Microscopic identification of brazilian commercial wood species via machine-learning

ABSTRACT

Background:

Multiple challenges are faced by industry and certification agencies when commercializing tropical species. Anatomical similarities of tropical hardwoods impair identification. Deep learning models can facilitate microscopic identification of wood by using sophisticated techniques such as deep convolutional networks (DCNN). Our objective was to microscopically identify 23 commercially available Brazilian wood species using a custom DCNN model.

Results:

Photographs from microscopic slides of each wood species were processed, and the final data set contained 2,448 images. We applied stratified k-fold cross-validation technique during training to increase model’s robustness and trustworthiness. Thus, the dataset was divided into approximately 80% training (1,958 images) and 20% validation (490 images) for each fold. A series of augmentations were performed only on training data to include variations in rotation, zoom, and perspective. Image augmentation was performed on-the-fly. The network consisted of convolutions, max pooling, global average pooling, and fully connected layers. We tested the performance of the DCNN against accuracy, precision, recall, and F1-score on the validation set for each fold.

Conclusion:

The custom machine learned model accuracy was higher than 0.90. The model’s worst performance was identified in distinguishing between Toona ciliate and Khaya ivorensis, which was due more to wood variability than to a machine learning deficiency. Future studies should focus on integration, verification/monitoring, and updating of current models for end user manipulation, trust, ethics, and security.

Keywords:
convolutional neural networks (CNN); deep learning; tropical species; wood anatomy; wood identification

HIGHLIGHTS

Novel, robust, and fast methods to accurately identify wood are needed.

Machine-learning can be applied to help anatomists’ judgment in forensic wood identification.

The custom machine-learned model achieved accuracy higher than 0.90.

Sequential convolutional layers offered the best performance to identify Brazilian commercial wood species.