University of Birjand-Research Group of Drought and Climate Change Journal of Drought and Climate change Research 3092-6076 Articles in Press 2026 07 17 Analysis of Vegetation Cover Trends Using MODIS NDVI Time Series in the Maroon Watershed Analysis of Vegetation Cover Trends Using MODIS NDVI Time Series in the Maroon Watershed 4130 10.22077/jdcr.2026.11284.1231 FA Leila Mokaram Ph.D. Student in Climatology, University of Yazd 0009-0009-0947-9162 Ahmad Mazidi Associate Professor of Climatology, Department of Geography, Yazd University, Yazd, Iran 0000-0003-4558-9907 Kamal Omidvar 3- Professor, Department of Geography and Climatology, Yazd University, Yazd, Iran, 0000-0002-4956-3002 Journal Article 2026 05 06 Abstract Long-term monitoring of vegetation cover plays an important role in understanding ecosystem dynamics and supporting sustainable natural resource management. In this study, spatial and temporal variations of vegetation cover in the Maroon watershed during 2001–2023 were investigated using a time series of the Normalized Difference Vegetation Index (NDVI). First, the spatiotemporal distribution of annual NDVI was analyzed. Then, the non-parametric Mann–Kendall test and Sen’s slope estimator were applied to determine the direction and significance of trends. In addition, the Sequential Mann–Kendall (SQMK) test was used to detect change points in vegetation cover trends. The results showed that despite temporal fluctuations, vegetation cover in the watershed maintained a relatively stable spatial pattern, with the highest vegetation density concentrated in the southern and southwestern parts of the basin. Among the study years, 2008 represented the minimum vegetation cover, while 2023 showed the highest greenness across the entire period. Trend analysis indicated that the lower NDVI classes (≤0.1 and 0.1–0.2) experienced a significant decreasing trend at the 99% confidence level, whereas the 0.2–0.4 class showed a significant increasing trend. Higher NDVI classes showed no significant trends and remained relatively stable. The SQMK test also identified major change points around 2012–2014. Overall, the reduction of low-NDVI areas and the expansion of moderate NDVI classes indicate a gradual shift from very sparse to denser vegetation, suggesting a relative improvement in vegetation conditions in parts of the Maroon watershed over the past two decades. Abstract Long-term monitoring of vegetation cover plays an important role in understanding ecosystem dynamics and supporting sustainable natural resource management. In this study, spatial and temporal variations of vegetation cover in the Maroon watershed during 2001–2023 were investigated using a time series of the Normalized Difference Vegetation Index (NDVI). First, the spatiotemporal distribution of annual NDVI was analyzed. Then, the non-parametric Mann–Kendall test and Sen’s slope estimator were applied to determine the direction and significance of trends. In addition, the Sequential Mann–Kendall (SQMK) test was used to detect change points in vegetation cover trends. The results showed that despite temporal fluctuations, vegetation cover in the watershed maintained a relatively stable spatial pattern, with the highest vegetation density concentrated in the southern and southwestern parts of the basin. Among the study years, 2008 represented the minimum vegetation cover, while 2023 showed the highest greenness across the entire period. Trend analysis indicated that the lower NDVI classes (≤0.1 and 0.1–0.2) experienced a significant decreasing trend at the 99% confidence level, whereas the 0.2–0.4 class showed a significant increasing trend. Higher NDVI classes showed no significant trends and remained relatively stable. The SQMK test also identified major change points around 2012–2014. Overall, the reduction of low-NDVI areas and the expansion of moderate NDVI classes indicate a gradual shift from very sparse to denser vegetation, suggesting a relative improvement in vegetation conditions in parts of the Maroon watershed over the past two decades.

https://jdcr.birjand.ac.ir/article_4130_c929f2210333206f417e3862f431776d.pdf