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Journal of Arid Land  2022, Vol. 14 Issue (1): 70-81    DOI: 10.1007/s40333-022-0003-2
Research article     
Spatial variability of leaf wetness under different soil water conditions in rainfed jujube (Ziziphus jujuba Mill.) in the loess hilly region, China
GAO Zhiyong1, WANG Xing2,*()
1State Key Laboratory of Eco-hydraulics in Northwest Arid Region of China, Xi'an University of Technology, Xi'an 710048, China
2School of Agriculture, Ningxia University, Yinchuan 750021, China
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Leaf wetness provides a wide range of benefits not only to leaves, but also to ecosystems and communities. It regulates canopy eco-hydrological processes and drives spatial differences in hydrological flux. In spite of these functions, little remains known about the spatial distribution of leaf wetness under different soil water conditions. Leaf wetness measurements at the top (180 cm), middle (135 cm), and bottom (85 cm) of the canopy positions of rainfed jujube (Ziziphus jujuba Mill.) in the Chinese loess hilly region were obtained along with meteorological and soil water conditions during the growing seasons in 2019 and 2020. Under soil water non-deficit condition, the frequency of occurrence of leaf wetness was 5.45% higher at the top than at the middle and bottom of the canopy positions. The frequency of occurrence of leaf wetness at the top, middle and bottom of the canopy positions was over 80% at 17:00-18:00 (LST). However, the occurrence of leaf wetness at the top was earlier than those at the middle and bottom of the canopy positions. Correspondingly, leaf drying at the top was also latter than those at the middle and bottom of the canopy positions. Leaf wetness duration at the middle was similar to that at the bottom of the canopy position, but about 1.46-3.01 h less than that at the top. Under soil water deficit condition, the frequency of occurrence of leaf wetness (4.92%-45.45%) followed the order of top>middle>bottom of the canopy position. As the onset of leaf wetness was delayed, the onset of wet leaf drying was advanced and the leaf wetness duration was shortened. Leaf wetness duration at the top was linearly related (R2>0.70) to those at the middle and bottom of the canopy positions under different soil water conditions. In conclusion, the hydrological processes at canopy surfaces of rainfed jujube depended on the position of leaves, thus adjusting canopy structure to redistribute hydrological process is a way to meet the water need of jujube.

Key wordscanopy position      leaf wetness      rainfed jujube      soil water condition      loess hilly region     
Received: 19 October 2021      Published: 31 January 2022
Corresponding Authors: * WANG Xing (E-mail:
Cite this article:

GAO Zhiyong, WANG Xing. Spatial variability of leaf wetness under different soil water conditions in rainfed jujube (Ziziphus jujuba Mill.) in the loess hilly region, China. Journal of Arid Land, 2022, 14(1): 70-81.

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Fig. 1 (a), Dwarf jujube trees on the 25° east-facing terraced land; (b), leaf wetness measurement sensors.
Year Growing period T2m (°C) RH2m (%) v2m (m/s) Precipitation (mm)
2019 1 May-14 Oct 20.15 62.01 1.04 436
2020 7 May-16 Otc 20.10 60.18 1.13 333
Table 1 Average values of meteorological factors during the growing seasons in 2019 and 2020
Fig. 2 Rainfall (a and b) and soil water (c and d) in the 20, 40 and 60 cm soil layers during the growing seasons of jujube in 2019 and 2020. R, rainfall; UNR, ineffective rainfall (<0.5 mm); LR, light rainfall (<10.0 mm); MR, moderate rainfall (10.0-25.0 mm); HR, heavy rainfall (25.0-50.0 mm); RS, rainstorm (50.0-100.0 mm).
Fig. 3 Dynamic changes of relative humidity (RH, a) and temperature (T, b) at different canopy positions during the growing seasons of jujube in 2019 and 2020
Fig. 4 Relative days (a and b) and frequencies (c and d) of leaf wetness at different jujube canopy positions under soil water deficit (θe<0.4) and non-deficit (θe>0.4) conditions in 2019 and 2020. θe, relative extractable water.
Fig. 5 Leaf wetness duration (LWD) at different canopy positions under soil water deficit (θe<0.4) and non-deficit (θe>0.4) conditions in 2019 (a) and 2020 (b). Different lowercase letters indicate significant differences at different canopy positions within the same soil water condition (P<0.05); different uppercase letters indicate significant differences under different soil water conditions within the same canopy position (P<0.05). Lower and upper whiskers denote the 10th and 90th percentiles, respectively; top and bottom box boundaries denote the 75th and 25th percentiles, respectively; solid dot in box denotes the mean value; solid horizontal line in box denotes the median value; θe, relative extractable water.
Fig. 6 Correlations among leaf wetness durations (LWDs) at different canopy positions under soil water non-deficit (θe>0.4; a and b) and deficit (θe<0.4; c and d) conditions in 2019 and 2020. θe, relative extractable water.
Year Position θe>0.4 θe<0.4
MD (h) MAD (h) MD (h) MAD (h)
Onset Drying Onset Drying Onset Drying Onset Drying
2019 Top/Middle 0.32 -3.03 2.65 3.03 0.59 -2.26 2.13 2.84
2020 Top/Middle 0.44 -0.19 0.68 1.56 0.29 -0.54 0.41 0.63
Average Top/Middle 0.38 -1.61 1.67 2.30 0.44 -1.40 1.27 1.74
2019 Top/Bottom 0.51 -2.69 2.40 2.69 0.68 -2.21 1.98 2.73
2020 Top/Bottom 0.46 -2.05 1.69 2.05 0.83 -0.90 1.12 0.95
Average Top/Bottom 0.49 -2.37 2.05 2.37 0.76 -1.56 1.55 1.84
Table 2 Mean difference (MD) and mean absolute difference (MAD) between the time of onset and drying of leaf wetness at different canopy positions in 2019 and 2020
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