## 3 Results  
### Seasonal Dynamics of Hydrothermal Conditions, Vegetation Indices, and Gross Primary Production  
The dynamics of the main meteorological variables are given in Figure 3. There was significant seasonal variation of daily air temperature (Ta) during 2009-2010, varying between \(-\)11.0 and 33.4 \({}^{\circ}\)C. The maximum and minimum values of Ta were found during July and January, respectively.  
But, no strong inter-annual difference among the different temperature regimes was found. The mean annual Ta were 13.9 and 13.3 \({}^{\circ}\)C in 2009 and 2010, respectively, both warmer than the long-term average (12.1 \({}^{\circ}\)C). The annual precipitation (rainfall and snowfall), measured at the tower in the experiment were 571.4 and 523.5 mm for 2009 and 2010, respectively, both higher than the long-term average (520.0 mm). In 2009, there were 68 days with precipitation. In 2010, there were 66 days with precipitation (Figure 3). The results also show that the rainy season started in early June, and it ended in late August.  
The EVI, NDVI, and LSWI curves can better demonstrate the development and the senescence of coastal wetland vegetation (Figure 4a-c). Both time series EVI and NDVI from 2009 to 2010 showed a strong seasonality for this coastal wetland ecosystem. They increased in spring and peaked in mid-August (21 August), and then declined and kept low in winter, corresponding well with the seasonal dynamics of GPP\({}_{\mathrm{EC}}\) (Figure 4). However, seasonal variation in EVI within the growing seasons differed slightly with the NDVI in terms of phase and magnitude (Figure 4a,b). The values of NDVI were obviously higher than that of EVI from late March to early November in both years. The maximum values of EVI (0.21 and 0.32) were much lower than the peaks of NDVI (0.40 and 0.61) in 2009 and 2010, respectively. The LSWI also exhibited seasonal variation, but it did not vary with time as significantly, as did NDVI or EVI, especially during plant growing season (Figure 4c). As shown in Figure 4c, the peak LSWI values were 0.27 (28 July) and 0.26 (12 August) for 2009 and 2010, respectively, advancing about 8-24 days as compared with the peak values of NDVI and EVI. High EVI and LSWI in August indicated that the canopy was rapidly developed photosynthetically active, while the quick drop of both EVI and LSWI in late September indicated an early plant senescence (Figure 4).  
The time series GPP\({}_{\mathrm{EC}}\) also shows an obviously seasonal and inter-annual variability (Figure 4d). With the raise of Ta and PAR, the photosynthetic capacity of coastal wetland ecosystem gradually increased. GPP\({}_{\mathrm{EC}}\) began to increase in mid-April (1 g C m\({}^{-2}\) day\({}^{-1}\) or higher), achieved the maximum values in early August (2009) or mid-July (2010), and it then decreased to below 1 g C m\({}^{-2}\) day\({}^{-1}\) in late October (2009) or early November (2010). The peak and annual values of GPP\({}_{\mathrm{EC}}\) in 2009 were 9.05 g C m\({}^{-2}\) and 1068.51 g C m\({}^{-2}\), respectively; whereas, the respective values of GPP\({}_{\mathrm{EC}}\) in 2010 were 9.88 g C m\({}^{-2}\) and 1102.84 g C m\({}^{-2}\), respectively (Figure 4d). The C uptake period (CUP) of wetland plant, as defined by GPP\({}_{\mathrm{EC}}\) > 1 g C m\({}^{-2}\) day\({}^{-1}\), ranges from mid-April to early November, which can be partly explained by the variation of Ta and PAR (Figures 3 and 4d). Further, the growing season  
Figure 3: Seasonal variation in daily air temperature, precipitation, and aggregated eight-day PAR from eddy covariance (EC) tower during 2009–2010.  
period for coastal wetland vegetation, as defined by Vis, agreed with the CUP defined by GPPEC over the two study years (Figure 4d).