## 2 Study Site and Data Processing
### Eddy Covariance Measurements and Meteorology Data at the Xiangtang Station  
Up to date, the eddy-covariance technique has been the standard method in the ET and GPP measurements at scales of 10\({}^{2}\)-10\({}^{3}\) m [34]. To measure the fluxes of sensible heat, latent heat, and CO\({}_{2}\), we have set up an open-path eddy covariance system (Li-COR 7500) at a height of 2.5 m since October 2016 at the Xiangtang station. The three-dimensional wind velocities and CO\({}_{2}\)/H\({}_{2}\)O concentrations were recorded by a datalogger (model CR3000, Campbell Scientific, Inc., Logan, UT, USA) at a frequency of 10 Hz. Other microclimate variables were measured as 30 min averages, including net radiation (R\({}_{n}\)) (CNR4, Kipp and Zonen, Delft, The Netherlands), air temperature (T\({}_{a}\)), and relative humidity (RH) (HMP155A, Vaisala, Inc., Vantaa, Finland), wind speeds (U) and wind direction (WD) (model 03002, RM Young, Inc., Dundee, MI, USA), and precipitation (model 52202, RM Young, Inc.). The soil heat fluxes (model HFP01 SC, Campbell Scientific, Inc.) were measured at 0.05 m below the soil surface. All data were collected by a CR3000 datalogger as 30 min averages. The data were selected from October 2016 to December 2018, except from 16 November 2017 to 15 March 2018, due to an instrument malfunction. The data were divided into 18 periods according to the growing stages of early rice and late rice, as shown in Table 1.  
Figure 1: Location of the study area, flux site, and the land cover in 2000, 2005, 2010, and 2015 in this area. We used the EddyPro software v6.1.0 (www.licor.com/eddypro, accessed on 15 December 2019) to process the high-frequency raw data. After the 30-min scale fluxes were calculated using the high-frequency measurements in the air temperature, humidity, CO\({}_{2}\), and three-dimensional wind velocity, the post-field data processing program was developed following FLUXNET's standard procedures [35]. The main data processing steps on the 30-min scale fluxes included spike removal [36], double coordinate rotation [37], frequency response corrections [38; 39], and WPL corrections [40] for the air density fluctua \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Periods** & **Date** & **Plantation** & **Growing Stages of Rice** \\ \hline P\({}_{1}\) & 01/10/2016–24/10/2016 & Late Rice & Grouting and ripeness \\ \hline P\({}_{2}\) & 25/10/2016–23/03/2017 & & Chinese milk vetch \\ \hline P\({}_{3}\) & 24/03/2017–23/04/2017 & & Rice seedling transplant and resume growth \\ P\({}_{4}\) & 24/04/2017–23/05/2017 & & Resume growth before jointing \\ P\({}_{5}\) & 24/05/2017–23/06/2017 & & Joiting, booting, heading, and blooming \\ P\({}_{6}\) & 24/06/2017–14/07/2017 & & Grouting and ripeness \\ \hline P\({}_{7}\) & 15/07/2017–23/08/2017 & & Rice seedling transplant and resume growth \\ P\({}_{8}\) & 24/08/2017–24/09/2017 & Late Rice & Joiting, booting, heading, and blooming \\ P\({}_{9}\) & 25/09/2017–24/10/2017 & & Grouting and ripeness \\ \hline P\({}_{10}\) & 25/10/2017–23/03/2018 & & Chinese milk vetch \\ \hline P\({}_{11}\) & 24/03/2018–23/04/2018 & & Rice seedling transplant and resume growth \\ P\({}_{12}\) & 24/04/2018–23/05/2018 & & Resume growth before jointing \\ P\({}_{13}\) & 24/05/2018–23/06/2018 & & Joiting, booting, heading, and blooming \\ P\({}_{14}\) & 24/06/2018–14/07/2018 & & Grouting and ripeness \\ \hline P\({}_{15}\) & 15/07/2018–23/08/2018 & & Rice seedling transplant and resume growth \\ P\({}_{16}\) & 24/08/2018–24/09/2018 & Late Rice & Joiting, booting, heading, and blooming \\ P\({}_{17}\) & 25/09/2018–24/10/2018 & & Grouting and ripeness \\ \hline P\({}_{18}\) & 25/10/2018–31/10/2018 & & Chinese milk vetch \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The cropping system and management measures at the Xiangtang station.