## 3 Results
### Variations in Climatic Elements
An examination of the trends of the NDVI makes it clear that with the rising temperatures starting from April, the NDVI exhibited a gradual and fluctuating increase to reach its peak value in late August, followed by a gradual decline (Figure 3b). By contrast, values of the BR and EF exhibited opposite trends (Figure 3c,d). Specifically, the BR decreased during the growing season while the EF increased, once again highlighting the combined impact of the increasing SH and the decreasing LE on the distribution of surface energy fluxes. Furthermore, the SM, NDVI, BR, and EF all exhibited significant interannual fluctuations, demonstrating the pronounced interannual differences in land-atmosphere coupling in the transitional climate zone. The surface energy, water, and processes of carbon exchange are crucial components in the process of coupling between the land surface and the atmosphere. The process of carbon exchange is directly influenced by the levels of activity of the first two processes and is closely related to conditions of the surface vegetation, as reflected by the LAI and NDVI [31]. [PERSON] et al. [32] found that prior to the harvest season in the southern Great Plains of the United States, the EF was highly coupled with the LAI of winter wheat. However, the EF exhibited a higher correlation with the SM after harvest. [PERSON] et al. [9] \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Time** & **SH** & **LE** & **Rn** & **Ta** & **SM\({}_{\text{40}}\)** & **SM\({}_{\text{80}}\)** & **BR** & **EF** \\ \hline
2007 & Ave & 36.87 & 53.85 & 96.84 & 15.73 & 0.153 & 0.148 & 1.22 & 0.56 \\  & STD & 21.16 & 28.85 & 42.03 & 4.73 & 0.058 & 0.059 & 1.24 & 0.21 \\
2008 & Ave & 45.46 & 51.59 & 99.99 & 15.84 & 0.136 & 0.119 & 1.27 & 0.50 \\  & STD & 22.70 & 21.20 & 42.20 & 4.75 & 0.038 & 0.030 & 1.10 & 0.15 \\
2009 & Ave & 36.37 & 55.34 & 97.99 & 16.06 & \(-\) & \(-\) & 1.98 & 0.44 \\  & STD & 25.49 & 24.73 & 40.94 & 4.20 & \(-\) & \(-\) & 1.72 & 0.23 \\
2010 & Ave & 45.08 & 42.86 & 99.64 & 15.75 & 0.135 & 0.121 & 1.91 & 0.45 \\  & STD & 22.80 & 24.21 & 44.84 & 5.44 & 0.027 & 0.022 & 1.80 & 0.20 \\
2011 & Ave & 48.94 & 30.33 & 108.61 & 16.03 & 0.109 & 0.092 & 2.27 & 0.36 \\  & STD & 25.59 & 19.86 & 48.07 & 4.97 & 0.015 & 0.004 & 2.31 & 0.20 \\
2012 & Ave & 40.34 & 50.09 & 110.43 & 15.74 & 0.138 & 0.116 & 1.54 & 0.52 \\  & STD & 21.49 & 28.69 & 49.82 & 4.21 & 0.034 & 0.026 & 1.78 & 0.21 \\
2007–2012 & Ave & 42.18 & 47.35 & 103.75 & 15.86 & 0.135 & 0.121 & 1.70 & 0.47 \\  & STD & 23.21 & 24.59 & 44.65 & 4.72 & 0.038 & 0.032 & 1.66 & 0.20 \\ \hline \hline \end{tabular} Notes: The above outcomes were derived from the daily average values in the growing season. “Ave” means the average for the given calendar year, “STD” means the standard deviation, “Ta” means the air temperature, “SM\({}_{\text{40}}\)” represents the water content in the range of 0–40 cm, “SM\({}_{\text{80}}\)” represents the water content in the range of 40–80 cm, “BR” represents the Bowen ratio, and “\(-\)” represents missing data.  
\end{table} 
Table 1: Statistical information of the elements of land–atmosphere coupling in the growing season from 2007 to 2012.  
also researched the southern Great Plains region of the United States and discovered that the EF had a sound non\(-\)linear correlation with the LAI in grasslands and a good linear correlation with the LAI and GPP in areas with crops, with R\(-\)squared values of 0.53 and 0.67, respectively. Moreover, the correlation between the EF and the SM in the case of different underlying surfaces was not consistent. Figure 3: Variations in the (**a**) SM at 0–40 cm, (**b**) NDVI, (**c**) BR, and (**d**) EF in the growing season from April to September. All of the data are the \(21-\)point moving average of the daily values from 2007 to 2012. Figure 2: Variations in the (**a**) SH, (**b**) LE, (**c**) Rn, and (**d**) Ta of air from April to September. All of the data represent the \(21-\)point moving average of the daily values from 2007 to 2012.