Dew/hoar frost on the canopies and underlying surfaces of two typical desert shrubs in Northwest China and their relevance to drought.

[Display omitted] • Dew/hoar frost can be distinguished by leaf wetness sensor and air temperature. • The differences in dew duration on and below canopy depended on plant species. • Sky view factor and shading effects were main factors leading to the differences. • Dew can be an important water supply during sharp declines of soil water. Dew and hoar frost are important sources of water available in dryland ecosystems in arid and semi-arid areas, however, little is known about the quantitative characteristics of dew/hoar frost on the canopies and underlying surfaces of typical shrubs in Northwest China. Few studies have examined the ecological relevance of dew/hoar frost to drought. We conducted an observational experiment regarding the frequency, duration, and amount of dew/hoar frost on both canopies and underlying surfaces of the Artemisia ordosica (AO) and Salix psammophila (SP)—two common species in northern China—using leaf wetness sensor (LWS) in a desert shrubland in Northwest China from May to December 2015. Potential dew/hoar frost was estimated using the Penman–Monteith (P–M) equation, while measuring meteorological parameters. Results showed that dew/hoar frost exhibited a significant diurnal variation that occurred mainly between 20:00 and 09:00 the following day, while peaking at about 04:00–06:00 (i.e., before dawn). The monthly mean duration of dew/hoar frost was longer in November and December, and shorter in May and June. Eighty percent of daily dew values were within 0–0.4 mm d−1. For SP, the durations of dew and hoar frost were both longer on the canopy than on the underlying surface. For AO, however, the duration of dew was longer and that of hoar frost was shorter on the canopy than on the underlying surface. The P–M equation may underestimate dew/hoar frost during cold times with higher wind speed. Dew may be an important water supply, especially during two periods of sharp declines of soil water during the long (the period > one month) and short term (the period < one month) droughts (equal to 63.77 and 96.18% of rainfall, respectively). Our findings suggest that AO is more conducive to the formation of dew/hoar frost than SP, and dew/hoar frost can serve as a sustainable significant water resource during periods of drought, especially in desert areas. [ABSTRACT FROM AUTHOR]