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Non-rainfall water contributions to dryland jujube plantation evapotranspiration in the Hilly Loess Region of China
Journal of Hydrology ( IF 6.4 ) Pub Date : 2020-04-01 , DOI: 10.1016/j.jhydrol.2020.124604 Zhiyong Gao , Wenjuan Shi , Xing Wang , Youke Wang
Journal of Hydrology ( IF 6.4 ) Pub Date : 2020-04-01 , DOI: 10.1016/j.jhydrol.2020.124604 Zhiyong Gao , Wenjuan Shi , Xing Wang , Youke Wang
Non-rainfall water inputs (NRWIs) provide crucial water resources for dryland ecosystems in arid and semi-arid regions. However, little is known about the quantitative characteristics and formation of NRWIs, and the relative importance of NRWIs as water sources in a dryland jujube (Ziziphus jujuba Mill.) plantation in the Hilly Loess Region of China. The objectives of this study were to determine the characteristics of NRWIs during the jujube growing season with regard to amount, duration, and contributions to transpiration, evaporation, and evapotranspiration. Dew intensity and duration were monitored using dielectric leaf wetness sensors, Also sap flow, soil water content, soil temperature, and meteorological variables were measured during the 2017 and 2018 growing seasons. NRWIs were found to be composed of canopy dew (CD) and water vapor adsorption (WVAS) in the 0–5 cm soil layer, amounting to 75.218 mm in 2017 and 75.309 mm in 2018 (CD accounted for about 81% of NRWI). Daily average CD was significantly greater than WVAS (P < 0.05), and CD duration was 2.09–9.14 h more than WVAS duration (P < 0.05). The CD rate and frequency generally exceeded that of WVAS. CD occurred from 19:00 to 9:00. WVAS mainly occurred from 6:30 to 9:00. CD reduced nocturnal sap flow by 7.36–55.64%, but increased soil water storage (in the 5–100 cm root zone) by 0.274–0.717 mm. WVAS had no effect on soil water evaporation. Over the entire growing season, the ratio of CD to total transpiration was 0.218 in 2017 and 0.258 in 2018, and the ratio of WVAS to soil water evaporation was 0.082 in both years. NRWIs occurred more frequently and were quantitatively more stable than rainfall events. Their contributions to evapotranspiration reached a maximum value of 0.184 in 2018. NRWIs are important components of the hydrological cycle in this region, and probably have potential positive ecological effects on dryland jujube plantations in the Hilly Loess Region of China.
更新日期：2020-04-01
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