## 3 Results  
### Seasonal and Interannual Variations in Ecosystem Carbon Fluxes and Environmental Factors  
The results showed strong seasonal patterns in GPP and biophysical factors (Figure 2). Daily mean T\({}_{\text{a}}\) varied seasonally from low values of about \(-\)14.6 \({}^{\circ}\)C in winter to high values exceeding 27.2 \({}^{\circ}\)C in summer (Figure 2a). T\({}_{\text{s}}\) showed a similar pattern, but had a higher annual mean T\({}_{\text{s}}\) (11.2 \({}^{\circ}\)C) than annual mean T\({}_{\text{a}}\) (9.4 \({}^{\circ}\)C) during the study period. SWC fluctuated following large rainfall events (e.g., >20 mm day\({}^{-1}\), Figure 2b). The seasonal dynamics of GPP\({}_{\text{w}}\) and NEE\({}_{\text{w}}\) were closely related to crop development and phenology (Figures 2c and 3). The GPP\({}_{\text{w}}\) increased from 33.30 g C m\({}^{-2}\) month\({}^{-1}\) in September to an initial peak of 58.76 g C m\({}^{-2}\) month\({}^{-1}\) in November (Figure 3a), while NEE\({}_{\text{w}}\) decreased from \(-\)4.53 g C m\({}^{-2}\) month\({}^{-1}\) to \(-\)45.04 g C m\({}^{-2}\) month\({}^{-1}\) (Figure 3b). During the wintering stage, GPP\({}_{\text{w}}\) decreased to the minimum value at 13.19 g C m\({}^{-2}\) month\({}^{-1}\) in January, and increased to the maximum value at 158.62 g C m\({}^{-2}\) month\({}^{-1}\) in May; the corresponding NEE\({}_{\text{w}}\) decreased from \(-\)5.03 g C m\({}^{-2}\) month\({}^{-1}\) to \(-\)125.82 g C m\({}^{-2}\) month\({}^{-1}\). After the ripening and harvesting stage, GPP\({}_{\text{w}}\) decreased to 37.57 g C m\({}^{-2}\) month\({}^{-1}\) in July, while NEE\({}_{\text{w}}\) increased to 4.80 g C m\({}^{-2}\) month\({}^{-1}\), the ecosystem changed from carbon sink to carbon source (Figure 3). Figure 2: Temporal variations in (**a**) daily mean T\({}_{\text{a}}\) and T\({}_{\text{s}}\) at 10 cm depth, (**b**) SWC at 10 cm depths and rainfall, (**c**) daily GPP, and (**d**) daily ET of winter wheat and agroforest ecosystems. The seasonal trends of GPP\({}_{\text{a}}\) and NEE\({}_{\text{a}}\) in AFE showed significant differences compared to the WWE from March to September (Figure 3). Monthly mean GPP\({}_{\text{a}}\) showed a unimodal trend, with the minimum value of 14.42 g C m\({}^{-2}\) month\({}^{-1}\) in January and the maximum of 121.30 g C m\({}^{-2}\) month\({}^{-1}\) in July (Figure 3a). Conversely, NEE\({}_{\text{a}}\) reached its maximum in January and its minimum in July, with values of \(-\)8.56 g C m\({}^{-2}\) month\({}^{-1}\) and \(-\)92.66 g C m\({}^{-2}\) month\({}^{-1}\) (Figure 3b). The annual sums of GPP\({}_{\text{w}}\) ranged from 677.49 g C m\({}^{-2}\) a\({}^{-1}\) to 784.96 g C m\({}^{-2}\) a\({}^{-1}\), with the minimum and maximum occurred in the 2004-2005 and 2008-2009 seasons, respectively. The maximum GPP\({}_{\text{a}}\) value occurred in the 2004-2005 season, which was 798.94 g C m\({}^{-2}\) a\({}^{-1}\) (Table 1). The difference between the annual average GPP was not significant, while the NEE values showed a larger difference, with the mean annual NEE\({}_{\text{w}}\) and NEE\({}_{\text{a}}\) being \(-\)446.28 and \(-\)549.08 g C m\({}^{-2}\) a\({}^{-1}\), respectively. This indicates that both of the WWE and the AFE are strong carbon sinks during the wheat growth seasons.