Igating the water use characteristics of different epiphyte groups remains scarce and challenging. With the possible aggravation of drought predicted by future climate models [37], epiphytes will face additional extreme water anxiety inside the dry season resulting from their high sensitivity to water fluctuations [7,38]. Understanding how different epiphytes obtain water and retain regular life activities inside the dry season is urgently required to predict their potentially various responses to alterations in the rainfall pattern. To fill the understanding gap described above, 12 dominant species belonging to four epiphyte groups were selected from a subtropical MCF in SW China to study their water use in the peak of the dry season. The distinct objectives of this study are to quantify the water sources of differentWater 2021, 13,three ofepiphyte groups in the dry season based on steady isotope techniques (two H and 18 O), and explore the intrinsic water use efficiency (WUEi ) of a variety of epiphyte groups applying 13 C. We expected that the water use patterns of epiphytes show group-specific and interspecific differentiations, and fog water plays a important role in maintaining the water absorption of epiphytes throughout the dry season. 2. Supplies and Methods 2.1. Study Web site The study was performed in the Ailaoshan Station for Subtropical Forest Ecosystem Research (ASSFE, 23 35 4 44 N, 100 54 01 01 E), situated in the Ailao Mountain, Jingdong County, Yunnan Province, SW China [39]. Co-affected by the western monsoon from India-Pakistan and the southeast monsoon, the seasonal distribution of GYY4137 Data Sheet precipitation is uneven, with only about 16 on the precipitation occurring PK 11195 web within the dry season (November to April) (Figure 1a). The mean annual relative humidity (RH) was 84 , and also the imply air temperature was 11.six C [9]. Even so, fogs are frequent in this research region (212 days per year). The foggy days (Visibility 1000 m, Rainfall = 0 mm) in the dry season are 12 days per month on typical [40]. Meanwhile, the average annual evaporation and annual net radiation are 1126 mm and 2444 W/m2 , respectively (Figure 1b).Figure 1. Meteorological conditions on the study site. Average monthly foggy days and precipitation (during 2015019; (a)), as well as average month-to-month number of evaporation and net radiation (b) in the study internet site. The dry seasons from November to April are remarked by grey bars. Every vertical bar represents an average ( E) for that month.These meteorological data were obtained from the Ailaoshan weather station, that is located near the study web page. All information had been collected employing a suite of micro-meteorological sensors, like air temperature (HMP45, VaisalaInc., Helsinki, Finland), radiation (CNR1, Kipp and Zonen Inc., Delft, The Netherlands), and rainfall amount (52203, RM Young Inc., Traverse City, MI, USA). An evaporation pan (E-601, Weinasa Inc., Sichuan, China) with 0.62 m in diameter and 0.69 m in height was applied to monitor everyday evaporation. The water depth in E-601 was 0.six m and also the surface in the water is at ground level. FurtherWater 2021, 13,4 ofdetails about the site are supplied in Song et al. [9] and Zhang, et al. [41]. This region has abundant epiphytic communities, like more than 217 species of epiphytic lichens [42], 176 species of bryophytes [16], 93 species of ferns, and 125 species of seed plants [43,44]. two.two. Isotopic Sampling Hydrogen (two H) and oxygen (18 O) steady isotopes are widely utilized to trace the water sources of plants, which rest on th.