Integrating multi-source datasets in exploring the covariation of gross primary productivity (GPP) and solar-induced chlorophyll fluorescence (SIF) at an Indian tropical forest flux site.

Accurate measurement and monitoring of ecosystem productivity play a pivotal role in comprehending the intricate dynamics of the Earth system, particularly in the light of anthropogenic forcing. Sun-induced chlorophyll fluorescence (SIF), serving as a proxy, has garnered attention for its potential to elucidate the dynamics of terrestrial productivity by the existence of its mechanistic link with photosynthesis. Nevertheless, physiological mechanisms that regulate the relationship between the dynamics of gross primary productivity (GPP) and SIF remain shrouded in mystery. To better accommodate the research community on GPP–SIF relation, our study attempts to offer potential results by integrating multi-source Earth observation SIF and in-situ eddy flux datasets at an ecosystem level in India. The results elucidate that the studied ecosystem consistently acted as a steady CO₂ sink over the observed period, displaying a prominent double-hump seasonality and a solid correlation with SIF. Notably, this correlation was synchronous with the daily transitions of GPP. The integration of multi-source carbon fluxes and SIF datasets demonstrated a strong agreement with the in-situ data, reinforcing the reliability of our results. Our redundancy analysis by threshold binning underscores the significant positive influence of vapour pressure deficit (VPD) and photosynthetically active radiation (PAR), critical factors driving GPP and SIF, across a spectrum of temporal scales, ranging from the transient fluctuations of a day to annual panoramas. In essence, our study advocates for the synergistic utilisation of diverse datasets to unravel the underlying processes governing the relationship between GPP and SIF at multiple temporal scales. Our results and analyses are poised to propel interdisciplinary research forward by introducing novel dimensions to the GPP–SIF relationship in the Indian subcontinent. [ABSTRACT FROM AUTHOR]