The database compiled for the Braun-Blanquet project is a compilation of various national and regional vegetation databases. The maintenance of these databases is in principle in the hands of the custodians. However, before uploading the databases into Braun-Blanquet database a quality check is performed by Alterra and Masaryk University. If possible, detected errors are corrected and reported back to the data provider. For the modelling of the habitat suitability map the Maxent software is used ( https://biodiversityinformatics.amnh.org/open_source/maxent/). The grid values in the map represent the probability (ranging from 0-1) that the cell is suitable for the habitat.

The grid file represents the habitat suitability of the EUNIS type. For the modelling the widely used software Maxent for maximum entropy modelling of species’ geographic distributions was used. Maxent is a general-purpose machine-learning method with a simple and precise mathematical formulation, and has a number of aspects that make it well-suited for species distribution modelling when only presence (occurrence) data but not absence data are available (Philips et al. 2006). Because EUNIS habitats have a particular species composition, they are assumed to respond to specific ecological requirements, allowing us to generate correlative estimates of geographic distributions. Modelling habitats that have been floristically defined is a well-known procedure for ecological modelling at local scales, and a promising technique to be applied also at the continental level.

The Maxent method considers presence data (known observations of a given entity) and the so-called background data. Background data comprise a set of points used to describe the environmental variation of the study area according to the available environmental layers. It is assumed that these layers represent well the most important ecological gradients on a European scale. As layers the following environmental parameters have been used: Potential Evapotranspiration, Topsoil pH, Solar radiation, Temperature Seasonality (standard deviation *100), Mean Temperature of Wettest Quarter, Annual Precipitation, Precipitation Seasonality (Coefficient of Variation), Precipitation of Warmest Quarter & Distance to water (rivers, lakes, sea).

Statistical output of the model:

#Training samples: 54

Regularized training gain: 3.6547

Unregularized training gain: 3.9416

Iterations: 500

Training AUC: 0.9935

#Test samples: 5

Test gain: 3.456

Test AUC: 0.9902

AUC Standard Deviation: 0.002

#Background points: 5054

bio_12_etrs2_ras contribution: 0

bio_15_etrs2_ras contribution: 49.1531

bio_18_etrs2_ras contribution: 23.7552

bio_4_etrs2_ras contribution: 13.0809

bio_8_etrs2_ras contribution: 0.1344

bld_m_sd1_1km_eu_ll contribution: 0.1621

cecsum_m_sd1_1km_eu_ll contribution: 0.0163

clyppt_m_sd1_1km_eu_ll contribution: 1.3448

crfvol_m_sd1_1km_eu_ll contribution: 0.2328

dist2water1km contribution: 0.0032

orcdrc_m_sd1_1km_eu_ll contribution: 1.0544

pet_he_yr contribution: 10.193

phihox_m_sd1_1km_eu_ll contribution: 0.6572

sltppt_m_sd1_1km_eu_ll contribution: 0.0147

sndppt_m_sd1_1km_eu_ll contribution: 0.0856

solar_1km contribution: 0.1124

bio_12_etrs2_ras permutation importance: 0

bio_15_etrs2_ras permutation importance: 66.3024

bio_18_etrs2_ras permutation importance: 0.1262

bio_4_etrs2_ras permutation importance: 23.4347

bio_8_etrs2_ras permutation importance: 0.3119

bld_m_sd1_1km_eu_ll permutation importance: 0.1595

cecsum_m_sd1_1km_eu_ll permutation importance: 0.0405

clyppt_m_sd1_1km_eu_ll permutation importance: 0.0262

crfvol_m_sd1_1km_eu_ll permutation importance: 0.6285

dist2water1km permutation importance: 0

orcdrc_m_sd1_1km_eu_ll permutation importance: 1.2308

pet_he_yr permutation importance: 2.7829

phihox_m_sd1_1km_eu_ll permutation importance: 3.6757

sltppt_m_sd1_1km_eu_ll permutation importance: 0.8761

sndppt_m_sd1_1km_eu_ll permutation importance: 0.0595

solar_1km permutation importance: 0.3452

Entropy: 4.8843

Prevalence (average of logistic output over background sites): 0.0121

Fixed cumulative value 1 cumulative threshold: 1

Fixed cumulative value 1 logistic threshold: 0.0036

Fixed cumulative value 1 area: 0.1173

Fixed cumulative value 1 training omission: 0

Fixed cumulative value 1 test omission: 0

Fixed cumulative value 1 binomial probability: 2.22E-05

Fixed cumulative value 5 cumulative threshold: 5

Fixed cumulative value 5 logistic threshold: 0.0458

Fixed cumulative value 5 area: 0.0386

Fixed cumulative value 5 training omission: 0

Fixed cumulative value 5 test omission: 0

Fixed cumulative value 5 binomial probability: 8.55E-08

Fixed cumulative value 10 cumulative threshold: 10

Fixed cumulative value 10 logistic threshold: 0.1365

Fixed cumulative value 10 area: 0.0239

Fixed cumulative value 10 training omission: 0

Fixed cumulative value 10 test omission: 0

Fixed cumulative value 10 binomial probability: 7.87E-09

Minimum training presence cumulative threshold: 12.7992

Minimum training presence logistic threshold: 0.1708

Minimum training presence area: 0.0198

Minimum training presence training omission: 0

Minimum training presence test omission: 0

Minimum training presence binomial probability: 3.03E-09

10 percentile training presence cumulative threshold: 19.3516

10 percentile training presence logistic threshold: 0.2726

10 percentile training presence area: 0.014

10 percentile training presence training omission: 0.0926

10 percentile training presence test omission: 0.2

10 percentile training presence binomial probability: 1.93E-07

Equal training sensitivity and specificity cumulative threshold: 13.1147

Equal training sensitivity and specificity logistic threshold: 0.1738

Equal training sensitivity and specificity area: 0.0194

Equal training sensitivity and specificity training omission: 0.0185

Equal training sensitivity and specificity test omission: 0

Equal training sensitivity and specificity binomial probability: 2.74E-09

Maximum training sensitivity plus specificity cumulative threshold: 12.7992

Maximum training sensitivity plus specificity logistic threshold: 0.1708

Maximum training sensitivity plus specificity area: 0.0198

Maximum training sensitivity plus specificity training omission: 0

Maximum training sensitivity plus specificity test omission: 0

Maximum training sensitivity plus specificity binomial probability: 3.03E-09

Equal test sensitivity and specificity cumulative threshold: 15.5867

Equal test sensitivity and specificity logistic threshold: 0.2255

Equal test sensitivity and specificity area: 0.0168

Equal test sensitivity and specificity training omission: 0.037

Equal test sensitivity and specificity test omission: 0

Equal test sensitivity and specificity binomial probability: 1.35E-09

Maximum test sensitivity plus specificity cumulative threshold: 15.5867

Maximum test sensitivity plus specificity logistic threshold: 0.2255

Maximum test sensitivity plus specificity area: 0.0168

Maximum test sensitivity plus specificity training omission: 0.037

Maximum test sensitivity plus specificity test omission: 0

Maximum test sensitivity plus specificity binomial probability: 1.35E-09

Balance training omission, predicted area and threshold value cumulative threshold: 2.0977

Balance training omission, predicted area and threshold value logistic threshold: 0.0103

Balance training omission, predicted area and threshold value area: 0.073

Balance training omission, predicted area and threshold value training omission: 0

Balance training omission, predicted area and threshold value test omission: 0

Balance training omission, predicted area and threshold value binomial probability: 2.08E-06

Equate entropy of thresholded and original distributions cumulative threshold: 8.8366

Equate entropy of thresholded and original distributions logistic threshold: 0.1086

Equate entropy of thresholded and original distributions area: 0.0261

Equate entropy of thresholded and original distributions training omission: 0

Equate entropy of thresholded and original distributions test omission: 0

Equate entropy of thresholded and original distributions binomial probability: 1.21E-08