The grass is not always greener on the other side: Seasonal reversal of vegetation greenness in aspect-driven semiarid ecosystems

Kumari, Nikul; Saco, Patricia M; Rodriguez, Jose F; Johnstone, Samuel A; Srivastava, Ankur; Chun, Kwok P; Yetemen, Omer

Abstract

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.

• Journal Article Type: Article
• Acceptance Date: Jun 8, 2020
• Online Publication Date: Jul 8, 2020
• Publication Date: Aug 16, 2020
• Deposit Date: Jan 19, 2022
• Publicly Available Date: Jan 20, 2022
• Journal: Geophysical Research Letters
• Print ISSN: 0094-8276
• Electronic ISSN: 1944-8007
• Publisher: American Geophysical Union
• Peer Reviewed: Peer Reviewed
• Volume: 47
• Issue: 15
• Article Number: e2020GL088918
• DOI: https://doi.org/10.1029/2020GL088918
• Public URL: https://uwe-repository.worktribe.com/output/8545520