Radar backscatter modelling of forests using a macroecological approach
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Date
25/06/2012Author
Brolly, Matthew
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Abstract
This thesis provides a new explanation for the behaviour of radar backscatter of
forests using vegetation structure models from the field of macroecology. The forests
modelled in this work are produced using allometry-based ecological models with
backscatter derived from the parameterisation of a radiative transfer model. This
work is produced as a series of papers, each portraying the importance of
macroecology in defining the forest radar response. Each contribution does so by
incorporating structural and dynamic effects of forest growth using one of two
allometric models to expose variations in backscatter as a response to vertical and
horizontal forest profiles. The major findings of these studies concern the origin of
backscatter saturation effects from forest SAR surveys. In each work the importance
of transition from Rayleigh to Optical scattering, combined with the scaling effects of
forest structure, is emphasised. These findings are administered through evidence
including the transition’s emergence as the region of dominant backscatter in a
vertical profile (according to a dominant canopy scattering layer), also through the
existence of a two trend backscatter relationship with volume in the shape of the
typical “saturation curve” (in the absence of additional attenuating factors). The
importance of scattering regime change is also demonstrated through the
relationships with volume, basal area and thinning. This work’s findings are
reinforced by the examination of the relationships between forest height and volume,
as collective values, providing evidence to suggest the non-uniqueness of volume-toheight
relationships. Each of the studies refer to growing forest communities not
single trees, so that unlike typical studies of radar remote sensing of forests the
impact of the macroecological structural aspects are more explicit. This study
emphasises the importance of the overall forest structure in producing SAR
backscatter and how backscatter is not solely influenced by electrical properties of
scatteres or the singular aspects of a tree but also by the collective forest parameters
defining a dynamically changing forest.