CSIRO’s 3-PG Forest Growth Modeller

3-PG productivity modelling

Forest growth modelling software to help forest managers produce accurate growth predictions across a range of species, with minimal data input requirements.

• 4 September 2008 | Updated 14 October 2011

• Software
• 3-PG Services
• More about 3-PG

3-PG is a well-established forest growth model, which is used commercially and non-commercially around the world. It is capable of producing accurate growth results across a number of parameterised species, with minimal input data requirements.

Software

CSIRO has developed both plot and spatial implementations of the 3-PG model. 

The plot-based model is available free of charge for research purposes. 

The spatial version uses surfaces for a number of the climate, soils and site input variables to model forest growth over entire landscapes, and is currently being prepared for commercial release.  

To access the basic 3-PG program in either the spatial version or the Excel non-spatial version, or for further information about the new version of the 3-PG Toolbox, please contact Mr Anders Siggins.

3-PG Services

We offer the following 3-PG services:

• software training
• species parameterisation
• model testing and validation.

We can advise on or develop the spatial layers required to run the 3-PG software, including:

• long-term (average) climatic surfaces (representing climatic trends across the year)
• detailed climatic surfaces (representing monthly data for the length of time modelled)
• soil layers.

We also provide development services to adapt the 3-PG spatial software to specific needs.

More about 3-PG

The 3-PG model (the acronym stands for Physiological Processes Predicting Growth) was developed by Mr Joe Landsberg and Mr Dick Waring (1997).

It was developed to bridge the gap between conventional, menuration-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 (the model includes continuous calculation of water balance), atmospheric vapour pressure deficits and stand age.

The carbon produced by the canopy is allocated to leaves, stems and roots, using dynamic equations that update the state of the system on a monthly time step. Calculations can be started at any time for which the state of the forest is specified; the model is then self-constrained.

The model is generic but needs to be parameterised for individual species. The software makes this relatively simple.

The 3-PG model requires, as inputs, standard weather data and information about soil depth and water-holding characteristics. Initial tree populations are specified and changes in stem populations calculated using a well-established mortality function.

The model has relatively few parameters and is simple to use. Output includes stem biomass and volume, average stem diameters, stand basal area at any time and the time course of Leaf Area Index.

3-PG can be used to evaluate site potential and analyse the probable effects of varying growing conditions or management actions such as thinning or fertilisation. It has considerable potential as a tool for estimating carbon sequestration by forests and plantations and has been shown to be a very valuable teaching tool.

Learn more about Forests.