[Responses of solar-induced chlorophyll fluorescence to meteorological drought across the Loess Plateau, China.]

With the intensification of climate change, the frequency, duration and scope of drought have become more and more serious. Exploring the responses of plant photosynthesis to drought and the impacts of meteorological factors on photosynthesis is of great significance to the dealing with drought stress. Solar-induced chlorophyll fluorescence (SIF) based on remote sensing has the potential for early monitoring and accurate assessment of regional vege-tation photosynthesis under drought conditions. Based on the spaceborne SIF information and the standardized precipitation evapotranspiration index (SPEI), we investigated the responses of vegetation photosynthesis to drought and the influence of meteorological factors in the growing season (April to October) of the Loess Plateau during 2001-2017. The results showed that about 87.8% of total areas of the Loess Plateau had a significant positive correlation between SIF and SPEI. Vegetation photosynthesis in semi-arid area was more sensitive to drought and less sensitive in semi-humid area. Different vegetation types had different photosynthetic responses to drought. Grassland had the highest sensitivity to drought with three to four months SPEI time-scale, while forest had the lowest sensiti-vity with three to ten months SPEI time-scale. There was a significant correlation between meteorological factors and SIF. Temperature and precipitation were the most important factors affecting vegetation photosynthesis on the Loess Plateau. Photosynthetically active radiation showed a similar controlling strength to temperature. The impacts of drought and meteorological factors on vegetation photosynthesis were largely determined by differences in drought resistance among ecosystem types and climate regions.