Assessing the utility WorldView-2 imagery for tree species mapping in South African subtropical humid forest and the conservation implications: Dukuduku forest patch as case study |
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| Institution: | 1. Earth Observation Group, Natural Resources and Environment, Council for Scientific and Industrial Research (CSIR), Pretoria, South Africa;2. School of Agricultural Earth and Environmental Sciences, University of KwaZulu-Natal, Pietermaritzburg, South Africa;3. South African National Space Agency (SANSA), PO Box 484, Silverton 0127, South Africa;1. Institut National de la Recherche Scientifique, Centre INRS-Institut Armand-Frappier, 531 boulevard de Prairies, Laval, Québec, H7V1B7, Canada;2. Korea Polar Research Institute, Incheon, 21990, Republic of Korea;3. Graduate School of Public Health, Seoul National University, Seoul, 151-742, Republic of Korea;4. The Mina and Everard Goodman Faculty of Life Science, Bar-Ilan University, Ramat-Gan 52900, Israel;5. Cranfield Soil and Agriculture Institute, Cranfield University, College Road, Cranfield, MK43 0AL, UK;1. Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile;2. Departamento de Ciencias Biológicas y Biodiversidad, Universidad de los Lagos, Av. Fuchschlocher 1305, Osorno, Chile;3. Instituto de Ecología y Biodiversidad (IEB), Las Palmeras 3425, Santiago, Chile;4. Instituto de Conservación, Biodiversidad y Territorio, Facultad de Ciencias Forestales y Recursos Naturales, Universidad Austral de Chile, Casilla 567, Valdivia, Chile;1. Laboratory of Geo-Information Science and Remote Sensing, Wageningen University and Research, Droevendaalsesteeg 3, 6708 PB Wageningen, The Netherlands;2. Forest Ecology and Forest Management Group, Wageningen University and Research, P.O. Box 47, NL-6700 AA Wageningen, The Netherlands;3. CAVElab – Computational & Applied Vegetation Ecology, Ghent University, Belgium;4. Department of Geographical Sciences, University of Maryland, College Park, MD 20742, USA;5. GOFC-GOLD Land Cover Project Office, Wageningen, The Netherlands;1. Council for Scientific and Industrial Research (CSIR), P.O. Box 395, Pretoria 0001, South Africa;2. University of the Witwatersrand, School of Geography, Archaeology and Environmental Studies, Private Bag 3, WITS 2050, South Africa;3. University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, South Africa;4. Plant and Soil Sciences, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa;1. University of KwaZulu-Natal, School of Agricultural, Earth & Environmental Sciences, Geography Department, P/Bag X01, Scottsville, Pietermaritzburg 3209, South Africa;2. University of Witwatersrand Johannesburg, School of Geography, Archaeology and Environmental Studies, Private Bag X3, Wits 2050, Johannesburg, South Africa |
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| Abstract: | Indigenous forest biome in South Africa is highly fragmented into patches of various sizes (most patches < 1 km2). The utilization of timber and non-timber resources by poor rural communities living around protected forest patches produce subtle changes in the forest canopy which can be hardly detected on a timely manner using traditional field surveys. The aims of this study were to assess: (i) the utility of very high resolution (VHR) remote sensing imagery (WorldView-2, 0.5–2 m spatial resolution) for mapping tree species and canopy gaps in one of the protected subtropical coastal forests in South Africa (the Dukuduku forest patch (ca.3200 ha) located in the province of KwaZulu-Natal) and (ii) the implications of the map products to forest conservation. Three dominant canopy tree species namely, Albizia adianthifolia, Strychnos spp. and Acacia spp., and canopy gap types including bushes (grass/shrubby), bare soil and burnt patches were accurately mapped (overall accuracy = 89.3 ± 2.1%) using WorldView-2 image and support vector machine classifier. The maps revealed subtle forest disturbances such as bush encroachment and edge effects resulting from forest fragmentation by roads and a power-line. In two stakeholders’ workshops organised to assess the implications of the map products to conservation, participants generally agreed amongst others implications that the VHR maps provide valuable information that could be used for implementing and monitoring the effects of rehabilitation measures. The use of VHR imagery is recommended for timely inventorying and monitoring of the small and fragile patches of subtropical forests in Southern Africa. |
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| Keywords: | Subtropical forest Tree species Remote sensing WorldView-2 Forest conservation |
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