## 5 Discussion  
### Trends in Vegetation Phenology and Growing Season Integral  
The calculated trends in LOS, including SOS and EOS (Figure 2A-C), are consistent with the spatial patterns of phenological trends in [PERSON] et al. [52], who extracted vegetation phenological changes above 40\({}^{\circ}\)N of the NH during 1982-2013 from GIMMS3g NDVI data. They also employed the TIMESAT approach, but with different parameter settings as compared to this study, indicating the robustness of the method for phenology retrieval and consequently the results obtained in this study. Moreover, the calculated trends in GSI (Figure 2D) are in agreement with the result from [PERSON] et al. [53], although their study period (1982-2011) was two years shorter than this study. This study suggests that EA is dominated by significant increasing trends in LOS, whereas decreasing trends are more common in NA (Figure 2C and Table 2). These results are supported by [PERSON] et al. [54] who showed that the overall increasing trend in LOS was stronger and more significant in EA than that in NA. [PERSON] et al. [55] found that areas with greatest growing \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & **NH** & & **NA** & & **EA** & \\ \cline{3-8}  & & **n** & **\%** & **n** & **\%** & **n** & **\%** \\ \hline \multirow{4}{*}{**Trends**} & \(\mathbf{-1}\) & 343,738 & 31.14\% & 90,384 & 25.92\% & 253,354 & 33.55\% \\  & **0** & 321,249 & 29.10\% & 94,718 & 27.16\% & 226,531 & 30.00\% \\ \cline{1-1}  & **1** & 438,933 & 39.76\% & 163,639 & 46.92\% & 275,294 & 36.45\% \\ \cline{1-1}  & **Total** & 110,3920 & & 348,741 & & 755,179 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Statistics (number of pixels and percentages) of significant trends in correlations between LOS and GSI (Figure 7) at hemispheric and continental scales (\(p\) = 0.1). Figure 8: **(A)** Distribution of pixels with significant trends in correlations between LOS and GSI from 1982–1997 to 1998–2013 (17 moving windows) within each major biome (only distributions within eight major biomes are shown). **(B)** Percentages of pixels with significant trends in correlations between LOS and GSI for major biomes. season lengthening are concentrated in pockets of continental Europe, western Russia, and southern Fennoscandia, whereas regions with growing season shortening are mainly found in the Po valley, western France, and around the Caspian Sea for Europe from 1982 to 2011, which is also consistent with the result of this study (Figure 2C). However, the findings that an increasing LOS is due to both advancing SOS and delaying EOS for most areas, but decreasing LOS is caused by both delaying SOS and advancing EOS in most regions are contradictory to [PERSON] et al. (2016) who showed that EOS was positively correlated with SOS in China's temperate regions during 1999-2013 (using SPOT-VGT data). This difference may be explained by the different periods of analysis and data sources between the two studies. Moreover, the observed dominance of greering trends in EA (Figure 2D) is also supported by [PERSON] et al. (2016), who reported a significant positive trend in average growing season NDVI for temperate and boreal EA during 1982-2006. It has been shown that changes in ecosystem properties can be better characterized by separating the whole study period into individual time-periods representing specific vegetation conditions through time ([PERSON] et al., 2016; [PERSON] et al., 2016). From such approach, both increasing LOS and vegetation greenness have been shown to be slowing down or have experienced abrupt changes around 2000 in the NH using break point analysis techniques ([PERSON] et al., 2016; [PERSON] et al., 2016; [PERSON] et al., 2016; [PERSON] et al., 2016; [PERSON] et al., 2016). Nevertheless, a recent study by [PERSON] et al.