Comparison of time-integrated NDVI and annual maximum NDVI for assessing grassland dynamics. (March 2022)

• Record Type: Journal Article
• Authors: Yan, Junjie; Zhang, Guangpeng; Ling, Hongbo; Han, Feifei
• Is Part Of: Ecological indicators. Volume 136(2022)
• Publication Date: 2022-03
• Subjects: Ecological heterogeneity -- Time-Integrated NDVI -- Annual maximum NDVI -- Grassland; Environmental monitoring -- Periodicals; Environmental management -- Periodicals; Environmental impact analysis -- Periodicals; Environmental risk assessment -- Periodicals; Sustainable development -- Periodicals; 333.71405
• DOI: 10.1016/j.ecolind.2022.108611
• Languages: English
• ISSNs: 1470-160X

Abstract

Highlights: Annual maximum NDVI (NDVI max ) and time-integrated NDVI (TI-NDVI) were compared. Spatial and temporal variations of grassland revealed by TI-NDVI differ a lot from that revealed by NDVI max . TI-NDVI captures more spatial and temporal heterogeneity of high covered grassland. TI-NDVI also captures more about the close correlations between grassland dynamics and precipitation or temperature than NDVI max. Abstract: The saturation of NDVI makes the annual maximum NDVI(NDVI max ) underestimate vegetation with high coverage. Time-Integrated NDVI(TI-NDVI) accumulates NDVIs of vegetation at different growing stages in one growing season. TI-NDVI might alleviate the saturation effect of NDVI max when vegetation dynamics are assessed at annual time scale. Taking grassland in Ili Valley at the west end of Tianshan Mountain as the study area, this paper compared NDVI max and TI-NDVI systematically for assessing grassland dynamics and also their correlations with precipitation and temperature. Data of time-series Moderate Resolution Imaging Spectroradiometer(MODIS) NDVI were used and methods of Mann-Kendall trend test, Sen's slope estimator test, coefficient of variation(CV) and partial correlation coefficient were employed. We found that there were 28.69% grassland in Ili Valley where the TI-NDVI and NDVI max showed different changing trends over the years of 2000–2019. TI-NDVI not only revealed more about the spatial and temporal heterogeneities of grassland with high coverage than NDVI max at annual time scale, but also captured more about the close relationship between grassland dynamics and precipitation or temperature in Ili Valley.