A new NDVI measure that overcomes data sparsity in cloud-covered regions predicts annual variation in ground-based estimates of high-arctic plant productivity

Stein Rune Karlsen, Helen B. Anderson, Rene Van der Wal, Brage Bremset Hansen

Research output: Contribution to journalArticle

12 Citations (Scopus)
9 Downloads (Pure)

Abstract

Efforts to estimate plant productivity using satellite data can be frustrated by the presence of cloud cover. We developed a new method to overcome this problem, focussing on the high-arctic archipelago of Svalbard where extensive cloud cover during the growing season can prevent plant productivity from being estimated over large areas. We used a field-based time-series (2000-2009) of live aboveground vascular plant biomass data and a recently processed cloud-free MODIS-NDVI data set (2000-2014) to estimate, on a pixel-by-pixel basis, the onset of plant growth. We then summed NDVI values from onset of spring to the average time of peak NDVI to give an estimate of annual plant productivity. This remotely sensed productivity measure was then compared, at two different spatial scales, with the peak plant biomass field data. At both the local scale, surrounding the field data site, and the larger regional scale, our NDVI measure was found to predict plant biomass (adjusted R<sup>2</sup> = 0.51 and 0.44, respectively). The commonly used 'maximum NDVI' plant productivity index showed no relationship with plant biomass, likely due to some years having very few cloud-free images available during the peak plant growing season. Thus, we propose this new summed NDVI from onset of spring to time of peak NDVI as a proxy of large-scale plant productivity for regions such as the Arctic where climatic conditions restrict the availability of cloud-free images.
Original languageEnglish
Article number025011
JournalEnvironmental Research Letters
Volume13
Issue number2
Early online date6 Dec 2017
DOIs
Publication statusPublished - 14 Feb 2018

Keywords

  • cloud cover
  • plant productivity
  • MODIS
  • NDVI
  • growing degree days
  • Svalbard
  • High Arctic
  • variability

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