Response of vegetation to drought and yield monitoring based on NDVI and SIF

An increase in global warming has resulted in a global increase in meteorological droughts. As droughts play a key factor regulating vegetation growth, they inevitably have social and economic effects. Understanding vegetation dynamics and its response to climate change is therefor highly important to reveal the behavior mechanism of terrestrial ecosystems and to guide environmental management. In this investigation, Solarinduced Chlorophyll Fluorescence (SIF) and the Normalized Difference Vegetation Index (NDVI) were applied as vegetation indicators to describe vegetation dynamics and meteorological drought was described using the standardized precipitation evapotranspiration index (SPEI). Bias correction of precipitation and crop yield data of major crop producing areas was also used. By employing correlation coefficient of the maximum absolute value, a drought impact degree and propagation time to vegetation were defined. Dimensions of SIF and NDVI were unified by normalization. Results indicated that: (1) SIF and NDVI generally had a high level of consistency over China, and NDVI had a higher normalized value distribution level than SIF for different vegetation types. (2) Drought generally had a negative impact on vegetation in northern China and a positive impact in southern China. (3) Drought propagation time based on NDVI was larger than that based on SIF. (4) SIF had some advantages when monitoring crop yields among different crop producing areas. Results from this investigation will enable a greater understanding of SIF and NDVI for their application to monitor droughts and crop yield.