Defining tafoni

Groom, Kaelin M.; Allen, Casey D.; Mol, Lisa; Paradise, Thomas R.; Hall, Kevin

doi:10.1177/0309133315605037

Cited by 38 publications

(9 citation statements)

References 68 publications

(114 reference statements)

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“…Detection of differentially abundant OTUs was carried out using ALDEx2 (Fernandes et al, 2014). Plots were generated using the gg-plot2 (Wickham, 2016) and ggtern (Hamilton, 2017) packages.…”

Section: Sequence Processing and Analysis Of Bacterial Communitiesmentioning

confidence: 99%

The origin and role of biological rock crusts in rocky desert weathering

et al. 2019

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Abstract. In drylands, microbes that colonize rock surfaces have been linked to erosion because water scarcity excludes traditional weathering mechanisms. We studied the origin and role of rock biofilms in geomorphic processes of hard lime and dolomitic rocks that feature comparable weathering morphologies, although these two rock types originate from arid and hyperarid environments, respectively. We hypothesized that weathering patterns are fashioned by salt erosion and mediated by the rock biofilms that originate from the adjacent soil and dust. We used a combination of microbial and geological techniques to characterize rock morphologies and the origin and diversity of their biofilms. Amplicon sequencing of the SSU rRNA gene suggested that bacterial diversity is low and dominated by Proteobacteria and Actinobacteria. These phyla only formed laminar biofilms on rock surfaces that were exposed to the atmosphere and burrowed up to 6 mm beneath the surface, protected by sedimentary deposits. Unexpectedly, the microbial composition of the biofilms differed between the two rock types and was also distinct from the communities identified in the adjacent soil and settled dust, showing a habitat-specific filtering effect. Moreover, the rock bacterial communities were shown to secrete extracellular polymeric substances (EPSs) that form an evaporation barrier, reducing water loss rates by 65 %–75 %. The reduced water transport rates through the rock also limit salt transport and its crystallization in surface pores, which is thought to be the main force for weathering. Concomitantly, the biofilm layer stabilizes the rock surface via coating and protects the weathered front. Our hypothesis contradicts common models, which typically consider biofilms to be agents that promote weathering. In contrast, we propose that the microbial colonization of mineral surfaces acts to mitigate geomorphic processes in hot, arid environments.

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Section: Sequence Processing and Analysis Of Bacterial Communitiesmentioning

confidence: 99%

The origin and role of biological rock crusts in rocky desert weathering

et al. 2019

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“…Neither the prevalence of weathering nor its morphology seemed to differ between sites despite the different climates and underlying geology. In all cases, weathering type was classified as tafoni or honeycomb weathering (Goudie, Viles, & Parker, 1997;Groom, Allen, Mol, Paradise, & Hall, 2015;Fig. 1A), and it was coupled with the presence of sub-aerial biofilm, burrowed underneath the surface and protected by sedimentary deposits (Fig.…”

Section: Field and Mineralogical Observationsmentioning

confidence: 99%

Reply to Anonymous Reviewer #1

Angel¹

2019

Preprint

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This article is a non-peer reviewed preprint published at EarthArXiv Highlights/significance:  Tafoni (honeycomb) weathering patterns were observed at similar frequency and magnitude in hard lime and dolomitic rocks originating from arid and hyperarid environments, respectively, despite different lithologies and climate.  In drylands, rock surfaces are colonised by an epilithic microbial community, dominated by bacteria that form a biological rock crusts.  The microbial communities on the hard lime and dolomitic rocks were dominated by members of the phyla Proteobacteria and Actinobacteria that are typical to drylands.  The two BRC communities were nevertheless distinct from each other, but also from the surrounding soil and dust, showing the habitat filtering effect of the rock surfaces.  Microbial and geological tools applied in this study suggest that in drylands biological rock crusts mitigate rock weathering processes by forming an evaporation barrier.

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“…Neither the prevalence of weathering nor its morphology seemed to differ between sites despite the different climates and underlying geology. In all cases, weathering type was classified as tafoni or honeycomb weathering (Goudie et al, 1997;Groom et al, 2015); Fig. 1A), and it was coupled with the presence of sub-aerial biofilm, burrowed underneath the surface and protected 15 by sedimentary deposits (Fig.…”

Section: Field and Mineralogical Observationsmentioning

confidence: 99%

The origin and role of biological rock crusts in rocky desert weathering

Wieler¹,

Gillor²,

Angel³

2018

Preprint

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<p><strong>Abstract.</strong> In drylands, microbes that colonise rock surfaces were linked to erosion because water scarcity excludes traditional weathering mechanisms. We studied the origin and role of rock biofilms in geomorphic processes of hard lime and dolomitic rocks that feature comparable weathering morphologies though originating from arid and hyperarid environments, respectively. We hypothesised that weathering patterns are fashioned by salt erosion and mediated by the rock biofilms that originate from the adjacent soil and dust. We used a combination of microbial and geological techniques to characterise rocks morphologies and the origin and diversity of their biofilm. Amplicon sequencing of the SSU rRNA gene suggested that bacterial diversity is low and dominated by Proteobacteria and Actinobacteria. These phyla formed laminar biofilms only on rock surfaces that were exposed to the atmosphere and burrowed up to 6&#8201;mm beneath the surface, protected by sedimentary deposits. Unexpectedly, the microbial composition of the biofilms differed between the two rock types and was also distinct from the communities identified in the adjacent soil and settled dust, showing a habitat-specific filtering effect. Moreover, the rock bacterial communities were shown to secrete extracellular polymeric substances that form an evaporation barrier, reducing water loss rates by 65&#8211;75&#8201;%. The reduced water transport rates through the rock also limit salt transport and its crystallisation in surface pores, which is thought to be the main force for weathering. Concomitantly, the biofilm layer stabilises the rock surface via coating and protects the weathered front. Our hypothesis contradicts common models, which typically consider biofilms as weathering-promoting agents. In contrast, we propose the microbial colonisation of mineral surfaces acts to mitigate geomorphic processes in hot, arid environments.</p>

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Defining tafoni

Cited by 38 publications

References 68 publications

The origin and role of biological rock crusts in rocky desert weathering

The origin and role of biological rock crusts in rocky desert weathering

Reply to Anonymous Reviewer #1

The origin and role of biological rock crusts in rocky desert weathering

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