Characteristics of chlorophyll fluorescence in Hulunbuir grassland and its response to meteorological conditions
Chlorophyll fluorescence is a non-invasive technique used to study the photosynthetic activity of plants.Recently,solar-induced chlorophyll fluorescence(SIF)has been developed to measure chlorophyll fluores-cence in plants.This study uses hourly meteorological observation data and ERA5 reanalysis atmospheric data.The growth of pasture in the Hulunbuir grassland during the growing season was continuously and stably observed u-sing the orbital daylight-induced chlorophyll fluorescence observatory.The variational characteristics of SIF and its response to changes in meteorological conditions are analyzed.During the 2022 growing season,SIF measurements were conducted in the Hulunbuir Grassland using the DR-SIF01 orbital observation instrument.Compared to the normalized difference vegetation index(NDVI),the low-frequency components of SIF can characterize plant growth changes during the growing season,while high-frequency variations can more clearly monitor the physio-logical processes of intrinsic photosynthesis in plants,closely related to meteorological conditions.Notably,the re-lationship between soil water content and SIF is nonlinear.When continuous excessive precipitation leads to soil waterlogging,the physiological metabolism of grass is weakened,and photosynthesis slows down,resulting in low SIF.Conversely,adequate early precipitation resulting in moist soil and strong solar radiation can maintain SIF at a relatively high level,indicating vigorous plant photosynthesis.In the late-growing season,cool autumn rains signif-icantly reduce plant photosynthesis,resulting in difficult recovery.The in-situ measurements of chlorophyll fluores-cence conducted in this study contribute to a quantitative understanding of grass growth status.Combined with the revealed response of SIF to meteorological conditions,early warning for crop disasters and optimization of man-agement measures can be further achieved.Although the in-situ chlorophyll fluorescence data used in this study are more accurate than satellite inversion data,there are still challenges,such as short observation periods and lim-ited observation sites.The SIF variation characteristics and responses to meteorological conditions revealed in this paper are based on data from a single site during the 2022 growing season,which introduces uncertainties.Future studies should focus on the data assimilation of satellite inversion and in-situ observation to achieve quantitative descriptions and real-time monitoring of plant photosynthesis and carbon sources and sinks in the Hulunbuir grass-land.Additionally,applying chlorophyll fluorescence and NDVI observation data to the parametrization of land surface models to improve the simulation of dynamic plants and related water balance,energy balance,and carbon absorption remains a key scientific problem worth exploring.
ecosystemsphotosynthesischlorophyll fluorescenceprecipitationsoil water
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