## 4 Results
### Trends in VI SOS Estimates
#### 4.3.1 Ppi
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**IGBP Land Cover Classes** & **PPI** & **EVI** & **NDVI** \\ \hline Average for all land cover classes & \(-0.28\pm 0.53\) & \(-0.23\pm 0.72\) & \(-0.26\pm 0.65\) \\ Evergreen Needleleaf forest & \(-0.25\pm 0.58\) & \(-0.06\pm 0.92\) & \(0.04\pm 0.81\) \\ Deciduous Needleleaf forest & \(-0.47\pm 0.37\) & \(-0.62\pm 0.36\) & \(-0.74\pm 0.36\) \\ Deciduous Broadleaf forest & \(-0.54\pm 0.31\) & \(-0.34\pm 0.22\) & \(-0.18\pm 0.25\) \\ Mixed forest & \(-0.06\pm 0.45\) & \(0.02\pm 0.78\) & \(-0.18\pm 0.67\) \\ Open shrulands & \(-0.37\pm 0.51\) & \(-0.39\pm 0.57\) & \(-0.44\pm 0.50\) \\ Woody Savannas & \(-0.37\pm 0.55\) & \(-0.22\pm 0.71\) & \(-0.20\pm 0.57\) \\ Savannas & \(-0.56\pm 0.54\) & \(-0.37\pm 0.63\) & \(-0.41\pm 0.67\) \\ Grasslands & \(-0.12\pm 0.70\) & \(-0.12\pm 0.79\) & \(0.03\pm 0.84\) \\ Wetlands & \(-0.17\pm 0.51\) & \(-0.27\pm 0.70\) & \(-0.20\pm 0.61\) \\ Croplands & \(0.16\pm 0.63\) & \(0.24\pm 0.46\) & \(0.32\pm 0.46\) \\ Cropland/Natural vegetation & \(0.05\pm 0.49\) & \(0.14\pm 0.39\) & \(0.16\pm 0.50\) \\ Boreal regions & & & \\ East Siberian Taiga & \(-0.35\pm 0.52\) & \(-0.43\pm 0.55\) & \(-0.56\pm 0.55\) \\ Iceland Boreal Birch Forests And Alpine Tundra & \(-0.23\pm 0.66\) & \(0.34\pm 0.97\) & \(0.50\pm 1.00\) \\ Kamchatka-Kurile Meadows And Sparse Forests & \(-0.27\pm 0.31\) & \(-0.46\pm 0.38\) & \(-0.47\pm 0.44\) \\ Kamchatka-Kurile Taiga & \(-0.33\pm 0.28\) & \(-0.32\pm 0.30\) & \(-0.30\pm 0.35\) \\ Northeast Siberian Taiga & \(-0.35\pm 0.42\) & \(-0.36\pm 0.49\) & \(-0.42\pm 0.41\) \\ Okhotsk-Manchurian Taiga & \(-0.11\pm 0.41\) & \(-0.14\pm 0.46\) & \(-0.15\pm 0.53\) \\ Sakhalin Island Taiga & \(-0.12\pm 0.32\) & \(-0.16\pm 0.47\) & \(-0.10\pm 0.41\) \\ Scandinavian and Russian Taiga (Russian part) & \(-0.30\pm 0.39\) & \(-0.04\pm 0.92\) & \(-0.10\pm 0.55\) \\ Trans-Baikal Conifer Forests & \(0.36\pm 0.43\) & \(0.18\pm 0.42\) & \(0.11\pm 0.70\) \\ Ural Montane Forests And Tundra & \(-0.22\pm 0.35\) & \(-0.11\pm 0.67\) & \(-0.25\pm 0.52\) \\ West Siberian Taiga & \(0.13\pm 0.48\) & \(0.03\pm 0.80\) & \(-0.15\pm 0.67\) \\ Alaska Range & \(-0.32\pm 0.55\) & \(-0.24\pm 0.72\) & \(-0.13\pm 0.68\) \\ Boreal Cordillera & \(-0.21\pm 0.54\) & \(-0.17\pm 0.83\) & \(-0.10\pm 0.67\) \\ Boreal Plains & \(-0.03\pm 0.50\) & \(0.02\pm 0.58\) & \(0.16\pm 0.73\) \\ Boreal Shield & \(-0.26\pm 0.63\) & \(0.02\pm 0.80\) & \(0.04\pm 0.87\) \\ Cook Inlet Basin & \(-0.09\pm 0.35\) & \(-0.03\pm 0.48\) & \(0.01\pm 0.51\) \\ Eastern Taiga Shield & \(-0.45\pm 0.53\) & \(-0.40\pm 0.49\) & \(-0.32\pm 0.52\) \\ Hudson Plains & \(-0.26\pm 0.50\) & \(0.06\pm 0.49\) & \(0.21\pm 0.47\) \\ Interior Alaska Taiga & \(-0.29\pm 0.51\) & \(-0.26\pm 0.70\) & \(-0.33\pm 0.61\) \\ Taiga Plains & \(-0.41\pm 0.43\) & \(-0.22\pm 0.70\) & \(-0.25\pm 0.68\) \\ Western Taiga Shield & \(-0.50\pm 0.47\) & \(-0.44\pm 0.77\) & \(-0.42\pm 0.60\) \\ Yukon Plateau And Flats & \(-0.32\pm 0.62\) & \(-0.33\pm 0.75\) & \(-0.43\pm 0.64\) \\ Scandinavian and Russian Taiga (Scandinavian part) & \(-0.53\pm 0.49\) & \(-0.25\pm 0.89\) & \(-0.27\pm 0.53\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Average \(\pm\) one standard deviation trends in vegetation index (VI) start of season (SOS) dates (days/year) for different land cover types and boreal regions (Figure 1A,B). Figure 4: Per pixel trend of VI SOS (2000–2014). **(A)** PPI SOS significant pixels; **(B)** PPI SOS all pixels; **(C)** EVI SOS significant pixels; **(D)** EVI SOS all pixels; **(E)** NDVI SOS significant pixels; **(F)** NDVI SOS all pixels.