Determining optimal new generation satellite derived metrics for accurate C3 and C4 grass species aboveground biomass estimation in South Africa
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Date
2018
Journal Title
Journal ISSN
Volume Title
Publisher
MDPI
Abstract
While satellite data has proved to be a powerful tool in estimating C3 and C4 grass species
Aboveground Biomass (AGB), finding an appropriate sensor that can accurately characterize the
inherent variations remains a challenge. This limitation has hampered the remote sensing community
from continuously and precisely monitoring their productivity. This study assessed the potential of a
Sentinel 2 MultiSpectral Instrument, Landsat 8 Operational Land Imager, and WorldView-2 sensors,
with improved earth imaging characteristics, in estimating C3 and C4 grasses AGB in the Cathedral
Peak, South Africa. Overall, all sensors have shown considerable potential in estimating species AGB;
with the use of different combinations of the derived spectral bands and vegetation indices producing
better accuracies. However,WorldView-2 derived variables yielded better predictive accuracies (R2
ranging between 0.71 and 0.83; RMSEs between 6.92% and 9.84%), followed by Sentinel 2, with R2
between 0.60 and 0.79; and an RMSE 7.66% and 14.66%. Comparatively, Landsat 8 yielded weaker
estimates, with R2 ranging between 0.52 and 0.71 and high RMSEs ranging between 9.07% and
19.88%. In addition, spectral bands located within the red edge (e.g., centered at 0.705 and 0.745 m
for Sentinel 2), SWIR, and NIR, as well as the derived indices, were found to be very important in
predicting C3 and C4 AGB from the three sensors. The competence of these bands, especially of the
free-available Landsat 8 and Sentinel 2 dataset, was also confirmed from the fusion of the datasets.
Most importantly, the three sensors managed to capture and show the spatial variations in AGB for
the target C3 and C4 grassland area. This work therefore provides a new horizon and a fundamental
step towards C3 and C4 grass productivity monitoring for carbon accounting, forage mapping, and
modelling the influence of environmental changes on their productivity.
Description
Keywords
WorldView-2, Landsat 8, Sentinel 2, Festuca costata, Themeda triandra
Citation
Shoko, C., Mutanga, O., & Dube, T. (2018). Determining Optimal New Generation Satellite Derived Metrics for Accurate C3 and C4 Grass Species Aboveground Biomass Estimation in South Africa. Remote Sensing, 10(4), 564. MDPI AG. Retrieved from http://dx.doi.org/10.3390/rs10040564