Site Suitability Assessment of Native Tree Species in Angat Watershed using GIS-based Multi-Criteria Decision-Making

Abstract. Forests are one of the Philippines’ most valuable resources but due to reasons such as deforestation, its forest cover drastically decreased, requiring reforestation efforts. Reforestation efforts fail due to poor planning and inadequate consideration of success factors like the site suitability of planted trees. This study utilized Geographic Information System-based Multi-Criteria Decision Making (MCDM) to identify Reforestation Target Areas (RTA) in the Angat Watershed, established a site-suitability framework for tree species based on their respective silvical requirements, and determined the suitable sites for tree growth and survival based on species-site suitability. Using the silvical requirements of native tree species Guijo (Shorea guiso), Kalumpit (Terminalia microcarpa), and Dao (Dracontomelon dao), suitability scores, and weights derived from expert opinions, weighted overlay analysis determined the suitability of the tree species within the RTA. Results show that 18.88% of Angat Watershed requires reforestation. Moreover, results revealed that Guijo and Dao are highly suitable in 99.98% of this area, and Kalumpit is highly suitable in 54.78% of the area. With having the right tree species to be planted being a major driving factor for reforestation success, these maps can aid the effectiveness of such initiatives by identifying optimal sites and supporting data-driven decision-making.