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Summary of Proposal LAN1504

TitleWoody cover, height, and biomass assessment in savannas of the Greater Kruger National Park region, South Africa, using TerraSAR-X and TanDEM-X products
Investigator Naidoo, Laven - Council for Scientific and Industrial Research, Natural Resources and Environment - Earth Observation Unit
Team Member
Dr Smit, Izak - South African National Parks, Scientific Services, Kruger National Park
Dr Erasmus, Barend - University of Witwatersrand, School of Animal, Plant and Environmental Sciences
Dr Kleynhans, Waldo - CSIR, Meraka Institute - Remote Sensing Research Unit
Dr Mathieu, Renaud - Council for Scientific and Industrial Research, Natural Resources and Environment - Earth Observation Unit
SummaryMore than half of the Southern African subcontinent is covered by savannas and woodlands, occupying between 10-50% of total tree cover, which play a critical role in the global carbon storage pool (mean net primary productivity of 7.2 tC/ha/year) (Grace et al. 2006). Tree structural dynamics, such as tree cover and aboveground woody biomass, are critical variables to consider in these African savannas as they play an important role in the provision of ecosystem services and impact widely on food and energy security, either through bush encroachment and the reduction of grassland for meat production, or the depletion of woody resource used for domestic energy. This information has large implications for assessing carbon stocks (e.g. REDD+) in savannas and woodlands as both variables, tree height and tree cover, are required as proxy to estimate above ground woody biomass.Remote sensing has proven to be a tool of choice for measuring such tree attributes largely because of its synoptic view, wide spatial coverage, and revisit capacity.Synthetic Aperture Radar (SAR) technology offers the advantage of being non sensitive to cloud cover and haziness, two conditions prevalent in Southern Africa, either during the growing season in summer-rainfall areas or during the dry season as a result of frequent bush fires. The objective of this project is to assess the potential of the high resolution TerraSAR-X and TanDEM-X products to quantify tree cover and height, and woody biomass, in southern African savannas, together with ground and LiDAR data, as well as in combination with multi-frequency C- and L-band satellite-based SAR. The main outcome is the development of much needed methodologies, which include the required data and processing criteria, tailored specifically for typically open and heterogeneous savannas. This will lead to the development of specific guidelines for the development of local African research capacity and capability in ecosystem structural remote sensing, woody biomass estimation and carbon accounting.The project will have two key objectives: 1)Assessing the potential of TerraSAR-X StripMap dual-polarised products for extracting woody biomass and cover. 2)Assessing the potential of interferometric pairs (TerraSAR-X and TanDEM-X SpotLight products) for extracting fine scale (crown level) tree height variation.Tree cover and biomass models will be developed using the backscattering intensity signal while tree height models will be using the coherence information of interferometric pairs. The SAR predictors will be calibrated and validated using recent large coverage of airborne LiDAR data already available, as well as ground data assessment. Analysis will examine performance at single dates, but most importantly will develop a multi-temporal approach (at various phenological seasons) by combining individual estimates of tree cover, biomass and other tree structural metric estimates. The funding for this project is available within the CSIR through multi-year external secured projects (e.g. DST and FP7 AGRICAB). The project will run over the course of 3 years (2012-2014). The deliverables for this project will be at least two conference proceedings, two peer reviewed journal publications, 1 PhD degree, and result dissemination to the African community via conferences and workshops.

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