Preprints
https://doi.org/10.5194/bg-2019-28
https://doi.org/10.5194/bg-2019-28

  14 Feb 2019

14 Feb 2019

Review status: this discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The manuscript was not accepted for further review after discussion.

Mapping trends in woody cover throughout Namibian savanna with MODIS seasonal phenological metrics and field inventory data

Vladimir R. Wingate1, Nikolaus J. Kuhn1, Stuart R. Phinn2, and Cornelis van der Waal3 Vladimir R. Wingate et al.
  • 1Physical Geography and Environmental Change, University of Basel, Basel, Switzerland
  • 2Remote Sensing Research Centre, School of Earth and Environmental Sciences, The University of Queensland, St Lucia, Australia
  • 3Agri-Ecological Services, P.O. Box 28, Omaruru, Namibia

Abstract. Woody vegetation is an integral component of savannas. Here, two main change processes alter woody vegetation, namely shrub encroachment and deforestation. Both impact a range of ecosystem services and functions across scales. Accurate estimates of change, including spatial extent, rate and drivers are lacking. This is primarily due to savanna vegetation comprising woody and herbaceous vegetation, each of which exhibit divergent phenological characteristics, and vary importantly in their response to climatic and environmental factors. This study uses phenological metrics derived from the MODIS MOD13Q1 NDVI time-series to model woody cover as a function of field measurements, and to map trends across Namibia. These metrics enhance the contrasting phenological characteristics of woody and herbaceous vegetation, and standardizes their annual response to climatic and environmental factors by integrating short term variation. Trends in woody cover are excellent indicators of shrub encroachment and deforestation. Trend significance was computed using the Mann-Kendall test, while change statistics, including the rate and spatial extent of change were derived using the Theil-Sen slope. Change was evaluated in relation to drivers including land-use, population, biomes and precipitation. An overall decrease in woody cover was identified, with the most pronounced decreases found in urban and densely populated areas. Decreases in woody cover were not homogenously distributed; losses predominated in tropical desert and dry forests, but gains were found across shrub lands.

Vladimir R. Wingate et al.

 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Vladimir R. Wingate et al.

Vladimir R. Wingate et al.

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