# Water-Use Characteristics and Physiological Response of Moso Bamboo to Flash Droughs
## 3 Results  
### Meteorological Variables  
Daily mean temperature ranged from 11.4 \({}^{\circ}\)C to 22.5 \({}^{\circ}\)C in 2012-2014. The flash drought occurred from 10 July to 17 August in 2013, and temperatures above 40 \({}^{\circ}\)C lasted for 12 days, mainly occurring in early August. During the days, the average temperature was 38.6 \({}^{\circ}\)C and the highest temperature reached 43.1 \({}^{\circ}\)C. The hot weather gradually receded after August 17. Mean temperatures were 30.7 \({}^{\circ}\)C and 28.7 \({}^{\circ}\)C at the same period in 2012 and 2014, respectively (Figure 2a). Daily mean RH ranged from \(\sim\)47.5-86.4% in 2012-2014. The average daily RH was 37.8% during the flash drought periods, which was lower than the RH of 76.4% and 76.3% in the same period of 2012 and 2014, respectively (Figure 2b). The daily average VPD ranged from 0.6-1.1 kPa. The maximum VPD reached 4.30 kPa in 2013, which is significantly higher than the VPD of 2.45 kPa and 2.41 kPa observed in 2012 and 2014, respectively (Figure 2c). Total Rn was 3071 MJ\(\cdot\)m\({}^{-2}\) in 2013, which was higher than the 360 MJ\(\cdot\)m\({}^{-2}\) and 537 MJ\(\cdot\)m\({}^{-2}\) observed in 2012 and 2014, respectively (Figure 2d). The wind speed was lower in the study site at an average of 0.34-0.37 m\(\cdot\)s\({}^{-1}\) (Figure 2e). Figure 2: The daily dynamics of environmental variables in the Moso bamboo forest in Anji country from 2012–2014. (**a**) Air temperature: green line represents the maximum daily temperature (Ta_max) and the orange line represents the minimum daily temperature (Ta_min); (**b**) relative humidity: green line represents the maximum relative humidity (RH_max) and the orange line represents the minimum relative humidity (RH_min); (**c**) vapor pressure deficit (VPD, kPa); (**d**) net radiation (Rn, MJ\(\cdot\)m\({}^{-2}\)-day\({}^{-1}\)); (**e**) wind speed (m\(\cdot\)s\({}^{-1}\)), (**f**) precipitation (P, mm), and soil volumetric water content (SWC, m\({}^{3}\cdot\)m\({}^{-3}\))\(>\) SWC_5 cm, SWC_50 cm, and SWC_100 cm are the volumetric water content of soil at a depth of 5 cm, 50 cm, and 100 cm. The variation in annual and monthly precipitation from 2012 to 2014 is shown in Figure 2f. Total precipitation (P) of each year was 1625 mm, 1314 mm, and 1349 mm in the study site from 2012-2014. There was an inter-annual change in precipitation, in that the annual precipitation decreased. The annual average P for 2012-2014 was 1426 mm, which was close to the long-term average value recorded at the nearest meteorological observatory (761-1780 mm). Precipitation occurred more frequently during summer than winter. There were 10 times the amount of rainfall from 10 July to 17 August, and the total precipitation was 29.3 mm during the flash drought periods in 2013, which is the lowest value recorded for 50 years. Heavy rainfall occurred on 10 August 2013 with a total precipitation of 20.7 mm. On other days, precipitation was less than 3 mm. The dynamic of soil volumetric water content (SWC, m\({}^{3}\cdot\)m\({}^{-3}\)) generally changed with precipitation and the difference in SWC was obvious at different soil depths (Figure 2f). The average SWC\(\_\)5 cm, SWC\(\_\)50 cm, and SWC\(\_\)100 cm was 0.26 m\({}^{3}\cdot\)m\({}^{-3}\), 0.33 m\({}^{3}\cdot\)m\({}^{-3}\), and 0.35 m\({}^{3}\cdot\)m\({}^{-3}\) from 2012 to 2014, respectively. The value of SWC\(\_\)5 cm decreased from 0.29 m\({}^{3}\cdot\)m\({}^{-3}\) to 0.14 m\({}^{3}\cdot\)m\({}^{-3}\), SWC\(\_\)50 cm decreased from 0.35 m\({}^{3}\cdot\)m\({}^{-3}\) to 0.17 m\({}^{3}\cdot\)m\({}^{-3}\), and SWC\(\_\)100 cm decreased from 0.37 m\({}^{3}\cdot\)m\({}^{-3}\) to 0.30 m\({}^{3}\cdot\)m\({}^{-3}\). Soil volumetric water content at 0-50 cm depth decreased by 0.15 m\({}^{3}\cdot\)m\({}^{-3}\) and 0.18 m\({}^{3}\cdot\)m\({}^{-3}\) from 1 July to 31 July 2013, respectively, which was greater than the value of 0.07 m\({}^{3}\cdot\)m\({}^{-3}\) for SWC\(\_\)100 cm (Figure 2f).