Sample tree data from the Swedish National Forest Inventory

The data set include a list of sample trees ≥10 cm DBH from the Swedish National Forest Inventory. Individual sample trees measured and cored within a ten metre wide transect during the 1923-1929 survey or circular sample plots during the 1953-1962, 1983-1992, and 2013-2022 surveys are included. The 10 cm threshold was used to exclude smaller diameter trees measured on small parts of sections or plots. Variables include cluster and plot ID, tree species, diameter, tree age at breast height and total tree age, land-cover class and expansion factors for estimation of number of trees and volumes. The current NFI is based on an annual sample of about 20,000 circular plots, grouped into clusters, of which about 12,000 are surveyed in the field each year. Data for additional sample trees and more variables for individual sample trees can be obtained from the Swedish National Forest Inventory. More details are presented in the article, see Jacobsson, Jonas, Fridman, Jonas, Axelsson, Anna-Lena, Milberg, Per (2025). An aging population? A century of change among Swedish forest trees. Forest Ecology and Management. 580:122509. https://doi.org/10.1016/j.foreco.2025.122509 The data file contains 17 columns and 384790 rows.