Target Tailored Forest Damage Inventory (TFDI) - Inventory of damage by bark beetle in Götaland and Svealand 2023

Inventories of forest damage are carried out within the Swedish University of Agricultural Sciences (SLU) Forests programme. An annual monitoring of the most important sources of forest damage is carried out by the Swedish National Forest inventory (NFI). Although the Swedish NFI is an objective and uniform inventory of forest damage in Swedish forests at national and regional scales, less common or less widespread occurrences of forests pests and pathogens are difficult to survey solely through large-scale monitoring programmes. There is a need for complementary inventories to facilitate timely delivery of relevant information. Thus Target-tailored forest damage inventories (TFDI) aiming at providing data for operational decisions making at local level, and linked to specific damage events were introduced. TFDI’s are developed to give rapid response to requested information of specific damage outbreaks. The TFDIs are carried out in limited and concentrated samples, with flexible but robust methods and design. The data collected in the TFDI shall also be of such quality that it can be useful in research. During 2023 TFDI carried out a sample inventory of the volume Norway spruce (Picea abies) damage by European spruce bark beetle (Ips typographus) and/or damage by Four eyed spruce bark beetle (Polygraphus poligraphus) in older spruce forest. The inventory were conducted in the region of eastern Götaland (county of Östergötland, Kronoberg, Kalmar and Blekinge) and in Svealand in the county Södermanland, Örebro, Västmanland, Stockholm, Uppsala, Värmland and southern part of Dalarnas (municipality of Ludvika, Avesta, Hedemora, Falun, Smedjebacken, Leksand, Gagnef och Vansbro) and in the southern part of Gävleborgs region (Gästrikland). This as a follow-up to the extremely hot and dry summer in 2018, which resulted in many drought stressed spruce trees that favored the spruce bark beetle. The spruce bark beetle populations, which were already high before, increased rapidly and have in recent years caused extensive damage to spruce in Götaland och Svealand. This year´s inventory is a follow-up to the inventories carried out in 2020, 2021 and 2022. The inventory includes both standing infested trees as well as infested wind-felled trees and stumps from felled infested trees. The purpose of the inventory was to estimate the volume Norway spruce damage by the given bark beetles, but also to highlight geographical distribution and the appearance of the damage in different forest sites. The results from the inventory should be available for decisions making basis in forestry managements. The inventory was stratified by an objective sample of all the National Forest Inventory permanent sample plots in Götaland and Svealand. Included plots within the sample was all older thinning forest and final felling mature forest consisting of at least 7/10 proportion of spruce. For the selection of plots LPM (local pivotal method, Grafström et al) is used where the selection was spread based on the geographical position and the spruce volume of the sample plots. The radii of sample plots used for the damage inventory was 20 m, the area which was included for the described site. This means that the inventoried area was smaller than during the 2020 inventory, when the radius was 25 m. Other parts of the plot were not included in the inventory. The inventory in 2023 includes both trees with fresh infestations (season 0) by the European spruce bark beetle and/or damage by Four eyed spruce bark beetle and trees infested last year (season 1) by the European spruce bark beetle. Diameter at breast height was measured on damage trees and wind-felled trees. Diameter on stump from cut trees with fresh damage was measured. From 2022, the sample was expanded in order to possibly provide reliable estimates at the county level. In 2023, the inventory was limited to the eastern parts of Götaland, as previous years' inventories showed declining damage in western Götaland. However, the area in the north was expanded to include southern Dalarna and southern Gävleborg counties after indications of increased damage in these areas. In 2023, fresh infestations by the four eyed spruce bark beetle were also included after reports of increased damage by this bark beetle species as well. The dataset consist at plot level of 1142 rows with 28 columns, at tree level (season 0) of 292 rows with 16 columns and at tree level (season 1) of 350 rows with 12 columns. The content and scope of the inventory has been developed in consultation with Swedish Forest Agency. References: Grafström, A., Lundström, N., & Schelin, L. Spatially Balanced Sampling through the Pivotal Method. Biometrics, 68(2), 514-520, https://doi.org/10.1111/j.1541-0420.2011.01699.x Some assessed and used variables: At sample plot level: Plot area measured The proportion of spruce at the sample plot Maturity class Number of infested trees Logging Sanitation At tree level season 0: Is the tree dead or alive? Position of tree – standing, wind-felled, stump Diameter at breast height Tree volume At tree level season 1: Diameter at breast height Tree volume See the document "Data_description" for more detailed information. As additional documentation, field instructions for the inventories are also provided, both for the specific inventory and for the National Forest Inventory (NFI). An English version of the National Forest Inventory field instruction is available for year 2021 only, which is why this is included here.