## 3 Results
### Interaction between Environmental Drivers and Vegetation Variables  
To investigate the dominant factors controlling the seasonal and inter-annual variations in vegetation, the biome-specific relationships of the time series of principle environmental drivers and vegetation variables (SIF, SIF\({}_{\text{PAR}}\), SIF\({}_{\text{yield}}\), and EVI) during 2014-2019 are shown in Figure 8. Apart from forests and woodlands, root zone soil moisture was most relevant for EVI (\(r^{2}\): 0.42-0.79) relative to other drivers; among those, temperature-related drivers were poorly correlated (\(r^{2}\) \(<\) 0.16) (Figure 8a2-a4). By contrast, both moisture-related drivers, as well as land surface temperature highly corresponded with EVI over northern humid forests and woodlands (Figure 8a1). There were strong correlations (\(r^{2}\) \(>\) 0.8) between SIF and EVI over forests and woodlands and Tussock grasslands as compared with moderate correlations (\(r^{2}\): 0.21, 0.38) over water-limited ecosystems (Figure 8b1-b4). Similarly, compared with temperature-related drivers (\(r^{2}\): 0-0.3), water-related factors (especially soil moisture) were more associated with SIF among all biomes. After removing the impact of solar radiation, there was an enhanced agreement between EVI and PARnormalized SIF (SIF\({}_{\text{PAR}}\)) over Tussock grassland, shrublands, and Hummock grasslands (\(r^{2}\): 0.51-0.86) (Figure 8c2-c4). Likewise, the correlation between root zone soil moisture and SIF\({}_{\text{PAR}}\) was strengthened relative to those with SIF regardless of different vegetation types. Precipitation and surface soil moisture agreed well with the effective fluorescence yield (SIF\({}_{\text{yield}}\)) over forests and woodlands, as well as Tussock grasslands (\(r^{2}\): 0.38-0.62) (Figure 8d1-d2). In addition, there was a moderately increased correlation between air temperature and SIF\({}_{\text{yield}}\) (\(r^{2}\): 0.22-0.4) in comparison to those with SIF or SIF\({}_{\text{PAR}}\) (\(r^{2}\): 0-0.2).  
Figure 5: Spatial patterns of vegetation phenology based on EVI over the NATT study area across three representative hydrological years, (**a**,**d**,**g**) 2014–2015 (normal year), (**b**,**e**,**h**) 2016–2017 (wet year), and (**c**,**f**,**i**) 2018–2019 (dry year). The filled pixels (grey shaded areas) are either water body or without detectable phenology. SOS: the start of growing season; POS: the peak of growing season; EOS: the end of growing season. Blank circles represent 5 selected eddy covariance flux tower sites.  
Figure 6: Spatial patterns of vegetation phenology based on (**a-h**) GOME-2 SIF and (**i–k**) TROPOMI SIF over the NATT study area across three representative hydrological years, 2014–2015 (normal year), 2016–2017 (wet year), and 2018–2019 (dry year). The filled pixels (grey shaded areas) are either water body or without detectable phenology. SOS: the start of growing season; POS: the peak of growing season; EOS: the end of growing season. Blank circles represent 5 selected eddy covariance flux tower sites.  
Figure 7: Scatter plot between spring green-up rates (RSP) and autumn senescence rates (RAU) of (**a-d**) EVI and (**e-h**) SIF among four major biomes across the entire study region. Red dashed lines refer to a –1:1 diagonal.