# Water-Use Characteristics and Physiological Response of Moso Bamboo to Flash Droughs
## 1 Introduction  
In recent years, changes in global climate have increased the frequency of extreme weather events, including frequent summers with rapidly increasing temperatures and decreasing precipitation, which seriously threaten the health and stability of ecosystems [1]. This coupling of high temperatures and low precipitation can lead to flash droughs, which involve abnormally high evapotranspiration (ET) and low soil water moisture [2; 3; 4]. This process significantly reduces the net primary productivity in terrestrial ecosystems [5; 6], affects plant functions, and alters forest water yields and hydrological budgets [7; 8; 9]. However, the frequency of flash-drought events will increase over the next few decades in both tropical and subtropical regions [2; 10]. This will aggravate already limited water resources in terrestrial ecosystems [11], and may alter the distribution of plants [12]. Evapotranspiration is animportant pathway in atmospheric water recycling. It controls water loss from the land surface [13] and is an important component in estimating potential productivity of forest ecosystem and budget of water resources [14]. Evapotranspiration also plays an important role in the process of water-carbon recycling and energy exchange in terrestrial ecosystems [15]. Therefore, a detailed understanding of the water consumption and physiological adjustment mechanism underlying forest response to flash drought is essential to accurately assess the role of forest ecosystems in the water cycle under the rapidly changing global climate.  
Moso bamboo (_Phyllostachys edulis_) is widely distributed in the tropical and subtropical regions of East and Southeast Asia [16]. It is widely planted in China, covering an area of about 4.43 Mha, which comprises 70% of the total bamboo forest area in China and 80% of the Moso bamboo forest area globally [6]. Moso bamboo is highly valued both ecologically and economically. The annual C uptake rate of a Moso bamboo stand was reported as 5.1 t-ha\({}^{-1}\)[17]. Therefore, Moso bamboo is of great significance for C absorption and mitigation of climate change [18]. Furthermore, bamboo shoots are delicious and are widely cultivated in southern China [16]. The area of bamboo forests has increased rapidly and the total area in Zhejiang Province is 60,000 ha, which is the site of the present study [19]. As the fastest growing plant in the world [20], bamboo uses a large amount of water [18]. Therefore, Moso bamboo will be extremely sensitive and respond rapidly to flash droughts. Flash-drought events occur 16-24 times every 10 years in southern China. During the summer of 2013, a flash-drought event affected 13 provinces in southern China, including Zhejiang province [21]. In recent years, study of flash-drought events has become the focus of research globally [1; 2]. However, most previous studies on Moso bamboo focused on the C cycle [6; 22], soil respiration, and C storage [23] under drought conditions of Moso bamboo. However, few studies have reported on the water-use characteristics and physiological adjustment mechanisms of Moso bamboo under flash drought conditions [24]. In the present study, we investigated the water-use characteristics and physiological adjustment mechanism of Moso bamboo response to flash droughts. Our findings provide a reference for developing bamboo forest management strategies, planning regional hydrological budgets, and modelling ET in regions affected by flash droughts.