The goal of quantifying the woody cover and biomass of tropical savannas, woodlands
and forests using satellite data is becoming increasingly important, but limitations in
current scientific understanding reduce the utility of the considerable quantity of satellite
data currently being collected. The work contained in this thesis reduces this knowledgegap,
using new field data and analysis methods to quantify changes using optical, radar
and LiDAR data.
The first paper shows that high-resolution optical data (Landsat & ASTER) can be used
to track changes in woody vegetation in the Mbam Djerem National Park in Cameroon.
The method correlates a satellite-derived vegetation index with field-measured canopy
cover, and the paper concludes that forest encroached rapidly into savanna in the region
from 1986-2006. Using the same study area, but with radar remote sensing data from
1996 and 2007 (ALOS PALSAR & JERS-1), the second paper shows that radar
backscatter correlates well with field-measured aboveground biomass (AGB). This
dataset confirms the woody encroachment within the park; however, in a larger area
around the park, deforestation dominates.
The AGB-radar relationships described above are expanded in the next paper to include
field plots from Budongo Forest (Uganda), the Niassa Reserve (north Mozambique), and
the Nhambita Community Project (central Mozambique). A consistent AGB-radar
relationship is found in the combined dataset, with the RMSE for predicted AGB values
for a site increasing by <30 %, compared with a site-specific equation, when using an
AGB-radar equation derived from the three other sites. The study of the Nhambita site is
extended in the following paper to assess the ability of radar to detect change over short
time periods in this environment, as will be needed for REDD (Reducing Emissions
from Deforestation and Degradation). Using radar mosaics from 2007 and 2009, areas
known (from detailed ground data) to have been degraded decreased in AGB in the radar
change detection, whereas areas of agroforestry and forest protection showed small
increases