Eigenfeature-enhanced deep learning: advancing tree species classification in mixed conifer forests with lidar

Accurately classifying tree species using remotely sensed data remains a significant challenge, yet it is essential for forest monitoring and understanding ecosystem dynamics over large spatial extents. While light detection and ranging (lidar) has shown promise for species classification, its accuracy typically decreases in complex forests or with lower lidar point densities. Recent advancements in lidar processing and machine learning offer new opportunities to leverage previously unavailable structural information. In this study, we present an automated machine learning pipeline that reduces practitioner burden by utilizing canonical deep learning and improved input layers through the derivation of eigenfeatures. These eigenfeatures were used as inputs for a 2D convolutional neural network (CNN) to classify seven tree species in the Mogollon Rim Ranger District of the Coconino National Forest, AZ, US. We compared eigenfeature images derived from unoccupied aerial vehicle laser scanning (UAV-LS) and airborne laser scanning (ALS) individual tree segmentation algorithms against raw intensity and colorless control images. Remarkably, mean overall accuracies for classifying seven species reached 94.8% for ALS and 93.4% for UAV-LS. White image types underperformed for both ALS and UAV-LS compared to eigenfeature images, while ALS and UAV-LS image types showed marginal differences in model performance. These results demonstrate that lower point density ALS data can achieve high classification accuracy when paired with eigenfeatures in an automated pipeline. This study advances the field by addressing species classification at scales ranging from individual trees to landscapes, offering a scalable and efficient approach for understanding tree composition in complex forests.