# Influences of Extreme Weather Conditions on the Carbon Cycles of Bamboo and Tea Ecosystems
## 3 Results and Discussion
### Observed and Modeled Total Soil Respiration and Heterotrophic Respiration  
Figure 7 presents the measured SR data at the two plots (\(n=552\)). At the bamboo plot, the mean (SD) observed SR values at sites B1-B4 from April 2016 to October 2017 were 2.57 (1.37), 2.79 (1.40), 2.86 (1.71), and 1.79 (0.96) umol m\({}^{-2}\) s\({}^{-1}\), respectively. The modeled mean SR during 09:00-11:00 on the days when the measurements were conducted was 3.40 (0.98) umol m\({}^{-2}\) s\({}^{-1}\), which was similar to the observations at sites B2 (difference: 22%) and B3 (difference: 19%). The mean hourly modeled SR during 2016-2017 was 3.14 umol m\({}^{-2}\) s\({}^{-1}\), illustrating that the mean value during 09:00-11:00 (3.40) was similar  
Figure 6: MODIS and the modeled 8-day Gross Primary Production (GPP) at the study site. The grey rectangle shows the period when drought affects GPP. (**a**) time series of the modeled GPP and MODIS data; correlations between MODIS and the modeled GPP at bamboo (**b**) and tea (**c**) plot. to the daily value. The model also captured the seasonal dynamics of the observed SR, and the \(R^{2}\) values between the observed and modeled SR at sites B1-B4 were 0.87, 0.83, 0.49, and 0.43, respectively. At the tea plot, the mean (SD) observed SR values at sites T1-T4 from April 2016 to October 2017 were 1.39 (0.73), 1.50 (0.81), 1.34 (0.73), and 1.46 (0.72) umol m\({}^{-2}\) s\({}^{-1}\), respectively. The modeled mean SR (SD) and HR (SD) during 09:00-11:00 on the days when the measurements were conducted were 3.81 (0.96) and 1.57 (0.38) umol m\({}^{-2}\) s\({}^{-1}\), respectively. In contrast to the bamboo plot, the modeled HR (1.57) was closer to the observed HR (1.34-1.50) than to the modeled SR (3.81). This was unsurprising,  
Figure 7: Observed and modeled soil respiration (SR) at the two study plots. (**a**,**b**) show the seasonal dynamics of the observed SR at the bamboo and tea plots, respectively; (**c**–**e**) show the time series of the observed and modeled SR.  
because bamboo has a fibrous root system, and the measured SR at the bamboo plot reflected the sum of RR and HR, whereas tea has a tap root system, and the measured SR between two rows at the tea plot (Figure 2b) reflected mainly HR (Figure 7d). The \(R^{2}\) values between the observed and modeled SR (HR) at sites T1-T4 were 0.71 (0.31), 0.69 (0.35), 0.59 (0.23), and 0.58 (0.44), respectively (Figures 7d and 8b), and the correlation between the observed SR and modeled SR (Figure 7d) was markedly greater than that between the observed SR and modeled HR (Figure 8b) at all four sites, implying that RR contributed to the observed SR to some extent, although HR was the primary component of the observed SR at the tea plot. The drought in August 2016 (monthly precipitation: 16.7 mm) caused a 55% decrease in the mean observed SR at the tea plot, from 2.12 (1.58-2.70) umol m\({}^{-2}\) s\({}^{-1}\) on 12 July 2016 to 0.96 (0.17-1.32) umol m\({}^{-2}\) s\({}^{-1}\) on August 25, 2016 (Figure 7d). In contrast, the corresponding mean observed SR at the bamboo plot only decreased by 23% (Figure 7c). The larger decrease in the observed SR at the tea plot (55%) than at the bamboo plot (23%) partially reflected the larger contribution of HR to the observed SR at the tea plot, because HR is influenced by soil water content and subsequent anaerobic conditions. The simulations offered interesting results for the comparisons of SR, RR, and HR between the two plots (Figures 7e and 8c). The modeled HR was larger at the bamboo plot than at the tea plot (Figure 8c), whereas the modeled SR showed the opposite trend (Figure 7e), indicative of a smaller  
Figure 8: Observed soil respiration (SR) and modeled heterotrophic respiration (HR) at the bamboo (**a**) and tea (**b**) plots. Panel (**c**) shows the comparisons between the modeled HR at the two plots. modeled RR (SR \(-\) HR) at the bamboo plot than at the tea plot.