Evaluation of ALOS/PALSAR L-Band Data for the Estimation of Eucalyptus Plantations Aboveground Biomass in Brazil

PROJECT TITLE :

Evaluation of ALOS/PALSAR L-Band Data for the Estimation of Eucalyptus Plantations Aboveground Biomass in Brazil

ABSTRACT:

The Phased Array L-band Artificial Aperture Radar (PALSAR-1) has provided terribly useful pictures dataset for several applications such as forestry. L-Band radar measurements have been widely used however with somewhat contradictory conclusions on the potential of this radar wavelength to estimate the aboveground biomass (AGB). The first objective of this study was to analyze the L-band SAR backscatter sensitivity to forest biomass for Eucalyptus plantations. The results showed that the radar signal is highly obsessed on biomass only for values lower than 50 t/ha, that corresponds to plantations of approximately 3 years old. Next, random forest (RF) regressions were performed to evaluate the potential of PALSAR knowledge to predict the Eucalyptus biomass. Regressions were constructed to link the biomass to each radar signal and age of plantations. Results showed that the age was the variable that best explained the biomass followed by the PALSAR HV polarized signal. For biomasses less than fifty t/ha, HV signal and plantation age were found to possess the same level of importance in predicting biomass. For biomasses above fifty t/ha, plantation age was the main variable within the RF models. The employment of PALSAR signal alone failed to correctly predict the biomass of Eucalyptus plantations [ℝtwo below zero.5 and root-mean-squared error (RMSE) more than forty six.seven t/ha]. The employment of plantation age additionally to the PALSAR signal improved slightly the prediction results (ℝ2 increased from 0.eighty eight to zero.ninety two and RMSE decreased from twenty two.seven to 18.9 t/ha). PALSAR imagery does not allow an immediate estimation of planting date of Eucalyptus stands but will follow efficiently the incidence of clear-cuts if images are acquired sequentially, thus permitting a rough estimate of the following plantation date as a result of a stand of Eucalyptus is generally replanted two-4 months after cutting. With a time series of radar pictures, it may be, therefore, doable to estimate the pla- tation age, and thus improving the estimates of plantation biomass.

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