Development of a subarctic peatland linked to slope dynamics at Lac Wiyâshâkimî (Nunavik, Canada)

The Holocene ◽  
2019 ◽  
Vol 29 (9) ◽  
pp. 1459-1467 ◽  
Author(s):  
Najat Bhiry ◽  
Armelle Decaulne ◽  
Myosotis Bourgon-Desroches
Keyword(s):  
Aquatic Invertebrates ◽  
Fine Sand ◽  
Larix Laricina ◽  
Loss On Ignition ◽  
Long Distance ◽  
Carex Aquatilis ◽  
Carex Rostrata ◽  
Hippuris Vulgaris ◽  
Sandy Sediments ◽  
Minerotrophic Peatland

A palaeoecological study of a subarctic minerotrophic peatland was undertaken to reconstruct the formation of the site as an archive of slope geomorphological processes. The study peatland is located about 400 m from Caribou slope (unofficial name) on Lepage Island, Lac Wiyâshâkimî, Nunavik (northern Québec, Canada). The site is close to the lakeshore and receives runoff directly from Caribou slope and its catchment. Gravity processes have been active on Caribou slope since the deglaciation of the region at approximately 6000 cal. yr BP. These processes may be differentiated in terms of Holocene stages of intensity. The objective of our study was to detect evidence of gravity processes in the peatland and to note their frequency since its establishment using loss-on-ignition testing, macrofossil analysis and radiocarbon dating. Our results indicate that peat began to accumulate over the sandy-gravelly sediments at around 4900 cal. yr BP. Larix Laricina, Carex aquatilis and Carex rostrata were present at this time until 4660 cal. yr BP, at which point these taxa were replaced by aquatic taxa such as Hippuris vulgaris and Daphnia (aquatic invertebrates). The percentage of mineral sediments (sand) remained high during this period, which could be linked to slope activity. After 4660 cal. yr BP, sandy sediments diminished while episodes of aquatic conditions and sand inflow occurred on at least three occasions (at 4660, 3905 and 3130 cal. yr BP). The increase in water flow and the introduction of more medium to fine sand into the peatland could be linked to slope movements and the long-distance runout of debris flow that we observed in the field. Given these factors, conditions at the study site remained wet from the earliest phases until the present. Unlike the subarctic permafrost peatlands in northern Québec, permafrost did not become established at the study site.

scholarly journals Influence of gut morphology on passive transport of freshwater bryozoans by waterfowl in Doñana (southwestern Spain)

2004 ◽  
Vol 82 (6) ◽  
pp. 835-840 ◽  
Author(s):  
Jordi Figuerola ◽  
Andy J Green ◽  
Katrina Black ◽  
Beth Okamura
Keyword(s):  
Aquatic Invertebrates ◽  
Bird Species ◽  
Passage Time ◽  
Passive Dispersal ◽  
Long Distance Dispersal ◽  
Long Distance ◽  
Active Dispersal ◽  
Intestine Length ◽  
Internal Transport

Waterbirds have been proposed as important vectors for the passive dispersal of those aquatic invertebrates and plants that lack a capacity for active dispersal between isolated water bodies. We analysed the frequency of internal transport of bryozoan propagules (statoblasts) by waterbirds in Doñana, Spain, by examining their presence in the intestines and ceca of dead birds and analysing the role of different aspects of gut characteristics in explaining variation in the presence/absence and abundance of statoblasts. Of the 228 samples examined, 7.9% presented intact statoblasts of Plumatella fungosa (Pallas, 1768), Plumatella emarginata Allman, 1844, and two unidentified Plumatella species. For a given bird species, individuals with heavier gizzards and shorter ceca had a lower incidence and abundance of statoblasts in the lower gut. Grit mass and intestine length were unrelated to the presence or abundance of statoblasts. Our results suggest that waterbirds frequently transport bryozoans on a local scale, with lighter gizzards and longer ceca favouring such transport. Lighter gizzards are likely to destroy fewer propagules before they reach the lower gut. Species and individuals with longer ceca are particularly good candidates for long-distance dispersal of bryozoans, given the longer passage time of propagules that enter the ceca.

Productivité en larves de moustiques (Diptera: Culicidae) des milieux aquatiques peu profonds d'un secteur du Moyen-Nord Québécois (LG-1, Territoire de la Baie de James)

1981 ◽  
Vol 59 (5) ◽  
pp. 738-749 ◽  
Author(s):  
Claude Tessier ◽  
Alain Maire ◽  
Antoine Aubin
Keyword(s):  
Relative Frequency ◽  
Larval Density ◽  
James Bay ◽  
Ecological Distribution ◽  
Carex Aquatilis ◽  
Aedes Mosquitoes ◽  
Carex Rostrata ◽  
Quantitative Results ◽  
The Mean ◽  
Ecological Unit

The LG-1 area (53°46′ N; 77°30′ W) is located on La Grande Rivière, 28 km upstream of its mouth at James Bay. It is a Middle Subarctic landscape. The ecological distribution of mosquito larval populations of 21 species is analyzed. For each ecological unit the following data are taken into account: the density of the larval community (larvae per metre cubed) and relative frequency (percentage) of the species per sample.The larval productivity of snowmelt Aedes mosquitoes is evaluated for each ecological unit from the percentage of the area covered by water (percentage), the average depth of the shallow pools (in metres) and the mosquito larval density. The mean number of larvae (log x) per hectare and the standard error of mean range from 4.77 ± 0.255 (33 000 < 59 000 < 106 000) in the Carex rostrata unit with peat bog substrate up to 7.12 ± 0.413 (5.1 × 106 < 1.3 × 107 < 3.4 × 107) in the silty Carex aquatilis unit. The mapping of a typical area of 2 500 ha in which 626 ha are mosquito-productive wetlands, shows an average productivity (log x) of 5.29 ± 0.146 (140 000 < 200 000 < 280 000). These data are compared with quantitative results published from similar northern localities.

Seasonal changes in the standing crop of two montane sedges

1973 ◽  
Vol 51 (6) ◽  
pp. 1097-1108 ◽  
Author(s):  
Eville Gorham ◽  
Maureen Gibson Somers
Keyword(s):  
Life Span ◽  
Production Rate ◽  
Late Summer ◽  
Dry Weight ◽  
Early Spring ◽  
Pure Stand ◽  
Carex Aquatilis ◽  
Maximum Production ◽  
Carex Rostrata ◽  
Maximum Production Rate

Aboveground green biomass of a montane pure stand of Carex rostrata varies from about 125 g/m2 (air-dry weight) at the end of November to about 640 g/m2 in early August. The maximum production rate of about 6 g/m2 per day occurs in May. For a nearby stand of Carex aquatilis with a prominent moss layer the aboveground green biomass of sedge material varies from about 40 g/m2 in February to about 380 g/m2 in mid-August. The maximum production rate for sedge material is about 4 g/m2 per day in July. Both species exhibit two main populations of shoots, one emerging in late summer and the other through winter and early spring. The winter and spring shoots of Carex rostrata flower and die after about 18 months, while the late summer shoots, which do not mature vegetatively until the following summer, have a life-span of about 2 years. The late summer shoots of Carex aquatilis mature vegetatively before winter, and flower and die within about 12 months; while the winter and spring shoots live through the next winter, and flower and die the following summer after a life-span of about 18 months.

scholarly journals Swampy mesotrophic peatmoss spruce forests of European Russia and Urals

2021 ◽  
pp. 74-106
Author(s):  
Илья Борисович Кучеров ◽  
Станислав Анатольевич Кутенков
Keyword(s):  
Picea Abies ◽  
Southern Urals ◽  
European Russia ◽  
The Southern Urals ◽  
Data Set ◽  
Carex Aquatilis ◽  
Spruce Forests ◽  
Rubus Chamaemorus ◽  
Carex Rostrata ◽  
Menyanthes Trifoliata

На основе выборки из 130 геоботанических описаний, сделанных авторами в 1995-2019 гг. или взятых из литературы, проведена доминантно-детерминантная классификация топких мезотрофных (Picea abies s.l.) ельников сфагновых, развивающихся при подтоплении либо периодическом затоплении в Европейской России и на Урале. Ценотическое разнообразие этих сообществ определяется спецификой названных процессов в сочетании с климатическими факторами, тогда как роль почвообразующих пород почти не выражена. Выделено 6 ассоциаций с 6 субассоциациями и 2 вариантами, всего 11 синтаксонов (табл. 1). В их числе подтопленные ельники вейниковые сфагновые с господством Calamagrostis purpurea s.l. и Equisetum sylvaticum в травяном ярусе (4 субассоциации в разных подзонах тайги либо долготных секторах), вздутоосоковые с Carex rostrata и C. vesicaria и вахтовые с Menyanthes trifoliata (2 субассоциации). Кроме того, выделены эндемичные для Южного Урала ельники малоцветковоосоковые с C. pauciflora и Rubus chamaemorus, развивающиеся на поверхностном дождевом стоке (2 варианта), приречные северотаежные водноосоковые с Carex aquatilis и затопленные южно- и подтаежные белокрыльниковые с Calla palustris. Для большинства синтаксонов характерны Swampy mesotrophic peatmoss spruce forests, dominated by Picea abies s.l. and originated due to inundation or periodical flooding, have been classified in European Russia and the Urals using the dominant-determinant approach to vegetation. The data set involves 130 relevés made by the authors in 1996-2019 or taken from the published sources. 11 syntaxa are totally recognized (see Table 1). Inundated reedgrass-peatmoss (with the dominance of Calamagrostis purpurea s.l. and Equisetum sylvaticum in the field layer; 4 subassociations in different subzones or longitudinal sectors), sedge-peatmoss (with Carex rostrata and C. vesicaria), and trefoil-peatmoss (with Menyanthes trifoliata; 2 subassociations) spruce forests are recognized. In addition, one can distinguish sedge-cloudberry-peatmoss spruce forests with Carex pauciflora и Rubus chamaemorus in the subalpine belt of the Southern Urals, developing due to surficial rain flow, also riverine northern-boreal sedge-peatmoss forests with Carex aquatilis and flooded southern- and hemiboreal calla-peatmoss spruce forests with Calla palustris. The observed syntaxonomic diversity is governed by inundation/flooding intensity and longevity together with latitudinal zonation and climate continentality, whereas the role of bedrock type influence is minimal. Multi-dominance and mutual replaceability are typical for peatmosses in most of the syntaxa.

Assemblages of the moulluscan fauna in subtidal soft bottoms of the Ría de Aldán (north-western Spain)

2006 ◽  
Vol 86 (1) ◽  
pp. 129-140 ◽  
Author(s):  
Antía Lourido ◽  
Loreto Gestoso ◽  
Jesús S. Troncoso
Keyword(s):  
Grain Size ◽  
Spatial Distribution ◽  
Multivariate Analyses ◽  
Fine Sand ◽  
Typical Species ◽  
Soft Bottoms ◽  
Western Spain ◽  
Faunal Distribution ◽  
Sandy Sediments ◽  
North Western

The composition and spatial distribution of the mollusc fauna on the subtidal soft bottoms of the Ría de Aldán (Galicia, north-western Spain) were studied by means of quantitative sampling and multivariate analyses. The faunal distribution was mainly conditioned by a sedimentary gradient that was defined by a decreasing grain size from the mouth towards the inner margins of the ría. Several assemblages were determined which could be defined according to the classic terms of ‘community’ and ‘facies’. A ‘Venus fasciata community’ and a ‘facies of Goodallia triangularis–Pisione parapari’ are present in coarser sandy sediments of the outer ría area. The communities characterized by ‘Venus gallina’ and ‘Tellina fabula–Tellina tenuis’ were found in the fine sand bottoms at the centre and margins of the ría. The shallower and muddier sediments in the inner ría showed a mix of typical species from the ‘Abra alba’ and the ‘Venus gallina’ communities, and in the Río Aldán's mouth could be distinguished a facies of a protected zone.

scholarly journals Engineering Innovation of a Length of Nearly 3300m large Diameter Pipeline Installed by HDD

2016 ◽  
Vol 20 (1) ◽  
pp. 1-5
Author(s):  
Li Guohui ◽  
Ma Xiaocheng ◽  
Yang Chunling
Keyword(s):  
Yangtze River ◽  
Large Diameter ◽  
Fine Sand ◽  
Hole Drilling ◽  
Scour Depth ◽  
The Yangtze River ◽  
Directional Drilling ◽  
Horizontal Directional Drilling ◽  
Long Distance ◽  
Pilot Hole

<p>The Yangtze River Crossing Project, which is part of the Chinese gas pipeline trunk network and aims to transmit the natural gas to the Yangtze River Delta area, sets up a record for the length of Horizontal Directional Drilling (HDD) in the world. The term of pipeline installed is 3300m, and the diameter is 40in. Many technical difficulties have been inevitably encountered in a large diameter hole reaming in fine sand, the calculation of section scour depth which determines the minimum buried depth of the pipe, protection of outside coating and the method of long distance pilot hole drilling, such other challenges. In view of this, it was recommended that two pipelines of 711mm should be installed to replace the existing one of 1016mm in diameter and 1% flooding scour depth obtained by reliable statistical analysis. In period of installation, application glass fiber reinforced epoxy resin as a protective coating, executing the pilot hole by Intersect Method. As a result, this super project is finished successfully on May 21.2013. The experience can be applied to any pipeline engineering the installed by horizontal directional drilling or similar works.</p>

scholarly journals Experimental Study on Local Scour and Related Mechanical Effects at River-Crossing Underwater Oil and Gas Pipelines

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Fan Cui ◽  
Yunfei Du ◽  
Xianjie Hao ◽  
Suping Peng ◽  
Zhuangzhuang Bao ◽  
...  
Keyword(s):  
Particle Size ◽  
Oil And Gas ◽  
Fine Sand ◽  
Scour Depth ◽  
Gas Pipelines ◽  
Long Distance ◽  
Oil And Gas Pipelines ◽  
Riverbed Sediment ◽  
Water Damage ◽  
Equilibrium Scour Depth

Among the various geological disasters that threaten the safe operation of long-distance oil and gas pipelines, water-damage disasters are numerous and widely developed. Especially the pipelines crossing river channels or gullies are vulnerable to scouring hazards from storms and floods. A water-damage disaster physical model was established to investigate the characteristics of the riverbed scour profile and the pipeline force when the pipeline was buried at different depths under the condition of different particle size riverbed sediment. Results indicated that the equilibrium scour depth changed in a spoon shape with the gradual increase of the embedment ratio in general. The equilibrium scour depth formed by the fine sand riverbed was the largest, about 1.5 times the pipeline diameter. When the pipeline was half exposed, the clay riverbed was more resistant to the scour of the river than the riverbed of fine sand and very fine pebbles with a larger particle size. In the riverbed of three particle sizes, fine sand was more difficult to withstand the scour of the river. The scour profile formed by the sand bed around the pipeline and the force and deformation of the pipeline were related to pipeline location and riverbed sediment type. Results of this study might be useful for the safety warning and protection measures of underwater pipeline crossing.

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