Impact model: Sibyla

SIBYLA is the simulator of forest biodynamics. It belongs to the category of semi-empirical tree growth simulators. It consists of the set of mathematical models and algorithms that are transformed into an integrated software package SIBYLA Suite. The model has been developed at the Department of Forest Management and Geodesy, Technical University in Zvolen, Slovakia. The basis of the model was the modelling principle and algorithms implemented in SILVA 2.2 (Pretzsch 1992, Kahn 1994). The model is sensitive to climatic factors that modify height and diameter growth potential, and consequently tree increment. More detailed information about Sibyla can be found in Fabrika (2005),


Information for the model Sibyla is provided for the simulation rounds shown in the tabs below. Click on the appropriate tab to get the information for the simulation round you are interested in.

Person responsible for model simulations in this simulation round
Marek Fabrika:, 0000-0001-6993-1143, Technical University in Zvolen (Slovakia)
Katarína Merganičová:, 0000-0003-4380-7472, Czech University of Life Sciences in Prague (Czech Republic)
Additional persons involved: Katarina Merganicova
Basic information
Model Version: SIBYLA 10.0 alpha (11/2015
Model Output License: CC0
Model Homepage:
Reference Paper: Main Reference: Fabrika Marek et al. Simulátor biodynamiky lesa SIBYLA, koncepcia, konštrukcia a programové riešenie2005
Spatial Aggregation: forest stand
Temporal Resolution Of Input Data: Climate Variables: annual
Temporal Resolution Of Input Data: Co2: annual
Temporal Resolution Of Input Data: Land Use/Land Cover: annual
Temporal Resolution Of Input Data: Soil: constant
Input data sets used
Observed Atmospheric Climate Data Sets Used: Historical observed climate data
Climate Variables: tasmax, tas, tasmin, pr
Was A Spin-Up Performed?: No
Natural Vegetation
Soil Layers: no
Management & Adaptation Measures
Management: neutral thinning
Model set-up specifications
How did you initialize your model, e.g. using Individual tree dbh and height or stand basal area? How do you initialize soil conditions?: number of trees per diameter class, stand age
Which data from PROFOUND DB did you use for initialisation (name of variable, which year)? From stand data or from individual tree data?: species, dbh_1_cm Collelongo - year 1997 Solling beech and spruce - year 1967 Soro -year 1996
How is management implemented? E.g. do you harvest biomass/basal area proportions or by tree numbers or dimensions (target dbh)?: volume proportion
When is harvesting simulated by your model (start/middle/end of the year, i.e., before or after the growing season)?: at the beginning of the year
How do you regenerate? Do you plant seedlings one year after harvest or several years of gap and then plant larger saplings?: Both can be used, but none was implemented in these simulations.
How are the unmanaged simulations designed? Is there some kind of regrowth/regeneration or are the existing trees just growing older and older?: Regrowth is possible in the case of unmanaged development, but was not implemented in these simulations.
How are models implementing the noco2 scenario? Please confirm that co2 is follwing the historical trend (based on PROFUND DB) until 2000 (for ISIMIPFT) or 2005 (for ISIMIP2b) and then fixed at 2000 or 2005 value respectively?: They follow the historical trend until today
Does your model consider leap-years or a 365 calendar only? Or any other calendar?: No leap years are considered in the model.
In hyytiälä and kroof, how did you simulate the "minor tree species"? e.g. in hyytiälä did you simulate only pine trees and removed the spruce trees or did you interpret spruce basal area as being pine basal area?: We did not simulate these plots because plots were not growing in the model.
How did you simulate nitrogen deposition from 2005 onwards in the 2b picontrol run? Please confirm you kept them constant at 2005-levels?: Nitrogen deposition was not kept constant but increased based on the equation implemented in the model as a function of the calendar year (Kahn 1994)
What is the soil depth you assumed for each site and how many soil layers (including their depths) do you assume in each site? Please upload a list of the soil depth and soil layers your model assumes for each site as an attachment (Section 7).: Soil depth and number of soil layers are not used as an input in the model.
Is there any stochastic element in your model (e.g. in the management or mortality submodel) that will lead to slightly different results if the model is re-run, even though all drivers etc. remain the same?: yes, there is
What is the minimum diameter at which a „tree is considered a tree“? and is there a similar threshold for the minimum harvestable diameter?: 1 cm
Has your model been "historically calibrated" to any of the sites you simulated? e.g. has the site been used for model testing during model development?: No
Please upload a list of your parameters as an attachment (Section 7). The list should include species-specific parameters and other parameters not depending on initialization data including the following information: short name, long name, short explanation, unit, value, see here for an example (
Key model processes
dynamic vegetation: yes, it depends on individual tree growth, inter-tree competition, and mortality
nitrogen limitation: yes, it affects tree increment
CO2 effects: yes, it affects tree increment
light interception: yes, it affects tree increment
light utilization: no
phenology: no
water stress: yes, it affects tree increment
heat stress: yes, it affects tree increment
Evapo-transpiration approach: no
Differences in rooting depth: no
Root distribution over depth: no
closed energy balance: no
Coupling/feedback between soil moisture and surface temperature: no
latent heat: no
sensible heat: no
Assimilation: no
Respiration: no
Carbon allocation: no
Regeneration/planting: yes
Soil water balance: no
Carbon/Nitrogen balance: no
Are feedbacks considered that reflect the influence of changing carbon state variables on the other system components and driving data (i.e. Growth (leaf area), light, temperature, water availability, nutrient availability)?: yes
Causes of mortality in vegetation models
Age/Senescence: yes, it is indirectly dependent on climate through tree increment
Fire: yes, but not implemented in this study
Drought: yes, but not implemented in this study
Insects: yes, but not implemented in this study
Storm: yes, but not implemented in this study
Stochastic random disturbance: yes, but not implemented in this study
NBP components
Fire: no
Land-use change: no
Harvest: no
Species / Plant Functional Types (PFTs)
List of species / PFTs: (Picea abies), (Fagus sylvatica), (Pinus sylvestris), (Abies alba), (Quercus spp.)
Model output specifications
Do you provide the initial state in your simulation outputs (i.e., at year 0; before the simulation starts)?: yes
Output format: mdb
Output per PFT?: yes
When you report a variable as "xxx-total" does it equal the (sum of) "xxx-species" value(s)? or are there confounding factors such as ground/herbaceous vegetation contributing to the "total" in your model?: only trees
Did you report any output per dbh-class? if yes, which variables?: no
Additional Forest Information
Forest sites simulated: Collelongo, Soro, Solling beech, Solling spruce