## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Index** & **Preset** & **SOS** & **MOE** & **EOS** \\ \hline \multirow{4}{*}{GGR} & 1 (CK) & 83 (24 March) & 109 (19 April) & 307 (3 November) \\ \cline{2-5}  & 3 (DIFI) & 83 (24 March) & 111 (21 April) & 313 (9 November) \\ \cline{2-5}  & 5 (BIFI) & 83 (24 March) & 111 (21 April) & 313 (9 November) \\ \hline \multirow{4}{*}{GCC} & 1 (CK) & 83 (24 March) & 111 (21 April) & 307 (3 November) \\ \cline{2-5}  & 3 (DIFI) & 83 (24 March) & 111 (21 April) & 315 (11 November) \\ \cline{2-5}  & 5 (BIFI) & 83 (24 March) & 111 (21 April) & 314 (10 November) \\ \hline \multirow{4}{*}{GEI} & 1 (CK) & 83 (24 March) & 111 (21 April) & 307 (3 November) \\ \cline{2-5}  & 3 (DIFI) & 83 (24 March) & 111 (21 April) & 315 (11 November) \\ \cline{2-5}  & 5 (BIFI) & 83 (24 March) & 111 (21 April) & 314 (10 November) \\ \hline \multirow{4}{*}{GRVI} & 1 (CK) & 83 (24 March) & 109 (19 April) & 307 (3 November) \\ \cline{2-5}  & 3 (DIFI) & 83 (24 March) & 111 (21 April) & 313 (9 November) \\ \cline{1-1} \cline{2-5}  & 5 (BIFI) & 83 (24 March) & 111 (21 April) & 313 (9 November) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Growth of the same vegetation index at different preset points. growth rate would be higher than that of BIFI. This indirectly implies that DIFI is more advantageous than BIFI, which is supported by the work of others [40; 41], who found that efficient irrigation was able to significantly improve stand growth. Additional studies also indicate that drip irrigation could improve water use efficiency when compared with other irrigation methods [42; 43]. Before the rainy season began, the tree species at CK (preset point 1) always had the lowest growth rate. This further shows that sufficient water has a significant impact on the growth of the trees; therefore, improved irrigation could increase the productivity of planted forests [44]. In addition, different moisture treatments could influence soil diseases and insect pests, and therefore changes in vegetation phenology [45]. [PERSON] [46] deemed that the main meteorological factor affecting the woody plant phenology in China was air temperature, and that precipitation and sunshine have relatively less impact. [PERSON] et al. believed that the temperature was the most important factor affecting phenological change, but that when water content becomes the stress factor, its influence on phenology is of great significance. Drought would delay the phenological period of plant development. When drought occurs, the plant is not able to use the light and heat, even if they meet the requirements for growth. Under such circumstances, water has become the main ecological factor affecting plant growth and development [47]. [PERSON] et al. [48] analyzed the phenology and soil temperature response in the Hengill geothermal area, Iceland, and observed that the phenotypic response of phenology toward global warming may often be the integration of a short-term plastic reaction and a long-term evolutionary response. Our research results indicate that changes in the phenological cycle could be reflected by monitoring the canopy vegetation index, and that the same vegetation index may show different performances under the three irrigation modes, because irrigation can affect the growth cycle changes in the forest. Therefore, it can be inferred from this study that sufficient water content can influence the phenological change of tree plantations. When the precipitation was greater than 60 mm, the growth rate was accelerated significantly under BIFI (preset point 5), while the growth rate may decrease in DIFI (preset point 3). In contrast, when the precipitation was lower than 60 mm, the growth rate under DIFI (preset point 3) was faster than that under BIFI (preset point 5). In the rainy season, different levels of precipitation may affect the original growth environment. For example, [PERSON] et al. [49] found that, compared with air temperature, vegetation index was more sensitive to precipitation. [PERSON] et al.