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A growing tree absorbs carbon from the atmosphere, storing it to wood biomass. The Carbon binding demo of UPM Forest Life demonstrates carbon absorption of a Norway Spruce (Picea abies) tree growing in Southern Finland. You will also get an idea of carbon absorption capacity of trees and forests in comparison to emissions from our everyday life. Attached text article provides with more information on climate impacts of trees, forests and sustainable forestry.
Our model tree is a 40 years old Norway spruce (Picea abies) growing on herb-rich heath forest in Southern Finland. Besides the species, biological age, site and geographical location, also forest stand structure and implemented forest management activities affect growth and carbon absorption rates of a tree. In this case, forest stand is established by planting and it has been thinned once. Stem number is 990 trees per hectare. Based on these factors, modelled carbon absorption of the model tree is 24,8 kg carbon dioxide per year.
Trees absorb carbon dioxide from the atmosphere for their growth. Trees utilize carbon dioxide, water and sunlight in a biochemical process called photosynthesis. Products from photosynthesis are glucose and oxygen. Glucose is used for tree’s nutrition, oxygen gets released to atmosphere and carbon is stored to wood biomass – of which around half consists of carbon.
Trees sequester atmospheric carbon dioxide, but they also breath it out in cellular respiration. Some of the carbon is thus returned to the atmosphere. Respiration releases residual carbon from tree’s metabolic processes. For a growing tree, carbon absorption is however significantly higher than its release and growing trees act as a carbon sink.
Availability of sunlight is up to the time of day. Trees adapt their processes to light conditions. Photosynthesis is most active in abundant light, during dark hours it’s inhibited. In northern forests the momentary carbon balance of a tree is also a question of time of year and consequent timing of growing season. During growing season, when photosynthesis is on, trees absorb carbon. During winter dormancy trees do not grow and they are mainly a weak carbon source. Over a one-year period a growing tree has a clearly positive carbon balance.
In comparing carbon binding to the carbon dioxide emissions from different activities, binding rates of a one tree in 80 years (volume of a tree: 1 m3) and one forest hectare (100m x 100m) in one year have been used. Forest hectare here is a 40 years old spruce stand growing on herb-rich heath forest in Southern Finland. Forest stand has been thinned once and has a stem number of 990 trees per hectare.
In northern boreal forests it takes up to 70 - 100 years for a spruce tree to reach its full dimensions. The volume of full-grown spruce tree varies a lot, but assuming it to be one cubic meter, carbon content of it corresponds around 750 kg of carbon dioxide. One hectare of 80 years old spruce forest might have a standing volume of, for example, 300 cubic meters, resulting in 225 tons of captured carbon dioxide.
Northern managed forest landscape is a mosaic of different aged forest stands. Some of them are young seedling stands just having started their growth, some are mature forests ready to be regenerated. In between there are middle-aged stands that are peaking their growth. There are also forests protected for their biodiversity or other value. For the forest carbon sink capacity, it is important that harvesting volumes do not exceed the growth in landscape level, that forest health and biodiversity are addressed to secure vital growth and new tree generation is always established after final harvestings.
Climate positive forestry means, that forests are managed as carbon sinks. It also entails good forest management practices, improving forest growth. Sustainable and climate positive forest management is one of the key elements in world’s transition to fossil-free economics. Many traditionally fossil-based items can be replaced by using renewable wood-based products. When trees are harvested and used for manufacturing different wood-based products the same carbon that was captured from the atmosphere by trees during their growth keeps stored in those products over their lifecycle.
Carbon binding modelling and comparisons to emissions
Modeling is based on measurement data from a single tree, recorded in SMEAR II research station of Helsinki University over the past 20 years. Most comprehensive data is recorded for Scotch pine (Pinus sylvestris) but the data can also be used to model the carbon sequestration of Norway spruce (Picea abies) by correcting the relationships between the canopy, foliage, roots, trunk and other parts of the tree with allometric models and so-called BEF-coefficients (Biomass Expansion Factor). Furthermore, the model can be scaled to the desired level of growth so that the increment of the wood, as well as carbon sequestration, correspond as closely as possible to the tree individual in focus. This modeling results in both daily and hourly carbon sequestration and release forecasts (CO2/day, CO2/hour), corresponding to the average annual figures of a spruce tree in question.
In comparison between carbon sequestration and emissions from different sources, following emission figures have been used. The figures are indicative.
One kilometer drive by gasoline driven private car: 155g/CO2
6 kg load of laundry washed: 750g/CO2
One serving of chicken with rice: 870g/CO2
One hour mobile phone call: 3,42g/CO2
Helsinki – Singapore flight per passenger: 377 000 g/CO2