Kuplich, T.M., Curran, P.J. and Atkinson, P.M.
Relating SAR image texture to the biomass of regenerating tropical forests
International Journal of Remote Sensing, 26, (21), . (doi:10.1080/01431160500239107).
Full text not available from this repository.
An accurate global carbon budget requires information on terrestrial carbon sink
strength. Regenerating tropical forests are known to be important terrestrial
carbon sinks but information on their location, extent and biomass (from which
carbon content can be estimated) is incomplete. The use of remotely sensed data
in optical wavelengths has been of limited use due to both the weak relationship
between optical radiation and forest biomass and near-constant cloud cover in
the tropics. L-band Synthetic Aperture Radar (SAR) backscatter, however, is
related positively to biomass (but only up to an asymptote of around
40–90 Tha21) and can be obtained independently of cloud cover.
Both canopy structure and biomass change over time as pioneer species are
replaced by early and late regenerating species. These structural changes are
related to an increase in (i) tree height, (ii) tree species richness and (iii) canopy
thickness and influence the roughness of the canopy surface and consequently
SAR image texture. Therefore, we investigated the degree to which textural
information could be used to increase the correlation between image tone
(backscatter) and biomass. Field data were used to estimate the biomass of 37
regenerating forests plots in Brazilian Amazonia. Texture measures derived from
local statistics, the grey level co-occurrence matrix (GLCM) and the variogram
were evaluated using simulated images on the basis of their ability to identify
significant differences in image texture independently of image contrast. The
selected texture measures were applied to L-band JERS-1 (Japanese Earth
Resources Satellite) SAR images and the correlation between backscatter and
biomass was determined for regenerating tropical forests. A strong correlation
was found for the texture measures and biomass. The ra
2 (adjusted coefficient of
determination), measuring the correlation between backscatter and biomass,
increased from 0.74 to 0.82 with the addition of GLCM-derived contrast. The
addition of image texture (GLCM-derived contrast) to image tone (backscatter)
potentially increases the accuracy with which JERS-1 SAR data can be used to
estimate biomass in tropical forests.
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