Comparison of time-integrated NDVI and annual maximum NDVI for assessing grassland dynamics

•Annual maximum NDVI (NDVImax) 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 NDVImax.•TI-NDVI captures more spatial and temporal heterogeneity of high covered grassland.•TI-NDVI also captures more...

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Bibliographic Details
Published in:Ecological indicators 2022-03, Vol.136, p.108611, Article 108611
Main Authors: Yan, Junjie, Zhang, Guangpeng, Ling, Hongbo, Han, Feifei
Format: Article
Language:English
Subjects:
Annual maximum NDVI
Ecological heterogeneity
Grassland
Time-Integrated NDVI
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Summary:•Annual maximum NDVI (NDVImax) 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 NDVImax.•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 NDVImax. The saturation of NDVI makes the annual maximum NDVI(NDVImax) 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 NDVImax 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 NDVImax 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 NDVImax 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 NDVImax at annual time scale, but also captured more about the close relationship between grassland dynamics and precipitation or temperature in Ili Valley.
ISSN:1470-160X
1872-7034
DOI:10.1016/j.ecolind.2022.108611