Dew measurement and estimation of rain-fed jujube (Zizyphus jujube Mill) in a semi-arid loess hilly region of China
WANG Xing1, GAO Zhiyong2, WANG Youke1,3*, Wang Zhi4, JIN Shanshan3
1 Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling 712100, China;
2 Department of Water Conservancy, Yangling Vocational & Technological College, Yangling 712100, China;
3 College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling 712100, China;
4 Department of Earth and Environmental Sciences, California State University, California 93740, USA
Abstract Dew is an important water source for plants in arid and semi-arid regions. However, information on dew is scarce in such regions. In this study, we explored dew formation, amount, and duration of rain-fed jujube (Zizyphus jujube Mill) trees in a semi-arid loess hilly region of China (i.e., Mizhi County). The data included dew intensity and duration, relative humidity, temperature, and wind speed measured from 26 July to 23 October, 2012 and from 24 June to 17 October, 2013 using a micro-climate system (including dielectric leaf wetness sensors, VP-3 Relative Humidity/Temperature Sensor, High Resolution Rain Gauge, and Davis Cup Anemometer). The results show that atmospheric conditions of relative humidity of >78% and dew point temperature of 1°C–3°C are significantly favorable to dew formation. Compared with the rainfall, dew was characterized by high frequency, strong stability, and long duration. Furthermore, heavy dew accounted for a large proportion of the total amount. The empirical models (i.e., relative humidity model (RH model) and dew point depression model (DPD model)) for daily dew duration estimation performed well at 15-min intervals, with low errors ranging between 1.29 and 1.60 h, respectively. But it should be noted that the models should be calibrated firstly by determining the optimal thresholds of relatively humidity for RH model and dew point depression for DPD model. For rain-fed jujube trees in the semi-arid loess hilly regions of China, the optimal threshold of relative humidity was 78%, and the optimal upper and lower thresholds of dew point depression were 1°C and 5°C, respectively. The study further demonstrates that dew is an important water resource that cannot be ignored for rain-fed jujube trees and may affect water balance at regional scales.
This study was funded by the National Key Technology R&D Program (2015BAC01B03) and the Science and Technology Coordination and Innovation Project of Shaanxi Province (2014KTCG01-03).
Corresponding Authors: WANG Youke
E-mail: gjzwyk@vip.sina.com
Cite this article:
WANG Xing,GAO Zhiyong,WANG Youke et al. Dew measurement and estimation of rain-fed jujube (Zizyphus jujube Mill) in a semi-arid loess hilly region of China[J]. Journal of Arid Land, 2017, 9(4): 547-557.
2017, Vol. 9 
