Introduction: Increment cores were sampled across 17 different monoculture stands in Finland. Coring and annual ring width measurements were conducted in 2004 and 2005. Data is in 4 separate files based on tree species. Metadata file has been included as an excel file. This dataset was used in the following publication: Lehtonen, A., Lindholm, M., Hokkanen, T., Salminen, H., & Jalkanen, R. (2008). Testing dependence between growth and needle litterfall in Scots pine--a case study in northern Finland. Tree Physiology, 28(11), 1741–1749. https://doi.org/10.1093/treephys/28.11.1741 This dataset is linked to [Long-term litter fall data series from 34 boreal forest stands in Finland]. Both datasets originate from partially overlapping study sites but include different measurements collected under the same field campaign. They should be considered complementary but independent datasets. Tree increment data has been used with litterfall data for statistical analysis by Lehtonen et al. (2008) and data collections has been described there. Increment core files: The widths of the annual growth rings are measured from the increment core samples with a precision of 0.01 mm. Metadata: Metadata file includes information on stand level, tree level and core level. README: Site level: - Location and tree stand information was measured 10-15 years prior to the increment coring. - Number of samples refer to total amount of annual rings measured from a stand and not how many cores were measured. For each tree, only 1 core was measured. Tree level: - No SocialStatus information available. Each tree's DBH and Height measurement year in a new column. Core level: - For each tree, only 1 core was sampled. sampleID is just a combination of siteID and TreeID. The data files dont have a column for sampleID. sampleID = TreeID. - PithOffset: If the core did not reach pith, samplers estimated how many rings were remaining until pith. Otherwise set as 0. - Heartwood boundary (additional column): Number of rings from the outermost ring until the heartwood boundary. Increment core files: - The increment core measurements were combined into files based on the tree species of the site. - File names: - Pinus_sylvestris_increment_core.csv - Picea_abies_increment_core.csv - Larix_sibirica_increment_core.csv - Larix_decidua_increment_core.csv