## 3 Results  
### Temporal Dynamics of SIF, Tr, and Environmental Factors  
From May to September in 2021-2022, daily SIF in Chinese cork oak, poplar, and arborviate plantations exhibited day-to-day variations, with variation ranges of 0.0003-0.949 mW\(\cdot\)m\({}^{-2}\cdot\)sr\({}^{-1}\cdot\)nm\({}^{-1}\), 0.008-0.526 mW\(\cdot\)m\({}^{-2}\cdot\)sr\({}^{-1}\cdot\)nm\({}^{-1}\), and 0.031-1.133 mW\(\cdot\)m-sr\({}^{-1}\)-nm\({}^{-1}\), respectively. Overall, the daily SIF of the arborviate plantation did not show a downward trend, while the daily SIF of the Chinese cork oak and poplar plantations began to decline in August, with the decline being more pronounced in the poplar. This could be due to differences in phenology and physiological changes among the species (Figure 1a). The NDVI of Chinese cork oak and poplar plantations remained relatively stable, whereas that of poplar plantation exhibited a marked decline during September (Figure 1c). The MTCI of Chinese cork oak and poplar plantations showed a declining trend in late August, while that of arborviate remained stable throughout the observation period (Figure 1d). For two deciduous tree species, the earlier decline in MTCI relative to NDVI indicates that leaves might be transitioning into the senescence phase, during which chlorophyll decomposition occurs prior to the onset of the deciduous stage. Similar to the seasonal dynamics of SIF, Tr exhibited significant fluctuations. The daily Tr values in Chinese cork oak, poplar, and arborviate plantations showed variation ranges of 0.028-0.462 mm\(\cdot\)h\({}^{-1}\), 0.056-0.486 mm\(\cdot\)mm\(\cdot\)h\({}^{-1}\), and 0.032-0.424 mm\(\cdot\)h\({}^{-1}\), respectively. The Tr in Chinese cork oak and poplar plantations began to show a declining trend in August, whereas the arborviate plantation did not exhibit such a trend (Figure 1b). The trends in environmental factors (including Ta, PAR, VPD, and SM) in the three plantations were relatively consistent (Figure 2). Ta began to decrease in September, with the range of variation being 15.1-37.0 \({}^{\circ}\)C (Chinese cork oak), 14.8-33.7 \({}^{\circ}\)C (poplar), and  
Figure 1: Seasonal dynamics of canopy solar-induced chlorophyll fluorescence (SIF, (**a**)), transpiration (Tr, (**b**)), normalized difference vegetation index (NDVI, (**c**)), and MERIS terrestrial chlorophyll index (MTCI, (**d**)), in Chinese cork oak (red line), poplar (blue line), and arborviate (gray line) plantations. Dots and shaded areas represent mean values and standard deviations, respectively, calculated from all half-hour data between 7:00 and 17:30 each day. 15.5-36.3 \({}^{\circ}\)C (arborvitae). PAR in poplar plantation was slightly higher than that in Chinese cork oak and arborvitae plantations. VPD at all three sites reached its peak in June. The degree of air drought in Chinese cork oak and arborvitae plantations was greater than that in poplar plantation. SM was significantly affected by precipitation and showed considerable variation among the three sites, with the poplar plantation had notably lower levels compared to the Chinese cork oak and arborvitae plantations. This may be related to the differences in soil structure and water retention capacity among the sites. In general, the SIF and Tr of the three plantations exhibited a diurnal pattern of increasing and then decreasing (Figure 3a,d,g), and the time of maximum value for SIF occurred earlier than that for Tr. After categorizing the observation days by weather conditions, distinct SIF peaks were observed for both Chinese cork oak and poplar, with Chinese cork oak peaking (12:00) earlier than poplar (12:30). The SIF of the arborvitae had no obvious peak, remaining at a relatively high level from 10:00 to 14:00. The diurnal dynamics of Tr and SIF were similar, but Tr exhibited more fluctuations and midday saturation/depression in most conditions.