Description, calibration and validation of the CARBWARE single-tree-based stand simulator

There is an increasing resource assessment and management requirement for single-tree-based stand models due to a shift towards mixed-species and 'back to nature' forestry. This paper describes the validation and calibration of the CARBWARE stand simulator, a distance-independent single-tree growth modelling framework specifically modified to include spatially explicit climatic and soil factors. Tree growth functional analysis suggests that stand competition factors contribute to most (21-33 per cent) of the observed variation in diameter increment, followed by tree size factors (17-20 per cent). Edaphic and other site factors, particularly soil nutrition and moisture status, explained 4-11 per cent of the observed site-to-site variation. The developed empirical relationships may provide a deterministic framework for improving developed ecological site classification systems. Independent validation showed that the CARBWARE simulator provides a robust and un-bias estimate of single-tree and stand-based variables for both pure and intimate mixed stands. However, refinements to the simulator are still required, particularly improvement to climatic and genetic response factors, mortality functions for mixed-species stands and inclusion of regeneration/recruitment models.