## 3 Results
### Growth Monitoring Results  
As discussed in Section 3.1, the spatial distribution information of walnut planting in the research area extracted by the method is reliable and accurate. This research carries out a statistical analysis of the annual walnut planting area in Ganquan Town from 2018 to 2021 and calculates the number of pixels corresponding to the NDVI increment from 2018 to 2021 with the use of the NDVI difference model compared to the same period in previous years (as shown in Figure 5). It can be observed from Figure 5a that, although the NDVI increment in 2018 increased at \(-0.3\) compared with the same period in 2017, the number of pixels within the NDVI increment range from 0.6 to 0.7 is significantly higher than the number of pixels within the NDVI increment range from 0 to \(-0.3\), indicating that \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Classification Feature**} & \multirow{2}{*}{**Year**} & **Extraction Area (hm2)** & **Statistical Area (hm2)** & **Absolute Error (hm2)** & **The Relative Error (\%)** \\ \hline \multirow{6}{*}{Spectrum + Terrain + Texture + NDVI} & 2017 & 7700 & 8800 & 1100 & 12.5 \\  & 2018 & 7000 & 8800 & 1800 & 20.4 \\  & 2019 & 4900 & 5333.3 & 433.3 & 8 \\  & 2020 & 5200 & 5333.3 & 133.3 & 2 \\  & 2021 & 4600 & 5333.3 & 733.3 & 13 \\ \hline \multirow{6}{*}{Spectrum + Topography + Texture + NDVI + EVI} & 2017 & 7700 & 8800 & 1100 & 12.5 \\  & 2018 & 7000 & 8800 & 1800 & 20.4 \\ \cline{1-1}  & 2019 & 5000 & 5333.3 & 333.3 & 6 \\ \cline{1-1}  & 2020 & 5400 & 5333.3 & 66.7 & 1 \\ \cline{1-1}  & 2021 & 4700 & 5333.3 & 633.3 & 11 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of the walnut planting area extracted by remote sensing and the statistical walnut planting area. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Classification Feature**} & \multirow{2}{*}{**Year**} & **Overall Accuracy (\%)** & **Kappa (\%)** & **Walnut Classification Accuracy (\%)** \\ \hline \multirow{6}{*}{Spectrum + Terrain + Texture + NDVI} & 2017 & 89.95 & 86.75 & 92.40 \\  & 2018 & 90.43 & 87.41 & 90.90 \\ \cline{1-1}  & 2019 & 93.29 & 90.70 & 89.41 \\ \cline{1-1}  & 2020 & 94.47 & 92.38 & 88.37 \\ \cline{1-1}  & 2021 & 94.47 & 92.40 & 92.77 \\ \hline \multirow{6}{*}{Spectrum + Topography + Texture + NDVI + EVI} & 2017 & 89.95 & 86.84 & 94.66 \\ \cline{1-1}  & 2018 & 91.38 & 88.65 & 92.30 \\ \cline{1-1}  & 2019 & 93.29 & 90.72 & 89.28 \\ \cline{1-1}  & 2020 & 95.02 & 93.11 & 89.53 \\ \cline{1-1}  & 2021 & 94.50 & 92.40 & 92.80 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of the extraction accuracy of the walnut planting area based on the confusion matrix in the research area. the NDVI value of most regions planted with walnut in this period is higher than that of previous years, and walnut growth is better than that of previous years. Compared with the same period in 2019, the number of NDVI increment pixels in 2020 is concentrated between 0.5 and 0.6, indicating that overall growth is good; the growth of more than 90% of walnut planting areas is the same as that of previous years. Compared with the same period in 2020, the number of NDVI increment pixels in 2021 is concentrated between 0.6 and 0.7, and the overall growth of the planting areas is better than that of 2020. Walnut growth is greatly influenced by climate change. As a result, this thesis conducts statistical calculations on meteorological weekly report data from April to September during the period from 2017 to 2021, as released by the Alar Meteorological Bureau and analyzes walnut growth in Ganquan Town. Figures 5 and 6 show that, compared to the same period in previous years, the growth of walnuts in 2020 is better than that of 2019. Figure 7 shows that the temperature in July 2020 is higher than that of 2019, and higher than the same period in previous years. In July, walnuts enter the fruit core-hardening stage, and a sufficient light duration is conducive to walnut growth, so walnut growth is better than that of 2019.