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Validation of the Jack pine version of CroBas-PipeQual

University of British Columbia

The objective of this study was to validate the performance of the jack pine (Pinus banksiana L.) version of the growth simulator CroBas-PipeQual. A data-based approach and a simulation approach were applied. For the data-based validation, Ontario permanent sample plots (PSPs) were used as input to the CroBas-PipeQual simulator to obtain predicted values for growth of dbh, height, basal area per ha, changes in crown height and number of trees per ha. The corresponding growth (change) in these variables was compared with the measured growth (change) on the PSPs. For the simulation studies, I assessed the impact of different initial stand densities, different initial heights, and different values of the model parameters on the output variables and compared the simulated response to biological expectations. CroBas-PipeQual simulator generally underestimated growth/change of all variables at the stand and single tree level using both default and adjusted values of alpha-r. Running the simulator with the adjusted values of alpha-r did not show marked improvements in the simulator´s performance. The simulator generally produced logical results based on the simulations conducted. In denser stands, trees had a smaller average dbh at a given age, and basal area growth and change in number of trees were higher. Initial density had almost no influence on height and crown height growth. The number of stems per ha remained essentially the same on sites with different productivities, indicating that there may be problems with estimating mortality in the simulator. Varying the initial heights had almost no impact on the number of stems per ha, dbh growth and basal area growth. Overall, the simulator performed reasonably. However, it requires further testing. More testing with suitable data will allow assessing the simulator´s applicability to other site types and geographical locations. Another area that needs attention is modelling mortality. Recalibrating some of the equation parameters internal to the jack pine version of CrosBas-PipeQual is recommended, followed by further testing. Finally, the accuracy of predictions of variables not evaluated in this study (e.g., branch sizes, numbers, and locations) should be assessed before these components of the simulator are used operationally.

Text

2012-10-11

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/43368

Forestry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/