One‐year‐long evaluation of non‐rainfall water available to soil biocrusts in the Negev Highlands

Kidron, Giora J.; Kronenfeld, Rafael

doi:10.1002/eco.2529

Cited by 11 publications

(12 citation statements)

References 62 publications

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“…During the current research some published reports were examined: (a) reports stating that maximum NRW may be higher (sometimes substantially higher) than the theoretical threshold that practically can be reached of 0.45 mm, and (b) that the amounts obtained at the soil surface are sufficiently high to activate soil biocrusts. Even when considering mornings with the highest NRW, our 2 year‐long analysis show that (a) while occasionally surpassed by fog, the 0.45 mm of the theoretical maximum value of dew was never surpassed not even at 1 m height above ground, (b) dew formation within a given night is largely dependent on the substrate temperatures and (c) while cobbles may be regarded as most conducive for vapour condensation, and vapour condensation may occasionally also take place on the rock slabs, vapour condensation is rare at the soil surface, (d) subsequently, and in agreement with our previous analysis (Kidron, 2024; Kidron, Kronenfeld, Starinsky, et al, 2023), NRW may not be sufficiently high to benefit the growth of arid soil biocrusts and they may therefore solely rely on rainwater for growth.…”

Section: Discussionsupporting

confidence: 90%

“…In this regard one should note that since biocrust moistening by NRW begins during the night, the organism experiences some carbon loss due to dark respiration (Lange et al, 1992), and may therefore necessitate ≥2 h of daylight photosynthesis in order to compensate for the carbon loss during the night (Csintalan et al, 2000; Tuba et al, 1996). As thoroughly discussed (Kidron & Kronenfeld, 2023), even if the threshold amount of NRW will be reached at the soil, the likelihood that these amounts will allow for 2‐h long daylight activity is rather small, and therefore there is a high likelihood that NRW may trigger carbon loss rather than carbon gain.…”

Section: Discussionmentioning

confidence: 99%

“…As thoroughly discussed, microlysimeters (MLs) tend to grossly overestimate the amounts of NRW (Kidron, 2024; Kidron et al, 2021). With the increased adaptation of this technique in recent decades, the traditional ‘old’ values were replaced by ‘new’ values, with the ‘new’ values becoming more and more ‘embedded’ in recent literature.…”

Section: Discussionmentioning

confidence: 99%

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Mornings with the highest non‐rainfall water during 2 years of measurements in the Negev–Ecological implications

Kidron,

Kronenfeld,

Starinsky

2024

Hydrological Processes

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By providing water during the long dry rainless season, non‐rainfall water (NRW), principally dew and fog, is commonly thought to serve as an important water source for arid soil biocrusts, which require water threshold of 0.05 (for lichens) and 0.1 mm (for cyanobacteria) for growth. Such values are commonly reported in the literature. Moreover, values of >0.45 mm/d (considered as the practical theoretical threshold for dew) are also reported. Following an analysis of limited (29 days) dewy mornings, it was recently reported that dew is incapable of forming on the soil surface. Being of limited scope, we therefore analyse days that yielded the highest amounts of NRW during 2 years (2021–2023) of measurements (22 days with NRW ≥0.15 mm). We conducted measurements at 1 m above ground, cobbles, rocks, and the soil surface, and compared them to the cloth‐plate method. Additionally, periodical temperature measurements were conducted, and the dewpoint temperature (Td) was calculated. Our findings indicate that (a) dew yield never surpassed 0.4 mm, (b) while the water threshold amounts were reached on the rocks and especially on the cobbles, these thresholds were seldom reached on soil (a single morning with 0.1 mm and 3 days with ≥0.05 mm), (c) in comparison to air temperatures at 0.05 m and especially at 1 m‐height above ground, surface nocturnal soil temperatures were 2–3°C warmer, thus eliminating possible vapour condensation. Our data cast doubt on values of >0.45 mm reported from various deserts. Additionally, while supporting the view that NRW may provide water for the growth of rock‐dwelling lichens, NRW in the Negev does not provide the soil biocrusts with sufficient water for growth.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Mornings with the highest non‐rainfall water during 2 years of measurements in the Negev–Ecological implications

Kidron,

Kronenfeld,

Starinsky

2024

Hydrological Processes

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“…In other words, while the substrate temperature may reach the dewpoint temperature at 1 m‐height above ground and may therefore facilitate vapour condensation there, the soil temperatures may not reach the dewpoint temperatures during the same very night. Under these conditions, dew formation will not take place on the ground (Kidron & Kronenfeld, 2020b, 2023).…”

Section: The Critical Approachmentioning

confidence: 99%

Is nonrainfall water a likely water source for arid and semiarid biocrusts? A critical perspective

Kidron

2024

Ecohydrology

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It is commonly believed that nonrainfall water (NRW) serves as an important and even a central source of water for biocrusts in arid and semiarid regions. Known also as biological soil crusts, they mainly consist of cyanobacteria (that dwell within the upper 2 mm of the soil) and crustose chlorolichens that commonly protrude 1–2 mm above ground. It is commonly assumed that due to the prolonged dry season in deserts, a constant source of water is required for their survival. Overestimated, nonrealistic NRW values, whether due to the use of improper measurement devices or erroneous interpretation of the recorded values as well as instances during which distillation was regarded as dewfall, supported the notion that the amounts of NRW are sufficiently high to allow for biocrust activation. In the current commentary, a short account of the reasons that led scholars to believe that NRW may be utilized by biocrusts is presented, and the findings that led to this belief are critically analysed. It is argued that the amounts of NRW reaching the surface are below the critical thresholds of 0.05 and 0.1 mm required for net photosynthesis by the chlorolichens and cyanobacteria, respectively. Moreover, it is argued that even if these thresholds are seldom reached, their duration is too short to result in net carbon gain. As shown for the dewy Negev and may be applicable for other arid and semiarid regions, biocrusts rely on rainwater for their growth and survival.

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“…In the Negev, only negligible amounts of NRW were obtained at the surface. The amount obtained by 1‐mm‐thick cloths attached to the surface (thus reflecting the 1 mm‐thick air film above ground) or by direct measurements (soil samples taken with a corer and weighed) was <0.04 mm (Kidron et al, 2002, 2017; Kidron & Kronenfeld, 2023). This amount is lower than the 0.05 mm required for net photosynthesis by green algae and chlorolichens, that is, lichens with green algae as photobionts that predominate in deserts and temperate zones (Büdel, 2005), as clearly evident in the Negev and the Tabernas deserts (Lázaro et al, 2008), and substantially below the 0.1 mm threshold required for net photosynthesis by cyanobacteria (Lange et al, 1992).…”

Section: The Assuptions Behind the Paradigmmentioning

confidence: 99%

A false paradigm? Do biocrust types necessarily reflect ‘successional stages’?

Kidron,

Xiao

2023

Ecohydrology

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The term ‘succession’ was first proposed to describe the gradual development of plants from an initial stage such as a bare ground to a well‐developed plant community, which at its peak, may reach a climax (primary succession). Accordingly, the earlier and fast growing stage (such as an annual plant community) may grant stability, organic matter and nutrients to the latter, high‐biomass and slow‐growing stages, such as trees. Commonly, reference to the different successional stages is also made once intact and disturbed communities (such as due to mechanical disturbance, tillage, fire, etc.) are compared (secondary succession). The concept was borrowed by many ecologists to describe variable biocrust types. Cyanobacterial or algal biocrust is regarded as an initial stage before turning to a later, more mature biocrust, whether composed of lichens or mosses. The underlain assumptions are that (a) the cyanobacteria provide essential stability and (b) nutrients that are required for the development of the later stages; (c) the initial biocrusts improve the water regime for the later successional stages; (d) cyanobacteria promote the lichen symbiosis; (e) due to substantial differences in the recovery time, a linear succession is inevitable, commonly from cyanobacterial/alga to lichen and lastly to moss; and (f) the cyanobacterial/algal biocrust is a temporary stage, just before being outcompeted by a later stage. It is argued hereafter that the above‐mentioned assumptions are not necessarily correct. As with higher plants, unless a direct comparison between disturbed and intact crusts justifies a reference to successional stages, different types of biocrusts commonly reflect the abiotic conditions at their site, and as such, unless the abiotic conditions change, they reflect stable communities of variable crust types. This paradigm shift may have important implications regarding inoculation efforts and directions and may explain the low success thus far obtained following inoculation experiments once performed with the more developed biocrusts, lichens and mosses.

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One‐year‐long evaluation of non‐rainfall water available to soil biocrusts in the Negev Highlands

Cited by 11 publications

References 62 publications

Mornings with the highest non‐rainfall water during 2 years of measurements in the Negev–Ecological implications

Mornings with the highest non‐rainfall water during 2 years of measurements in the Negev–Ecological implications

Is nonrainfall water a likely water source for arid and semiarid biocrusts? A critical perspective

A false paradigm? Do biocrust types necessarily reflect ‘successional stages’?

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