Abstract
As a newly emerging satellite form of data, solar-induced chlorophyll fluorescence (SIF) provides a direct measurement of photosynthetic activity. The potential of SIF for drought assessment in different grassland ecosystems is not yet clear. In this study, the correlations between spaceborne SIF and nine drought indices were evaluated. Standardized precipitation evapotranspiration index (SPEI) at a 1, 3, 6, 9, 12 month scale, Palmer drought severity index (PDSI), soil moisture, temperature condition index (TCI), and vapor pressure deficit (VPD) were evaluated. The relationships between different grassland types and different seasons were compared, and the driving forces affecting the sensitivity of SIF to drought were explored. We found that the correlations between SIF and drought indices were different for temperate grasslands and alpine grasslands. The correlation coefficients between SIF and soil moisture were the highest (the mean value was 0.72 for temperate grasslands and 0.69 for alpine grasslands), followed by SPEI and PDSI at a three month scale, and the correlation coefficient between SIF and TCI was the lowest (the mean value was 0.38 for both temperate and alpine grasslands). Spaceborne SIF is more effective for drought monitoring during the peak period of the growing season (July and August). Temperature and radiation are important factors affecting the sensitivity of SIF to drought. The results from this study demonstrated the importance of SIF in drought monitoring especially for temperate grasslands in the peak growing season.
Highlights
Drought influences the functions of the terrestrial ecosystem and the carbon budget [1]
The results demonstrated that temperate grasslands and alpine grasslands have different solar-induced chlorophyll fluorescence (SIF) sensitivity to drought variables
This study examined the characteristics of spaceborne SIF correlations to drought variables in arid and semiarid regions from 2007 to 2018 for two typical grassland ecosystems
Summary
Drought influences the functions of the terrestrial ecosystem and the carbon budget [1]. Several studies have highlighted the negative impact of drought on groundwater availability [2,3], agricultural production and food security [4,5], ecosystem net primary production [6], and socio-economic status [7]. These impacts are projected to be exacerbated under the current and future changing climate [8]. The physiological functions impacted by drought can occur in time scale of hours to days.
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