Academic literature on the topic 'Terracettes'

Abstract. Alpine and mountain slopes represent important pathways that link high-altitude grazing areas to meadows and rangelands at lower elevations. Given the often acute gradients associated with such environments, they potentially represent highly efficient runoff conveyance routes that facilitate the downslope movement of runoff and associated material during erosion events. Many such slopes host series of small steps, or "terracettes". The juxtaposition of terracettes against the natural downslope flow path of non-complex slopes leads us to hypothesise that they may influence typical hillslope processes by intercepting or capturing surface runoff. Here we report preliminary results and some tentative conclusions from ongoing work to explore this possibility. Google Earth was used to initially identify a ca. 400 m2 well-developed terracette system situated on a west-facing slope with gradients ranging from 25 to 40° (46 to 84 %). A digital elevation model (DEM) of the terracettes was constructed using spatial data taken from a relevant section of topographic map. The DEM was then queried using a flow-accumulation algorithm and the results displayed in a geographic information system. The output data provided "proof of concept" that terracettes can capture surface runoff. The generation of empirical data from a series of rainfall/runoff simulations performed on the same section of terracettes supports this finding. Results from both work components indicate that sections of a terracette system may intercept runoff and could act as preferential flow pathways. By contrast, some sections appeared to act as depositional sites. We cautiously predict that these areas could act as retention zones for the temporary storage of runoff-associated substances. Greater understanding of the exact influence of terracettes on surface hydrology in steep-sloping and subalpine environments could benefit the future management of grazing and rangelands in such areas.

Small, irregular terraces on hillslopes, or terracettes, are common landscape features throughout west central China. Despite their prevalence, there is limited understanding of the nature of these topographic features, the processes that form them, and the role humans played in their formation. We used an interdisciplinary approach to investigate the geology, ecology, and cultural history of terracette development within Jiuzhaigou National Park, Sichuan Province, China. Terracettes occur on south facing, 20° slopes at 2500 m elevation, which appears to coincide with places people historically preferred to build villages. Ethnographic interviews suggest that traditional swidden agricultural cycles removed tree roots, causing the loess sediments to lose cohesion, slump, and the terrace risers to retreat uphill over time. This evidence is supported by landslide debris at terracette faces. Archaeological analysis of terracette sites reveal remains of rammed spread soil structures, bones, stone tools, and ceramics dating from at least 2200 years before present within a distinct paleosol layer. Radiocarbon and optically stimulated luminescence dating of terracette sediments ranged in age from between 1500 and 2000 14C yr BP and between 16 and 0.30"ka, respectively. These multiple lines of evidence indicate a long history of human habitation within Jiuzhaigou National Park and taken together, suggest strong links between terracette formation and human-landuse interactions.

AbstractThe relationships between vegetation patterns and periglacial features and their underlying ecology are still poorly understood and lack specific investigations in Antarctica. Here we present the results of vegetation colonization of different types of sorted patterned ground and gelifluction features (lobes and terracettes) at four sites in northern Victoria Land. This paper aims to understand the relationships between vegetation and the most widespread periglacial features in Victoria Land, discuss the role of periglacial features and vegetation in determining the ground surface temperature, and assess whether periglacial features provide ecological niches for vegetation colonization and development. Vegetation patterns are influenced by the feature type, mainly relating to patterned ground and debris island versus gelifluction features. The relations between vegetation and the periglacial features investigated in continental Antarctic are similar to those described for the Arctic, although in this part of the Antarctic vegetation is exclusively composed of cryptogams. Frost heave, ground texture and relief associated with different types of periglacial features provide a range of ecological niches sustaining vegetation biodiversity. Our data confirm the importance of periglacial features in shaping flora and vegetation biodiversity, as previously assessed only for the soil fauna in continental Antarctic.

Many of the siliceous hot springs in Yellowstone National Park contain subaqueous, spinose siliceous precipitates up to 5 cm high that occupy shallow terracettes in siliceous terraced mound accumulations, discharge channels, etc. These siliceous "shrubs" are composed of opal-A with an arborescent or branching pattern and have strong morphological similarities to bacterial shrubs from carbonate-precipitating hot springs. Siliceous shrubs constitute a major precipitate style associated with discharge channel – flow-path facies throughout most of the 20 m of flow path at Cistern Spring, Norris Geyser Basin. They are found in siliceous spring waters ranging in temperature from 76.4 to 16.2 °C and pH from 6.0 to 7.4. At every scale, siliceous shrubs contain abundant evidence of microbial life in the form of bacterial body fossils and extracellular polymeric substances. The presence of relict organic constituents and bacterial morphological fossils indicates that the shrub fabric and architecture are dominated by bacteria, i.e., there is potentially a strong biotic effect on the precipitation process. Precipitation of opal in siliceous shrubs is very likely the result of either active bacterially induced precipitation or passive mediation through organic templates. On a larger scale, siliceous shrubs contain abundant evidence of former microbial activity in hot springs, thus they are good microbial biomarkers.

AbstractThe structure and microbiology of active travertines is described from Canary and Minerva springs, with emphasis on ‘shrubs’ growing in terracette pools. These dendritic growths of aragonite consist of intricately branched sprays containing thousands of radiating needles. Shrub microstructure could be explained by the principle of ‘Keimauslese” and the preferential elongation of sharp protuberances in a rapidly depositing environment.The shrubs, and other active travertines, contain unicellular and filamentous bacteria. Estimates of total bacteria numbers ranged from 0.6−1.7 × 105 mm−3 but biomass was low, and always less than 1% of the travertine by weight. No evidence was found to indicate that bacteria played a role in shrub growth or morphology, but crystal trapping on bacterial strings may influence travertine fabrics on cascades. The shrubs are considered to have developed by inorganic processes, in hot spring waters supersaturated with aragonite.

A dissertação de mestrado desenvolvida tem como objetivo colaborar com a avaliação conceitual da forma erosiva terracete de pisoteio de gado, ainda pouco desenvolvida e, avaliar as perturbações do meio físico associadas ao pisoteio de gado. O objetivo da pesquisa torna-se relevante ao constatar que a temática desenvolvida é objeto de poucas produções acadêmicas. Além disso, no caso brasileiro, a grande área de terras utilizadas para a pastagem gera a necessidade de entendimento do funcionamento dessa paisagem antrópica para se produza formas corretas de manejo e possíveis restrições para o uso do solo a fim de evitar perturbações no meio físico difíceis de serem revertidas. Para elaborar a análise proposta, utilizou-se como embasamento teórico-metodológico a Geomorfologia Antropogênica em que a sociedade humana é inserida como agente de formação do relevo mesmo que indiretamente como no caso de áreas para a pastagem. Na perspectiva da Geomorfologia Antropogênica é necessário uma abordagem multiescalar para entender a magnitude das perturbações geradas no meio físico pelo ser humano. A primeira linha de investigação para o desenvolvimento da dissertação foi a pesquisa bibliográfica multilíngüe sobre o verbete terracete de pisoteio de gado. Completando a pesquisa bibliográfica, a segunda linha de investigação foi a analise em campo das perturbações do meio físico associadas aos terracetes de pisoteio de gado, com parâmetros físicos do solo e morfológicos da vertente. Como área de estudo, foi escolhida uma vertente amostral da parte rural da cidade de Joanópolis SP. A vertente amostral pertence ao Planalto Atlântico com solos pouco espesso e uso agrícola intensa, possibilitando a comparação entre do trecho da vertente preservado e o trecho antrópico com pastagem. Na vertente amostral foram aplicadas técnicas de campo reconhecidas academicamente. Como procedimento inicial utilizou-se o pantômetro por permitir o cálculo preciso da declividade. Com a análise inicial em campo e a elaboração do perfil topográfico, foram selecionados três pontos de controle para a medição de resistência a penetração; medição da densidade do solo e; a análise morfológica do solo. Os resultados evidenciaram que as perturbações geomorfológicas e pedológicas criadas pelo rebanho bovino são intensas e de diversos tipos. O caminhar do gado também promove a exposição do solo, visto que dificulta ou impede o crescimento da pastagem, pois ao compactar o solo, gera resistência a penetração superior ao limite de crescimento radicular. A compactação do solo é mais profunda que o horizonte A e, em solos pouco espessos, como o neossolo estudado nessa pesquisa, o terracete de pisoteio de gado tem um limite físico para a sua profundidade a rocha parental.
The developed dissertation aims to collaborate with the conceptual evaluation of cattle-tracks erosive form, which studies are still little developed, and to evaluate the physical disturbance associated with cattle trampling. The objective of this research is relevant to add the developed subject itself, which has been presented in few academic productions. Besides that, in Brazilian case, the large land area used for grazing, generates the necessity to understand the functionality of the anthropic landscape, in order to produce correct forms of handling and possible use of land restrictions to avoid disturbances in the physical environment, which are difficult to be reversed. Composing the proposed analysis, it was applied as theoretic and methodological praxis the Antropic Geomorphology where in the society is an agent of relief formation even indirectly, like the case of grazing. In perspective of anthropic geomorphology is necessary a multi-scale approach to understand the magnitude of the disturbance generated in the physical environment caused by human being. The first investigation line for the development of this dissertation was the bibliographic multilingual search about the word cattletracks. In completion of the bibliographic search, the second investigation line was the analyses in field about the disturbance in physical environment associated to the cattle-tracks, with physical soil parameters and morphological slope parameters analyses. As study area, a sample slope of Joanópolis rural area was selected. The sample slope belongs to Atlantic plateau with shallow soil e intense agricultural use enabling comparison between the segment with cover forest and segment with grazing. In the sample slope, it was applied field techniques academical lyre cognized. And as an initial procedure it was used the pantometer, which allows accurate calculation of slope. Up the initial field analysis and profile elaboration, three control points were selected in order to measure the penetration resistance, measure the soil density and morphology. The results showed that geomorphological and pedological disturbance created by cattle was intense and from several types.The cattle grazing causes naked soil, because hinders or prevents the growth of pasture, therefore compacts the soil, creates penetration resistance upper to the limit root growth. The soil compact is deeper than the horizon A and, in shallow soil, as the soil of this research, the cattle-tracks has a physical limit for its deepness, which is the parent rock.

Terracettes are a widely occurring form of micro-relief found throughout regions displaying various climatic and environmental conditions. Much speculation surrounds the processes responsible for their formation and development. An investigation of these micro-forms, their associated soil physical properties, sustaining mechanisms, and their relationship to slope stability was undertaken in Giant's Castle Game Reserve, KwaZulu - Natal Drakensberg, South Africa. The study showed that relationships between terracette morphology and soil physical properties within the Reserve are few, and that current soil conditions cannot be used to infer process related to terracette formation. However dry bulk density data indicated that soil creep is the dominant formative mechanism within the Reserve. Throughflow at riser surfaces was the dominant sustaining mechanism, with needle ice growth, wind, surfacewash and animal disturbance contributing minor retreat at both treads and risers. Aspect played an important role in determining soil physical characteristics. It was inferred that terracettes imparted stability to the slopes on which they are found, and with continued retreat at both treads and risers the slope was again placed under conditions of instability.
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998.

Terracettes and turf-banked terraces exist at Tiffindell Ski Resort in the Drakensberg of the Province of the Eastern Cape at altitudes between 2750 m and 2880 m on slopes of between 15°and 26°. Ice lenses and interstitial ice exist within turf-banked terraces in winter. During post-winter thaws, soil moisture reaches saturation in at least the upper part of the regolith in which turf-banked terraces occur. These terraces move downslope under the influence of gelifluction (which is essentially a combination of frost creep and solifluction). Terracettes appear to move as a result of frost creep, processes associated with needle ice, and slope wash. Both turf-banked terraces and terracettes are part of the periglacial environment and are active under present climatic conditions at Tiffindell.

Terracettes and turf-banked terraces exist at Tiffindell Ski Resort in the Drakensberg of the Province of the Eastern Cape at altitudes between 2750 m and 2880 m on slopes of between 15°and 26°. Ice lenses and interstitial ice exist within turf-banked terraces in winter. During post-winter thaws, soil moisture reaches saturation in at least the upper part of the regolith in which turf-banked terraces occur. These terraces move downslope under the influence of gelifluction (which is essentially a combination of frost creep and solifluction). Terracettes appear to move as a result of frost creep, processes associated with needle ice, and slope wash. Both turf-banked terraces and terracettes are part of the periglacial environment and are active under present climatic conditions at Tiffindell.