Population biology of Ammophila breviligulata and Calamovilfa longifolia on Lake Huron sand dunes. I. Habitat, growth form, reproduction, and establishment

1985 ◽  
Vol 63 (1) ◽  
pp. 113-124 ◽  
Author(s):  
M. A. Maun
Keyword(s):  
Population Biology ◽  
Growth Form ◽  
Sand Dunes ◽  
Perennial Grasses ◽  
Lake Huron ◽  
Long Distance ◽  
Ammophila Breviligulata ◽  
Concentric Circles ◽  
Almost All ◽  
Calamovilfa Longifolia

Some aspects of the population biology of two dune-forming perennial grasses, Ammophila breviligulata Fern. and Calamovilfa longifolia (Hook) Scribn., growing along Lake Huron shoreline, were investigated under natural and controlled conditions. Plants of A. breviligulata exhibit erratic flowering, ranging from no panicles in some areas to 16 per hundred tillers in others. Calamovilfa longifolia plants occur as single clumps of varying diameters and flower profusely. Ammophila breviligulata expands into adjacent areas by producing plagiotropic rhizomes ranging in length from 1 to several m and then producing ramets on some of the nodes. Such a growth form is best suited for rapid colonization of bare areas. Clumps of C. longifolia expand outward in concentric circles through the development of diving rhizomes, and the radius of a clump increases by about 15 to 31 cm per year. This growth form is well suited for local occupancy. Ammophila breviligulata is more tolerant of burial (100 cm) in sand than C. longifolia (60 cm). Calamovilfa longifolia produces larger number of caryopses per square metre than A. breviligulata. The weight per caryopsis of both species is similar, but the significantly greater surface area per fruit of A. breviligulata improves its flotation ability in water, thus facilitating long-distance dispersal of fruits. Establishment of C. longifolia plants under natural conditions occurred almost exclusively from seedlings. In contrast, the establishment of A. breviligulata seedlings was rare and almost all new plants along the beach originated from clonal fragments cast on the drift line by high waves.

Population biology of Ammophila breviligulata and Calamovilfa longifolia on Lake Huron sand dunes. III. Dynamic changes in plant community structure

1989 ◽  
Vol 67 (4) ◽  
pp. 1267-1270 ◽  
Author(s):  
M. A. Maun
Keyword(s):  
Population Biology ◽  
Sand Dunes ◽  
Perennial Grasses ◽  
Lake Huron ◽  
Oenothera Biennis ◽  
Ammophila Breviligulata ◽  
Cakile Edentula ◽  
Dune Ridge ◽  
Artemisia Campestris ◽  
Calamovilfa Longifolia

Changes in vegetation and physiography of Lake Huron shoreline were studied by recording total counts and by comparing photographs taken in 1977, 1985, and 1987. In 1977, a large number of annual and biennial plant species such as Cakile edentula, Corispermum hyssopifolium, Salsola kali, Euphorbia polygonifolia, Artemisia campestris, and Oenothera biennis were found growing in association with two perennial grasses, Calamovilfa longifolia and Andropogon scoparius. Ammophila breviligulata was absent at that time, but became abundant through establishment of ramets from rhizome fragments after the storms of 1979 and 1981. Two damaging storms, one in October 1986 and the second in April 1987, wiped out almost all of Ammophila breviligulata, leaving a few remnant shoots among clumps of Calamovilfa longifolia. Observations suggest that the low density (two shoots∙m−2) of Ammophila breviligulata tillers among Calamovilfa longifolia populations on the first dune ridge has resulted from landward extensions of plagiotropic rhizomes from the once abundant Ammophila breviligulata populations on the lakeward end of the beach.

Population biology of Ammophila breviligulata and Calamovilfa longifolia on Lake Huron sand dunes. II. Ultrastructure of organelles and photosynthetic properties

1986 ◽  
Vol 64 (9) ◽  
pp. 2151-2159 ◽  
Author(s):  
Beverly Elfman ◽  
M. A. Maun ◽  
W. G. Hopkins
Keyword(s):  
Chlorophyll A ◽  
Population Biology ◽  
Protein Complexes ◽  
Sand Dunes ◽  
Bundle Sheath ◽  
Lake Huron ◽  
Mesophyll Cells ◽  
Ammophila Breviligulata ◽  
Calamovilfa Longifolia ◽  
Photosynthetic Properties

Organellar ultrastructure and photosynthetic properties of two grasses, Calamovilfa longifolia (Hook) Scribn. and Ammophila breviligulata Fern., growing on Lake Huron sand dunes were compared. Thylakoids of C. longifolia contained a relatively greater complement of the photosystem I (PSI) – chlorophyll a – protein complex, whereas thylakoids from A. breviligulata had a relatively greater complement of light-harvesting chlorophyll a + b complex. The chlorophyll a/b ratios of the mesophyll chloroplast thykaloids reflected the content of chlorophyll–protein complexes present in the membranes. Digitonin fractionation of mesophyll thylakoids from C. longifolia revealed that the PSI-enriched fraction contained more chlorophyll than the photosystem II (PSII) enriched fraction. Conversely, the PSII-enriched fraction accounted for the larger proportion of total chlorophyll in thylakoids from A. breviligulata. Whole chain electron transport (PSII + PSI) activity was greater in C. longifolia mesophyll thylakoids, at all light intensities. Chloroplast and mitochondrial ultrastructure were compared. The bundle sheath chloroplasts of C. longifolia contain extensive grana stacking and are distributed throughout the cell. The mitochondria of the bundle sheath and mesophyll cells are strikingly dimorphic. A suberin lamella is apparently absent from the bundle sheath cell walls. These results support the designation of C. longifolia as a C4 species of the nicotinamide adenine dinucleotide – malic enzyme type.

Seed germination and seedling establishment of Calamovilfa longifolia on Lake Huron sand dunes

1981 ◽  
Vol 59 (4) ◽  
pp. 460-469 ◽  
Author(s):  
M. A. Maun
Keyword(s):  
Sand Dunes ◽  
Linear Increase ◽  
Lake Huron ◽  
Fluorescent Light ◽  
Seedling Mortality ◽  
High Soil ◽  
Soil Temperatures ◽  
Number Of Leaves ◽  
Growth Chambers ◽  
Calamovilfa Longifolia

Caryopses ("seeds") of Calamovilfa longifolia (Hook.) Scribn. are dimorphic (brown and white) and are each enclosed in a lemma and palea. The most complete germination was obtained in lighted (fluorescent light of 1600 lx) growth chambers set at alternating temperatures of 25 °C day (14 h) and 10 °C night. Seed stratification did not increase total germination but the rate of germination was increased. The seeds imbibed about 50% by weight of water before germination was initiated.Under field conditions seeds accumulated in depressions. Seedlings failed to emerge from depths greater than 6 cm. The survival rate of seedlings was very low (0.5%) during 1978 because of a dry summer but was considerably higher in 1979 on south slopes (33%), under willow clumps (44%), and on north slopes (56%). Seedling mortality was due to high soil temperatures, desiccation, burial or exposure of seedlings, and biotic agents. Seedlings emerged from the soil mainly by elongation of the first internode. The coleoptile seemed to act as a protective sheath against high soil temperatures for the growing point enclosed within it. A significantly linear increase in height of seedlings, root length, and number of leaves occurred with an increase in the age of seedlings during both years.

Leaf demography and decline of Panicum racemosum populations in coastal foredunes of southern Brazil

1991 ◽  
Vol 69 (7) ◽  
pp. 1593-1599 ◽  
Author(s):  
César S. B. Costa ◽  
Ulrich Seeliger ◽  
César V. Cordazzo
Keyword(s):  
Population Biology ◽  
Sand Dunes ◽  
Salt Spray ◽  
Nutrient Status ◽  
Southern Brazil ◽  
Leaf Demography ◽  
Growth Vigour ◽  
Sand Movement ◽  
Mobile Dune ◽  
Sand Deposition

We studied the effect of nutrient status and sand movement on the population biology of Panicum racemosum Spreng. over a 5-year period (1982–1986) on mobile, semifixed and fixed coastal foredune habitats in southern Brazil. The soils were deficient in nitrate, phosphate, and potassium (<0.5, 0.2–1.2, and 3–5 mg/kg, respectively) in all habitats, and a gradient of decreasing availability existed from the mobile to the fixed dunes. Half-lives of leaves were shorter in the fixed dune as compared with the mobile dune. Similarly, half-lives of leaves were shorter in summer than in winter. Experiments using cuttings of P. racemosum tillers showed that as P. racemosum plants grew, so did the deposition of sand on mobile foredunes. The mechanical deposition of sand itself did not stimulate P. racemosum growth. The deposition of saline sand provided a substrate that supported vertical growth of P. racemosum rhizomes and tillers and was a source of adsorbed nutrients. Also, active sand deposition limited the invasion of frontal dunes by other species. Panicum racemosum populations changed from "invader" to "mature" to "regressive" age states over a 5-year period, apparently in response to the spatial patterns of sand deposition and salt spray input. Key words: Panicum, leaf demography, growth vigour, sand dunes, temporal changes.

scholarly journals Snow is Not an Enemy, But another Road in Winter

2020 ◽  
pp. 1-2
Author(s):  
Oleg Khalidullin ◽  
Keyword(s):  
Road Surface ◽  
Long Distance ◽  
Surface Formation ◽  
Different Temperatures ◽  
Almost All

Snowfalls and blizzards block roads and create massive congestion on city streets and long-distance routes. Considering the processes of road surface formation during snowfall, it can be noted that snow during the fall is light fluffs, which, at an indefinite time, with different intensities, at different temperatures, stacked in layers, gradually by the wheels of cars, are compacted into a slippery tuberous canvas. The rubber tread, rolling through the freshly deposited layers, compresses the snow, forming a rut. The resulting trail adheres firmly to the asphalt. Almost all cars go on the trail, therefore the wheels of the following cars condense mainly the same track. On inactive roads, leaving the track during overtaking or detour leads to smoothing and compaction of the freezing walls of the track

Colonization of depopulated crinoids by symbionts: who comes from the bottom and who from the water column?

2015 ◽  
Vol 95 (8) ◽  
pp. 1607-1612 ◽  
Author(s):  
E.S. Mekhova ◽  
P.Y. Dgebuadze ◽  
V.N. Mikheev ◽  
T.A. Britayev
Keyword(s):  
Water Column ◽  
Field Experiments ◽  
Dispersal Ability ◽  
Long Distance ◽  
Sandy Substrate ◽  
Limited Dispersal ◽  
Set Up ◽  
Almost All ◽  
High Degree

Previous experiments with the comatulid Himerometra robustipinna (Carpenter, 1881) demonstrated intensive host-to-host migration processes for almost all symbiotic species both within host aggregations and among hosts separated by several metres. The aim of this study was to check the ability of symbionts to complete long-distance migrations, by means of two in situ experiments which depopulated the crinoid host. Two different sets of field experiments were set up: exposure of depopulated crinoids (set 1) on stony ‘islands’ isolated from native crinoid assemblages by sandy substrate, and (set 2) in cages suspended in the water column. Hosts from set 1 were exposed for 1, 2, 3 and 4 weeks to assess whether substrate has an influence on the symbionts' long-distance migrations. In set 2 cages were exposed for 10–11 days, aiming to check whether symbionts were able to disperse through the water column with currents. These experiments allow the conclusion that post-settled symbionts can actively migrate among their hosts. Symbionts are able to reach their hosts by employing two different ‘transport corridors’, by drifting or swimming in water column, and by moving on the bottom. Comparison of experimental results allows the division of symbionts into two conventional groups according to the dispersal ability of their post-settled stages: (1) species able to complete long-distance migrations, (2) species unable to migrate or having limited dispersal ability. The finding of the free-living shrimp Periclimenes diversipes Kemp, 1922 in set 2 raises the question about the factors that affect such a high degree of specialization of crinoid assemblages.

Growth of Online Schooling in Canada

2011 ◽  
pp. 1060-1065
Author(s):  
M. Haughey
Keyword(s):  
Rural Areas ◽  
Secondary School Students ◽  
New Technology ◽  
Alternative Form ◽  
School Students ◽  
Long Distance ◽  
School Aged Children ◽  
Based Instruction ◽  
Almost All

In Canada, a country of vast landscapes, northern climates and relatively few people, the formal provision of education has always involved alternatives. Records going back to the late 1800s discuss pilot projects that provided education to school-aged children in remote rural areas. Correspondence education, beginning in 1919 and offered by almost all provincial authorities, depended on the post and long-distance haulage to link students and teachers (Haughey, 1990). Each new technology became a part of an educational provision that was of particular importance to secondary school students, who were unable to obtain sufficient courses at their local school to qualify for a high school diploma. More recently, the advent of computers and the Internet have transformed this alternative form of education. It has changed from one for those unable to attend classroom-based instruction to one that is being chosen by students for its adaptability and flexibility, as well as for the ongoing reasons associated with long distances to schools, unavailable courses, and family and personal circumstances. In this chapter, I review the development and present configurations of online schooling in Canada and discuss trends and issues this new form of provision has raised.

Reconstructing the age of coastal sand dunes along the northwestern shore of Lake Huron in Lower Michigan: Paleoenvironmental implications and regional comparisons

2010 ◽  
Vol 2 (2-3) ◽  
pp. 83-92 ◽  
Author(s):  
Alan F. Arbogast ◽  
Michael E. Bigsby ◽  
Mark H. DeVisser ◽  
Shaun A. Langley ◽  
Paul R. Hanson ◽  
...  
Keyword(s):  
Sand Dunes ◽  
Lake Huron ◽  
Coastal Sand Dunes ◽  
Coastal Sand ◽  
Regional Comparisons

Population biology of Microlaena stipoides in a south-eastern Australian pasture

2014 ◽  
Vol 65 (8) ◽  
pp. 767 ◽  
Author(s):  
M. L. Mitchell ◽  
J. M. Virgona ◽  
J. L. Jacobs ◽  
D. R. Kemp
Keyword(s):  
Seed Predation ◽  
Population Biology ◽  
Seedling Recruitment ◽  
Perennial Grass ◽  
Early Summer ◽  
Seed Rain ◽  
Perennial Grasses ◽  
South Eastern ◽  
Eastern Australia ◽  
Microlaena Stipoides

Microlaena (Microlaena stipoides var. stipoides (Labill.) R.Br.) is a C3 perennial grass that is native to areas of south-eastern Australia. In this region, perennial grasses are important for the grazing industries because of their extended growing season and persistence over several years. This series of experiments focused on the population biology of Microlaena by studying the phenology (when seed was set), seed rain (how much seed was produced and where it fell), seed germination, germinable seedbank, seed predation and seedling recruitment in a pasture. Experiments were conducted at Chiltern, in north-eastern Victoria, on an existing native grass pasture dominated by Microlaena. Seed yields were substantial (mean 800 seeds m–2), with seed rain occurring over December–May. Microlaena has two distinct periods of high seed rain, in early summer and in early autumn. Seed predation is high. Within a 24-h period during peak seed production, up to 30% of Microlaena seed was removed from a pasture, primarily by ants. Microlaena seedlings recruited throughout an open paddock; however, seedling density was low (5 seedlings m–2). Microlaena represented only low numbers in the seedbank (0.01–0.05% of total); hence, any seedlings of Microlaena that germinate from the seedbank would face immense competition from other species. Management strategies for Microlaena-dominant pastures need to focus on the maintenance of existing plants.

The Stone Tripods from Plataea

1970 ◽  
Vol 65 ◽  
pp. 175-178
Author(s):  
Nikolaos Pharaklas
Keyword(s):  
Outer Surface ◽  
Total Height ◽  
Concentric Circles ◽  
Almost All ◽  
Outer Half

Two stone tripods—in fact the only known stone tripods of early times—have for many years been in the Museum of Thebes. They are made of the local poros limestone. Even though they have been exhibited, hitherto they have not been cleaned and are virtually unpublished. Villagers found them by chance in the vicinity of Plataea; in 1899 they were handed over to A. Keramopoulos, who was then conducting excavations at Plataea. Keramopoulos, in the same year, wrote a brief note about them, in which he entirely misunderstood their dating. Karouzos included a paragraph about them in his Guide to the Thebes Museum, accompanied by a photograph of one of them.The first tripod, Thebes 19, is intact (Plates 43, 44a–c; Fig. 1). There are a few breaks on the feet, and in places the surface of the stone has decayed, forming holes of various sizes. The height of the bowl is greater than its width, and its greatest diameter is at the mouth. As for the lip, its outer half is bevelled, its inner half horizontal. The feet are short, plump, and broad; they taper downwards because their inner surfaces, which begin at the bottom of the bowl, splay outwards. The feet are not strictly vertical, but open out slightly towards their base; they reach up to the rim. Their outer surface is slightly curved, roughly following the curve of the lip. There were no handles. The total height is 0·38 m.; the lip has a diameter of 0·31 m. outside, and 0·22 m. inside. The bevelled surface of the lip, the front surfaces of the feet and the upper half of the bowl's outer surface are covered with incised decoration: the motifs consist of zigzags, simple circles, circles with inscribed cross, and concentric circles, almost all with deep holes in the centre.

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