Seeing trees from space: above-ground biomass estimates of intact and degraded montane rainforests from high-resolution optical imagery

• Main Authors: Phua, Mui How, Ling, Zia-Yiing, David Anthony Coomes, Wilson Wong, Alexius Korom, Satoshi Tsuyuki, Keiko Ioki, Yasumasa Hirata, Hideki Saito, Gen Takao
• Format: Article
• Language: English; English
• Published: SISEF-Italian Society of Silviculture and Forest Ecology 2017
• Subjects: QK1-474.5 General Including geographical distribution; SD1-669.5 Forestry
• Online Access: https://eprints.ums.edu.my/id/eprint/34060/1/Seeing%20trees%20from%20space.pdf; https://eprints.ums.edu.my/id/eprint/34060/2/Seeing%20trees%20from%20space1.pdf; https://eprints.ums.edu.my/id/eprint/34060/; https://iforest.sisef.org/abstract/?id=ifor2204-010; https://doi.org/10.3832/ifor2204-010
• Institution: Universiti Malaysia Sabah

Accurately quantifying the above-ground carbon stock of tropical rainforest trees is the core component of “Reduction of Emissions from Deforestation and Forest Degradation-plus” (REDD+) projects and is important for evaluating the effects of anthropogenic global change. We used high-resolution optical imagery (IKONOS-2) to identify individual tree crowns in intact and degraded rainforests in the mountains of Northern Borneo, comparing our results with 50 ground-based plots dispersed in intact and degraded forests, within which all stems > 10 cm in diameter were measured and identified to species or genus. We used the dimensions of tree crowns detected in the imagery to estimate above-ground biomasses (AGBs) of individual trees and plots. To this purpose, preprocessed IKONOS imagery was segmented using a watershed algorithm; stem diameter values were then estimated from the cross-sectional crown areas of these trees using regression relationships obtained from ground-based measurements. Finally, we calculated the biomass of each tree (AGBT, in kg), and the AGB of plots by summation (AGBP, in Mg ha-1). Remotely sensed estimates of mean AGBT were similar to ground-based estimates in intact and degraded forests, even though small trees could not be detected from space-borne sensors. The intact and degraded forests not only had different AGB but were also dissimilar in biodiversity. A tree-centric approach to carbon mapping based on high-resolution optical imagery, could be a cheap alternative to airborne laser-scanning.