Modelling N driven biodiversity changes in Austrian forest and grassland habitats Thomas Dirnböck & Ika Djukic 1

Exceedance of Eutrophication Critical Loads 2 In 2010 CL for eutrophication were exceeded at 94 % of the forested area Mean exceedance in forests: 4,1 kg N/ha/yr > 50% of the Natura 2000 area will be exceeded until 2020 (Gothenburg Protocol) Exceedance will be relatively moderate: mean at 1.5 kg N/ha/yr

Forest monitoring in Austria 3 Site code altitude [m a.s.l.] Total Deposition [kg N.ha -1.yr -1 ]* emp. CL [kg N.ha -1.yr -1 ]EUNIS classes AT01_ Mixed Abies - Picea - Fagus woodland (G4.6) AT01_ Mixed Abies - Picea - Fagus woodland (G4.6) AT Thermophilous deciduous woodland (G1.7) AT Fagus woodland (G1.6) AT Abies and Picea woodland (G3.1) AT Abies and Picea woodland (G3.1) AT Abies and Picea woodland (G3.1) AT Abies and Picea woodland (G3.1)

Methods for VSD+ soil model Total Deposition (measurements and canopy budget model) Low deposition scenario: Gothenburg protocol and other legislation High deposition scenario: no reduction after the year 2010 Measured soil and soil water data (1995 to 2010) Methyd for reduction factors, Temperature and Precip Growup for C, N and base cation uptake and litterfall Standard forest yield model and steady state after

Results VSD+ The former limitations to model soils with very high C content are solved: reliable results were achieved Biomass growth, uptake and litterfall can be modelled with Growup 5

In forests a broad-scale N driven biodiversity signal remains unobserved 6 Stevens et al Sp. richness in acid grassland is lower where N deposition is high Verheyen et al In decideous temperate forests, plant nutrient indicators increased, but no relation with N deposition Ellenberg N value

… only the cover of oligotrophic species decreased during the last years 7 R²=0.3 p-value=0.004 Oligotrophic species showed a downward trend (p = 0.004) Eutrophic species showed no trend …but these species dominated among newly ocurring plant species (p = 0.091) Species loss was not related with CL exceedance (p = 0.872) … but oberservation lenght was related with species loss (Pearson r =0.52) Excess Nitrogen Dirnböck et al. Global Change Biology (2014)

Which changes in plant diversity we can expect? 1. Cover of oligotrophic species decreases 2. Cover of eutrophic species increases 3. Species composition becomes more homogenous between plots (beta diversity) 4. Loss of oligotrophic species (alpha/gamma diversity) Oligotrophic species Eutrophic species

Methods for PROPS and BD metric Species pool selection All species provided in PROPS for the respective EUNIS class (Level III) (Zöbelboden (AT01): entire species pool of the study area (90ha)) Biodiversity metrics (Species number, Shannon diversity) Weighted mean probability of oligotrophic/eutrophic species Oligotrophic species with Ellenberg value 1-3 (transformed to 3-1) Eutrophic species with Ellenberg value 7-9 (transformed to 1-3) Homogenisation (Beta diversity)? 9

Preliminary results PROPS The gradient of species richness and Shannon index is mostly due to the species pool selection The weighted mean probabilty of species groups (oligotrophic /eutrophic) very well reflect the N status of the sites Only one site (AT01) is exposed to reasonable eutrophication; this is reflected in the indicator 10

Conclusions / Next steps VSD+ is well suited to model soil chemical changes in mountain forests of Austria The PROPS approach is also well suited, but … The species pool selection remains an open issue; national inventories of typical plant species of habitats (indicator species), such as implemented in BERN, could be used Enlargement of the geographical plant species domain of PROPS is important in order to derive unbiased niche models (that´s ongoing) Indicator species metrics such as derived from Ellenberg values are better reflecting observed changes than gross numbers (species number) In Austria, 10 additional forest and grassland sites will be modelled in the course of the project „CCN- adapt“ until

Contact & Information Dr. Thomas Dirnböck Tel Umweltbundesamt