Keywords
3pg+, process-based modelling, water balance, native forest, mountain ash
Start Date
1-7-2010 12:00 AM
Abstract
The amount of water derived from forested water supply catchments depends largely on forest evapotranspiration, which in turn depends on forest age and structure. There is increasing interest to predict the effects of forest disturbance (e.g. fire) and management (e.g. thinning) on streamflow. One approach is to incorporate present knowledge of water use into process-based models that simultaneously predict water use and growth of forests. We take 3PG+, an enhanced version of the 3PG forest growth model with a daily multi-layered water balance, and validate it for multi-species Eucalyptus regnans forests. The model has to date been applied to single-species forests or plantations, and adaptation to native forest systems with multiple canopy layers required the vertical distribution of radiation propagation, rainfall interception, humidity gradients, canopy conductance and evapotranspiration, and soil water uptake. Assigning species parameters for complex forest systems presented a challenge. We assigned the overstorey and an understorey component each with a set of species parameters. Simulations of over 230 years were able to capture well the trends and magnitude of forest structure (stocking, leaf area index) and water balance components (transpiration, evapotranspiration, rainfall interception and runoff). Further validation across additional sites is required before the model is used to predict the likely effects of changes in forest age and structure and catchment water balances arising from disturbances such as fire, land use change, and climate change.
Using 3PG+ to simulate longterm growth and transpiration in Eucalyptus regnans forests
The amount of water derived from forested water supply catchments depends largely on forest evapotranspiration, which in turn depends on forest age and structure. There is increasing interest to predict the effects of forest disturbance (e.g. fire) and management (e.g. thinning) on streamflow. One approach is to incorporate present knowledge of water use into process-based models that simultaneously predict water use and growth of forests. We take 3PG+, an enhanced version of the 3PG forest growth model with a daily multi-layered water balance, and validate it for multi-species Eucalyptus regnans forests. The model has to date been applied to single-species forests or plantations, and adaptation to native forest systems with multiple canopy layers required the vertical distribution of radiation propagation, rainfall interception, humidity gradients, canopy conductance and evapotranspiration, and soil water uptake. Assigning species parameters for complex forest systems presented a challenge. We assigned the overstorey and an understorey component each with a set of species parameters. Simulations of over 230 years were able to capture well the trends and magnitude of forest structure (stocking, leaf area index) and water balance components (transpiration, evapotranspiration, rainfall interception and runoff). Further validation across additional sites is required before the model is used to predict the likely effects of changes in forest age and structure and catchment water balances arising from disturbances such as fire, land use change, and climate change.
