A multitaxon biodiversity dataset from hemiboreal forests of different stand ages and management histories.

Data description: This dataset compiles standardized multitaxon biodiversity data from >300 forest stands in the European hemiboreal region. It includes species lists and species-level abundance data for six groups - beetles, bryophytes, lichens, polypore fungi, molluscs, and vascular plants - surveyed across a wide range of forest types, stand ages, and management histories. Species identifications are of high taxonomic resolution; for polypores and lichens, morphological determinations were often complemented by DNA barcoding or chemical analyses to ensure accuracy. A subset of stands has been surveyed repeatedly, enabling assessment of temporal changes in forest biodiversity. Study area: Estonia, hemiboreal forest zone. Field sampling was conducted between 2005 and 2025. Data coverage: The dataset covers 338 forest stands (including recent cutover stands) represented by 2-ha plots and includes records of >2200 taxa across six major groups. All six groups were recorded in 16% of the stands, and half of the stands include data for at least three groups, with the most complete coverage for polypores and lichens. The stands represent the major hemiboreal forest types along gradients of dominant tree species and soil fertility, ranging from low-productivity dry Scots pine forests to black alder-dominated swamps, with strong representation of productive Norway spruce-deciduous mixed forests. Stand ages range from recent post-clearcut stages to forests with dominant tree layers exceeding 200 years. Old stands without signs of management are distinctly represented and serve as natural baselines for old-growth biodiversity in the region. This is the most comprehensive and representative multitaxon forest biodiversity dataset currently available from the European hemiboreal zone. Methods: Within each species group, field sampling was performed by experts and followed consistent standardized protocols across study stands, yielding comparable species-level abundance data. Applications: The dataset enables analyses of within- and cross-taxon biodiversity patterns in relation to forest type, stand age, and management history. Combined with detailed forest structure data available for most study stands from a parallel published dataset, it enables linking biodiversity variables to habitat availability and above-ground tree carbon. Geopositioned plots facilitate integration with spatial layers and remote sensing products, enabling extrapolation of biodiversity-habitat (or aboveground tree carbon) relationships across larger forest landscape mosaics, also beyond the hemiboreal region. The temporal span of the dataset enables both repeated surveys of the same stands to assess biodiversity change over time and comparisons with stands of similar characteristics to infer broader temporal shifts in forest biodiversity. The strong representation of old-growth stands establishes a robust natural baseline for evaluating biodiversity responses to forest management and long-term landscape change.