NUKAFI

Utilization of standing-stored damaged spruce timber from calamity areas, depending on damage progress and wood quality

The "NUKAFI" project is a merger of the "KalaNutzBau" and "Spruce2Use" projects, which were submitted to the Agency for Renewable Resources (FNR) as part of the "Dealing with calamity areas and calamity wood" funding call under the Forest-Climate-Fund funding guideline.

The background to the project is that forestry and forest management are strongly influenced by climate and weather events, which has been reflected in an increase in forest damage caused by storm events, droughts and insect infestation. Three dry years in a row, hurricane Friederike in January 2018, forest fires and the mass proliferation of insect pests have damaged large areas of native trees and are still causing massive damage. Enormous quantities of damaged timber are the result. Due to the high number of spruce trees dying or already dead from beetle infestation, private and public forest owners have found themselves in the unusual situation of having to remove large quantities of damaged timber from the forest in a short space of time. With increasingly fewer workers and a high technical capacity required for utilisation, priorities have to be set for the harvest. The first step is to clear traffic routes of fallen or broken trees and to remove and log any safety-relevant trees that are still standing from the forest. However, as most of the storage areas near the forest are full, many forest owners are faced with the question of whether and for how long the dead spruce trees (snags) can remain standing in the forest and how long this wood can still be used for harvesting and value-adding purposes. The same question applies to dry storages outside the forest. The aim of the project is to carry out systematic investigations on dead or damaged Norway spruce (Picea abies (L.) KARST.) from bark beetle infestation, to show how their wood quality changes if the trees are not initially harvested, but remain standing in the forest - in the sense of "standing storage" - until their further use. In addition to this, tests are to be carried out on dry-stored calamity spruce wood of different storage durations. The focus here is on the question of whether and how the wood quality changes depending on the duration of standing storage and the respective location the timber is from. Also, it is important to determine at what quality it is still possible to use the wood in durable construction products, such as cross-laminated timber. Standing storage is not intended to be a permanent solution for dealing with the resource or an incentive to leave bark beetle infested spruce trees in the forest. Rather, it should be seen as a possible reaction to the oversupply of salvage timber and the associated problems, such as a lack of processing capacities. With the creation of guidelines for forest owners and wood processors, the project is also pursuing the implementation of a product-specific sorting procedure for standing bark beetle infested spruce, which is intended to assess the potential uses and limitations of the wood that is stored standing. With a view of optimising the material utilisation of calamitous wood, this should result in understandable recommendations for action, especially for product-specific sorting of standing spruce trees in the stand for forest users. If the outcome is positive, the research project can thus contribute to an increase in efficiency in the material utilisation of spruce calamity wood.

The aim of the project-partner, the University of Göttingen, is to record the wood quality and damage progress for representative damaged spruce stands. The results form the essential basis for deriving possible material utilisation pathways. The qualities determined on the basis of quality grading are to be analysed statistically and included in a guideline. This should enable the forest owner or forest manager to carry out simple sorting of the trees.

As part of a further work package, lamellas of different qualities, from different locations and from the dry storages, will be brought to Göttingen in order to analyse the technical drying process and derive recommendations from the drying qualities. Due to the damage and the dying process, it can be assumed that the drying schedules used to date will have to be adapted. The reasons for this are the presumably different wood moisture distribution, but also the generally low wood moisture content. In the area of the drying process, the lamellas are to be analysed with regard to moisture distribution, cracking, deformation and stresses in accordance with the guidelines of the European Drying Group (EDG) for assessing the quality of technical drying. In addition, tests on the elastomechanical properties, sorption behaviour, bulk density profile and microscopic images are planned.