Estimating above ground biomass as an indicator of carbon storage in vegetated wetlands of the grassland biome of South Africa

Show simple item record Naidoo, Laven Van Deventer, Heidi Ramoelo, Abel Mathieu, Renaud Nondlazi, Basanda Gangat, Ridhwannah 2019-12-10T06:05:49Z 2019-06
dc.description.abstract Wetlands store higher carbon content relative to other terrestrial ecosystems, despite the small extent they occupy. The increase in temperature and changes in rainfall pattern may negatively affect their extent and condition, and thus the process of carbon accumulation in wetlands. The introduction of the Sentinel series (S1 and S2) and WorldView space-borne sensors (WV3) have enabled monitoring of herbaceous above ground biomass (AGB) in small and narrow wetlands in semi-arid areas. The objective of this study was to assess (i) the capabilities of the high to moderate resolution sensors such as WV3, S1A and S2A in estimating herbaceous AGB of vegetated wetlands using SAR backscatter, optical reflectance bands, vegetation spectral indices (including Leaf Area Index or LAI measurements) and band ratio datasets and (ii) whether significant differences exists between the AGB ranges of wetland and surrounding dryland vegetation. A bootstrapped Random Forest modelling approach, with variable importance selection, was utilised which incorporated ground collected grass AGB for model calibration and validation. WorldView-3 (WV3) yielded the highest AGB prediction accuracies (R2 = 0.63 and RMSE = 169.28 g/m2) regardless of the incorporation of bands only, indices only or the combination of bands and indices. In general, the optical sensors yielded higher modelling accuracies (improvement in R2 of 0.04-0.07 and RMSE of 11.48–17.28 g/m2) than the single Synthetic Aperture Radar (SAR) sensor but this was marginal depending on the scenario. Incorporating Sentinel 1A (S1) dual polarisation channels and Sentinel 2A (S2) reflectance bands, in particular, yielded higher accuracies (improvement in R2 of 0.03–0.04 and RMSE of 5.4–16.88 g/m2) than the use of individual sensors alone and was also equivalent to the performance of the high resolution WV3 sensor results. Wetlands had significantly higher AGB compared to the surrounding terrestrial grassland (with a mean of about 80 g/m2 more). Monitoring herbaceous AGB at the scale of the wetland extent in semi-arid to arid grasslands enables improved understanding of their carbon sequestration potential, the contributions to global carbon accounting policies and also serving as a proxy for functional intactness. en_ZA
dc.description.department Geography, Geoinformatics and Meteorology en_ZA
dc.description.embargo 2020-06-01
dc.description.librarian hj2019 en_ZA
dc.description.sponsorship The Water Research Commission (WRC) under the project K5/2545 “Establishing remote sensing toolkits for monitoring freshwater ecosystems under global change” as well as the Council for Scientific and Industrial Research (CSIR) by the project titled “Common Multi-Domain Development Platform (CMDP) to Realise National Value of the Sentinel Sensors for various land, freshwater and marine societal benefit areas”. en_ZA
dc.description.uri en_ZA
dc.identifier.citation Naidoo, L., Van Deventer, H., Ramoelo, A. et al. 2019, 'Estimating above ground biomass as an indicator of carbon storage in vegetated wetlands of the grassland biome of South Africa', International Journal of Applied Earth Observation and Geoinformation, vol, 78, pp. 148-129. en_ZA
dc.identifier.issn 1569-8432 (print)
dc.identifier.issn 1872-826X (online)
dc.identifier.other 10.1016/j.jag.2019.01.021
dc.language.iso en en_ZA
dc.publisher Elsevier en_ZA
dc.rights © 2019 Elsevier B.V. All rights reserved. Notice : this is the author’s version of a work that was accepted for publication inInternational Journal of Applied Earth Observation and Geoinformation. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. A definitive version was subsequently published in International Journal of Applied Earth Observation and Geoinformation, vol. 78, pp. 118-129, 2019. doi : 10.1016/j.jag.2019.01.021. en_ZA
dc.subject Synthetic aperture radar (SAR) en_ZA
dc.subject Above ground biomass (AGB) en_ZA
dc.subject WorldView space-borne sensors (WV3) en_ZA
dc.subject Vegetation biomass en_ZA
dc.subject Wetland types en_ZA
dc.subject Carbon sequestration en_ZA
dc.subject Remote sensing en_ZA
dc.subject Earth observation en_ZA
dc.subject Sentinel sensors en_ZA
dc.subject South Africa (SA) en_ZA
dc.title Estimating above ground biomass as an indicator of carbon storage in vegetated wetlands of the grassland biome of South Africa en_ZA
dc.type Postprint Article en_ZA

Files in this item

This item appears in the following Collection(s)

Show simple item record