Are coastal deserts necessarily dew deserts? An example from the Tabernas Desert

Kidron, Giora J.; Lázaro, Roberto

doi:10.2478/johh-2020-0002

Cited by 13 publications

(7 citation statements)

References 59 publications

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“…Only once RH >95% was recorded (95.5% during July 11 th , 2007). Similar findings were also found for the rainless months of June, July, August, and September of 2003-2012 in the Tabernas, during which RH >95% occurred on average for only 0.9-1.1 days a month (Kidron and Lázaro, 2020). These values imply that dew formation is relatively infrequent.…”

Section: Resultssupporting

confidence: 83%

“…Dew formation was frequently reported as taking place in the Tabernas and its vicinity (Moro et al, 2007;Uclés et al, 2013Uclés et al, , 2016. Although, as recently substantiated, the occurrence of dew in the Tabernas is actually infrequent as compared to the Negev Desert and therefore the Tabernas cannot be considered a dew desert (Kidron and Lázaro, 2020), many reports concluded that dew formation may play an important role as a water provider for this ecosystem. It was therefore assumed that dew will facilitate the survival and growth of many organisms, such as crustose soil lichens (Moro et al, 2007;Pintado et al, 2010), and will facilitate organism survival also during the harsh dry season (Uclés et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Atmospheric humidity is unlikely to serve as an important water source for crustose soil lichens in the Tabernas Desert

Kidron

Kronenfeld

2020

Journal of Hydrology and Hydromechanics

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Dew is commonly regarded as an important water source for lichens. This is also the case for crustose lichens that are attached to the substrate, whether rocks or soil. While being verified during ample research on rock-dwelling lichens in the Negev, the findings from soil-dwelling lichens (lichen biocrusts) are not conclusive. In the Tabernas Desert, the soil surface is characterized by a lush cover of crustose lichens. These soil biocrusts (biological soil crusts) were reported to use dew for photosynthesis while, at the same time, it was also observed that these crustose chlorolichens are relatively non-wettable. In an attempt to explore the apparent controversy, two year-long meteorological data (minimum air temperature and relative humidity, RH), during which chlorolichens were thought to utilize dew for photosynthesis (2006–2007) were analyzed. The analysis includes a comparison to the meteorological conditions that prevailed in the Negev during 135 days of manual dew measurements. As found for the Negev, net photosynthesis by the chlorolichens is expected once the RH, as measured at the meteorological station, is ≥90% while vapor condensation (dew) is expected once RH is ≥95%. RH in the Negev was substantially higher than the average RH of 75.0–87.2% registered during the rainless days of 2006–2007 in the Tabernas, implying that RH in the Tabernas is too low to facilitate frequent dew formation and net photosynthesis by the lichens. Photosynthesis in the Tabernas is mainly confined to rainy periods, taking place either due to direct wetting by rain, or following vapor condensation from the subsurface (distillation). Our findings do not support the view that dew is an important water source for the establishment and growth of crustose soil lichens in the Tabernas. Moreover, the low RH in the Tabernas may also imply that dew may only have a very limited role in providing water to lithobionts in this ecosystem.

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Section: Resultssupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Atmospheric humidity is unlikely to serve as an important water source for crustose soil lichens in the Tabernas Desert

Kidron

Kronenfeld

2020

Journal of Hydrology and Hydromechanics

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“…However, the fact that atmospheric vapor during the winter is lower than during the summer (Evenari et al, 1971) point to the central role played by the TIVF. Also, the relatively low amounts of NRW of ≤0.04 mm (Kidron & Kronenfeld, 2020a, 2020bKidron & Lázaro, 2020) that reach the soil surface from the atmosphere even during heavy dewy days in comparison to the high amounts (up to 0.20-0.30 mm) recorded during the winter, further support the conclusion regarding the central role played by distillation and that TIVF may serve as a principal causative factor for the WDCs. This is supported by the limiting wetting capability of the dewfall reported also from other ecosystems (Fischer et al, 2012;Lázaro et al, 2008).…”

Section: Resultssupporting

confidence: 55%

“…Also, in most cases, capillarity was not excluded. With the Negev regarded as dew desert (Kidron & Lázaro, 2020), pinpointing at the specific causative factor may be more complicated. However, we can rely on numerous dew data that were thoroughly analyzed in the Negev (see review by Kidron & Starinsky, 2019).…”

Section: Introductionmentioning

confidence: 99%

Wet–dry cycles on sandy and loessial Negev soils: Implications for biocrust establishment and growth?

et al. 2021

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Long-term field campaigns in the Negev observed wet-dry cycles (WDCs) following rain events, principally on sand. Aiming to assess the relevant mechanism (whether dewfall, water capillarity or distillation derived by temperature-induced vapor flux[TIVF] which stems from the soil), a set of outdoor experiments was conducted on sand and loess. They included nonrainfall water (NRW) and temperature measurements during the rainless dry seasons (summer, fall) and during the winter, which was divided to a wet (following rain) and dry periods. Dew measurements were conducted on cloths, whether directly attached to the soil or located at 0.5 cm above ground, aiming to eliminate capillarity and assessing the possible contribution of dewfall and TIVF-induced distillation. Our findings show that (a) WDCs were only observed following rainstorms, particularly on sand, (b) WDCs could not have been explained by capillarity (they continued at the presence of an air gap), (c) significantly lower minimum surface temperatures (averaging 0.8 C) characterized the sand, which following rainstorms resulted in higher NRW due to TIVF, that is, visibly noted WDCs. With sand being characterized by a lush cover of biocrusts in the Negev dunefields, while being largely absent from the loessial playas scattered within the dunefield, it is suggested that WDCs may play an important role in the establishment and growth of biocrusts over sand dunes of the Negev and possibly in other arid dunes.

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“…In a similar semi-arid steppe ecosystem in Spain, the mean number of days per year with suitable conditions for dew formation was 285 d (Uclés et al, 2014). However, this finding is based on measurements with micro-lysimeters consisting of PVC sampling cups with < 0.1 m length, for which it has been shown that they tend to overestimate dew when compared with alternative sampling approaches (Kidron and Lázaro, 2020;Kidron and Kronenfeld, 2020a, b). Our observation that especially nights are prone to the formation of NRW is also documented in the literature.…”

Section: Non-rainfall Water Frequency Duration and Amountsmentioning

confidence: 99%

Resolving seasonal and diel dynamics of non-rainfall water inputs in a Mediterranean ecosystem using lysimeters

Paulus

El-Madany²,

Orth³

et al. 2022

Hydrol. Earth Syst. Sci.

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Abstract. The input of liquid water to terrestrial ecosystems is composed of rain and non-rainfall water (NRW). The latter comprises dew, fog, and the adsorption of atmospheric vapor on soil particle surfaces. Although NRW inputs can be relevant to support ecosystem functioning in seasonally dry ecosystems, they are understudied, being relatively small, and therefore hard to measure. In this study, we apply a partitioning routine focusing on NRW inputs over 1 year of data from large, high-precision weighing lysimeters at a semi-arid Mediterranean site. NRW inputs occur for at least 3 h on 297 d (81 % of the year), with a mean diel duration of 6 h. They reflect a pronounced seasonality as modulated by environmental conditions (i.e., temperature and net radiation). During the wet season, both dew and fog dominate NRW, while during the dry season it is mostly the soil adsorption of atmospheric water vapor. Although NRW contributes only 7.4 % to the annual water input, NRW is the only water input to the ecosystem during 15 weeks, mainly in the dry season. Benefitting from the comprehensive set of measurements at our experimental site, we show that our findings are in line with (i) independent measurements and (ii) independent model simulations forced with (near-) surface energy and moisture measurements. Furthermore, we discuss the simultaneous occurrence of soil vapor adsorption and negative eddy-covariance-derived latent heat fluxes. This study shows that NRW inputs can be reliably detected through high-resolution weighing lysimeters and a few additional measurements. Their main occurrence during nighttime underlines the necessity to consider ecosystem water fluxes at a high temporal resolution and with 24 h coverage.

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Are coastal deserts necessarily dew deserts? An example from the Tabernas Desert

Cited by 13 publications

References 59 publications

Atmospheric humidity is unlikely to serve as an important water source for crustose soil lichens in the Tabernas Desert

Atmospheric humidity is unlikely to serve as an important water source for crustose soil lichens in the Tabernas Desert

Wet–dry cycles on sandy and loessial Negev soils: Implications for biocrust establishment and growth?

Resolving seasonal and diel dynamics of non-rainfall water inputs in a Mediterranean ecosystem using lysimeters

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