The purpose of this study is to estimate forest biomass using ALOS PALSAR imagery and forest inventory data. Above all, it is only appropriate for farmland which is small biomass values in the case of SAR Sigma-nought(σ 0 ), and is affected by shadow of bidirectional effects. On the other side, the terrain slope parameters are calculated using an estimation of the gradients in the two directions of the coordinate plane of the Digital Elevation Model (DEM) and so reduces the shadow phenomenon of topographic effects and revises it. To estimate forest biomass, topographic effects should be considered in SAR data processing, because most forests are located on mountainous areas in Korea.This study is for region of Unduryeong forest, and divided directions using DEM. That is, revision of directional effect by incidence angle is needed therefore SAR images are separated in fore-slope(here, west-slope) and far-slope(here, east-slope). As a result, the gamma-nought(γ 0 ) values are always lower compared to the sigma-nought values at all polarizations for Unduryeong forest areas of the fore-slope and are always higher in case of far-slope.Backscatter coefficient shows saturations in about 302.56ton/ha, and it is useful in REDD++ mechanism because forest biomass values based on estimated gammanought include the information of location coordinate.
Theme Sessions, ThS 7 KEY WORDS: Gamma-Nought, Growing Stock, ALOS PALSAR, PALSAR-2, Backscattering Coefficient, Stand Growth
ABSTRACT:This study demonstrates the possibility of detecting the changes of growing stocks in mountainous forest stands derived from ALOS PALSAR and PALSAR-2 images. The ALOS PALSAR were obtained over the Kwangneung Experiment Forest (KEF, Korea) during the period of nineteen and a half months from the April 26, 2009 to December 12, 2010, whereas the PALSAR-2 data were acquired on the April 7, 2015. The KEF test site comprises 58 stands, which cover approximately 1,000ha and have steep slope topography. Owing to topographic effects of SAR data in mountainous areas, the DEM-assisted topographic normalized backscattering coefficient γ 0 was applied to the evaluation of the relationships between the ALOS PALSAR / PALSAR-2 HV backscatter and the field inventory-based stand stock volume. The results indicate that: 1) the γ 0 values for the volume obtained from ALOS PALSAR data on December 12, 2010 show a gradual increase higher than those computed from the data on April 26, 2009, here the γ 0 value increases in accordance with an increase in the volume: 2) the γ 0 values determined from the PALSAR-2 data increase with the same inventory-based volume, when compared with those computed from both ALOS PALSAR data. They also increase substantially as the values of the volume rise, with the exception of the volume interval from 130 m 3 ha -1 to 160 m 3 ha -1 . This is understandable because the volume of the aforementioned interval has been reduced through clearing. Consequently, the γ 0 -based relationship between PALSAR-2 HV backscatter and growing stock can lead to detecting the stand growth changes in the KEF of Korea.
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