Advancing tree inventory systems through remote sensing: species-level detection of almaciga (Agathis philippinensis Warb.) trees in Governor Genoroso, Davao Oriental, Philippines
2024
Cinco, A.P.
Accurately classifying forest tree species coverage such as almaciga (Agathis philippinensis, Warb.) trees or stands using remote sensing (RS) techniques as a science-based approach to develop an inventory system for almaciga resources. Since field-based inventory method is expensive and difficult to implement especially in almaciga stands that are in inaccessible areas. Sentinel-2A satellite and unmanned aerial vehicle (AUV) images were used to derive tree level information through Green Chromatic Coordinate Index (GCCI) and Normalized Difference Vegetation Index (NDVI). Five barangays [villages] in Governor Generosos, Davao Oriental serves as study sites to explore the possibility of determining the spatial distribution of alamaciga trees. The results show that almaciga trees or stands exists between GCCI values of 0.3661 to 0.4601 and NDVI values of 0.3902 to 0.5689. The overall accuracy for both vegetation indices using the 20% validation sample were 87.93% and 95.71%, respectively. The mean distance of 11m and percent occurrence of 15.15% using geolocated trees and 50mx50m subplots were also computed to estimate the number of the almaciga trees in the study areas. Based on the results, the estimated number of almaciga trees in the study areas. Based on the results, the estimated number of almaciga trees in five barangays is 59,775 trees or 12 trees per ha. Meanwhile, the study revealed that RS-based has the least cost with an approximate amount of Php2,016 per ha as compared with the field-based and semi-field-based inventory methods. This research recommends the use of the latest Sentinel-2A, drone, and spectroradiometer in refining the tree level classification. Moreover, the method developed in this study can help monitor forest resources and be a reference for a practical and cost-effective inventory system.
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