Abstract
Fuel load is the key factor driving fire ignition, spread and intensity. The current literature reports the light detection and ranging (LiDAR), optical and airborne synthetic aperture radar (SAR) data for fuel load estimation, but the optical and SAR data are generally individually explored. Optical and SAR data are expected to be sensitive to different types of fuel loads because of their different imaging mechanisms. Optical data mainly captures the characteristics of leaf and forest canopy, while the latter is more sensitive to forest vertical structures due to its strong penetrability. This study aims to explore the performance of Landsat Enhanced Thematic Mapper Plus (ETM+) and Advanced Land Observing Satellite (ALOS) Phased Arrayed L-band Synthetic Aperture Radar (PALSAR) data as well as their combination on estimating three different types of fuel load—stem fuel load (SFL), branch fuel load (BFL) and foliage fuel load (FFL). We first analyzed the correlation between the three types of fuel load and optical and SAR data. Then, the partial least squares regression (PLSR) was used to build the fuel load estimation models based on the fuel load measurements from Vindeln, Sweden, and variables derived from optical and SAR data. Based on the leave-one-out cross-validation (LOOCV) method, results show that L-band SAR data performed well on all three types of fuel load (R2 = 0.72, 0.70, 0.72). The optical data performed best for FFL estimation (R2 = 0.66), followed by BFL (R2 = 0.56) and SFL (R2 = 0.37). Further improvements were found for the SFL, BFL and FFL estimation when integrating optical and SAR data (R2 = 0.76, 0.81, 0.82), highlighting the importance of data selection and combination for fuel load estimation.
Highlights
We evaluated the performances of optical and synthetic aperture radar (SAR) data as well as their backscattering information, which provided to references for feasibility subsequent selection of combination on Fuel load (FL) estimation individually explore the of data spectral band and
We found optical data and HH polarization have a higher correlation with foliage fuel load (FFL) than that of branch fuel load (BFL) and stem fuel load (SFL)
Spectral and HH polarization have a higher correlation with FFL than that of BFL and SFL
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Wildfires are disturbances that exist in various ecosystems, which play an important role in the formation and succession of ecosystems [1]. Humankind benefited from fires for millennia, since wildfires help to control pests and contribute to the regulation of biogeochemical cycles which benefit plants in adapting to novel climates, providing a range of goods and services (food, fiber, pollination, tourism, hunting) to us [2]. With global climate change and urban expansion, the negative effects of wildfires increased [3]
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