Spatiotemporal trends of NDVI and its response to climate variability in the Abbay River Basin, Ethiopia

Kassaye Hussien; Asfaw Kebede; Asnake Mekuriaw; Solomon Asfaw Beza; Sitotaw Haile Erena

doi:10.1016/j.heliyon.2023.e14113

Spatiotemporal trends of NDVI and its response to climate variability in the Abbay River Basin, Ethiopia

Heliyon. 2023 Feb 28;9(3):e14113. doi: 10.1016/j.heliyon.2023.e14113. eCollection 2023 Mar.

Authors

Kassaye Hussien¹, Asfaw Kebede², Asnake Mekuriaw³, Solomon Asfaw Beza⁴, Sitotaw Haile Erena⁴

Affiliations

¹ Department of Geographic Information Science, Haramaya University, Dire Dawa, Ethiopia.
² School of Water Resources and Environmental Engineering, Haramaya University, Dire Dawa, Ethiopia.
³ Department of Geography and Environmental Studies, Addis Ababa University, Addis Ababa, Ethiopia.
⁴ School of Geography and Environmental Studies, Haramaya University, Dire Dawa, Ethiopia.

Abstract

Woody vegetation plays a vital role in regulating the water budget and energy exchange in the Earth's system. This study aimed at analyzing the spatiotemporal variability of Normalized Difference Vegetation Index (NDVI) and its response to Potential Evapotranspiration (PET), rainfall (RF), soil moisture (SM), and temperature (TEM) in the study area. The trends, correlations, and relationships between NDVI and climate variables were executed using Mann-Kendall monotonic trend (MKMT), partial correlation coefficients (PCC), and multiple linear regression (MLR) methods, respectively. Over the last 26 years, the interannual NDVI increased by 0.0065 yr^-1 (R² = 0.159, p = 0.157). The spatiotemporal MKMT and Theil-Sen slope analysis showed that interannual NDVI increased significantly in 78% of the basin's total area. Of the 78% of the basin, 31%, and 47%, of the total area showed extremely significant increasing (Z_mk = 4.706, p ≤ 0.01), and significant increasing trends (Z_mk = 2.378, p ≤ 0.05) respectively. The interannual variation of NDVI was well explained (R² = 0.88, Adjusted R² = 0.84) by the climate variables in the eastern, southeastern, and central sub-basins where agriculture, grass, sparse vegetation and barelands are the predominant land use land cover (LULC) classes. The main climatic factors that control vegetation growth and greenness during the rainy season were found to be PET, SM, and RF with 0.91, 0.99, and 0.86 PCC with NDVI respectively. The current study broadens the scientific community's understanding of the relationship between climate variables and vegetation growth in highland ecosystems. Understanding the seasonal and long-term relationship between climate and NDVI contributes to the scientific knowledge of highland ecosystems, which are extremely vulnerable to climate change.

Keywords: Climate variability; Interannual variability; Mann-kendall monotonic trend; Multi-linear modeling; NDVI; Seasonal variability.