Linköping University | Department of Physics, Chemistry and Biology Bachelor thesis, 16 hp | Educational Program: Biology Spring term 2021 | LITH-IFM-x-EX—21/4006--SE
Effects of forest management on carbon
sequestration
Rasmus Viding
Lars Westerberg Karl-Olof Bergman
Contents
1 Abstract ... 1
2 Introduction ... 1
3 Material and method ... 2
4.1 Carbon sequestration in production forests and old growth forests ... 3
4.1.1 Above ground carbon ... 3
4.1.2 Below ground carbon ... 4
4.2 Carbon stocks in production forests and old growth forests ... 5
4.3 Effects from harvesting ... 7
4.4 The debate climate in Swedish newspapers ... 13
5 Conclusions ... 16
6 Societal considerations ... 17
7 Acknowledgments ... 18
1 1 Abstract
The warming of our planet is a direct consequence of anthropogenic emissions with carbon dioxide as the main driver. A need to mitigate carbon emissions is urgent and forests can be a part of the solution since they sequester and stock carbon during their lifetime This study has shown that production forests can sequester carbon to a higher degree since they consist of younger trees which are better at sequestration than older trees. But the study also show that older forests keep sequestering carbon and might not be carbon neutral as previously thought. Old growth forests contain higher carbon stocks than younger production forests since they often remain unmanaged and can continuously accumulate carbon into living and dead biomass as well as the soil. Production forests also accumulate carbon, but it is not nearly the same amount as in old growth forests. With regard to meeting the 1,5-degree goal set by the IPCC, i.e., cutting emissions with half until 2030 and having net zero carbon dioxide emissions until 2050. Harvesting with clear-cutting was found to be worse compared with harvesting at a lower frequency which causes less emissions but still supplies wood products to the industry. The result also show that we must protect more old growth and unmanaged forests that can sequester and stock carbon longer to be able to succeed with the 1,5-degree goal. The debate climate in Sweden is heated and opinions often differ. The difference may depend on the time frame or how results are interpretated.
Keywords: boreal forests, carbon stocks, carbon mitigation, carbon sequestration, clear cutting, forestry, managed forests, old growth forests.
2 Introduction
Global warming is one of the biggest problem’s humanity must face and one main factor which affects the global warming is anthropogenic release of carbon dioxide (Rogelj et al., 2018). We have until 2050 for carbon dioxide emissions to be net zero to be able to keep within the 1,5-degree goal at year 2100 and we must cut our emission with half until 2030 (Rogelj et al., 2018). Forests are already mitigating carbon dioxide emission, about one third of the global CO2 emission are captured by forests every year (Keeling et al., 1996; Pan et al., 2011). These forests act as carbon sinks when the atmospheric carbon dioxide is sequestered, the carbon accumulates in living biomass, deadwood and in soil (Zhou et al., 2006).
Different kinds of forests can act as a sink in different ways. Managed forests usually consist of younger trees that can sequester carbon to a higher rate than old growth forests. However old
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growth forests store more organic carbon in living and dead biomass (Cooper, 1983; Vitousek,1991; Kurz et al., 2013).
Forests also release carbon to the atmosphere mostly through heterotrophic respiration in the soil and litter from trees (Townsend et al. 1995). Disturbances such as harvest, insect outbreaks and fires can change forests from a sink into a source, meaning that the forests will contribute with more greenhouse gases to the atmosphere (Kurz et al., 2013).
In this literature review I will (1) compare how methods for boral forest management differ in climate mitigation, and (2) compare how mitigation by active forest management differ from unmanaged/reserves, and (3) compare how different harvesting methods differ and how they affect the forest and climate. This study will mostly focus on boreal forests since that is the dominating forest type in Sweden, some sources may be on different forest types, but they are still included because the results can be applied for boreal forests or will be at least similar. I will also review the heated debate regarding forestry in Sweden and the arguments behind it that is ongoing right now. As new research and new studies emerge regarding forestry and climate mitigation, this research also reach newspaper reporters and through the newspapers the information can reach a broader audience than just scientists or people interested in the subject. This review will cover some of the largest and most discussed debate articles from Sweden’s largest newspapers in recent years. This study will also try and show why opinions differ even among the scientific community.
3 Material and method
For this review, Google Scholar was the foremost used scientific search engine to find references. UniSearch which was accessed through Linköping university’s library website was the second search engine used. This one was used when no access was available from Google Scholar. Keywords was used to find the appropriate articles. The most used keywords were old growth forests, carbon mitigation, carbon sequestration, forestry, boreal forests, managed forests, clear cutting, and climate change. All these keywords were also used in different combinations with each other to get different results. Debate articles was found by googling, with tips from the supervisor of this study, and looking in the most read Swedish newspapers and seeing if they fit the subject. All figures and tables used in this study were taken from the sources with permission from the author or the publishing company.
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4.1 Carbon sequestration in production forests and old growth forests
Carbon sequestration can be described as the process when atmospheric carbon is assimilated in trees or other vegetation for long periods of time. This process contributes to mitigating the climate change by removing atmospheric carbon (Luyssaert et al., 2007). The sequestered carbon ends up in living biomass, soil and eventually deadwood and harvested wood products (Pukkala 2014; Heinonen et al. 2017). This process is what makes boral forests act as a sink, meanwhile autotropic respiration, respiration of heterotrophs in the decomposition processes, forest fires and harvest releases carbon back into the atmosphere. If these processes outweigh the sequestration the forest become a source instead (Kurz et al. 1996; Cairns et al. 1997; Li et al. 2003). One of the most debated questions is if forests should be managed in a way that maximizes their climate mitigation by replacing fossil fuel dependent industries such as production of steel and cement. Or if forest instead should be managed to a very small degree which would let carbon accumulate in living biomass, dead organic matter, and soil (Liu and Han., 2009; Pukkala 2014; Heinonen et al. 2017). Scientists are still divided in which of these methods are the most effective in climate mitigation.
4.1.1 Above ground carbon
The rate of sequestration is usually higher in young to middle-aged trees and decline with age and since production forests consist to a higher degree of younger trees than old growth forests, they are said to be more effective at mitigation of the climate change (Seely et al., 2002; Paw et al., 2004; Zha et al., 2009; Coomes et al., 2012; Kurz et al., 2013). However, there is a debate among researchers about when during the tree’s maturation this decline start to become equal or even exceed the sequestration (Buchmann and Schulze, 1999). There are also some researchers that disagree with this picture, they argue that old growth forests continue to sequester carbon at a higher rate than previously thought. It may not be as high as younger forests, but it is still higher than being carbon neutral or even a carbon source as some researchers claims. If you also take into consideration that old growth forest have more living biomass and more dead organic carbon the old growth forests will surpass the production forests in how much carbon the forest contains (Knohl et al., 2003; Paw et al., 2004; Luyssaert et al., 2008; Colombo et al., 2012). Because old growth forest contains more deadwood and litter, the decomposition rate in older forests is usually higher than in the younger managed forests. But that does not necessarily mean that old growth forest are larger carbon sources than production forests. Since the trees that die and start decomposing in old growth forest are usually larger and that means it takes a longer time for them to decompose, it can take decades for them to
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decompose and release carbon back into the atmosphere (Fontaine et al., 2007;Luyssaert et al., 2008). Meanwhile (Pukkala, 2018) has shown that pine trees that die at 10 cm dbh (diameter at breast hight) had two times the decomposition rate when they die than pine trees at 50 cm dbh. The decomposition rate can be affected by such things as temperature, moisture and soil that can speeds up the process (Noormets et al., 2015). In production forests trees are harvested for different uses such as wood for construction, biomass is burned for energy, cellulose and pulp can be used to replace oil-based products (Pukkala, 2018). Depending on what kind of harvest technique is used, the forest is affected in different ways, more about the effects from harvesting in section 4.3. After harvesting new trees are planted and as previously mentioned younger trees sequester carbon to a higher degree. But harvesting also lead to a release of carbon making the forest a source for a while. Researchers are not in agreement of how long and if the forest are a source, research from (Davis et al, 2009) shows that forests become a source for a short period but over 55 years there was no difference between harvested and unharvested area, respiration also declined with the harvest which made the forest carbon neutral. But (Davis et al, 2009) also show that during clear-cutting, carbon stocks in the forest that was studied declined with 33% compared with an un-harvested forest. While harvesting methods like single tree selection and diameter-limit cuts did not affect the carbon stocks as cutting did. Meanwhile a clear-cut boreal pine forest in Canada stayed a source for ten years before it became carbon neutral and did not become a major sink until 30 years after the clear-cut (Zha et al., 2009). Several studies have shown that after logging the regenerating forest is a source of carbon to the atmosphere for at least 14 years (Schulze et al., 1999; Jandl et al., 2007). In section 4.3 this review will examine the effects on harvesting more closely.
4.1.2 Below ground carbon
Forest soil and below ground biomass contain a large amount of carbon. Soil carbon has a slow build up originating from the trees photosynthesis (sequestration) and can accumulate over long periods of time and stay there for an even longer time. This means that boreal forest soil contains older stocks of carbon which if disturbed could increase the rate of which carbon is released back into the atmosphere (Jandl et al., 2007). It is the respiration of heterotrophs decomposing organic matter in the soil which causes the carbon to be released back into the atmosphere and several factor may affect this process. Such factors are soil moisture, temperature, access to nitrogen relative to organic matter in the soil, precipitation, pH, and properties of different soils (Lal, 2005; Jandl et al., 2007). In production forests the amount of carbon in the soil is usually much lower than in old growth forests. That is because productions forest soil becomes
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disturbed during harvest, this disturbance removes the above ground biomass which cuts off the supply of carbon that are being sequestered and transferred into the soil (Nave et al.,2010). Harvesting can decrease carbon soil with 30% and in spodosols which covers a large part of Sweden it can take up to 50-70 year to recover the lost carbon (Nave et al.,2010). At by that time, it might be time for harvest again. Following harvest, the forest becomes a source of carbon to the atmosphere and will continue to be a source until the newly planted trees sequester enough carbon so when it exceeds the amount released it will then become a sink (Kurz et al, 2013). Different harvesting technics affect the soil in different ways as well. Clear-cutting which causes the most disturbances remove more biomass and disturb the soil more than single tree selection or diameter cutting (Jandl et al., 2007; Noormets et al., 2015). However, some studies point out that the losses will be outweighed by the growth of the new trees that will sequester carbon so that it exceeds the losses to the atmosphere. Even if that method is clear-cutting which disturb the soil to a much higher degree than other harvesting methods (Lundmark et al., 2014; Clarke et al., 2015). This review will examine the effects of harvest on carbon in the soil more in section 4.3. Production forests have a higher capacity to be a sink than old growth forests, but old growth forest have a higher carbon density than younger productions forests. Older forests can continuously transfer a higher proportion if carbon into the soil than younger. A study in Sweden showed that old growth forests that are not disturbed by fire will continue to accumulate carbon for at least 5000 years (Wardle et al., 2012). Considering the section above where researchers found that old growth forest can still sequester carbon to high degree this mean more will go into the soil and increase the stock of carbon (Harmon et al., 1990; Schulze et al., 2000). As mentioned previously, older forests have more deadwood and litter which becomes a part of the forest floor soil layer and the rate of decomposition is higher than in younger production forests with much less dead biomass (Knohl et al., 2003; Paw et al., 2004; Luyssaert et al.,2008; Colombo et al., 2012). This means that old growth forest has the potential to be bigger sources or carbon neutral than younger forests because of the higher decomposition rate. When comparing management methods you must also take into consideration that old growth forests accumulate more carbon than younger production forests that are continuous disturbed from harvesting which do make them a source for a limited time repeatedly, at least when you look at clear-cutting.
4.2 Carbon stocks in production forests and old growth forests
When the rate of sequestration starts to decline as the forest mature the main carbon stock will be in living biomass, deadwood, and soil. This stock can be depleted by disturbances and
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filled by sequestration by the forest (Mackey et al., 2013). Old growth forest can accumulate carbon in living biomass, deadwood and soil over centuries and contain a large quantity of it. If these old forests become disturbed much of the carbon will then return to the atmosphere and increase the already dangerous high amount of carbon in the atmosphere (Fontaine et al., 2007; Luyssaert et al., 2008). Managed forests also stock carbon in the same way but since these forests are planted and harvested in regular intervals, they release carbon more frequently but since they are younger, they do not have the same amount of carbon stock as old growth forests. And since these areas are re-planted after harvest and start to sequester carbon again some researchers claims that it is a carbon neutral disturbance (Davis et al., 2009; Lundmark et al., 2014). Depending on what the harvested wood is used for it will impact the climate in different ways. Harvested wood products as sawn wood used for construction can store carbon much longer, that mean it will continue to be a stock for a longer time than pulp and paper products which consume energy during production and have a much shorter lifespan (Pukkala, 2018). You can also use the harvested wood for biofuel, which is burned to replace fossil fuels, but this also has a short lifespan. If harvested wood products are used to replace products such as cement or steel which needs a lot of energy to be made this could also help to mitigate the climate (Pukkala, 2018). Depending on what kind of harvesting method is used it will have a different impact on the forest and the effect of forests mitigating of the climate, but more on that in section 4.3. Since old growth forests have larger carbon stocks, they could release more carbon into the atmosphere if natural disturbances were to occur, such disturbances include wildfire, storms, and insect outbreaks. (Luyssaert et al., 2008; Coomes et al., 2012; Kurz et al., 2013). If these events are to great or uncontrolled it would lead to a great increase of carbon to the atmosphere. Luckily, uncontrolled fires do not happen to often since there is usually some kind of suppression to protect the forest and people living nearby (Martell and Sun, 2008). But fires are not just bad since old growth forest consists of mostly old trees which take up a lot of space the regeneration process is low. This means smaller fires can open the area and allow new trees to grow and sequester carbon (Schulze et al., 1999). Fires burn above ground litter and soil to release carbon at a much higher rate than decomposition, but fire also immobilizes carbon as charcoal (black carbon). This can increase the carbon in the soil and the burning also leads to trees dying and falling over which means it refills the dead wood carbon stock after the fire (Schulze et al., 1999). Of course, production forests are also exposed to these kind of natural disturbances as well as harvesting. With the changing climate, forest fires, storms and insect outbreaks are becoming more common and severe. This are already causing damage to the forests and might in the future change the carbon dynamics of the forests even more (Flannigan
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et al. 2005; Balshi et al. 2009; Krawchuck et al. 2009; Hely et al. 2010; Regniere et al. 2010; Safranyik et al. 2010). As mentioned previously old growth forests can continue to sequester carbon to an extent although it will not be as high as younger forests (Knohl et al., 2003; Paw et al., 2004; Luyssaert et al.,2008; Colombo et al., 2012). And with the living biomass already large in carbon stocks they cannot accumulate more to the same extent as trees that are still growing, but they continue to be a source of deadwood, litter and supplies the soil with carbon to a greater extent than the younger production forests (Harmon et al., 1990; Schulze et al., 2000). This means that the carbon stock in old growth forests continuously increases, meanwhile in managed forests the stock increases and are then removed repeatedly. The carbon stocks in managed forests can be used for a variety of products with sawn wood having a longer lifespan meaning it will be a stock of carbon longer than other products. Meanwhile old growth forests are a much larger stock of carbon and this stock is more exposed than productions forest since older forest have much larger stocks and if disturbances were to happen to a higher degree this could lead to a large release of carbon into the atmosphere.
4.3 Effects from harvesting
Forests are harvested by a few different methods which affect the carbon stock and sink capacity in different ways. The most used method in Sweden is clear-cutting (Lundmark et al., 2014). The clear-cutting method has an even aged stand structure which follows a cycle of harvest and regeneration and is classed as one of the more intense harvest practises (Krankina and Harmon, 1994; Lundmark et al., 2014). Stem-only harvesting means that only the stems are removed and harvest residues such as branches, twigs and leaves are left on site and the carbon from these residues can accumulate in the soil. Or they can be removed and used as biofuel (Clarke et al., 2015). With the thinning method you can practice stem-only thinning, meaning that only stems are removed, and biomass is left on site or whole-tree thinning which means that all above-ground biomass is removed. Selection-cutting is a method where the purpose is to create an all-aged stand structure, this means that single trees or a small group of trees are harvested, this can also be called continuous cover forestry (Jandl et al., 2007; Clarke et al., 2015). Whole-tree harvesting is a method that removes more harvest residues than only harvesting and stem-only thinning. Stump extraction is a method which is already included in clear-cutting since they need to prepare the site for re-plantation. In other methods the purpose with stump extraction is to limit fugal attacks to the roots and using the stumps for biofuel (Clarke et al., 2015). The different harvesting practices affect carbon sequestration and carbon stocks in different ways and keeping a forest unmanaged or choosing to keep an old growth forest will
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also have a different outcome. A study from (Davis et al., 2009) showed that a harvested forest had a significant negative effect on the short-term carbon storage but over 55 years the annual rate of sequestrations was similar between a harvested forest and an unmanaged forest. After the harvest, the sequestration declined but so did the respiration which resulted in the ecosystem becoming a sink. (Davis et al., 2009) also showed that clear-cutting caused the plant carbon stock to decline and even if clear-cutting were repeated 45 years after the latest harvest it would continue to cause a decline in future growth potential. Meanwhile if harvest was accomplished with single-tree selection or diameter limit cuts, the plant carbon stock was not affected, meaning that clear-cutting had a greater negative effect on the ecosystem (Davis et al., 2009). The study also showed that carbon sequestration changed with the frequency of harvest, with single tree selection and diameter cuts the area showed a 37% increase in carbon sequestration after 55 years compared to the reference forest which was a forest older than 100 years and mostly untouched during this time (Davis et al., 2009). A study on a boreal forest in Canada came to a similar conclusion, that after each harvest event the carbon stock in litter and biomass declined (Seely et al., 2012). A study on a boreal forest in Canada showed that after clear-cutting the site remained a source until it was approximate 10 years, it then turned into a weak sink or became carbon neutral and after 30 years it became a greater sink, only to become a weaker sink/carbon neutral at an age of 90 years (Zha et al., 2009). Similarly, a study on Eurosiberian boreal forest came to almost the same conclusion, this study shows that when an area is logged it remains a carbon source up to 14 years despite the high sequestration of the regenerating trees (Schulze et al., 1999). A study from (Pukkala, 2018) on a boreal forest in Finland showed that when trees are left to grow without management, they become larger, and larger trees are better carbon stocks than smaller ones. The study also showed that larger trees have a decomposition rate which is two times slower than smaller trees. The study also showed that old dead conifer was a better carbon stock than a large cut conifer for wood products. They showed that a large cut tree released carbon back into the atmosphere faster than a large dead tree. After 100 years the carbon stock of a large dead tree was over three times larger than the stock of a large cut tree (Puukala, 2018). But if the time period was extended to 300 years the result showed that sustainable cutting with a low frequency was the best strategy. But they also reached the conclusion that the only climate benefit from this strategy was avoided emissions from fossil fuels (Puukala, 2018). Colombo et al. (2012) showed in their study that protecting a boreal forest would lead to greater carbon stocks compared to different harvest regimes (Fig 1.) and protection had the greatest increase in carbon sequestration for about 30 years before the curve flattened.
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Figure 1: Forest carbon stock under five scenarios: Protection – no harvest and minimal natural disturbances; Lower harvest rate – harvest at the average historical (lower) rate, minimal natural disturbances; Higher harvest rate– harvest at the higher rate removing all sustainably available volume, minimal natural disturbances; Lower natural disturbances –lower rate of natural disturbance without fire suppression, no harvest; and Higher natural disturbance – higher rate of natural disturbance without fire suppression, no harvest. Reused with permission from Elsevier, from Colombo et al. (2012).
The figure above shows only the carbon in the forest and not what happens with the harvested wood, figure 2 shows a similar figure but with the harvested wood included and shows that with the wood in use or in landfills from the different harvest regimes the methods are much more similar to each other in carbon stock perspective. But still the only method which surpasses protection is harvest at a lower rate and it only passes the protection method after 90-100 years (Colombo et al., 2012). This shows that reduced harvest and protection of older forests has the best potential to increase the forests carbon stock. But figures 1 & 2 also shows that when the natural disturbance rate is either higher or lower it leads to a decrease in the forests carbons stocks. The reason for this might be because an overly old forest stand structure with lower natural disturbances results in low regeneration and this could be solved with harvesting, but it should be done at a low rate. And if the disturbance rate is higher because of fires, storms, insect outbreaks etc. there will be more carbon released into the atmosphere (Colombo et al., 2012).
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Figure 2: Total carbon stock combined in forests, wood products in use, and wood products in landfills, under five scenarios. Reused with permission from Elsevier, from Colombo et al. (2012).
Another study shows a similar figure but with some different results (Fig. 3.). In this study the authors simulated above ground carbon and carbon in wood products with different management methods which was no management, clear-cutting with a higher frequency (80 years) and with a lower frequency (120 years), shelterwood which is method with more structural retention and individual tree selection (ITS) with higher frequency (15 years) and lower frequency (30 years) the authors also combined frequencies of harvest in individual tree selection cuttings (Nunery et al., 2010). Figure 3 shows that the no management method had the greatest amount of above ground carbon of all management regimes and is in that perspective very similar to figure 2. But it also shows that no harvesting method come close to the carbon stock of the no management method during the 150-year period even with the carbon stock of wood products included (Nunery et al., 2010). The results show that passive management sequester more carbon than more intense, and that a lower harvest frequency and higher retention lead to more carbon sequestered than harvest methods with higher frequencies (Nunery et al., 2010).
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Figure 3: Simulation time series for 9 different management scenarios. Reused with permission from Elsevier, from Nunery et al. (2010).
A similar study on forestry in Sweden concluded that the current management practices and the use of wood products reduce global carbon dioxide emissions relative to a scenario where no forests-based products are available (Lundmark et al., 2014). The study also concluded that more intense forestry practices would lead to a higher forest productivity which also would reduce the carbon emissions (Lundmark et al., 2014). These finding goes in a completely different direction than many other sources which claims that lower intensity harvest is the better solution to mitigate the climate. Rotation length can affect how much carbon the forests will be able to sequester and stock before harvest and it will also affect the amount of wood products that will be available after harvesting. If rotation length is extended it can affect the carbon sequestration significantly according to a study from (Nunery et al., 2010). Another study made on extended rotation length of 10, 20 and 30 years and decreasing the rotation length by 10 years showed that mean annual carbon in biomass increased for the 10–30-year period. The results also showed that when the rotation period was shortened the carbon decreased (Lundmark et al., 2018). The authors conclusions are that lowering the rotation length by 10 years had a negative effect on the climate and on the amount of wood products available from harvesting, meanwhile prolonging the rotation length for pine lead to a positive effect for the climate but at a cost of decreased the economic return. There was an even larger climate benefit for prolonged rotation of spruce but also here it came at the cost of decreased economic return (Lundmark et al., 2018). Although the carbon stocks will increase during the prolonged rotation length the effects will be temporary and be replaced by a negative effect on the climate by lowering the annual harvested wood products. But prolonging the rotation length by 10 years
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for spruce would lead to a positive effect on the climate and the carbon stocks, while all the lengths for pine and prolonging spruce by 20 and 30 years would have a negative impact on the climate considering the lower yield from harvested wood products (Lundmark et al., 2018). Harvesting affects the soil stocks as well the living and dead biomass stocks, but researchers disagree about how much or if it at all have an effect. The forest soil floor is more vulnerable to disturbances from harvest, (Nave et al., 2010) showed that forest floor soil lost on average 30% of the soil carbon while the deeper mineral soil had no significant change. The same study also showed that the loss of carbon from soil had a greater impact on spodosols which is one of the dominant soil orders in Sweden. The result showed that spodosols took 50-70 years to recover from these losses. Looking at the mineral soil spodosols had no significant losses (Nave et al., 2010). (Schulze et al., 1999; Jandl et al., 2007) showed that a forest remained a source for 14 years after an intense harvesting event, the reason for it being a source was increased soil respiration. But the study also showed that less intense harvesting methods is a possible method to reduce the soil carbon losses. Another possible solution to reduce the soil carbon losses is prolonged rotation length, this would allow soil to accumulate more carbon while in shorter rotation length it maximizes above ground carbon in living biomass but not in soil carbon (Schulze et al., 1999; Jandl et al., 2007). A study on a boreal forest showed that a spruce forest lost up to 20% following frequent harvest rotations (Seely et al., 2002). Meanwhile some studies concluded that harvest does not or only have a small impact the soil carbon, but this depends in part on the already existing soil organic matter (Johnson & Curtis, 2001). Similarly, from a study on Swedish forestry the authors report a steady increase of soil carbon in relation with forest growth, they found this relationship despite clear-cutting being the main harvesting method (Lundmark et al., 2014). A study on boreal and northern temperate forests showed that many of the more intensive harvesting regimes often cause a loss of carbon in soil, but the authors also concluded that the carbon losses can be mitigated. The losses can be mitigated by less intense harvesting regimes or by leaving more litter after harvest, this could restore the lost carbon in the soil much quicker, the losses can also be outweighed by the growing trees sequestration during the next rotation (Clarke et al., 2015; Egnell et al., 2015). It is also important to note that if old growth forests were to be harvested or converted to production forest much of the carbon accumulated in these forests would disappear which would have a negative impact on the climate (Harmon et al., 1990; Johnson, 1992; Schulze et al., 2000; Fontaine et al., 2007; Luyssaert et al., 2008). This means that if old growth forests which have a large carbon stock in living biomass, deadwood and soil were to be disturbed the stocks would
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decline for decades and would be a source until the sequestration of the newly planted trees exceed the rate decomposition from the harvesting event (Trofymow et al., 2008).
4.4 The debate climate in Swedish newspapers
This section will cover the debate climate in Sweden concerning forestry. This section might be a bit less scientific than the previous sections since much of what is discussed comes from debate articles. But the authors to the debate articles have gotten their information from scientific articles or other respected sources that make the subject they discuss solid. The purpose of this section is to get an understanding of why the scientific community is split in its opinions on how forestry can help with climate mitigation.
The Swedish debate climate is quite infected to say the least, voices are being heard from many different points of view, all the way from politicians, lobbyists, forest owners, reporters, scientists, climate activist to just regular people. All these voices are being lifted in the Swedish newspapers and many of them have different opinions about how Sweden should manage the forestry to be able to mitigate the climate change. Previously this year newspaper reporters found that during the last 4 years forest companies have invested 150 million SEK on commercials, posters, newspaper ads, EU-lobbies, lectures for politicians and Swedish schools. The information that the company want to share is that Swedish forestry is sustainable and that the harvestings that are being done should continue or even increase (Röstlund et al., 3 Mars 2021a). On the pamphlets given to the schools the information says that unmanaged old forests are worse for the climate than managed since you cannot use the old growth forests, they also say that biofuel from the forest is climate neutral which is a fact that many researchers disagree with (Röstlund et al., 3 Mars 2021). This is a lot of money to influence Swedish people that the forests companies’ solution is the best way to go.
The split in opinions between more production forest and old growth forests exist even in Sweden scientific community. Some researchers want to keep managing or expand production forestry because growing forests sequester more carbon and harvested wood products can be uses to replace fossil fuels. At the same time other scientist wants to protect more forests and decrease the amount of forest that are being harvested. Their reasoning is that older forests have larger carbon stocks, protecting forest is good for the biodiversity, harvesting is releasing carbon and that many of the harvested wood products have a short lifespan which decreases their benefit for the climate (Röstlund et al, 7 February 2021). At the same time as, Swedish scientists are divided there has been a call to stop treating burning of wood as carbon neutral.
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500 scientists have written an open letter to USA and the European Union, in this letter they request that burning of wood should not be treated as carbon neutral and that subsidies to biofuel should stop. The reason for this request is according to these scientists that burning of wood, even when the trees are re-planted releases carbon dioxide which increases the amount in the atmosphere for decades or even centuries. They argue that the time to change and to meet the 1,5-degrees goal is now and burning wood will not help to stay below 1,5 degrees. They also point out that the trees will sequester carbon in time but since we are short on time regarding the 1,5-degrees goal, burning wood for biofuel and giving subsidies which increases the amount of biofuel is not a solution (Röstlund et al., 18 February 2021).
At the same time as the scientific community in Sweden is divided there is reports that research about Swedish forestry is biased. When reporters examined some of Sweden’s leading forestry scientists, they found that some had ties to big forest companies and got a salary from these companies at the same time as they are doing research about forestry in Sweden. Most of these scientists are pro production forestry and want to decrease the amount of protected forest and change it to managed forest for the climate benefit (Röstlund et al., 4 February 2021). Their response was that the other scientist who were against the intensive management of Sweden’s forests and wanted to protect more forest had ties to environmental organizations and thus also had an agenda. Some of the scientist that were against the current management of the forests were members of environmental organizations and some were not (Röstlund et al., 4 February 2021). It is clear that Sweden’s scientific community is polarised, if it is because of different interpretations from research or something else is hard to say. But it is important to note that a divide exists, and it might be contra productive in climate mitigation.
There has also been reports that forest companies are driving the research to favour their view of the situation. Future forests are a research program about forests and is financed by the Swedish government and the forest industry and scientist who were part of this program has reported that there was a resistance about research that opposed the forest industries point of view. There were also reports that the industry was tired of the climate movement and biologists that wanted to see more environmental consideration in the forest. But then there was also scientist who said there was no truth in this and that the research and results where independent and the results that pointed to continue or increase the management of forests was not angled by the industries view (Röstlund, 5 February 2021).
Sweden’s political parties are also a big part of the debate, in Sweden most of the forests are owned by private persons and not by the state, which means that ownership is strong and very
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protected. This means that some parties try to attract voters by wanting to protect their right to ownership and combining this with saying that the way Sweden is managing forests is sustainable and a good solution since trees can be used for biofuel and replace fossil fuel. They also support the people who own the forests and their income by not wanting to set a side forests for protection, even though the forest owner would be compensated for the lost income if they would choose to set a side forest (Polfjärd, 3 April 2021). Some other parties are arguing that Sweden already has enough protected forest and that the way that the forests are managed is sustainable. This is mostly from argumentation with other parties or responses to scientist who argue that we need to protect more forests and that the way Sweden manage the forests is not sustainable (Nordberg et al., 7 May 2021; Rosén, 8 February 2021).
For Sweden, forestry and the harvested wood are a great economic income for forest owners and forests workers and the forest industries are about 1,49% of Sweden’s BNP. However, it is also important to note it have been decreasing the last 40 years. During the same period tourism in Sweden that have increased and surpassed the BNP of the forest industry, and tourism now constitute 2,8% of the GDP. It is important to note that not all income from tourism comes from the Swedish forests (Tidholm, 12 May 2021). However, in a survey by Visit Sweden of the most important visitor markets Germany, France, the UK and the USA, Sweden placed second, just after Norway, when potential visitors spontaneously think of countries that offer sustainable nature experiences.
It is notable that the debate is very polarised, and you cannot really say that one side is right because both sides address valid research. However, they are looking at different time frames, debaters promoting production forests look at long time frames and debaters promoting protection point out the urgency that carbon dioxide in the atmosphere needs to decrease the coming decade. Production forests can mitigate the climate, but the effect of this method will only be shown much later. While reducing harvest and protecting forests will have a faster effect on climate mitigation. Younger forests help to mitigate the climate by sequestering carbon and biofuel is a good replacement for fossil fuel which we need to stop using. But it is also important to note that the monocultures that are spread over Sweden is not positive for biodiversity and clear-cutting do release carbon to the atmosphere. At the same time, we need more old growth forests which are a good habitat for biodiversity and are large carbon stocks which also helps to mitigate the climate.
16 5 Conclusions
This review has tried to highlight the different ways production forests and old growth forests can help to mitigate the climate change. Production forests can help to mitigate the climate change since younger trees sequester more carbon than old growth forests and the wood that is harvested can be used for biofuel which can be used to replace fossil fuels. Harvested wood products can also be used in construction, wood can replace energy intensive products such as cement or steel and using wood for building would mean that the carbon stock lasts longer than if it were burned for energy. Old growth forests on the other hand do not sequester the same amount of carbon from the atmosphere as younger but they accumulate carbon continuously and since they are unmanaged, they can be a carbon stock continuous if undisturbed. They also transfer more carbon into the soil than production forests which becomes an important carbon stock as well. Old growth forests are often better habitats for biodiversity than the production forests that usually are monocultures, this makes old growth forests even more valuable. Considering harvesting, it does give us wood products and biofuel which is useful to some extent but harvesting also has consequences. Harvesting leads to a release of carbon that can continue for over a decade or possibly even longer even though the replanted trees are sequestering large amounts of carbon. But depending on what method of harvesting is used this can also be mitigated. Low intensive harvest seems to be the best one with clear-cutting being one of the worst, clear-cutting is also the most used method in Sweden. But since we need wood for an array of different uses, low intensive harvesting with longer rotation cycles seems to be the best way forward. Of course, this also must work with the economic part and people and the forest industry must be willing to change. This might be hard since the scientific community is very divided on which way is the best one to mitigate the climate, and at the same time there is a lot of pressure from the industry to continue in the same way. But to be able to succeed with the 1,5-degree goal changes need to happen, we only have short amount of time to succeed and if large scale harvesting with a lot of disturbances, like clear-cutting is continued we might not be able to reach this goal. Since clear-cutting and other intense harvesting method transforms the forests to a source of carbon for decades and sequester carbon later in life, it is not method that fits into the time frame. The best solution is to increase the amount of unmanaged forests and protect old growth forest while harvesting forests with a low intensive method that do not cause the same amount of emissions. To be able to reach this goal scientists, politicians, the forest industry, and owners must come together and find a common path that benefits all in some way but most importantly helps the world the most.
17 6 Societal considerations
How Sweden and the rest of the world chooses to handle their forests is of major importance to mitigate climate change. If the choice is to reduce the amount of harvesting, this might lead to a shortage of wood products which could lead to needing to depend on more high energy products such as cement, steel, and fossil fuels and this would have a negative impact on the climate since it would continue to increase the carbon dioxide in the atmosphere. It might also cause job opportunities in the forest industry to disappear which would be a hard blow for the smaller forest owners rather than the big companies. The economy of countries such as Sweden that are dependent on their forests might also be affected but how much is hard to say. On the other hand, if we continue to harvest forests the way we are now with a lot of clear-cutting or even more it is going to cause at least a temporary increase of carbon in the atmosphere before the trees can sequester enough carbon so that the amount in the atmosphere decreases. And since there is a short time to reduce the atmospheric carbon before we get irreversible effects this might not be such a good idea. Harvesting old growth forest would also be a bad idea since they contain large stocks of carbon and harvesting would cause a lot of this carbon to be released back into the atmosphere. Old growth forests also have a higher ecological value than production forests that are monocultures since old growth forests become better habitats when looking at biodiversity. If an increase in harvesting were to happen the ecological system services that we get from the forests might also disappear and this would also be a huge problem. It is important to recognise that if or when fossil fuels become obsolete and replaced with renewable energy such as wind power, solar energy, hydrogen fuel. And if biofuel is still in used, biofuel will be the only fuel that will be a source of carbon. If this would happen the forests industries focus on biofuel would become obsolete and would probably be phased out. Which would mean that investments that the forest industry and governments make in biofuel might be in vain if the this change to renewable energy were to happen fast. But the thought of not needing to harvest forest for biofuel would be good for the climate mitigation process, it all depends on how fast the change from fossil fuel to renewable energy will happen. But considering that wind and solar energy are increasing every year it might be good not to put to much faith in biofuel. The best solution would probably be to use low intensive harvest with uneven aged forests so that there is a continuous flow of timber for the industry and use monocultures to a smaller degree so that biodiversity might thrive in production forests as well. The protection of old growth forests should continue and increase so that we do not lose these important carbon sinks and habitats. If these things were possibly then we might find a solution,
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where all sides gain something and with other actions to mitigate climate change we could mitigate the climate enough to decrease the chances of a climate disaster.
7 Acknowledgments
Special thanks to my supervisor Karl-Olof Bergman who guided and assisted me during the work with this thesis. I would also like send my appreciation to Linköping University who through their licenses gave me access to all the necessary literature.
8 References
Balshi, M.S., McGuirez, A.D., Duffy, P., Flannigan, M., Walsh, J., & Melillo, J. (2009). Assessing the response of area burned to changing climate in western boreal North America using a multivariate adaptive regression splines (MARS) approach. Global Change Biology, 15. 578–600. https://doi.org/10.1111/j.1365-2486.2008.01679.x.
Wardle, D.A., Jonsson, M., Bansal, S., Bardgett, R.D., Gundale, M.J. and Metcalfe, D.B. (2012). Linking vegetation change, carbon sequestration and biodiversity: insights from island ecosystems in a long‐term natural experiment. Journal of Ecology. 100. 16-30.
https://doi.org/10.1111/j.1365-2745.2011.01907.x.
Rogelj, J., D. Shindell, K. Jiang, S. Fifita, P. Forster, V. Ginzburg, C. Handa, H. Kheshgi, S. Kobayashi, E. Kriegler, L. Mundaca, R. Séférian, and M.V. Vilariño, (2018). Mitigation Pathways Compatible with 1.5°C in the Context of Sustainable Development. In: Global
Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J.
Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]. In Press.
Buchmann, N., & Schulze, E.D. (1999). Net CO2 and H2O fluxes of terrestrial ecosystems.
Global Biogeochemical Cycles. 13. 3. 751–760. https://doi.org/10.1029/1999GB900016. Cairns, M.A., Brown, S., Helmer, E.H., & Baumgardner, G.A. (1997). Root biomass
allocation in the world’s upland forests. Oecologia. 111. 1–11. doi:10.1007/s004420050201. Clarke, N., Gundersen, P., Jönsson-Belyazid, U., Kjønaas, O.J., Persson, T., Sigurdsson, B.D., Stupak, I., & Vesterdal, L. (2015). Influence of different tree-harvesting intensities on forest
19
soil carbon stocks in boreal and northern temperate forest ecosystems. Forest Ecology and
Management. 351. 9-19. https://doi.org/10.1016/j.foreco.2015.04.034
Colombo, S.J., Chen, J., Ter-Mikaelian, M.T., McKechnie, J., Elkie, P.C., MacLean, H.L., & Heath, L.S. (2012). Forest protection and forest harvest as strategies for ecological
sustainability and climate change mitigation. Forest Ecology and Management. 281. 140-151.
https://doi.org/10.1016/j.foreco.2012.06.016
Coomes, D.A., Holdaway, R.J., Kobe, R.K., Lines, E.R. & Allen, R.B. (2012), A general integrative framework for modelling woody biomass production and carbon sequestration rates in forests. Journal of Ecology, 100. 42-64.
https://doi.org/10.1111/j.1365-2745.2011.01920.x
Cooper, C.F. (1983). Carbon storage in managed forests. Canadian Journal of Forest
Research. 13. 1. 155–166. https://doi.org/10.1139/x83-022.
Davis, S.C., Hessl, A.E., Scott, C.J., Adams, M.B., & Thomas, R.B. (2009). Forest carbon sequestration changes in response to timber harvest. Forest Ecology and Management. 258. 9. 2101–2109. https://doi.org/10.1016/j.foreco.2009.08.009
Egnell, G., Jurevics, A., & Peichl, M. (2015). Negative effects of stem and stump harvest and deep soil cultivation on the soil carbon and nitrogen pools are mitigated by enhanced tree growth. Forest Ecology and Management. 338. 57–67.
https://doi.org/10.1016/j.foreco.2014.11.006.
Flannigan, M.D., Logan, K.A., Amiro, B.D., Skinner, W.R., & Stocks, B.J. (2005). Future area burned in Canada. Climatic Change. 72.1-2. 1-16. https://doi.org/10.1007/s10584-005-5935-y.
Fontaine, S., Barot, S., Barré, P., Bdioui, N., Mary, B., & Rumpel, C. (2007). Stability of organic carbon in deep soil layers controlled by fresh carbon supply. Nature. 450. 277–280.
https://doi.org/10.1038/nature06275.
Harmon, M.E., Ferrell, W.K., & Franklin, J.F. (1990). Effects of carbon storage of conversion of old-growth forests to young stands. Science. 247. 699–702.
https://doi.org/10.1126/science.247.4943.699.
Heinonen, T., Pukkala, T., Mehtätalo, L., Asikainen, A., Kangas, J., & Peltola, H. (2017). Scenario analyses for the effects of harvesting intensity on development of forest resources,
20
timber supply, carbon balance and biodiversity of Finnish forestry. Forest Policy and
Economics. 80.80–98. https://doi.org/10.1016/j.forpol.2017.03.011.
Hely, C., Girardin, M.P., Ali, A.A., Carcaillet, C., Brewer, S., & Bergeron, Y. (2010). Eastern boreal North American wildfire risk of the past 7000 years: a model-data comparison.
Geophysical research letter. 37. L14709. https://doi.org/10.1029/2010GL043706.
Jandl, R., Lindner, M., Vesterdal, L., Bauwens, B., Baritz, R., Hagedorn, F., Johnson, DW., Minkkinen, K., & Byrne, KA. (2007). How strongly can forest management influence soil carbon sequestration? Geoderma. 137, 3–4. 253-268.
https://doi.org/10.1016/j.geoderma.2006.09.003
Johnson D.W. (1992). Effects of Forest Management on Soil Carbon Storage. In: Wisniewski J., Lugo A.E. (eds) Natural Sinks of CO2. Springer. Dordrecht. https://doi.org/10.1007/978-94-011-2793-6_6.
Johnson, D.W., & Curtis, P.S. (2001). Effects of forest management on soil C and N storage: meta analysis. Forest Ecology and Management. 140.227–238.
https://doi.org/10.1016/S0378-1127(00)00282-6.
Keeling, RF., Piper, S., & Heimann, M. (1996) Global and hemispheric CO2 sinks deduced from recent atmospheric oxygen measurements. Nature. 381. 218-221.
Knohl, A., Schulze, E.D., Kolle, O., & Buchmann, N. (2003). Large carbon uptake by an unmanaged 250-year-old deciduous forest in Central Germany. Agricultural and Forest
Meteorology. 118, 151–167. https://doi.org/10.1016/S0168-1923(03)00115-1.
Krankina, O.N., & Harmon, M.E. (1994). The impact of intensive forest management on carbon stores in forest ecosystems. World Resource Review 6. 161–177.
Krawchuk, M., Cumming, S., & Flannigan, M. (2009). Predicted changes in fire weather suggest increases in lightning fire initiation and future area burned in the mixed wood boreal forest. Climatic Change. 92. 83–97. https://doi.org/10.1007/s10584-008-9460-7.
Kurz, W.A., Beukema, S.J., & Apps, M.J. (1996). Estimation of root biomass and dynamics for the carbon budget model of the Canadian forest sector. Canadian Journal of Forest
21
Kurz, W.A., Shaw, C.H., Boisvenue, C., Stinson, G., Metsaranta, J., Leckie, D., Dyk, A., Smyth, C., & Neilson, E.T. (2013). Carbon in Canada’s boreal forest — A synthesis.
Environmental Reviews. 21.4.260-292. https://doi.org/10.1139/er-2013-0041
Lal, R. (2005). Forest soils and carbon sequestration. Forest Ecology and Management. 220. 242–258. https://doi.org/10.1016/j.foreco.2005.08.015.
Li, Z., Kurz, W.A., Apps, M.J., & Beukema, S.J. 2003. Belowground biomass dynamics in the carbon budget model of the Canadian forest sector: recent improvements and implications for the estimation of NPP and NEP. Canadian Journal of Forest Research. 33. 1. 126–136.
https://doi.org/10.1139/x02-165.
Liu, G., & Han, S. (2009). Long-term forest management and timely transfer of carbon into wood products help reduce atmospheric carbon. Ecological Modelling. 220. 1719–1723.
https://doi.org/10.1016/j.ecolmodel.2009.04.005.
Lundmark, T., Bergh, J., Hofer, P., Lundström, A., Nordin, A., Poudel, B.C., Sathre, R., Taverna, R., & Werner, F. (2014). Potential Roles of Swedish Forestry in the Context of Climate Change Mitigation. Forests. 5. 557-578. https://doi.org/10.3390/f5040557
Lundmark, T., Poudel, B.C., Stål, G., Nordin, A., & Sonesson, J. (2018). Carbon balance in production forestry in relation to rotation length. Canadian Journal of Forest Research. 48. 6. 672-678. https://doi.org/10.1139/cjfr-2017-0410
Luyssaert, S., Inglima, I., Jung, M., Richardson, A.D., Reichstien, M., Papale, D., Piao, S.L., Sculze, E.D., Wingate, L., Matteucci, G., Aragoa, L., Aubinet, M., Beer, C., Bernhofer, C., Black, K.G., Bonal, D., Bonnefond, J.M., Chambers, J., Ciais, P., Cook, B., Davis, K.J., Dolman, A.J., Gielen, B., Goulden, M., Grace, J., Granier, A., Grelle, A., Griffis, T., Grünwald, R, T., Guidolotti, G., Hanson, P.J., Harding, R., Hollinger, D.Y., Hutyra, L.R., Kolari, P., Kruikt, B., Kutsch, W., Lagergren, F., Laurila, T., Law, B.E., Le Marie, G., Lindroth, A., Loustau, D., Malhi, Y., Mateus, J., Migliavacca, M., Misson, L., Montagnani, L., Moncrieff, J., Moors, E., Munger, J.W., Nikinmaa, E., Ollinger, S.V., Pita, G., Rebmann, C., Roupsard, O., Saigusa, N., Sanz, M.J., Seufert, G., Sierra, C., Smith, M.L., Tang, J., Valentini, R., Vesala, T., & Janssens, I.A. (2007). CO2 balance of boreal, temperate, and tropical forests derived from a global database. Global Change Biology 13. 2509–2537.
22
Luyssaert, S., Schulze, ED., Börner, A. Knohl, A., Hessenmöller, D., Law, BE., Ciais, P., & Grace, J. (2008). Old-growth forests as global carbon sinks. Nature 455, 213–215.
https://doi.org/10.1038/nature07276
Mackey, B., Prentice, I., Steffen, W., House, J.I., Lindenmayer, D., Keith, H., & Berry, S. (2013). Untangling the confusion around land carbon science and climate change mitigation policy. Nature Climate Change 3, 552–557. https://doi.org/10.1038/nclimate1804
Martell, D.L., & Sun, H. (2008). The impact of fire suppression, vegetation, and weather on the area burned by lightning-caused forest fires in Ontario. Canadian Journal of Forest
Research. 38. 6. 1547–1563. https://doi.org/10.1139/X07-210.
Nave, L.E., Vance, E.D., Swanston, C.W., & Curtis, P.S. Harvest impacts on soil carbon storage in temperate forests. (2010). Forest Ecology and Management. 259. 5. 857-866.
https://doi.org/10.1016/j.foreco.2009.12.009
Noormets, A., Epron, D., Domec, J.C., McNulty, S.G., Fox, T., Sun, G., & King, J.S. (2015). Effects of forest management on productivity and carbon sequestration: A review and
hypothesis. Forest Ecology and Management.355. 124-140.
https://doi.org/10.1016/j.foreco.2015.05.019.
Nordberg, M., Eklöf, S., Filper, R., Eriksson, Y. (7 May 2021). Kunskapen finns – vårt skogsbruk är hållbart. Aftonbladet. https://www.aftonbladet.se/debatt/a/Alokyn/kunskapen-finns--vart-skogsbruk-ar-hallbart.
Nunery, J.S., & Keeton, W.S. (2010). Forest carbon storage in the northeastern United States: Net effects of harvesting frequency, post-harvest retention, and wood products. Forest
Ecology and Management. 259.8. 1363-1375. https://doi.org/10.1016/j.foreco.2009.12.029 Pan, Y., Birdsey, R.A., Fang, J., Houghton, R., Kauppi, P.E., Kurz, W.A., Phillips, O.L., Shvidenko, A., Lewis, S.L., Canadell, J.G., Ciais, P., Jackson, R.B., Pacala, S.W., McGuire, A.D., Piao, S., Rautiainen, A., Sitch, S., & Hayes, D. (2011). A large and persistent carbon sink in the world’s forests. Science. 333.6045. 988–993.
https://doi.org/10.1126/science.1201609.
Paw U, K.T., Falk, M., Suchanek, T.H., Ustin, S.L., Chen, J., Park, Y., Winner, W.E., Thomas, S.C., Hsiao, T.C., Shaw, R.H., King, T.S., Pyles, R.D., Schroeder, M., & Matista, A.A. (2004). Carbon Dioxide Exchange Between an Old-growth Forest and the Atmosphere.
23
Polfjärd, J. (3 April 2021). MP är ett hot mot det svenska skogsbruket. Aftonbladet. https://www.aftonbladet.se/debatt/a/Alykvq/mp-ar-ett-hot-mot-det-svenska-skogsbruket.
Pukkala, T. (2014). Does biofuel harvesting and continuous cover management increase carbon sequestration? Forest Policy and Economics. 43.41–50.
https://doi.org/10.1016/j.forpol.2014.03.004.
Pukkala, T. (2018). Carbon forestry is surprising. Forest Ecosystems. 5. 11.
https://doi.org/10.1186/s40663-018-0131-5
Regniere, J., St-Amant, R., & Duval, P. (2010). Predicting insect distributions under climate change from physiological responses: spruce budworm as an example. Biological Invasions. 14. 1571–1586. https://doi.org/10.1007/s10530-010-9918-1.
Rosén, H. (8 February 2021). Centern: Målet för skyddad skog är uppnått. Dagens Nyheter. https://www.dn.se/sverige/centern-malet-for-skyddad-skog-ar-uppnatt/.
Röstlund, L. (5 February 2021). Forskare: Skogsindustrin styrde vår forskning. Dagens
Nyheter. https://www.dn.se/sverige/forskare-skogsindustrin-styrde-var-forskning/.
Röstlund, L., Alestig, P., Urisman-Otto, A., Westholm, M. (18 February 2021). Forskare uppmanar USA och EU: Sluta stödja biobränslen. Dagens Nyheter.
https://www.dn.se/sverige/forskare-uppmanar-usa-och-eu-sluta-stodja-biobranslen/.
Röstlund, L., Nantell, A. (4 February 2021). Skogsforskningschef avlönad av Europas största skogsbolag. Dagens Nyheter. https://www.dn.se/sverige/skogsforskningschef-avlonad-av-europas-storsta-skogsbolag/.
Röstlund, L., Nantell, A., Lindwall, E. (3 Mars 2021). Skogsbolagens berättelse om skogen – lobby för 150 miljoner. Dagen Nyheter.
https://www.dn.se/sverige/skogsbolagens- berattelse-om-skogen-lobby-for-150- miljoner/?forceScript=1&variantType=large#klarnaConfirm/url=https://auth.dn.se/klarna- instant-shopping/receipt?&variantType=large&loginURL=https%3A%2F%2Fwww.dn.se%2Flogin% 3FredirectToUrl%3D%252Fsverige%252Fskogsbolagens-berattelse-om-skogen-lobby-for- 150-miljoner%252F%253FforceScript%253D1%2526variantType%253Dlarge&price=5900&isM obileLayout=false&isEmbedded=true&KISPrice=5900&forcehit=true&orderSessionIdPrefix =1VlaKkqZ&bipFlow=true&isAutoLogin=true.
24
Röstlund, L., Westholm, M. (7 February 2021). Klimatet – frågan som splittrar den svenska skogsforskningen. Dagen Nyheter. https://www.dn.se/sverige/klimatet-fragan-som-splittrar-den-svenska-skogsforskningen/.
Safranyik, L., Carroll, A.L., Regniere, J., Langor, D.W., Riel, W.G., Peter, B., Cooke, B.J., Nealis, V.G., & Taylor, S.W. (2010). Potential for range expansion of mountain pine beetle into the boreal forest of North America. The Canadian Entomologist. 142. 5. 415-442.
https://doi.org/10.4039/n08-CPA01.
Schulze, E.D., Lloyd, J., Kelliher, F.M., Wirth, C., Rebmann, C., Lühker, B., Mund, M., Knohl, A., Milyukova, I.M., Schulze, W., Ziegler, W., Varlagin, A., Sogachev, A.F., Valentini, R., Dore, S., Grigoriev, S., Kolle, O., Panfyorov, M.I., Tchebakov, N., &
Vygodskaya. N.N. Productivity of forests in the Eurosiberian boreal region and their potential to act as a carbon sink — a synthesis. (1999). Global Change Biology.5. 703-722.
https://doi.org/10.1046/j.1365-2486.1999.00266.x
Schulze, E.D., Wirth, C., & Heimann, M. (2000). Managing forests after Kyoto. Science. 289. 2058–2059. https://doi.org/10.1126/science.289.5487.2058.
Seely, B., Welham, C., & Kimmins, H. (2002). Carbon sequestration in a boreal forest ecosystem: results from the ecosystem simulation model, FORECAST. Forest Ecology and
Management. 169. 1–2. 123-135. https://doi.org/10.1016/S0378-1127(02)00303-1.
Tidholm, B. (12 May 2021). Skogsnäringens propaganda är på väg att genomskådas. Dagens
Nyheter. https://www.dn.se/kultur/skogsnaringens-propaganda-ar-pa-vag-att-genomskadas/. Townsend, A.R., Vitousek, P.M., & Trumbore, S.E. (1995). Soil organic matter dynamics along gradients in temperature and land use on the island of Hawaii. Ecology. 76. 721-733.
https://doi.org/10.2307/1939339.
Trofymow, J.A., Stinson, G., & Kurz, W.A. (2008). Derivation of a spatially explicit 86-year retrospective carbon budget for a landscape undergoing conversion from old-growth to managed forests on Vancouver Island, BC. Forest Ecology and Management. 256. 10. 1677-1691. https://doi.org/10.1016/j.foreco.2008.02.056
Vitousek, P.M. (1991). Can planted forests counteract increasing atmospheric carbon dioxide?
Journal of Environmental Quality. 20. 348–354.
25
Zha, T., Barr, A.G., Black, T.A., McCaughey, J.H., Bhatti, J., Hawthorne, I., Krishnan, P., Kidston, J., Saigusa, N., Shashkov, A., & Nesic, Z. (2009). Carbon sequestration in boreal jack pine stands following harvesting. Global Change Biology.15. 1475–1487.
https://doi.org/10.1111/j.1365-2486.2008.01817.x
Zhou, G., Liu, S., Li, Z., Zhang, D., Tang, X., Zhou, C., Yan, J., & Mo, J. (2006). Old-growth forests can accumulate carbon in soils. Science 314.1417.
