Dew variability in three habitats of a sand dune transect in a desert oasis ecotone, Northwestern China

Abstract

Abstract:Dew, as a supplementary water source, may have an important ecological role in arid and semi-arid regions. During August and September of 2007 and 2008, measurements were taken to investigate the dew accumulation and evaporation patterns in the very early morning hours, in three different habitats (dunetop, footslope, and interdune lowland) of a fixed sand dune in Northwest China. Dew quantities were measured using the cloth-plate method. The results indicated that there was a positive correlation between dew amounts and relative humidity, but a negative correlation between dew amounts and mean temperature. Clear mornings were characterized by higher dew amounts and longer dew duration, whereas less dew was recorded during cloudy and especially windy mornings. Dew continued to condense even after sunrise, although a shorter warming time after dawn is also of vital importance in dew formation. The higher average maximum dew quantities (0.06 mm) and longer average dew duration (2.3 h) occurred in the interdune lowland; the lower and shorter average dew amounts (0.048 mm) and duration (1.9 h) were obtained at the dune top. The footslope habitat exhibited intermediate values. Clearly, the differences in dew deposition can be partially attributed to the distinguishing characteristics of the microhabitats. The present study highlighted the impacts of these characteristics on near-ground dew condensation accumulation and evaporation in a fixed sand dune and may facilitate evaluation of the role of dew in arid and semi-arid environments.

Measurements and ecological implications of non‐rainfall water in desert ecosystems—A review

“…By increasing nocturnal temperatures (Janssen & Römer, 1991;Lloyd, 1961;Price, Michaelides, Pashiardis, & Alpert, 1999;Scherm & van Bruggen, 1993), RH is decreased (Barradas & Glez-Medellín, 1999), resulting in the impediment of vapour condensation (Brunnenberg & Kühn, 1977;Hicks, 1983;Lloyd, 1961;Zangvil, 1996;Zangvil & Druian, 1980). Similarly to the Negev, maximum NRW was the highest during clear days, followed by cloudy and then by windy days (Pan et al, 2010;Zhang et al, 2015;Zhuang & Zhao, 2014). Similarly to the Negev, maximum NRW was the highest during clear days, followed by cloudy and then by windy days (Pan et al, 2010;Zhang et al, 2015;Zhuang & Zhao, 2014).…”

“…However, due to turbulence, high wind speed above 4.7 m s −1 will also impede dew formation (Monteith, 1957). Thus, reported wind speed limits for dew formation are 4.0 m s −1 (Clus et al, 2008;Nilsson, 1996), 4.3 m s −1 (Zhuang & Zhao, 2014), 4.5 m s −1 , 4.7 m s −1 ), or 5.7 m s −1 (Hanisch et al, 2015;Lekouch et al, 2012 at 10-m height), with winds of 1-3 m s −1 usually providing the best conditions for dew formation. Although some reported lower thresholds for the high wind speed (1.9 m s −1 see Zhang et al, 2015, or 2.4 m s −1 see Long, 1958), most researchers found a similar threshold of 5 m s −1 .…”

Dew formation characteristics at annual and daily scale in xerophyte shrub plantations at Southeast margin of Tengger desert, Northern China

“…The slow increase in ground temperature and reduction in relative humidity after sunrise under the plant canopies greatly extended the time dew remained after sunrise, allowing extended access to moisture for herbaceous plants, cryptogams, and microorganisms under plant canopies. Previous researchers have shown post‐sunrise dew formation to make important contributions towards total dew formation (Zhuang & Zhao, ).…”

Mechanism of biocrusts boosting and utilizing non-rainfall water in Hobq Desert of China

“…Vapor pressure and atmospheric pressure can also affect NRW by driving capillary effect (Agama and Berliner, 2006;Lan et al, 2010). Meanwhile, the presence of biocrusts significantly promotes the accumulation of NRW (Liu et al, 2006;Zhang et al, 2009;Lan et al, 2010;Pan et al, 2010;Uclés et al, 2015), which is attributed to roughness, or soil texture (Zhang et al, 2009;Pan et al, 2010;Zhuang and Zhao, 2014), exopolysaccharides and salinity (Kosmas et al, 2001;Kidron et al, 2002;Heusinkveld et al, 2006;Chen et al, 2014;Colica et al, 2014;Wang et al, 2014). However, NRW derives from both atmosphere and soil (Agam and Berliner, 2006;Lan et al, 2010), and the latter contains moisture stems from vapor and capillarity.…”