3.3 Project carbon sequestration

Useful meta analyses on forestry and carbon

Mathias Mayer o.fl. 2020. Tamm Review: Influence of forest management activities on soil organic carbon stocks: A knowledge synthesis. Forest Ecology and Management, Vol. 466. ISSN 0378-1127. https://doi.org/10.1016/j.foreco.2020.118127.

Ameray, A., Bergeron, Y., Valeria, O. o.fl. Forest Carbon Management: a Review of Silvicultural Practices and Management Strategies Across Boreal, Temperate and Tropical Forests. Curr Forestry Rep 7, 245-266 (2021). https://doi.org/10.1007/s40725-021-00151-w

A few words on land preparation

Tillage using a TTS harrow is a mild method of land preparation before tree planting compared to other methods available. The wounds heal quickly and tillage increases the life expectancy of the trees, accelerates their growth and thus the results expected from the relevant forestry project. Photographs of forested areas that have been processed with a TTS harrow show that the traces are quickly disappearing.

There has been some discussion about tillage, which is quite a widely used practise in Icelandic afforestation projects, where conditions call for such measures. There seems to be some misunderstanding going on concerning these practises. In the discussion, several things are claimed that do not stand up to closer scrutiny. Therefore, it is right to explain the purpose and consequences of land preparation in Icelandic forestry.

The purpose of tillage is mainly three-fold; 1) to create a planting site where competition of other vegetation with young tree seedlings is reduced, 2) to increase the summer soil temperature and 3) to facilitate planting. All this increases the survival and growth of the trees and reduces the cost of afforestation measures. Seedling die-offs are costly. The cost of loosing 20% of newly planted plants is about 100,000 ISK per hectare of land. Therefore, it is very important to put in all the effort to reduce those losses. That trees start growing relatively quickly and well is also important, i.a. so that they start to sequester carbon as soon as possible.

Gentle land preparation

The most widely used tillage machine today in Icelandic forestry is the so-called TTS harow. The machine has two coarse-toothed discs that roll over the top layer of the vegetation without cutting deep into ground. It rips rather than cuts and creates channels that are slightly irregular, unlike plowing which cuts through the vegetation and digs deeper into the soil. As a result, when the traces heal, they look more like hummocks, rather than plowshares. Although TTS land preparation tends to looks shockingly at first, it is actually a gentler tillage than most others, faster to heal and eventually forms a landscape unrecognizable from typical Icelandic hummock land. TTS tillage does not dry out the land and leads to much lower CO₂ emissions than deeper-reaching tillage methods. Since the tillage traces are quickly-healing, CO2 emissions are short-lived. The goal is to create good conditions for young tree seedlings in their first years of growth, not to create permanent wounds.

Afforestation mostly on eroded land

Sometimes it is criticized that planting is being done in "overgrown land" which calls for land preparation measures. On the one hand, this criticism is based on the idea that the only purpose of forestry is to revegetate sparsely vegetated or eroded land. On the other hand, there is the notion that what seems to be fully grown land is in some kind of "pristine" state. Both are far from the case. The purpose of forestry is multifaceted, sometimes replanting, sometimes timber production, sometimes restoration of ecosystems and habitats, sometimes outdoor recreation, sometimes shelter, and in later years not least the increased effort to sequester CO₂ from the atmosphere to curb escalating climate change. Most of these goals can be better achieved on land where soil is still present than on sites where soil has been washed away by erosion. The land types most commonly used for afforestation in Iceland are indeed eroded land, heathland and grassland. All those land types are shaped by the extensive deforestation which followed the human settlement of Iceland and the unsustainable form of land use that followed, mostly sheep grazing. Those ecosystems in question are far from being in their original or pristine condition.

Traces disappear quickly

It is easy to take pictures of recently harrowed land and call it a blemish. Tillage in forestry does a lot of good, however, and the methods currently used do not cause permanent damage; the traces are quick to heal. Tillage with a TTS harrow is a much better land preparation method than e.g. plowing or spraying herbicides. The Icelandic Fores Service – Skógræktin will therefore continue to recommend tillage and continue to monitor the development of such technologies to ensure the application of the best available methods at any time.

Example of land preparation and its results

Afforestation activities at Ormsstaðir in Breiðdalur, Iceland, began in the summer of 2021. Seedlings were planted there on around 140 hectares of land over the next two years with funding from the organization One Tree Planted. As traces of the tillage that took place there caught people's eyes, it was considered necessary to explain the purpose of those measures and describe how the traces disappear in a few years. Such land preparation accelerates the growth of forest seedlings when planted on sites with dense vegetation cover.

The goals of afforestation projects in Ormsstaðir are to sequester carbon, strengthen the ecosystem, create facilities for outdoor recreation and produce timber in the future. Part of achieving these goals is to ensure that the forest grows well so that we do not have to wait long for that future.

Part of the area has been tilled in preparation for planting, using the so-called TTS harrow for that purpose. The tillage greatly improves the conditions for planting and the growth conditions of the tree seedlings. Tillage increases soil temperature and releases nutrients, both of which are very useful for the initial growth of young tree plants. Tree growth is up to double in tilled areas compared with untilled areas. Research both in Iceland and abroad shows that the increased growth more than compensates for the small CO2 emissions that occur as a result of the tillage. Planting began immediately after the tillage, and the tree seedlings got a good start as a result.

Even thouth tillage may look shockingly at first, it is definitely beneficial and the wounds will heal in a few years. We hope that people will show understanding and celebrate with us the creation of a new and thriving forest.