Evaluating the utility of solar-induced chlorophyll fluorescence for drought monitoring by comparison with NDVI derived from wheat canopy

Leizhen Liu; Xi Yang; Hongkui Zhou; Shasha Liu; Lei Zhou; Xiaohan Li; Jianhua Yang; Xinyi Han; Jianjun Wu

doi:10.1016/j.scitotenv.2017.12.268

Evaluating the utility of solar-induced chlorophyll fluorescence for drought monitoring by comparison with NDVI derived from wheat canopy

Sci Total Environ. 2018 Jun 1:625:1208-1217. doi: 10.1016/j.scitotenv.2017.12.268. Epub 2018 Jan 12.

Authors

Leizhen Liu¹, Xi Yang², Hongkui Zhou¹, Shasha Liu³, Lei Zhou⁴, Xiaohan Li¹, Jianhua Yang¹, Xinyi Han¹, Jianjun Wu⁵

Affiliations

¹ Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China.
² Department of Environmental Sciences, University of Virginia, P.O. Box 400123, Charlottesville, USA.
³ College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China.
⁴ School of Geomatics and Urban Information, Beijing University of Civil Engineering and Architecture, Beijing 100044, China.
⁵ Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China. Electronic address: jjwu@bnu.edu.cn.

PMID: 29996417
DOI: 10.1016/j.scitotenv.2017.12.268

Abstract

Normalized Difference Vegetation Index (NDVI) has been extensively used in continuous and long-term drought monitoring over large-scale, but with late response to drought-related changes of photosynthesis. Instead, solar-induced chlorophyll fluorescence (SIF) is more closely related to photosynthesis and thus is proposed to track the impacts of drought on vegetation growth. However, the detailed difference between SIF and NDVI in responding to drought has not been thoroughly explored. Here we present continuous ground measurements of NDVI and SIF at 760nm over four plots of wheat with different intensities of drought (well-watered treatment, moderate drought, severe drought and extreme drought). The average values of seasonal SIF were significantly lower under severe drought and extreme drought, while NDVI means only showed significant reduction in extreme drought. In the seasonal patterns, daily SIF could clearly separate the difference of drought gradient, while the difference of daily NDVI was clearer in the end of the field campaign. Daily SIF also significantly and positively correlated with soil moisture, indicating that SIF could be considered as an estimator of soil moisture to detect the information about agricultural drought. Furthermore, in extreme drought plot, the correlation of SIF and soil moisture was higher than that of NDVI and soil moisture in a shorter time lag (<15-day) but weaker in a longer time lag (longer than 30-day). The relationships of growth parameters with SIF and NDVI were further analyzed, showing a saturation of NDVI and unsaturation of SIF at high values of leaf area index and relative water content. These results suggested that SIF is better fit in early drought monitoring, especially over closure canopy, while NDVI is more feasible when drought lasted over a long time scale. Our findings in the study might provide deep insight into the utility of SIF in drought monitoring.

Keywords: Drought; Leaf water content; NDVI; SIF; Soil moisture; Wheat.

MeSH terms

Chlorophyll / analysis*
Droughts*
Environmental Monitoring / methods*
Remote Sensing Technology*
Sunlight
Triticum*

Substances

Chlorophyll