## 3 Results
### Drought Impact on Phenology and Green Biomass Production  
#### 3.4.1 Changes in Forest Canopy Water Content--4 nNDII7 PC  
Diverse regional development of forest canopy water content between 2002 and 2012 was related to significant differences in forest phenology and green biomass production (Table A1, Figure 3). Stands revealing the lowest NDII7 between 2004 and 2007 (impact class 3) showed depleted CF (Figure 3a) accompanied by an overall 2003-2010 GPP decrease (Figure 3b), both being observed after a clear productivity increases in 2003. Although 2003 marked an earlier SBD (Figure 3c), the consecutive years showed progressive delay in the vegetation onset. At the same time length of the growing season demonstrated a strong inter-annual variation without a clear trend (Figure 3d). \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**4 nNDII7**} & \multicolumn{2}{c}{**3 nNDVI**} \\  & \multicolumn{2}{c}{**Drought Impact**} & \multicolumn{2}{c}{**Drought Impact**} \\ \hline
**[\%]** & **Class 1** & **Class 3** & **Class 1** & **Class 3** \\ \hline Coniferous & 91.04 & 95.38 & 76.10 & 96.85 \\ Broadleaved & 1.88 * & 0.58 * & 3.65 * & 0.33 * \\ Mixed & 7.08 * & 4.05 * & 20.25 & 2.82 * \\ \hline
0–700 m a.s.l. & 1.88 * & 3.90 * & 13.11 & 0.50 * \\
700–1400 m a.s.l. & 33.38 & 54.77 & 63.24 & 31.29 \\
1400–2100 m a.s.l. & 64.74 & 33.96 & 20.66 & 68.13 \\
2100–2500m a.s.l. & - & 7.37 & 2.99 * & 0.50 * \\ \hline N & 25.29 & 27.17 & 4.65 & 62.07 \\ E & 17.63 & 18.79 & 30.71 & 11.78 \\ S & 27.75 & 34.54 & 49.21 & 5.15 \\ W & 29.34 & 19.51 & 15.44 & 21.00 \\ \hline
0–10 deg. & 18.50 & 3.76 & 14.27 & 3.90 \\
10–20 deg. & 34.54 & 20.38 & 36.43 & 20.08 \\
20–30 deg. & 36.56 & 51.01 & 40.91 & 56.85 \\
30–40 deg & 10.26 & 23.70 & 7.97 & 18.67 \\
40–90 deg. & 0.14 * & 1.16 * & 0.41 * & 0.50 * \\ \hline \hline \end{tabular} \({}^{\star}\) Category with less than 50 observations.  
\end{table} 
Table 2: Drought footprints of the 4 nNDII7 and 3 nNDVI PCs (Figure 2a,b, respectively), inspected within four multilevel environmental factors of forest type, elevation, exposition and aspect. Class 3 denotes regions with the strongest positive, whereas class 1 the strongest negative fit to the respective PCs depicted in Figure 1g,l. A subsequent inspection of forest phenology and green biomass production in relation to site-specific environmental conditions showed considerable variation (Figure 4). Elevation had the strongest impact on all four inspected indices. Drought ingress in 2003 spurred CF rise within stands located above 1400 m a.s.l., but had almost no influence on forest growing at lower altitudes. Simultaneously, although GPP increase in 2003 was observed up to 2100 m a.s.l., GPP 2003-2007 increasing tendency was depicted exclusively at the highest elevations, and was paired with SL prolongation. Stands located below 1400 m a.s.l. demonstrated the earliest vegetation onset and a distinct 2002-2006 shift towards earlier SBD (pairwise comparison \(p<0.05\)). Aspect revealed limited impact on forest phenology and green biomass production within stands showing diminished foliage water content between 2004 and 2007 (Figure 4). North- and west-exposed woodlands demonstrated the greatest CF and GPP increase in 2003 and 2011. At the same time, the most significant CF decrease aligned with drought conditions was observed for west and south facing locations. Drought conditions enhanced aspect-specific differences in SL and SBD temporal responses. Vegetation onset occurred earlier in 2003, with the biggest change observed for west, south and east facing stands. On the contrary, 2011 marked particularly early SBD at all sites but south. Those anomalies were partly consistent with extended SL. A clear season length prolongation tendency was noted for east oriented areas only until 2007. Figure 4: Marginal means plots of repeated measures ANOVA showing CF, GPP, SBD and SL variability (in columns) in relation to elevation and aspect (in rows).