LIFE 4forest has sent a group of students into the forest to drill samples from the old trees The purpose is to collect material that can provide answers about how the trees grow. The research has been literally sparking, as the drilling is so demanding that all drilling machines spark. However, about 1000 drill samples have been collected and are now to be analysed.
The Width of the Annual Rings Is the Source of Knowledge
In this part of LIFE 4Forest, a selection of coniferous plantations converted to close to nature forest management or in the process of converting has been chosen. In a number of the trees, samples are drilled, and the width of the annual rings is measured to understand the tree's growth.
The width of the annual rings in converted plantations is compared with reference plantations nearby, which are managed as normal coniferous plantations.
Does the Trees Grow Faster?
Man ser altså på tilvæksten i bevoksningerne, ved at analysere årringsbredden. Tesen er, at når træerne i skærmen får mere lys, så vokser de også mere og hurtigere. Det skal analyser nu vise og målet er at udvikle modeller, der kan forudsige den tilvækst, træerne får med skærmstillingen.
Konvertering af nåleskov
We know a lot about upper storey and growth in deciduous tree plantations, but knowledge in coniferous trees is limited, and the drill samples are intended to change that. This study only looks at the conversion of coniferous plantations to close to nature forest management.
Changing the management form creates changes in the structure of the plantation and the composition of species. The effects of this change are addressed by LIFE 4forest in different ways: economically, biologically, and in this study, in the change of growth.
Good Decision Basis for Forest Owners
Ditlev Otto Juel Reventlow, from the Department of Geosciences and Natural Resource Management at the University of Copenhagen, leads the research, and his dream is to create new models:
“I dream of being able to create a good decision basis for those who need to convert spruce plantations of various ages, especially older forests. It is very motivating that we are now measuring on such a large scale. It gives hope that we can build models to predict how plantations are best treated and put figures on how much upper storey trees actually grow,” says Ditlev Reventlow.
The Design of the Experiment
There has already been a lot of measurements of how the forest develops when converting into close to nature forest management, including growth, which can be read in the article: "What we know about close to nature forest management today".
Therefore, good and bad examples of the conversion of coniferous plantations are already known. However, LIFE 4forest has so far primarily focused on whether the new regeneration succeeds. Now it's time for the upper storey, which is crucial for the economy of a conversion and therefore very relevant to clarify.
Five Forests Selected
Five forests for sampling have been selected: Kllosterheden, Feldborg, Gludsted/St. Hjøllund, Addit Skov (Salten Langsø), and Rold Skov. Except for Rold Skov and Addit Skov, these are heath plantations. Especially on the heath, the uniform coniferous plantations are common.
Monocultures Are Good for Experimental Design
The uniformity also makes it easier to make a good experimental design. The large uniform plantations provide the opportunity for part of a plantation to be converted while the rest of the plantation continues to be managed as a coniferous plantation. So, there is the perfect comparison basis.
Martelloscopes Make Us Wiser About Growth
Rold Skov and Addit Skov have been selected because this is where the martelloscopes are located, which represent plantations, which are already quite far into the conversion process. This provides an opportunity to learn more about the growth dynamics in more unevenly aged forest.
In Rold Skov a Douglas fir-dominated forest is sampled and a grand fir-dominated forest is sampled in Addit Skov. Rold Skov and Addit Skov do not represent outright conversions but make us wiser about the growth in more mature natural forest stands.
Which Plantations Are Sampled?
Some of the stands described in the preliminary manual for close to nature forest management are also included in this drill sample study to supplement knowledge about the economy of conversions. LIFE 4Forest also has four martelloscopes that cover 1 hectare of the forest, where all trees are measured.
How Do You Select the Trees?
A number of the plantations included in the LIFE 4Forest project were measured in 2020. Therefor the students from HedeDanmark, the Danish Nature Agency, and Salten Langsø who were sent into the forest to drill samples already had GPS coordinates to go after to find exactly the same trees again.
Two samples are taken from 10 trees of all species in the upper canopy of the forest. This provides knowledge on how different tree species perform. In the martelloscopes areas, where all trees are mapped and measured, measurements are taken for up to 25 trees per species. The martelloscope areas contribute new dimensions to the research by providing detailed information on a small area.
>> Read more about martelloscopes
Research Sparks
The sample collection has literally sparked. The resistance in the trees is so great that all the drilling machines used for sample collection spark when used afterwards. It should be noted that the setup shown probably would not work for deciduous trees, because they are simply too hard. In that case, a special high-torque setup is needed.
Written by Janne Bavnhøj