## 3 Results
### Phenological Characterisations  
The spatial distributions of the phenological metrics SOS, EOS, and LOS over the study area were summarised from 2010 to 2019 based on the MODIS data used (Figure 6). The pixels represent the mean SOS/EOS/LOS for all nine seasons. The SOS date ranged widely from DOY 150 (end of May) to DOY 270 (end of September). The EOS date ranged from DOY 120 (end of April) to DOY 240 (end of August). The LOS value over the region ranged from 270 days to 365 days. Compared to LOS, SOS, and EOS dates had a more considerable variation. In general, there were quite similar spatial patterns between SOS and EOS throughout the study area. Earlier SOS date pixels have earlier EOS and vice versa for later dates pixels. This indicates that certain parts of the study area start to refoliate and defoliate earlier than others, a finding consistent with multiclonal planting. The inter-annual variations of SOS and EOS for the study area during 2010 to 2019 are presented in Figure 7. In this figure, there were nine boxplots plotted for each phenological metric, indicating growing seasons from 2010/11 to 2018/19. There is no boxplot for growing season 2019/20 as the full cycle of this growing season was not complete. From the boxplots results, the overall mean of SOS and EOS was observed at DOY 230 and 185. Meanwhile the overall mean of LOS was found to be 318 days. Large differences in SOS (Figure 7a) and EOS (Figure 7b) boxplots are seen between years which may be expected to be driven by environmental factors. However, the LOS boxplot (Figure 7c) has all median lines overlapping with relatively small differences, indicating that LOS does not vary significantly between years and almost all parts of the study area experience a similar number of days per season. We calculated the overall mean, standard deviation, variance, and dispersion index for the SOS/EOS/LOS data of each growing season (Table 1). The low standard deviation and variance values indicate minimal fluctuation in the LOS data. Unlike SOS and EOS, the LOS dispersion index was almost 0, making it a constant random variable. Due to this, further analyses were only conducted with the phenological metrics of SOS and EOS. On the other hand, SOS and EOS datasets have high standard deviation and variance values. However, both are still under-dispersed with dispersion index values less than 1. Validation of MODIS Phenological Data  
The SOS and EOS determined using remote sensing were aligned with observed conditions on the ground. Rubber experts from the study area verified that the SOS and EOS dates detected from each season were within the expected range. In order to verify \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Phenological** & **Inter-Annual** & **Overall** & **Standard** & **Variance** & **Dispersion** \\
**Metrics** & **Mean Range** & **Mean** & **Deviation** & **Index** \\ \hline SOS & 201–245 & 230 & 13.1 & 174.6 & 0.76 \\ EOS & 169–201 & 183 & 12.9 & 164.9 & 0.90 \\ LOS & 311–328 & 318 & 4.9 & 23.2 & 0.07 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The inter-annual mean range, overall mean, standard deviation, variance, and dispersion index of the three phenological metrics. Figure 7: Inter-annual variations of: (**a**) SOS; (**b**) EOS; and (**c**) LOS for the corresponding years as observed with MODIS 8-day NDVI. The red dashed lines indicate the mean of SOS (DOY 230), EOS (DOY 183), and LOS (318 days). Each central rectangle spans from the first quartile to the third quartile. The whiskers above and below the box show the maximum and minimum values. The thick black lines inside the rectangle represent the median, and the dots are the outliers. the accuracy of the SOS, EOS, and LOS data extracted from MODIS NDVI data, the same methodology was applied to Sentinel-2 NDVI data from 2017 to 2019. The SOS, EOS, and LOS average value of seasons 2017/18 and 2018/19, from both datasets, were then compared.