Nationell riktad skadeinventering (NRS): inventering av skador på ungskog 2022 i Norrbotten, Västerbotten, Västernorrland och Jämtlands län

During 2022 SLU has carried out a sample inventory of forest condition and damage in young forest in northern Sweden within the national target-tailored forest damage inventory (TFDI) program. The inventory was conducted on behalf of the Swedish Forest Agency. A total of 594 sample plots were inventoried in the four northernmost counties. The sample areas were located in stands that were subject to final felling during the period 1983 – 2013, which corresponds to an area of just under 1.4 million ha. All trees / plants, in a certain height range, within three small plots (200 m2 ) were counted and assessed for damage. Some damage were assessed according to thresholds, while others such as resin top disease were recorded as soon as they could be found.The total number of trees increases from north to south, 6500 trees ha-1 in the county of Norrbotten and 9250 trees ha-1 in the county of Västernorrland. Broadleaf trees account for over half of the trees in all four counties. The density of young forests, described as the number of main tree stems ha-1, shows that 61% of the area has more than 2000 trees ha-1. The smallest proportion of trees are found in the county of Norrbotten (53 %) and the largest in the county of Västernorrland (71 %). Less than 1000 stems ha-1 are found on 7 % of the area, where the county of Västerbotten has the smallest proportion (3 %) and the county of Norrbotten the largest proportion of the area with less than 1000 stems ha-1 . Just under 40 % of all main tree stems have a damage. The most common type of damage is damage to the trunk. For older damage, it is difficult to trace the cause of the damage, which means that a large part of the registered damage ends up in the group of unknown / other damage. Grazing by wildlife predominate among the known causes of damage, especially in pine. Sixteen percent of all pine in young forest has damage caused by moose. Fresh damage caused by moose were observed at 9 % of the pine trees. Just under 15 % of all damage are caused by fungus. Damage by resin top disease occurs throughout the area. Larger damage resin top disease are mainly seen in the county of Norrbotten, where 5 % of pine in pine-dominated stands is affected. Compared with inventories carried out 10– 15 years ago, this year's inventory shows a tendency for more damage of resin top disease in Norrbotten's coastal country.