Response of spectral vegetation indices to soil moisture in grasslands and shrublands |
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| Authors: | Li Zhang Lei Ji Bruce K Wylie |
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| Affiliation: | 1. Key Laboratory of Digital Earth, Center for Earth Observation &2. Digital Earth, Chinese Academy of Sciences , No. 9 Dengzhuang South Road, Haidian District , Beijing , 100094 , PR China;3. Stinger Ghaffarian Technologies (SGT, Inc.), contractor (contract 08HQCN0005) to US Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center , Sioux Falls , SD , 57198 , USA lizhang@ceode.ac.cn;5. ASRC Research and Technology Solutions, contractor (contract 08HQCN0007) to US Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center , Sioux Falls , SD , 57198 , USA;6. US Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center , Sioux Falls , SD , 57198 , USA |
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| Abstract: | The relationships between satellite-derived vegetation indices (VIs) and soil moisture are complicated because of the time lag of the vegetation response to soil moisture. In this study, we used a distributed lag regression model to evaluate the lag responses of VIs to soil moisture for grasslands and shrublands at Soil Climate Analysis Network sites in the central and western United States. We examined the relationships between Moderate Resolution Imaging Spectroradiometer (MODIS)-derived VIs and soil moisture measurements. The Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) showed significant lag responses to soil moisture. The lag length varies from 8 to 56 days for NDVI and from 16 to 56 days for NDWI. However, the lag response of NDVI and NDWI to soil moisture varied among the sites. Our study suggests that the lag effect needs to be taken into consideration when the VIs are used to estimate soil moisture. |
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