Impact model: 3PG

The 3-PG model (Physiological Processes Predicting Growth) was developed by Landsberg and Waring (1997). It was developed to bridge the gap between conventional, mensuration-based growth and yield, and process-based carbon balance models. The output variables it produces are of interest and relevance to forest managers. 3-PG calculates the radiant energy absorbed by forest canopies and converts it into biomass production. The efficiency of radiation conversion is modified by the effects of nutrition, soil drought (thebook_cover model includes continuous calculation of water balance), atmospheric vapour pressure deficits and stand age.

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Information for the model 3PG 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.

Basic information
Model Version: 1.1
Reference Paper: Main Reference: Landsberg J, Waring R et al. A generalised model of forest productivity using simplified concepts of radiation-use efficiency, carbon balance and partitioning. Forest Ecology and Management,95,209-228,2002
Spatial Aggregation: forest stand
Temporal Resolution Of Input Data: Climate Variables: monthly
Temporal Resolution Of Input Data: Soil: constant
Input data sets used
Additional Information About Input Variables: tasmin, tasmax, pr, rsds, frostdays
Was A Spin-Up Performed?: No
Management & Adaptation Measures
Management: Forest management was applied
Key model processes
dynamic vegetation: yes: Forest dynamics are described by forest growth, regeneration/planting, management.
nitrogen limitation: no
CO2 effects: yes
light interception: yes: The total fraction of photosynthetically active radiation absorbed by each cohort is calculated each time based on the Lambert-Beer law.
phenology: only for deciduous trees using a beginning and end of growing season (Forrester and Tang 2016)
water stress: yes: After calculating water demand by forest stand and water supply from the soil for each cohort photosynthesis is being reduced if demand is greater than supply. Allocation is also affected.
Evapo-transpiration approach: yes: A single soil layer model with evapo- transpiration determined from Penman-Monteith equation.
Differences in rooting depth: no
Root distribution over depth: no
closed energy balance: It is not considered.
Coupling/feedback between soil moisture and surface temperature: no
latent heat: no
sensible heat: no
Causes of mortality in vegetation models
Age/Senescence: yes: Age related stress mortality is calculated.
Other: yes: Self-thinning mortality due to light availability is implemented (stress mortality).
NBP components
Harvest: The model includes harvests, which effect all fluxes.
Other processes: Dead biomass which is not harvested