## 1 Introduction
According to the analysis of environmental factors and SIF in the Greater Khingan Mountains, the satellite SIF of 16 and 8 days was only correlated with the air temperature [30]. The tower-based SIF of evergreen forests was mainly affected by the half-hour PAR and soil moisture, while, at the daily scale, SIF was mainly regulated by air temperature [31]. Leaf fluorescence and non-photochemical quenching (NPQ) in maize and Miscanthus were correlated with both PAR and the leaf temperature [32]. SIF at different temporal and spatial scales has different responses to environmental factors. Environmental factors not only affect the fluorescent light energy utilization, but they also indirectly affect SIF by affecting stomatal conductance. Stomata are gas exchange channels between plants and the atmosphere, and the water status will affect the opening and closing of stomata. Stomata conductance can determine the rate of gas exchange [33] and can influence radiation-use efficiency [34], which, in turn, affects photosynthesis and fluorescence light-use efficiency. [PERSON] et al. found that soil moisture deficiency and a high vapor pressure deficit (VPD) changed the dynamics and intensity of SIF, and even changed the relationship between SIF and photosynthetic physiology [35]. Therefore, understanding the dynamics of SIF in different weather conditions and different temporal scales, and analyzing the response of SIF to environmental factors, are of great significance in accounting for the relationship between photosynthesis and fluorescence. The dynamic change in SIF contains photosynthetic information, which is influenced by biological factors, abiotic factors, the canopy structure, the physiological state and other factors [36]. Due to differences in the fluorescence emission capacity and the canopy structure, different types of vegetation usually have different dynamics and intensities [37]. [PERSON] et al. found that the fluorescence emission was the highest in farmland, followed by broadleaf forests, and was the lowest in coniferous forests [38]. The leaf fluorescence yield was found to be determined by genotype and to be affected by shading [39] and nitrogen availability [40]. The differences among species in terms of their carbon fixation pathways were more significant [22]. It was found that a canopy with a similar fraction of PAR could emit SIF in different intensities [41]. Due to the differences in the phenological characteristics and the photosynthetic physiology, the seasonal and diurnal dynamics of SIF were different among the species [42; 43; 44]. Moreover, the fluorescence was collected at the top of the canopy after it was emitted from the leaves and then absorbed and reabsorbed through the canopy [45; 46]. For example, cropland ecosystems usually have a special row structure, and the observation angle will cause a variation in SIF [47]. Due to the special cluster structure of the leaves of coniferous forests, the light absorption capacity of the canopies in coniferous forests is higher than that in broadleaf forests [48]. Canopy structures, such as LAI and the leaf angle, not only determine the multiple scattering and absorption of radiation and fluorescence, they also affect the zenith and the azimuth angle [49]. According to previous studies on ecosystem water and the carbon flux constraints based on SIF, the simpler the canopy structure of vegetation, the higher the accuracy of the simulated value [50; 51]. The canopies with complex structures are more likely to be affected by the sunlight observation geometry [52]. Although the application of SIF on a global scale has been recognized [14], the variability of SIF among species remains unsolved [53]. To date, there have been many species-specific SIF observations and studies on croplands; however, there have been few studies on forests, especially for deciduous broad-leaved forests, with obvious canopy structures and physiological variations. In this study, the canopy SIF and the ecosystem's environmental factors in a _Quercus variabilis_ BI.