## 1. GENERAL INFORMATION
- **Title**: Agents of European beech decline
- **Authors** (author's first and last name, institution, ORCID):
Nikica Ogris, Slovenian Forestry Institute, https://orcid.org/0000-0002-4058-9417
Ana Brglez, Slovenian Forestry Institute, https://orcid.org/0000-0001-7714-8458
Andreja Kavčič, Slovenian Forestry Institute, https://orcid.org/0000-0002-0302-955X
Janja Zajc Žunič, Agricultural Institute of Slovenia, https://orcid.org/0000-0001-8479-7069
Maarten de Groot, Slovenian Forestry Institute, https://orcid.org/0000-0002-5721-6676
Barbara Piškur, Slovenian Forestry Institute, https://orcid.org/0000-0002-9914-4930
- **Institution address**:
Slovenian Forestry Institute, Večna pot 2, 1000 Ljubljana, Slovenia, ROR organization identifier: https://ror.org/0232eqz57
Agricultural Institute of Slovenia, Hacquetova ulica 17, 1000 Ljubljana, Slovenia, ROR organization identifier: https://ror.org/030dahd49
- **Contact address**: nikica.ogris@gozdis.si
- **Abstract**: Data collected in the project "Diseases, pests and drought stress of European beech at various climate change scenarios (V4-2026), Working package 2: Causes of the decline of European beech in Slovenia". Data was collected on 40 sampling plots, 39 plots on systematic grid 16 × 16 km and one additional plot in the Alps. On each sampling plot two trees were felled, altogether 80 trees: one visually healthy, and one damaged tree. Visual assessment of crown condition and damaging agents was evaluated following methods of ICP Forests. Rhizosphere soil was collected from each sampled tree for the Phytophthora baiting assay. For fungal isolations five parts of a tree were sampled: leaves, twigs (up to 20 mm in diameter), branches (over 20 mm in diameter), trunk, surface roots and root collar (up to 25 cm from the ground). Four samples from each tree part were collected. Finally, 20 samples per tree and 40 samples per plot were collected, yielding 1.600 samples in total. The samples were surface sterilized. Four subsamples were collected from one sample, altogether, 6.400 subsamples/tissue pieces. Four subsamples were plated on potato dextrose agar supplemented with streptomycin. Fungi and Phytophthora species were identified using molecular techniques, while insects were identified based on their morphological characteristics. 
- **Keywords**: Fagus sylvatica, decline, damage, complex disease, fungi, insects, Phytophthora, endophytes, stress
- **Date of data collection**: 
Field data: from May 2021 to September 2022
Identification of fungi: from 20 January 2023 to 9 October 2023
Identification of Phytophthora: 21 May 2025
- **Geographic coverage**: Slovenia
- **Data repository**: DiRROS repository, https://dirros.openscience.si
- **Funding Information**: The Ministry of Agriculture, Forestry and Food and the Slovenian Research and Innovation Agency (project V4-2026 Diseases, pests and drought stress of European beech at various climate change scenarios, Research Programs P4-0107 Forest Biology, Ecology and Technology and P4-0431 Next Generation Agriculture)

## 2. LICENSING & CITATION OF THE DATASET
- **License**: CC BY 4.0: https://creativecommons.org/licenses/by/4.0/ 
- **Recommended citation for this dataset**: Ogris N., Brglez A., Kavčič A., Zajc Žunič J., de Groot M., Piškur B. 2025. Agents of European beech decline. Complete scientific database of research data. 2025. Ljubljana, Slovenian Forestry Institute & Agricultural Institute of Slovenia. [Accessed "Date"]. Retrieved from: https://dirros.openscience.si/

## 3. RELATED RESOURCES
- **Associated publication**: Ogris N., Brglez A., Kavčič A., Zajc Žunič J., de Groot M., Piškur B. 2026. European beech decline in Slovenia is caused by a complex disease. Forest Ecology and Management, 603: 123464. https://doi.org/10.1016/j.foreco.2025.123464, https://www.sciencedirect.com/science/article/pii/S0378112725009727
- **Associated publication**: Ogris N., Kavčič A., Zajc J., Brglez A., de Groot M., Piškur B. 2023. Bolezni, škodljivci in sušni stres pri navadni bukvi v različnih scenarijih podnebnih sprememb (V4-2026). Aktivnost 2.1: Vzroki hiranja navadne bukve v Sloveniji. Ljubljana, Gozdarski inštitut Slovenije: 31 str. URL: https://www.zdravgozd.si/projekti/bukev/doc/A2.1_Vzroki_hiranja_navadne_bukve_v_Sloveniji_fin.pdf

## 4. DATA COLLECTION & PROCESSING
- **Methodology**: See associated publications.
- **Instruments/Tools Used**: Height was measured with Vertex III (Haglöf, Sweden). Coordinates were recorded with handheld GPS GPSMAP 64s (Garmin, USA).
- **Data processing steps**: Field data was collected using Microsoft Excel on tablet. Data from different plots were joined into one Excel file. Data from Excel File was copied to SQL Server 2022 database from where data analysis and data export was made. 
- **Quality assurance measures**: Data about damaging agents, damage extent, tree data and defoliation was collected using international ICP Forest methodology. Data collection in Excel used data validation with predefined lists of possible values. Total number of samples per tree part was always 4. 

## 5. FILE INVENTORY (file name, description, number of rows, size [bytes])
plots.csv, list of sampling plots and their location, 40 rows, 611 bytes
trees.csv, list of sampled trees and their data (diameter, height, defoliation, sampling date), 80 rows, 3451 bytes
samples.csv, list of samples (tree class, tree part and sample location), 400 rows, 23251 bytes
branches_diameter.csv, diameter of branches and twigs, 638 rows, 19475 bytes
damage_extent.csv, damage extent by ICP Forests methodology, 482 rows, 44010 bytes
insects.csv, damage extent by insects, 588 rows, 27157 bytes
morphotypes.csv, frequency of fungal morphotypes, 2896 rows, 90637 bytes
morphotypes_identification.csv, identification of fungal morphotypes, 72 rows, 1786 bytes
phytophthora.csv, identification of Phytophthora spp., 3 rows, 101 bytes
- **File format**: CSV, text file, column delimiter: TAB, row delimiter: CRLF, first row contains column names, character encoding: UTF-8
- **Recommended software to data open files**: Notepad, Microsoft Excel, R, etc.

## 6. DATA STRUCTURE (**file**, column name: description, unit)
- **plots.csv**
Plot: ID of the sampling plot
Lon: longitude (decimal, degrees, WGS1984)
Lat: latitude (decimal, degrees, WGS1984)
**Note**: Location of sampling plot is given approximately because sampling plot location is confidential. 

- **trees.csv**
ID: tree ID
Plot: ID of the sampling plot
Class: tree class (Damaged, Healthy)
DBH: diameter at breast height (cm)
Height: tree height (m)
Defoliation: defoliation (%), determined by ICP Forests methodology
Sampling Date: sampling date (YYYY-MM-DD)

- **samples.csv**
SampleID: ID of the sample
Sampling Date: sampling date (YYYY-MM-DD)
ID: tree ID
Plot: ID of the sampling plot
Class: tree class (Damaged, Healthy)
Affected part: affected part of tree [Trunk, Roots and collar, Leaves, Twigs (< 2 cm), Branches (> 2 cm)]
WD: number of samples from discoloured wood
WH: number of samples from healthy wood
BO: number of samples from outer bark
BI: number of samples from inner bark
BH: number of samples from healthy bark
LF: number of samples from diseased leaf
LH: number of samples from healthy leaf
Total: number of samples (always 4)

- **branches_diameter.csv**
ID: tree ID
Plot: ID of the sampling plot
Class: tree class (Damaged, Healthy)
Affected part: affected part of the tree [Twigs (< 2 cm), Branches (> 2 cm)]
Diameter: diameter (mm)

- **damage_extent.csv**
ID: tree ID
Plot: ID of the sampling plot
Class: tree class (Damaged, Healthy)
Affected part: affected part of the tree [Leaves; Branches, shoots and buds; Trunk and collar]
Specification of affected part: specification of affected part [Leaves, Twigs (diameter < 2 cm), Branches diameter 2 to < 10 cm, Branches diameter ≥ 10 cm, Top leader shoot, Main trunk within the crown, Trunk between the collar and the crown, Roots (exposed) and collar (≤ 25 cm height), Whole trunk] 
Location of affected part in crown: location of affected part in crown [Upper crown, Lower crown, Patches, Total crown]
Agent group: damaging agent group [Abiotic agents, Direct action of man, Fungi, Game & grazing, Insects, Other]
Age of the damage: age of the damage, category [Fresh, Fresh and old, Old]
Extent of the damage: extent of the damage (%, determined by ICP Forests methodology)
Damage extent on the stem: damage extent on the stem, category [< 1 dm2, 1-5 dm2, 5-20 dm2, > 20 dm2]

- **insects.csv**
ID: tree ID
Plot: ID of the sampling plot
Class: tree class (Damaged, Healthy)
Affected part: affected part of tree [Trunk, Roots and collar, Leaves, Twigs (< 2 cm), Branches (> 2 cm)]
Species: Latin name of insect species
Extent of the damage: extent of the damage (%, determined by ICP Forests methodology)

- **morphotypes.csv**
SampleID: ID of the sample
ID: tree ID
Plot: ID of the sampling plot
Class: tree class (Damaged, Healthy)
Sample location: sample location [WD=Discoloured wood, WH=Healthy wood, BO=Outer bark, BI=Inner bark, BH=Healthy bark, LD=Diseased leaf LH=Healthy leaf]
Morphotype: ID of morphotype
Frequency: number of cultures

- **morphotypes_identification.csv**
Morphotype: ID of morphotype
Species: Latin name of fungus

- **phytophthora.csv**
Plot: ID of the sampling plot
Species: Latin name of Phytophthora species