The Grass Is Not Always Greener on the Other Side: Seasonal Reversal of Vegetation Greenness in Aspect-Driven Semiarid Ecosystems

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Kumari N., Saco P. M., Rodriguez J. F., Johnstone S. A., Srivastava A., Chun K. P., ...More

GEOPHYSICAL RESEARCH LETTERS, vol.47, 2020 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 47
  • Publication Date: 2020
  • Doi Number: 10.1029/2020gl088918
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aerospace Database, Agricultural & Environmental Science Database, Aquatic Science & Fisheries Abstracts (ASFA), CAB Abstracts, Communication Abstracts, Compendex, Geobase, INSPEC, Metadex, Pollution Abstracts, Veterinary Science Database, Civil Engineering Abstracts
  • Keywords: NDVI, vegetation greenness, hillslope aspect, semiarid, ecosystem, remote sensing, SLOPE ASPECT, SNOW-COVER, TOPOGRAPHIC CORRECTION, CLIMATE-CHANGE, SOIL-MOISTURE, MODIS, INDEX, NDVI, HILLSLOPES, PATTERNS
  • Istanbul Technical University Affiliated: Yes


Our current understanding of semiarid ecosystems is that they tend to display higher vegetation greenness on polar-facing slopes (PFS) than on equatorial-facing slopes (EFS). However, recent studies have argued that higher vegetation greenness can occur on EFS during part of the year. To assess whether this seasonal reversal of aspect-driven vegetation is a common occurrence, we conducted a global-scale analysis of vegetation greenness on a monthly time scale over an 18-year period (2000-2017). We examined the influence of climate seasonality on the normalized difference vegetation index (NDVI) values of PFS and EFS at 60 different catchments with aspect-controlled vegetation located across all continents except Antarctica. Our results show that an overwhelming majority of sites (70%) display seasonal reversal, associated with transitions from water-limited to energy-limited conditions during wet winters. These findings highlight the need to consider seasonal variations of aspect-driven vegetation patterns in ecohydrology, geomorphology, and Earth system models.