2025 Stand Data from the Danish Mixed Forest Experiment 1512 with Beech, Douglas Fir, Silver Fir and Norway Spruce on Sandy Soil

Summary This dataset contains the first full stand-level measurements collected in 2025 from Experiment 1512, a long-term mixed forest experiment located in Gludsted Plantation, Central Jutland, Denmark. The data is collected as part of the MIXFOR project.The experiment examines the growth, structure, and management responses of four tree species—European beech (Fagus sylvatica), Douglas fir (Pseudotsuga menziesii), silver fir (Abies alba), and Norway spruce (Picea abies)—on nutrient-poor glaciofluvial sandy soils. The updated dataset marks the transition of Experiment 1512 from a shelterwood underplanting study to a mixed forest experiment designed to investigate mixed-species silviculture under different forest management strategies. The experimental design includes species combinations ranging from monocultures to mixtures, combined with two silvicultural thinning regimes: traditional low thinning and crop-tree thinning, with an embedded deer-protection testing as well. Measurements were carried out across five blocks representing variation in shelter conditions. The 2025 measurement campaign includes detailed stem-level data for the understorey and overstorey (DBH, status, species, position). On a subsample of trees, height, crown height, crown diameter and defoliation is also measured.  Specifically for the understorey, crop-tree identity, bark protections measures and bark stripping damages is also recorded. Based on this data, tree carbon stock is calculated. The dataset provides a baseline for long-term monitoring of stand development, species interactions, thinning responses, and soil processes in young mixed forests on sandy soils. Because mixed forest experiments on such sites remain rare in Northern Europe, this dataset supports research on climate-smart forestry, species complementarity, and resilience-oriented management under nutrient constraints. Acknowledgement This research was supported by the project MIXFOR (G-04-2023-5), funded by the European Union through FORWARDS (Horizon Europe Project No. 101084481) grants to third parties managed by European Forest Institute. This dataset was also made possible with financial support from Godfred Birkedal Hartmanns Familiefond (grant no. 2024-0003) although it was unfortunately not possible to specify this funding body under Funding in Zenodo. Citation Reventlow, D.O.J., Nord-Larsen, T., Standorf, M.F., Hansen, L-L.H., & Skovsgaard, J.P. (2025). 2025 stand data from the Danish mixed forest Experiment 1512 with beech, Douglas fir, silver fir and Norway spruce on sandy soil (Version 1.0) [Dataset]. Zenodo. https://doi.org/10.5281/zenodo.17831699 Data Use Notice These data represent the baseline measurements of Experiment 1512 collected in 2025. Further measurements and scientific analyses are ongoing. If you plan to use or analyse this dataset, collaboration with the project team is strongly encouraged, as additional context, metadata, and developing results may improve interpretation and scientific value.