Applicability of artificial neural network for estimating the forest growing stock

Knowledge on stand’s quantitative and qualitative characteristics (tree volume and growth) are fundamental requirements for monitoring close-to-nature forest management plans. In addition, future planning is based on statistics and information obtained from the forest. Thus, structural information such as standing stock, growth and diameter distribution are highly required. Volume increment provides the amount of allowable annual cut. In this study 768.4 ha of virgin forests located in Gorazbon district in Kheyroud educational- experimental Forest was inventoried by 258 permanent sample plots measured in 2012. Following elimination of statistical deficiency and exclusion of deviated points, the data were divided into 80% training and 20% test data to examine the applied neural network. The data was initially standardized by using training data. Neural network with back propagation error algorithm was developed. Furthermore, volume was regressed against diameter, height, slope and aspect using the allocated training data. Model diagnostics including R2, MAE and RMSE were applied for evaluating those two methods. The analysis resulted in R2=0.98, MAE=0.69 and RMSE=1.006, respectively. For the regression method the diagnostics amounted in R2=0.85, MAE=0.95 and RMSE=2.5. The results have suggest the higher accuracy of neural network for growing stock estimation compared to regression approach. However, care must be taken during data preparation, network design and network training to reach an optimum final model. It is concluded that this model should be further considered and applied for the estimation of volume across the study area.