Suitability of Interferometric Synthetic Aperture Radar (IFSAR) for biomass estimation in a selectively logged tropical rainforest in Peninsular Malaysia

Abstract

Weather-tolerant Interferometric Synthetic Aperture Radar (IFSAR) is expected to generate data for biomass estimation in tropical rainforests. We tested this prediction by examining the performance of X-band IFSAR data in estimating total biomass (TB), i.e., the sum of aboveground and belowground biomasses, in a selectively logged tropical rainforest. Our explorations incorporated the effects of topographic conditions on the accuracy of the procedure used. TB was estimated by a rectangular prism procedure, an original method developed for this study, using IFSAR-derived canopy height data and revised biomass density data (i.e., apparent density of total aboveground biomass [AGB] under a canopy tree). For gentle terrain conditions such as alluvial place, we found a significant correlation between TB estimates provided by IFSAR and field measurement data. Through application of a correction procedure, we were also able to adequately estimate the mean value and frequency distribution of TB. Estimation of TB in complex landscape topographies was restricted by the bias in IFSAR data.

Remote Sensing Approaches for Monitoring Mangrove Species, Structure, and Biomass: Opportunities and Challenges

“…Each band has its own characteristics and capability related to forest stand parameters [88]. Short wavelengths such as the X-band (3.75-2.5 cm) and C-band (7.5-3.75 cm) strongly interact with the surface of the canopy, whilst long wavelengths such as the L-band (30-15 cm) and P-band (68 cm) penetrate into the canopy and reflect information on branches and stems [89][90][91][92][93][94]. The longer wavelengths are more strongly correlated with forest biomass and other biophysical parameters than short wavelengths [95].…”

“…Interferometric synthetic aperture radar (InSAR) and polarimetric interferometric SAR (Pol-InSAR) techniques use at least two SAR images in the phase and the coherence of the waves [95]. InSAR and Pol-InSAR techniques can overcome the saturation problem of backscatter approaches [94,141] and provide more accurate results than using a single SAR image [142]. These techniques can be used to estimate tree height by subtracting a digital terrain model (DTM) from an InSAR height, or by dual Pol-InSAR data generated from TanDEM-X and TerraSAR-X, or at low frequencies (L and P-bands) [143][144][145]; then, forest AGB can be estimated based on regression analyses [146,147].…”

Effects of selective management system on biomass structure and forest sustainability: a case study of a tropical rainforest in Peninsular Malaysia

“…In C47, analyses of biomass structure were conducted in 29 ha of alluvium ( Figure 1) where the suitability of IFSAR for the total biomass estimation was preliminarily examined (Kubota et al 2015). Hill and stream swamp were excluded because of bias in the IFSAR data.…”

“…CTBi values at subplots without trees ≥ 30 cm DBH will vary because IFSAR detects some canopy height even in forest gaps (Kubota et al 2015) and, consequently, derived biomass obtained via the rectangular prism method will be different. In order to reduce effects of these differences, comparisons between TB 5 and CTBi were conducted at different spatial scales: both sites were divided into 10 m …”

“…We revised biomass density as the apparent density of the total aboveground biomass under a canopy tree (Kubota et al 2015). The estimated total biomass was calibrated to that of 7 years after logging (2012) using reference field census data, and it was referred to as CTBi (calibrated total biomass estimated from IFSAR data).…”