesson. The plan is to conduct 215 of these prescribed burns on around 3,400 hectares of Taiga forest, with the goal of creating habitats for a variety of different firedependent species. The idea is to change the structure of Taiga forests, and ensure that there is a diverse range of tree species and ages within them. “We want forests to not be too dense, but rather more open,
Melanophila acuminata
Tragosoma dipsarium
Illustration by Niklas Johansson
Illustration by Niklas Johansson
EU Research
with sunlit patches, creating warm microclimates on the ground and on lying stems. We’re also looking to maintain or increase the substrates for several different species groups, including insects, fungi, plants and mosses. So we’re talking about biodiversity in many different senses,” outlines Carlsson. The prescribed burns will be conducted in forests across Sweden and Finland, many of which have not seen a fire for long periods, beyond the historic norms. “These forests are, in most cases, in Natura-2000 areas. Some are young forests between 50-60 years old that need an initial disturbance, while others are older,” says Carlsson. Many of the forests in Sweden shaped by forestry techniques are dominated by a single tree species, often spruce or pine, while others influenced more by natural processes may have greater diversity, with a variety of species and ages. The project team are looking to conduct prescribed burns in different locations, when the conditions
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are right. “The burning season in southern Sweden lasts from the end of April to early September, it starts later in the North. It can’t be too dry in the soil or the vegetation layer, but it can’t be too moist either,” says Carlsson. Conditions can vary throughout the season, and Folkesson says this is an important consideration in deciding when to burn a forest. “Tree roots extend down into varying depths in the soil. In Sweden we may have quite thick top layers of organic soil that can burn effectively,” he outlines. “We may have very different targets in terms of how deep we want the fire to go and how hard it should burn, so how much of this top layer of organic soil we want to remove.” There is a choice here between burning early in the season, and effectively just burning the surface, or doing it later on in the year to reach greater depths. However, it’s difficult to plan too far ahead, as the weather conditions have to be right before a burn can go ahead. “We want the right
wind direction and wind speed, while we also consider the air temperature and other parameters. We have our own weather stations measuring those different values at the burning site, while we also follow the national meteorological institute’s fire weather index,” continues Carlsson. Ideally the wind should be blowing in just one direction, and a burn will be halted or called off altogether if the wind is too variable. “We might interrupt the burning if we see Geranium lanuginosum Photographer Per Folkesson
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