## 3 Results
### Influences of Meteorological and Soil Factors on the T-SIF Relationship  
To clarify the influences of meteorological and soil factors on the T-SIF relationship, we conducted an SIF-T linear regression for different variables value intervals: the lowest, <33%, medium, 33%-66% and highest, >66% at hourly and daily scales, respectively (Figures 4 and 5). The higher slope of SIF-T was 0.7 in PAR (>400 umol m\({}^{-2}\) s\({}^{-1}\)) and 0.9 in PAR (<200 umol m\({}^{-2}\) s\({}^{-1}\)) (Figure 4A). The lowest slope of the SIF-T was 0.2 in PAR (200-400 umol m\({}^{-2}\) s\({}^{-1}\)) at hourly scale (Figure 4A). At high air temperature (>22 \({}^{\circ}\)C), the slope of the SIF-T was the lowest at 0.4. As the temperature decreased, the slope of the SIF-T became higher (14-22 \({}^{\circ}\)C, slope was 0.7; <14 \({}^{\circ}\)C, slope was 0.6) (Figure 4B). The higher slopes of 0.7 and 0.9 for SIF-T were found in SWC (>14%) and SWC (<12%) (Figure 4C). The lowest slope 0.4 of the SIF-T was in SWC (12%-14%) (Figure 4C). At higher and lower  
Figure 4: Relationship between SIF and T over PAR (**A**), air temperature (**B**), soil water content (**C**), VPD (**D**) and soil temperature (**E**) at hourly scale. The dashed lines are linear regression fitted to the SIF and T for different variables value interval: the lowest (black, <33%), medium (green, 33%-66%) and highest (yellow, >66%) at hourly scale, respectively. Figure 5: Relationship between SIF and T over PAR (**A**), air temperature (**B**), soil temperature (**C**), VPD (**D**) and soil water content (**E**) at daily scale. The dashed lines are linear regression fitted to the SIF and T under different variables value interval: the lowest (black, <33%), medium (green, 33%-66%) and highest (yellow, >66%) at daily scale, respectively. VPD (>19 kPa and <10 kPa), the slope of the SIF-T was the same (0.8). The slope of the SIF-T was 0.7 at VPD (10-19 kPa) (Figure 4D). For the soil temperature, the slope of the SIF-T was 0.6-0.7 for different soil temperature intervals (Figure 4E). Our results indicated that the slopes between ENF canopy SIF and T significantly changed with the PAR, air temperature, SWC and slightly changed with VPD and soil temperature at hourly scale in the fall (Figure 4). The slope of SIF-T was analyzed for different meteorological and soil factors intervals at daily scale. We found that the higher slope of SIF-T was 0.6 in PAR (300-400 \(\upmu\)mol m\({}^{-2}\) s\({}^{-1}\)) and 0.5 in PAR (<300 \(\upmu\)mol m\({}^{-2}\) s\({}^{-1}\)) (Figure 5A). The lowest slope 0.3 of the SIF-T was in PAR (>400 \(\upmu\)mol m\({}^{-2}\) s\({}^{-1}\)) at daily scale (Figure 5A). The higher slopes 0.6 and 0.9 of SIF-T were found in air temperature > 17 \({}^{\circ}\)C and 10-17 \({}^{\circ}\)C and the lowest slope 0.3 of the SIF-T was in air temperature < 10 \({}^{\circ}\)C (Figure 5B). As the soil temperature decreased, the slope of the SIF-T became lower (>12.5 \({}^{\circ}\)C, slope was 0.9; 7.5-12.5 \({}^{\circ}\)C, slope was 0.7; <7.5 \({}^{\circ}\)C, slope was 0.6) (Figure 5C). The slopes of the SIF-T decreased with VPD reduction (>12 kPa, slope was 0.9; 10-12 kPa, slope was 0.7; <10 kPa, slope was 0.6) (Figure 5D). For the SWC, the slopes of the SIF-T in the three SWC intervals were 0.6-0.7 (Figure 5E). Our results indicated that the slopes between SIF and T significantly changed with PAR, air temperature, soil temperature and VPD at daily scale (Figure 5). To verify the key factors influencing the SIF-T relationship, we conducted LASSO regression at the hourly and daily scales with PAR, air temperature, VPD, soil temperature, SWC and SIF as input variables and T as target values. The LASSO accuracy assessments for training data results were: hourly: R\({}^{2}\) = 0.73, RMSE = 12%; daily: R\({}^{2}\) = 0.81, RMSE = 8%; and for the test data result was: hourly: R\({}^{2}\) = 0.72, RMSE = 12% and daily: R\({}^{2}\) = 0.75, RMSE = 10%. Among all the input variables, air temperature and PAR had the highest and second highest weights across hourly and daily scales.