## 3 Results
### Phenological Metrics Detection  
The phenological metrics of the start of the season and the end of the season over the Punjab Province were mapped from 2000 to 2019 using the NDVI, EVI, and SAVI time-series MODIS data. Their standard deviation (SD) and mean for each type of vegetation from the three VI datasets is shown in Table 5. The normal standard deviation at the start of the season ranged from 12.3 days to 33.4 days. The default end-of-season deviation ranged from 14.4 days to 40.7 days. Except for forest, the NDVI end of season exhibited a strong deviation from EVI and SAVI. Except for savanna and shrublands, the start of the season from the NDVI, MODIS time series showed greater deviation than EVI and SAVI.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Percentage** & **NDVI** & **EVI** & **SAVI** \\ \hline
0–10\% & 7.03 & 3.82 & 6.95 \\
10–20\% & 18.53 & 30.23 & 17.85 \\
20–30\% & 13.54 & 28.23 & 15.02 \\
30–40\% & 19.29 & 23.44 & 17.65 \\ \textgreater{}40\% & 41.61 & 14.28 & 42.53 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Mean annual VI variability in percentage for 2000 to 2019.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline
**S.** & **Vegetation** & \multicolumn{2}{c}{**SOS\({}_{\text{NDVI}}\)**} & \multicolumn{2}{c}{**EOS\({}_{\text{NDVI}}\)**} & \multicolumn{2}{c}{**SOS\({}_{\text{EVI}}\)**} & \multicolumn{2}{c}{**EOS\({}_{\text{EVI}}\)**} & \multicolumn{2}{c}{**SOS\({}_{\text{SAVI}}\)**} & \multicolumn{2}{c}{**EOS\({}_{\text{SAVI}}\)**} \\ \cline{3-13}
**No** & **Classes** & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** \\ \hline
1 & Grassland & 120.3 & 33.4 & 116.9 & 28.3 & 118.4 & 29.5 & 293.8 & 28.7 & 313.4 & 27.8 & 290.2 & 40.7 \\
2 & Evergreen & 115.9 & 27.3 & 113.5 & 26.9 & 116.9 & 27.8 & 29.5 & 26.8 & 306.2 & 26.9 & 288.3 & 33.5 \\
3 & Evergreen & & & & & & & & & & & & \\
3 & Needleleaf Forests & & & & & & & & & & & & \\
4 & Shrublands & 140.3 & 26.8 & 133.8 & 22.9 & 135.8 & 23.5 & 310.3 & 27.9 & 330.5 & 27.8 & 307.5 & 34.8 \\
5 & Cropland & 138.3 & 22.3 & 133.3 & 23.6 & 132.6 & 21.5 & 308.7 & 19.3 & 314.5 & 18.2 & 302.3 & 20.3 \\
6 & Savanna & 123.3 & 33.2 & 121.5 & 18.3 & 121.5 & 17.4 & 302.3 & 15.6 & 309.5 & 15.2 & 299.5 & 39.5 \\
7 & Mixed Forests & 126.3 & 17.9 & 121.3 & 14.3 & 118.3 & 12.3 & 299.7 & 16.9 & 315.3 & 14.4 & 286.5 & 26.2 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Phenological metrics detected by VIs over the study area for 2000–2019.  
Figure 6 illustrates the two-phonology metrics for different vegetation types. Despite the peak change, the season start and season-end distributions of the histograms from the three VIs agreed. Comprehensible bimodal dispersals are seen for the grassland season start, cropland season start, and season-end cropland. The bimodal cropland starts from the season and distribution at the end of the season, suggesting diverse phenological trends for dissimilar crop types because of the bare soil's effect on the vegetation index [53]. Different density grasslands and vegetation cover may exhibit varying green-up behaviors, causing the bimodal start of season distribution. Discrepancies for grassland start of the season, evergreen leaf forest end of the season, and grassland end of the season were observed from three VIs. \(Start\ of\ season_{NDVI}\) had a high peak and a secondary peak at MOD13Q1 for grassland, whereas the \(start\ of\ season_{NDVI}\) had two parallel peaks. Similar disagreements were noted at the grassland end of the season. \(End\ of\ season_{EVI}\) had bimodal distribution for the evergreen needleaf forest as associated with the unimodal dispersal of \(End\ of\ season_{NDVI}\) and \(end\ of\ season_{EVI}\). The values spread near the histogram's tail indicate over estimations of evergreen needle leaf forest, mixed forest, savanna, grassland, and shrubland at the \(end\ of\ season_{NDVI}\).