## 2 Materials and Methods
### Measurements  
An open-path eddy covariance system (EC) was installed on a flux tower platform at a height of 36 m to measure the latent heat flux (LE), sensible heat flux (H), and net ecosystem exchange (NEE) of the cork oak plantation. The entire system consisted of a three-dimensional sonic anemometer (CSAT3, Campbell Scientific Inc., Logan, UT, USA)  
Figure 1: The location of the experimental site. This picture is from [PERSON] et al. [33]. and an open-path infrared CO\({}_{2}\)/H\({}_{2}\)O analyzer (LI-7500, Li-Cor Inc., Lincoln, NE, USA). Raw data were collected at 10 Hz and recorded using a data logger (CR1000, Campbell Scientific Inc., Logan, UT, USA). A calibrated thermal infrared camera (FLIR A310F, FLIR Inc., Wilsonville, OR, USA) was used to automatically collect thermal infrared images of the cork oak plantation. The camera was equipped with an FLIR IR 18 mm lens (field of view: 25.00\({}^{\circ}\)\(\times\) 18.80\({}^{\circ}\)) for image capture. The pixel resolution of the camera was 320 \(\times\) 240 pixels, and each pixel corresponded to an effective temperature reading. An uncooled microbolometer was used in the camera to detect longwave radiation in the range of 7.50-13.00 \(\upmu\)m. The accuracy was reported as \(\pm\)4 \({}^{\circ}\)C or \(\pm\)4% of the reading. To prevent the canopy-reflected sunlight from entering the thermal infrared camera, the camera was installed on the tower platform 15 m above the canopy and faced southeast with a sensor zenith angle of 45\({}^{\circ}\). The thermal infrared images of the cork oak plantation were automatically collected every half hour. Detailed information on canopy temperature extraction from thermal infrared imagery and the measurement accuracy of canopy temperature in this plantation can be found in [PERSON] et al. (2018). The meteorological gradient observation system included a seven-layer air temperature (T\({}_{\mathrm{a}}\)), relative humidity (RH) sensor (HMP155, Vaisala Inc., Vantaa, Finland), and anemometer (WindSonic, Gill Inc., Lymington, UK), which were installed at heights of 5, 8, 11, 14, 18, 26, and 32 m, respectively (in order to reduce the impact of the vertical temperature gradient on canopy-air temperature differences, the average air temperature measured at 8 m and 11 m was selected for this study). A net radiometer (CNR1, Kipp & Zonen B.V., Delft, Netherlands) was installed at a height of 17 m. Soil moisture probes (EC-5, METER Group Inc., Pullman, WA, USA) were installed at soil depths of 5, 10, and 20 cm (soil depth was only 20 cm in most areas of the plantation). The soil heat flux plates were placed 5 cm below the surface at four points around the flux tower (HFT-3, Campbell Scientific Inc., Logan, UT, USA). These instruments were connected to a datalogger (CR1000, Campbell Scientific Inc., Logan, UT, USA), and the mean data were stored at 10 min intervals. Photosynthetically active radiation (PAR) connected to a separate data logger (CR1000, Campbell Scientific Inc., Logan, UT, USA) was collected at 10 min intervals using a PAR sensor (LI190 SB, Li-Cor Inc., Lincoln, NE, USA) at a standard meteorological station, 750 m from the tower. In addition, four linear light quantum sensors (RR-9753, RainRoot Inc., Beijing, China) were used to measure the reflected PAR (PAR\({}_{\mathrm{re}}\)) and transmitted PAR (PAR\({}_{\mathrm{tr}}\)) of the canopy, and the mean data were stored at 10 min intervals in the data logger (RR1016, RainRoot Inc., Beijing, China). In order to calibrate the soil moisture probe, the ring knife sampling and drying method was used to measure the soil moisture at depths of 5, 10, and 20 cm in sixteen plots around the flux tower. The observation interval was 10 days, and an additional observation was added after the rain ([PERSON] et al., 2018). A plant canopy analyzer (LAI-2200C, Li-Cor Inc., Lincoln, NE, USA) was used to measure the leaf area index (LAI) once a month (measurements were conducted in the middle of each month).