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

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

doi:10.1029/2020GL088918

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

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

^*Corresponding author for this work

Eurasia Institute of Earth Sciences

Research output: Contribution to journal › Article › peer-review

71 Citations (Scopus)

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.

Original language	English
Article number	e2020GL088918
Journal	Geophysical Research Letters
Volume	47
Issue number	15
DOIs	https://doi.org/10.1029/2020GL088918
Publication status	Published - 16 Aug 2020

Bibliographical note

Publisher Copyright:
©2020. The Authors.

Funding

We thank the editor (Valeriy Y. Ivanov), Todd Hawbaker, and three anonymous reviewers for comments and suggestions which improved the content of this paper. We thank Sandra C. Cooper for thorough and careful technical editing. O. Yetemen acknowledges support from the University of Newcastle Research Advantage for Early Career Researcher (ECR) Higher Degree by Research (HDR) scholarship and the Scientific and Technological Research Council of Turkey (TUBITAK) through Grant 118C329. P. M. Saco acknowledges support from the Australian Research Council through Grants FT140100610 and DP140104178. S. A. Johnstone was supported by the U.S. Geological Survey National Cooperative Geologic Mapping Program. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. We thank the editor (Valeriy Y. Ivanov), Todd Hawbaker, and three anonymous reviewers for comments and suggestions which improved the content of this paper. We thank Sandra C. Cooper for thorough and careful technical editing. O.?Yetemen acknowledges support from the University of Newcastle Research Advantage for Early Career Researcher (ECR) Higher Degree by Research (HDR) scholarship and the Scientific and Technological Research Council of Turkey (TUBITAK) through Grant 118C329. P.?M. Saco acknowledges support from the Australian Research Council through Grants FT140100610 and DP140104178. S.?A.?Johnstone was supported by the U.S. Geological Survey National Cooperative Geologic Mapping Program. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Funders	Funder number
TUBITAK	118C329
U.S. Geological Survey National Cooperative Geologic Mapping Program
U.S. Government
University of Newcastle Research
Australian Research Council	DP140104178, FT140100610
Türkiye Bilimsel ve Teknolojik Araştirma Kurumu

Keywords

ecosystem
hillslope aspect
NDVI
remote sensing
semiarid
vegetation greenness

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10.1029/2020GL088918

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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.",

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author = "Nikul Kumari and Saco, {Patricia M.} and Rodriguez, {Jose F.} and Johnstone, {Samuel A.} and Ankur Srivastava and Chun, {Kwok P.} and Omer Yetemen",

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

Abstract

Bibliographical note

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Keywords

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