Past geomorphic processes: The role of permafrost and periglacial processes in ice-free environments

2020 ◽  
pp. 125-137
Author(s):  
Mauro Guglielmin
Keyword(s):  
Geomorphic Processes

Role of weathering of pillow basalt, pyroclastic input and geomorphic processes on the genesis of the Monte Cerviero upland soils (Calabria, Italy)

CATENA ◽  
2018 ◽  
Vol 171 ◽  
pp. 299-315 ◽  
Author(s):  
Anna Chiara Tangari ◽  
Fabio Scarciglia ◽  
Eugenio Piluso ◽  
Lucia Marinangeli ◽  
Loredana Pompilio
Keyword(s):  
Pillow Basalt ◽  
Upland Soils ◽  
Geomorphic Processes

Towards a better understanding of past biotic drivers of river and floodplain geomorphology

2020 ◽  
Author(s):  
Annegret Larsen ◽  
Tony Reimann ◽  
Christoph Sperisen ◽  
Vincent Robin ◽  
Stuart N Lane
Keyword(s):  
Ecosystem Engineer ◽  
Human Impacts ◽  
Abiotic Factors ◽  
Genetic Material ◽  
Environmental Dna ◽  
Ecosystem Engineers ◽  
Transport Processes ◽  
Decadal Scale ◽  
Geomorphic Processes

<p>Geomorphology has long considered the role of abiotic factors in geomorphic processes, including tectonics, geology, climate and relief, as well as humans impact upon them. Biotic factors however, including not only plants but also bacteria and protists, biofilms, fungi, insects, invertebrates, and animals are increasingly recognized as governing geomorphic processes on many spatial and temporal scales. We argue that if fauna are important as geological agents, then understanding the complex response of geomorphic systems to fauna is necessary to understand the past, present and future of the fluvial environment. It is not surprising that studies of the Late Quaternary evolution of fluvial morphodynamics have largely focused upon changes in the sedimentary soil-sediment sequences that result from climate change; (ii) vegetation change; and/or (iii) human impacts. Reconstruction of vegetation and climate from pollen and other records facilitates these analyses. But if animals are shown to be an important influence on geomorphic processes today, then it is quite possible that they were also important historically. For example, conclusive interpretation of Holocene river changes may be limited because of an incomplete or partial account of the presence and/or absence of data on the role of ecosystem engineers in modifying the riparian and aquatic ecosystems, including hydro-geomorphic processes. DNA found within historical deposits may be used to constrain the role of past ecosystem engineers. Analysis of ancient environmental DNA up to date includes palaeo-environmental DNA from sedimentary deposits (sedaDNA) from disseminated genetic material found within sedimentary archives, including paleo-dietary ancient DNA. Here, we use an analogue study investigating the present hydro-geomorphic and biogeochemical changes that the ecosystem engineer beaver (Castor fiber) creates at four sites in central Europe to better understand and quantify the effects of beaver ecosystem engineering on a seasonal to decadal scale. We utilize these results to interpret the chrono-stratigraphy of two Holocene beaver sites, including macro-fossil and sedaDNA sampling, and test for the first time if sedaDNA can support the investigation of beaver-induced palao-environmental conditions in river floodplains. We find that sedaDNA data and other palaeo-botanical proxies complement each other showing wider diversity of species than if the methods are used separately. However, care must be taken with regards of experimental setup, and further investigation into the effects of transport processes and/or quantitative representativeness is needed.</p>

Effects of Holocene Climatic Change on some Tropical Geomorphic Processes

1976 ◽  
Vol 6 (4) ◽  
pp. 529-556 ◽  
Author(s):  
Rhodes W. Fairbridge
Keyword(s):  
Coral Reefs ◽  
Ice Age ◽  
Tropical Regions ◽  
Climatic Oscillations ◽  
Climatic Control ◽  
Low Latitudes ◽  
History Of ◽  
Climatic Transition ◽  
Geomorphic Processes

Man's interference with the landscape process places him in the role of a “paraglacial” agent: He tends to duplicate ice-age stresses such as deforestation, accelerated erosion, and climate alteration. Against a background climatic control dictated by the Milankovich mechanisms, the 10,000-year history of the Holocene has seen very large secondary modulations that must be better understood so that they may be distinguished from anthropogenic effects. If they are exogenetically controlled, as it seems, then they are probably predictable from astronomic data. Four geomorphic type areas are selected for demonstrating Holocene changes in tropical regions, because they have been somewhat neglected within the framework of Quaternary science and because they include some of the most fragile and easily disrupted environments: lakes, semiarid desert margins, coastlines, and coral reefs. In a nutshell, the tropical Holocene has seen three major changes: (a) the evolution from the hyperaridity of the last pleniglacial stage to the “postglacial pluvial”; (b) the “climatic optimum,” which was highly diachronous and strongly retarded as it shifted from low latitudes to high; (c) the postoptimum “deterioration” that has involved desiccation of lakes, readvances of the deserts, fall of sea level, and truncation of coral reefs. While this deterioration is predictable in terms of an interglacial-glacial climatic transition, strong natural climatic oscillations, not yet well understood, together with man's activities, make the future a cause for concern.

scholarly journals The implications of disconnectivity for the study of contemporary geomorphic processes

2017 ◽  
Vol 19 (1) ◽  
pp. 5-15
Author(s):  
SLAYMAKER Olav
Keyword(s):  
Human Activities ◽  
Spatial Scales ◽  
Scale Problem ◽  
Conservation Of Mass ◽  
Natural Processes ◽  
The Past ◽  
Temporal And Spatial ◽  
Spatio Temporal ◽  
Geomorphic Processes

The emphasis on the understanding of contemporary geomorphic processes that has dominated Anglophone geomorphological literature over the past 50 years has seen huge progress but also some set-backs. We now have reliable measurements of mean rates of operation of all subaerial processes responsible for modification of landforms and landscapes and have made good progress in estimating the role of human activities as compared with “natural” processes. Some limited progress has been achieved in understanding the scale problem but problems remain. Perhaps the single most surprising development has been the recognition of the ubiquity of disconnectivity in geomorphic systems, the need to calculate virtual velocities of whole geomorphic systems and the relevance of this understanding to the general spatio-temporal scale problem. We have always known that most geomorphic processes operate intermittently but we have continued to depend on models that imply that mass and energy move freely through geomorphic systems and that conservation of mass and energy occurrs uninterruptedly at all temporal and spatial scales.

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

2018 ◽  
Author(s):  
Nimrod Wieler ◽  
Hanan Ginat ◽  
Osnat Gillor ◽  
Roey Angel
Keyword(s):  
Extracellular Polymeric Substances ◽  
Amplicon Sequencing ◽  
Salt Transport ◽  
Rock Surface ◽  
Rrna Gene ◽  
Arid Environments ◽  
Microbial Composition ◽  
Adjacent Soil ◽  
Geomorphic Processes

Abstract. 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 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 65–75 %. 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.

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

2019 ◽  
Vol 16 (6) ◽  
pp. 1133-1145 ◽  
Author(s):  
Nimrod Wieler ◽  
Hanan Ginat ◽  
Osnat Gillor ◽  
Roey Angel
Keyword(s):  
Extracellular Polymeric Substances ◽  
Salt Transport ◽  
Microbial Colonization ◽  
Rock Surface ◽  
Rrna Gene ◽  
Microbial Composition ◽  
Rock Types ◽  
Adjacent Soil ◽  
Geomorphic Processes

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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